JP4190763B2 - Conductive adhesive sheet having anisotropy and method for producing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a conductive adhesive sheet that imparts conductivity only in the thickness direction of a sheet by conductive fine particles dispersedly arranged in the sheet surface, and a method for manufacturing the same.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a conductive adhesive sheet that imparts conductivity only in the thickness direction has been used at the time of connection between a liquid crystal display wiring and a flexible substrate, high density mounting of an integrated circuit component on a substrate, or the like. An example of a conventional conductive adhesive sheet is shown in FIG. In this example, the conductive fine particles 4 are randomly arranged in the sheet 20 made of an adhesive layer. This sheet has the following problems.
[0003]
In recent years, the dimensions of connected wiring patterns and land patterns have been increasingly miniaturized. When the dimension of the connected pattern is reduced, in the sheet in which the conductive fine particles are randomly dispersed and arranged, the connected pattern is arranged at the position A where the conductive fine particles do not exist as shown in FIG. The probability that As a result, the connected patterns may not be electrically connected.
[0004]
In order to solve this problem, it is effective to disperse smaller conductive fine particles in the sheet at a high density. However, when the size of the conductive fine particles is reduced, as shown in FIG. There is a problem that variations in the protruding height of the connection patterns P1, P2 from the surfaces of the substrates B1, B2 cannot be absorbed. Further, when the density of the conductive particles 4 in the sheet 20 is increased, as shown in FIG. 16B, when the patterns P1 and P2 are arranged at a fine pitch, a short (short circuit) occurs between adjacent patterns. ) Is likely to occur. That is, in these methods, the connection reliability of a conductive adhesive sheet in which conductive fine particles are randomly dispersed and arranged is not improved.
[0005]
On the other hand, JP-A-5-67480 and JP-A-10-256701 describe that conductive fine particles are dispersed in a predetermined arrangement in a sheet.
In the method described in Japanese Patent Laid-Open No. 5-67480, the conductive fine particles are charged before being dispersed in the sheet (adhesive layer), and the repulsive force between the conductive fine particles is utilized to make the conductive fine particles in the sheet. Are uniformly dispersed. In addition, each position of the conductive fine particles and the support is charged with different charges, and after the conductive fine particles are arranged on the support in a predetermined arrangement, the conductive fine particles are transferred to the adhesive layer in a state in which this arrangement is maintained. It is described to do.
[0006]
However, in this method, since the arrangement is maintained by the repulsive force between the charged conductive fine particles, it is impossible to bring the distance between the adjacent conductive fine particles within the sheet surface closer to 20 μm or less.
In JP-A-10-256701, a composition comprising a rubber material and conductive particles is formed into a sheet using conductive particles having magnetism, and a magnetic field is applied in the thickness direction of the sheet. It is described that the conductive particles are oriented to cure the rubber in this state.
[0007]
However, this method has the following problems. Since it is difficult to concentrate the magnetic field in a very narrow region, the distance between adjacent conductive fine particles in the sheet surface cannot be brought close to 20 μm or less. In some cases, the conductive particles are arranged so as to overlap in the thickness direction of the rubber sheet. It is difficult to arrange the conductive particles regularly (while maintaining a predetermined interval between adjacent particles). The conductive particles that can be used are limited to magnetic materials.
[0008]
[Problems to be solved by the invention]
The present invention has been made paying attention to such problems of the prior art, and conductive adhesion imparting conductivity only in the thickness direction of the sheet by conductive fine particles dispersed and arranged in the sheet surface. It is an object of the present invention to provide a conductive adhesive sheet in which conductive fine particles are regularly and densely arranged in a sheet surface so that the distance between adjacent conductive fine particles is 20 μm or less. To do.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides a conductive adhesive sheet that imparts conductivity only in the thickness direction of the sheet by conductive fine particles dispersed in the sheet surface, and is disposed in the center in the thickness direction. Adhesive layers are disposed on both surfaces of the core film, the core film and the adhesive layer are insulative, and the core film has a plurality of through-holes penetrating in the thickness direction in a predetermined arrangement in the film surface. An electrically conductive adhesive sheet having anisotropy, characterized in that conductive fine particles are disposed in the through holes.
[0010]
In the conductive adhesive sheet of the present invention, the average particle size of the conductive fine particles is 0.5 μm or more and 50 μm or less, and the standard deviation of the particle size distribution of the conductive fine particles is 50% or less of the average particle size. The thickness is 0.5 μm or more and 50 μm or less, the thickness of the adhesive layer is 1 μm or more and 50 μm or less, and the size of the through hole is 1 to 1.5 times the average particle diameter of the conductive fine particles. It is preferable.
[0011]
In the conductive adhesive sheet of the present invention, the conductive fine particles include copper, gold, silver, nickel, palladium, indium, tin, lead, zinc, or bismuth, or an alloy of any of these metals, or fine particles made of carbon, Alternatively, fine particles having a metal coating on the surface are preferable.
In the conductive adhesive sheet of the present invention, at least one of the adhesive layers disposed on both surfaces of the core film has two types of adhesive layers having a difference in softening temperature of 20 ° C. or more. The higher one is arranged on the core film surface side to provide a laminated product.
[0012]
In the present invention, as a first method for producing the conductive adhesive sheet of the present invention, a photosensitive resin layer forming a core film is formed on the first adhesive layer formed on the support. Thereafter, by patterning the photosensitive resin layer by photolithography, through holes are formed in a predetermined arrangement in the core film, and conductive fine particles are put into the through holes, and then a second film is formed on the core film. Provided is a method for producing a conductive adhesive sheet, wherein an adhesive layer is formed.
[0013]
In the present invention, as a second method for producing the conductive adhesive sheet of the present invention, a first adhesive layer is formed on one surface of a core film having a through hole, and then the conductive film is formed in the through hole. And a second adhesive layer is formed on the other surface of the core film after the conductive fine particles have been added.
In this second method, a core film having a through-hole is formed by (1) irradiating the core film with laser (the core film is dissolved by heat or the polymer molecular chain forming the core film is heated). Cutting: laser ablation), (2) a core film using a pressing mold comprising a male mold having a protrusion corresponding to the arrangement of the through-hole and a female mold having a recess for receiving the protrusion. It is preferable to employ a method of punching out with a press.
[0014]
In the present invention, as a third method for producing the conductive adhesive sheet of the present invention, a core film having a through hole is formed on a conductive substrate, and then the through hole is made conductive by an electrolytic plating method. After the fine particles are grown, the first adhesive layer is formed on the surface of the core film opposite to the conductive substrate, the conductive substrate is removed, and the conductive substrate is removed. A method for producing a conductive adhesive sheet is provided, wherein a second adhesive layer is formed on the surface.
[0015]
The present invention also provides, as a fourth method for producing the conductive adhesive sheet of the present invention, a core film in which a first adhesive layer is formed on one surface, and from the other surface side of the core film. By forming a through hole in the core film by performing laser irradiation, and then placing conductive fine particles in the through hole, a second adhesive layer is formed on the other surface of the core film. A method for producing a conductive adhesive sheet is provided.
[0016]
In the fourth method, it is necessary to prevent the through hole from being formed in the first adhesive layer when the through hole is formed in the core film by laser irradiation.
The laser light used in this method is a laser beam having an oscillation wavelength in the infrared region, such as a fundamental wave of a carbon dioxide laser or a YAG laser, a third or fourth harmonic of a YAG laser, an excimer laser, or the like. And those capable of emitting light in the ultraviolet or vacuum ultraviolet region. For example, by using a third or fourth harmonic of an YAG laser or an excimer laser, a minute through hole having a diameter of 20 μm or less can be easily formed.
[0017]
In particular, in a YAG laser that can be processed with a minute beam, the through hole can be tapered by making the beam shape tapered. Accordingly, the conductive fine particles can be held at the portion where the tapered through hole is narrowed so that the conductive fine particles do not protrude from the first adhesive layer.
[About core film]
The material of the core film used in the present invention is not particularly limited, and various engineering plastics can be used. For example, polyimide resin, polyamide resin, polyamideimide resin, polysulfone resin, polyester resin, unsaturated polyester resin, polyallyl resin, polyolefin resin, polycarbonate resin, polystyrene resin, polyphenylene ether resin, and the like.
[0018]
Moreover, as a core film, a thing with good dimensional stability is preferable. Therefore, as the material of the core film, as the polymer skeleton, a polymer containing an aromatic skeleton such as benzene, naphthalene, anthracene or pyrene or an alicyclic skeleton such as cyclohexane, bicyclohexane, bicyclohexene or adamantane is used. It is preferable to do.
[0019]
As the core film, a thermoplastic resin or a thermosetting resin containing a component that hardens after being softened by heating can also be used. In the case of using a core film that is softened by heat, the softening temperature of the core film is set to 20 ° C. or more higher than the softening temperature of the adhesive layer. The difference in softening temperature is preferably 50 ° C. or higher, and more preferably 80 ° C. or higher.
[0020]
Here, the softening temperature of the core film and the adhesive layer means that the viscosity decreases greatly when the temperature of the resin forming the core film and the adhesive forming the adhesive layer is increased from room temperature (the slope of the viscosity curve). Means the first temperature that changes. This softening temperature can be examined by measuring the viscosity using a viscoelasticity measuring device such as a rheometer while increasing the temperature of the resin and adhesive from room temperature at a constant rate.
[0021]
When the conductive adhesive sheet of the present invention is produced by the first method, a photosensitive resin is used as the material for the core film. Even when the conductive adhesive sheet of the present invention is produced by the second method and the third method, a photosensitive resin can be used as the material of the core film. When photosensitive resin is used as the core film material in the second method, a photosensitive resin layer is formed on the surface of the substrate having peelability, and through holes are formed by patterning the photosensitive resin layer by photolithography. Then, by removing the substrate, a core film having a through hole can be obtained.
[0022]
As the photosensitive resin used as the material of the core film, for example, a photopolymerizable polyimide resin, a photopolymerizable epoxy resin, a photopolymerizable polyester resin, and the like are useful. Further, in the conductive adhesive sheet of the present invention, in order to arrange minute conductive fine particles in the photosensitive resin layer with a minute pitch, it is necessary to form minute through holes with a minute pitch. Therefore, it is necessary to use a photosensitive resin with extremely high resolution that can form a pattern with a line width of several μm or less.
[0023]
The thickness of the core film greatly depends on the size of the conductive fine particles used. That is, when the conductive adhesive sheet of the present invention is used, it is necessary to contact the conductive fine particles with both patterns to be connected without deforming the core film. Therefore, the thickness of the core film is the same as that of the conductive adhesive sheet. The size needs to be the same as or smaller than the average particle size of the conductive fine particles. For example, when the average particle diameter of the conductive fine particles used is 0.5 to 50 μm, the thickness of the core film is set to 0.5 μm to 50 μm. When the thickness of the core film exceeds 50 μm, it is necessary to make the average particle diameter larger than 50 μm, so that it is not suitable for connecting a fine pattern.
[0024]
For the purpose of improving the adhesion with the adhesive layer, a sponge-like microporous film in which pores having a diameter of 1 μm or less are randomly arranged in the film can also be used as the core film. If this microporous film is used as a core film, an improvement in the adhesive strength between the core film and the adhesive layer can be expected due to the anchor effect that the adhesive enters the pores of the microporous film.
[0025]
The size of the through-hole formed in the core film depends on the size of the conductive fine particles used, but is 1 to 1.5 times the average particle size of the conductive particles. The arrangement of the through holes depends on the arrangement pitch of the connection patterns and the wiring width, but it is preferable to arrange the through holes at intervals of 0.3 to 1 times the arrangement pitch. It is also possible to form a through hole only in the pattern of the connected portion. However, in this case, it is necessary to align the connection pattern and the connection component.
[Conductive fine particles]
The conductive fine particles used in the present invention have an average particle size of 0.5 μm to 50 μm, preferably 1 μm to 20 μm, more preferably 2 μm to 10 μm. If the average particle size of the conductive fine particles is less than 0.5 μm, the variation in the height of the connection pattern may not be absorbed. On the other hand, when the size exceeds 50 μm, it is not suitable for connecting a fine pattern.
[0026]
The shape of the conductive fine particles used in the present invention is not particularly required to be spherical, and polyhedral and spherical particles may have a large number of protrusions. However, a flat shape is not preferable because it is difficult to enter the through hole. Conductive fine particles that are easily crushed during compression and that are easy to deform are preferable because they can increase the contact area with the connection pattern and absorb variations in the height of the connection pattern.
[0027]
In the above-described third method for producing the conductive adhesive sheet of the present invention, conductive fine particles are grown in the through holes of the core film by electrolytic plating. At that time, the conductive fine particles are formed by the following method. The shape and structure can be easily crushed during compression. The current density of electrolytic plating is adjusted so that the tips of the conductive fine particles are rounded or protruded. Alternatively, the conductive fine particles are made porous by electrolytic plating and subsequent treatment.
[0028]
In addition, when the core film having a through hole is formed on the conductive substrate by the third method, a photosensitive resin layer is formed on the conductive substrate, and the photosensitive resin layer is formed by photolithography. When the method of forming the through hole is adopted, the hole can be formed in the conductive fine particles by the following method.
First, in the negative photosensitive resin composition, an organic compound that is difficult to dissolve (or disperse) in a developer is mixed, and a photosensitive resin layer is formed from this composition. Next, the photosensitive resin layer is exposed using a mask in which the portion corresponding to the through hole is a light shielding portion, and the resin composition remains as it is in the through hole portion. In this state, development and electrolytic plating are performed. At this time, since the organic compound exists in the through hole, the conductive fine particles grow in a state containing this organic compound. Next, the organic matter in the conductive fine particles is removed by a dissolution or firing process. Thereby, conductive fine particles having a large number of holes therein are formed in the through holes.
[0029]
In addition, organic substances are mixed in the plating bath for electrolytic plating, and after processing such as a composite plating method in which organic substances are incorporated into the metal in the process of metal precipitation, the organic substances incorporated into the conductive fine particles are removed. The pores can be formed in the conductive fine particles also by the method of removing in the dissolution or firing step.
The particle size distribution of the conductive fine particles used in the present invention is such that the standard deviation is 50% or less of the average particle size. Preferably, the standard deviation is 20% or less of the average particle diameter, more preferably 10% or less. If the particle size distribution of the conductive fine particles is widely distributed with a standard deviation exceeding 50% of the average particle size, the conductive fine particles having a small particle size may cause clogging of the through holes, or may not be present in places other than the through holes. It becomes difficult to remove such small conductive fine particles. Moreover, it becomes difficult to absorb the height variation of the connection pattern. This leads to a decrease in electrical connection reliability between connection patterns. Moreover, it is preferable that one conductive fine particle is contained in one through hole.
[0030]
As a method for classifying the conductive fine particles, a conventional method, for example, a centrifugal classifier such as cyclone or clacyclon, a gravity classifier, an inertia classifier, an air classifier, or a classifier by sieving can be used. In order to classify fine conductive fine particles having a particle size of 10 μm or less to obtain conductive fine particles having a narrow particle size distribution, first, coarse classification is performed with an airflow classifier, followed by classification with a precision sieve. . In addition, if classification is performed in the air with a precision sieve, conductive fine particles may be clogged in the sieve hole. Therefore, ultrasonic vibration is applied to the precision sieve or classification is performed in a liquid that has been subjected to ultrasonic vibration. Is preferred.
[About adhesive layer]
As the adhesive forming the adhesive layer constituting the conductive adhesive sheet of the present invention, for example, a thermosetting adhesive, a thermoplastic adhesive, a pressure sensitive adhesive, or the like can be suitably used. In particular, it is preferable to use a type of adhesive containing a so-called latent curing agent in which a compound containing a curing agent is confined in a microcapsule and curing starts when the microcapsule is crushed by pressure or heat.
[0031]
Examples of the material for the adhesive layer include epoxy resins, polyimide resins, urea resins, amino resins, melamine resins, phenol resins, xylene resins, furan resins, isocyanate resins, benzocyclobutene resins, polyphenylene ethers. Examples thereof include a resin, a polysulfone resin, and a polyethersulfone resin. In particular, from the viewpoint of dimensional stability, heat resistance, etc., the resin constituting the adhesive used is an aromatic compound such as benzene, naphthalene, anthracene, pyrene, biphenyl, phenylene ether, cyclohexane, cyclohexene, bicyclooctane, bicyclo It is preferably composed of a compound having a skeleton of an aliphatic cyclic compound such as octene or adamantane in the molecular chain.
[0032]
In addition, if an adhesive made of a resin soluble in a solvent is used, an adhesive layer can be obtained by applying the adhesive on a support in a state dissolved in a solvent and then drying. The thickness of the adhesive layer after drying (solvent removal) is set to 1 μm to 50 μm, preferably 5 μm to 20 μm. When the thickness is less than 1 μm, it is difficult to obtain adhesion strength after bonding. When the thickness of the adhesive layer exceeds 50 μm, the amount of the adhesive is too large and it is difficult to electrically connect the conductive fine particles and the connection pattern.
[0033]
In the conductive adhesive sheet of the present invention, an adhesive layer (adhesive layer on one side of the core film: first adhesive layer and adhesive layer on the other side: second layer on both sides of the core film. Adhesive layers) are formed, but these adhesive layers may be the same or different in composition. In addition, the first and second adhesive layers may be formed by laminating a plurality of adhesive layers having different functions.
[0034]
In the conductive adhesive sheet of the present invention, the first adhesive layer and / or the second adhesive layer has two types of adhesive layers having a difference in softening temperature of 20 ° C. or higher. By arranging and laminating on the core film surface side, when the conductive adhesive sheet is used after being heated and compressed, the conductive fine particles are removed from the through-holes of the core film, and a predetermined position in the sheet surface is obtained. It can prevent moving to the position which shifted | deviated from.
[0035]
For example, when the conductive adhesive sheet of the present invention is used for connecting a substrate having a narrow interval between adjacent patterns of 10 μm or less, if the conductive fine particles move to a position deviated from a predetermined position in the sheet surface, the cause of a short circuit is caused. May be. In such a case, it is preferable to use a conductive adhesive sheet having the two-layered adhesive layer because a short circuit can be surely prevented. The difference in the softening temperature is preferably 50 ° C. or higher, and more preferably 80 ° C. or higher.
[0036]
In addition, when the taper-shaped through hole is provided in the core film in such a size that the conductive fine particles are held in the portion where the taper-shaped through hole is narrowed (the portion having a small opening size), the opening of the taper-shaped through hole Only the adhesive layer that adheres to the core film surface on the larger dimension side may have the two-layer structure.
When the conductive adhesive sheet of the present invention is exposed to an acidic aqueous solution, water, or the like in the production process, it is necessary to use an adhesive layer that does not cause alteration or reaction in the aqueous processing solution. Further, by using an adhesive layer having tackiness or tackiness, the conductive adhesive sheet of the present invention can be temporarily fixed to an object to be connected.
[0037]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described.
One embodiment of the conductive adhesive sheet of the present invention will be described with reference to FIG.
This conductive adhesive sheet is composed of a core film 1 disposed in the center in the thickness direction, adhesive layers 2 and 3 disposed on both surfaces of the core film 1, and spherical conductive fine particles 4. The core film 1 is made of polyimide resin or unsaturated polyester resin and has a thickness of 4 μm. The adhesive layers 2 and 3 are made of an epoxy thermosetting adhesive containing a latent curing agent and have a thickness of 12 μm. The conductive fine particles 4 are powders made of an alloy of copper and silver, and have an average particle size of 6 μm and a standard deviation of the particle size distribution of 1.5 μm.
[0038]
In the core film 1, a large number of through holes 10 penetrating in the thickness direction are regularly arranged in the film plane. In this embodiment, as shown in FIG.1 (b), the through-hole 10 is arrange | positioned in the position of the lattice point (intersection of the vertical line and horizontal line of a grating | lattice) in a film surface, and the face center position of a unit cell. Yes. The interval between adjacent lattice points along the vertical line is 15 μm, and the interval between adjacent lattice points along the horizontal line is 15 μm. The planar shape (cross-sectional shape along the film surface) of the through hole 10 is circular, and the diameter of this circle is 8 μm (1.33 times the average particle diameter of the conductive fine particles 4). In addition, one conductive fine particle 4 is disposed in every through hole 10 of the core film 1.
[0039]
The conductive adhesive sheet is pressed between the substrates to be connected in use. Thereby, the adhesive layers 2 and 3 are deformed, and the conductive fine particles 4 are brought into contact with both patterns to be connected. At this time, the arrangement of the conductive fine particles 4 in the sheet surface is fixed by the core film 1. In this conductive adhesive sheet, as described above, the conductive fine particles 4 are regularly and densely arranged in the sheet surface (so that the distance between adjacent conductive fine particles is 20 μm or less). ing.
[0040]
Therefore, according to the conductive adhesive sheet of this embodiment, even when the dimension of the pattern to be connected is small or when patterns arranged at a fine pitch are connected, highly reliable connection can be performed. In particular, by setting the pitch and size of the through holes 10 in accordance with the arrangement pitch and wiring width of the pattern to be connected, the position where the conductive fine particles 4 do not exist (indicated by symbol A in FIG. 15). ) Is eliminated.
[0041]
According to the conductive adhesive sheet of this embodiment, since the conductive fine particles are regularly arranged, the conductive fine particles are extremely small (for example, a diameter of 2 μm or less, as in the case of being randomly arranged). Even if it is not, the probability that the pattern to be connected is arranged at a position where the conductive fine particles do not exist (indicated by symbol A in FIG. 15) is zero in principle. Therefore, in the conductive adhesive sheet of this embodiment, the conductive fine particles are made to have a certain size, so that the connection pattern protrudes from the substrate surface more than the conductive adhesive sheet in which the conductive fine particles are randomly arranged. It becomes easy to absorb the variation in height.
[0042]
FIG. 1C shows a conductive adhesive sheet in which the arrangement of the through holes 10 in the plane of the core film 1 is different from the above. In this example, the through holes 10 are arranged at the positions of lattice points in the film plane. One conductive fine particle 4 is disposed in each of these through holes 10.
An embodiment of the first method for producing the conductive adhesive sheet of the present invention will be described with reference to FIG.
[0043]
First, after applying an adhesive solution (a liquid in which an adhesive is dissolved in a solvent) to a predetermined thickness on a support 5 made of a plastic film or the like, the first adhesive is removed by drying and removing the solvent. Layer 2 is formed. As a method for applying the adhesive solution, a usual method such as a blade coating method, a spray coating method, a spin coating method, a roll coating method, or the like can be employed.
[0044]
Next, a liquid negative photosensitive resin is applied onto the first adhesive layer 2, and in the case of a photosensitive resin containing a solvent, the photosensitive resin forming the core film 1 is dried by drying the solvent. Layer 11 is formed.
Next, the photosensitive resin layer 11 is patterned by photolithography. That is, as shown in FIG. 2A, first, an exposure mask M having a light shielding portion corresponding to the through hole 10 formed in the core film 1 (shape and arrangement in the sheet surface) is a negative type. It arrange | positions above the photosensitive resin layer 11, and irradiates high energy light from on this exposure mask M. FIG. Next, a predetermined development process is performed to remove a portion of the photosensitive resin layer 11 that was not exposed to light.
[0045]
In this embodiment, high-energy light that can be insolubilized by increasing the degree of polymerization of the negative photosensitive resin is irradiated. As the light source, an ultra-high pressure mercury lamp, a low-pressure mercury lamp, a halogen lamp, a xenon lamp, etc. Is mentioned. In order to form a fine pattern with a pore diameter of 20 μm or less, it is preferable to irradiate parallel rays. In addition, when using positive photosensitive resin, the exposure mask which has the light irradiation part corresponding to the through-hole 10 is used. In this case, in addition to the method of using the above-mentioned light source, a method of cutting the polymer chain bond of the light irradiation part by irradiating X-rays or electron beams extracted from synchrotron orbital radiation is adopted. it can.
[0046]
Thereby, the through holes 10 are formed in the photosensitive resin layer 11 in a predetermined arrangement. As a result, the core film 1 having the through holes 10 in a predetermined arrangement is formed on the first adhesive layer 2. FIG. 2B shows this state.
Next, in this state, a powder made of a large number of conductive fine particles 4 is sprayed from above the core film 1, and then the entire sheet made of the support 5, the first adhesive layer 2, and the core film 1 is vibrated. Thus, the conductive fine particles 4 are put into the through holes 10 of the core film 1. Further, as shown in FIG. 2C, the conductive fine particles 4a that do not enter the through hole 10 and exist on the upper surface of the core film 1 are removed by pressing with a film or the like with an adhesive.
[0047]
By vibrating the entire sheet, the conductive fine particles 4 can easily enter all the through holes 10. Alternatively, the conductive fine particles 4 may be put into the through-holes 10 of the core film 1 by passing the entire sheet through a plurality of times in a container containing the conductive fine particles.
Next, after the adhesive solution is applied on the core film 1 at a predetermined thickness, the solvent is dried and removed, thereby forming the second adhesive layer 3 on the core film 1. Further, the cover film 6 is covered on the second adhesive layer 3. Thereby, as shown in FIG.2 (d), a conductive adhesive sheet is obtained in the state by which the support body 5 was joined to one surface, and the cover film 6 was joined to the other surface, respectively.
[0048]
Instead of this, the cover film 6 on which the adhesive layer 3 is formed is heated by placing the adhesive layer 3 on the core film 1 with the adhesive layer 3 facing the core film 1 side, as shown in FIG. It is good also as a state. However, the heating temperature in this case needs to be a temperature at which the adhesive forming the adhesive layer 3 is not cured.
In addition, a conductive adhesive sheet is used in the state which peeled the support body 5 and the cover film 6. FIG. Therefore, it is preferable to apply a silicone-based release agent to the surface of the support 5 on which the first adhesive layer 2 is formed and the surface of the cover film 6 on the second adhesive layer 3 side. .
[0049]
As described above, according to the first method, the micro through-hole 10 having a diameter of 20 μm or less can be easily formed in the core film 1 by adopting photolithography.
Embodiment of the 2nd method of manufacturing the electroconductive adhesive sheet of this invention is described using FIGS.
[0050]
First, the first adhesive layer 2 is formed on the support 5 by applying an adhesive solution with a predetermined thickness on the support 5 and then drying. FIG. 3A shows this state. On the first adhesive layer 2, a core film 1 having a through hole 10 as shown in FIG. FIG. 3C shows this state. This joining is performed by placing the core film 1 on the first adhesive layer 2 and heating. This heating temperature is set to a temperature at which the adhesive forming the adhesive layer 2 is not cured.
[0051]
Next, the conductive fine particles 4 are filled into the through holes 10 of the core film 1 by the same method as the first method. Next, the second adhesive layer 3 is formed on the core film 1 and the cover film 6 is coated by the same method as the first method. Thereby, as shown in FIG.3 (d), a conductive adhesive sheet is obtained in the state by which the support body 5 was joined to one surface, and the cover film 6 was joined to the other surface, respectively.
[0052]
In this second method, as a method of forming the core film 1 having the through holes 10 as shown in FIG. 3B, (1) As shown in FIG. 4, the core film 1 is irradiated with laser. Method (2) As shown in FIG. 5, it is preferable to employ a method of punching the core film 1 with a press using press dies 90, 170.
As an embodiment of the method (1), first, as shown in FIG. 4A, a metal mask K having an opening K1 corresponding to the through-hole 10 formed in the core film 1 is formed on the support 5. It arrange | positions above the core film 1 which consists of a polyimide resin fixed on the top, and excimer laser is irradiated from on this mask K. FIG. Thereby, the part irradiated with the excimer laser of the core film 1 is removed, and the through hole 10 is formed. FIG. 4B shows this state. Next, the support 5 is removed from the core film 1.
[0053]
In the method {circle around (2)}, first, a press mold is prepared. An embodiment of this manufacturing method will be described with reference to FIGS.
First, a conductive substrate 7 such as an aluminum plate or a stainless steel plate is prepared, and a zinc substitution plating process is performed on the surface thereof to form a plating layer having a thickness of about 200 μm. On this plated layer, the negative photosensitive resin layer 8 is formed by the same method as the method for forming the photosensitive resin layer 11 described above.
[0054]
Next, an exposure mask M having a light shielding portion corresponding to the through hole 10 of the core film 1 is prepared, and this exposure mask M is disposed above the photosensitive resin layer 8. High-energy parallel light is irradiated from above the exposure mask M. Parallel light is obtained by processing light from a light source with a fly-eye lens and several reflecting mirrors. FIG. 6A shows this state.
[0055]
Next, a predetermined development process is performed to remove a portion of the photosensitive resin layer 8 that was not exposed to light. Thereby, a through hole 81 corresponding to the through hole 10 of the core film 1 is formed in the photosensitive resin layer 8. FIG. 6B shows this state.
Next, as a pretreatment for plating, the surface of the plate-like material composed of the conductive substrate 7 and the photosensitive resin layer 8 is cleaned by reactive ion etching or the like. That is, the development residue remaining on the plate after development is completely removed.
[0056]
Next, a plate-like material composed of the conductive substrate 7 and the photosensitive resin layer 8 is placed in a plating bath, and the conductive substrate 7 is energized, whereby electrolytic plating of nickel containing phosphorus is performed. Thereby, the plating layer 9 is formed on the photosensitive resin layer 8 and in the through hole 81. This state is shown in FIG. The thickness of the plating layer 9 is set to a thickness that can exhibit the strength required for a press mold. For example, the depth of the through hole 81 is about 50 times.
[0057]
Next, the conductive substrate 7 is removed from the plate-like material composed of the conductive substrate 7, the photosensitive resin layer 8, and the plating layer 9 by an etching method or physically peeling. Next, the photosensitive resin layer 8 is peeled from the plating layer 9. As shown in FIG. 6D, the plated layer 9 becomes a male mold 90 having protrusions 91 corresponding to the arrangement of the through holes 10 of the core film 1.
[0058]
Next, a copper mold 15 having the same shape as the male mold 90 is produced by performing the same method as the male mold 90 except that electrolytic copper plating is performed instead of electrolytic nickel plating. That is, the mold 15 has a protrusion 15 a corresponding to the arrangement of the through holes 10 of the core film 1. Next, the plating layer 17 is formed on the surface of the mold 15 on the side of the protrusions 15a by performing electrolytic plating of nickel containing phosphorus. This state is shown in FIG. The thickness of the plating layer 17 is set to a thickness that can exhibit the strength required for a press mold. For example, it is about 50 times the protruding length of the protrusion 15a.
[0059]
Next, the copper mold 15 is removed from the plating layer 17 by etching using a solution that dissolves copper, such as ammonium persulfate, ferric chloride aqueous solution, or cupric chloride aqueous solution. As shown in FIG. 6 (f), the plated layer 17 becomes a female die 170 having a recess 171 that receives the protrusion 91 of the male die 90.
The male mold 90 and the female mold 170 obtained in this way are mounted on a press device, and the patterns on both the upper and lower sides can be observed simultaneously so that the projection 91 of the male mold 90 and the recess 171 of the female mold 170 are accurately engaged with each other. While looking at the CCD camera, align at least two locations. Next, as shown in FIG. 5, the core film 1 is placed between the male mold 90 and the female mold 170 and pressed, so that a through hole is formed in a portion sandwiched between the projection 91 and the concave portion 171 of the core film. Is formed. As this pressing apparatus, a flip chip bonder or the like used when reversing an LSI bare chip and mounting it on a substrate can be used by modifying it.
[0060]
As described above, according to the second method, a minute through hole 10 having a diameter of 20 μm or less is easily formed in the core film 1 by employing a laser irradiation method or a press working method using a fine mold. be able to.
In this embodiment, as a method for forming the first adhesive layer 2 on one surface of the core film 1 having the through holes 10 in the second method of the present invention, the first adhesive layer 2 is formed on the support 5. Although the method of joining the core film 1 having the through holes 10 on the first adhesive layer 2 is adopted, instead of this, for example, an adhesive solution is formed on the core film 1 having the through holes 10. You may employ | adopt the method of apply | coating and drying.
[0061]
In this case, after forming the first adhesive layer on the core film, the core film side is turned up, and conductive fine particles are put in the through holes, and then the second adhesive layer is formed on the core film. Form. In addition, even when an adhesive enters the through-hole of the core film when the first adhesive layer is formed, the adhesive is also kept in an uncured state like the first adhesive layer. The conductive fine particles can be put into the through holes by, for example, pushing the conductive fine particles into the through holes.
[0062]
An embodiment of a third method for producing the conductive adhesive sheet of the present invention will be described with reference to FIG.
First, as shown in FIG. 7A, the negative photosensitive resin layer 11 is formed on the conductive substrate 7 by the same method as the first method, and an exposure mask M for the photosensitive resin layer 11 is formed. High-energy light irradiation and development processing are performed. As a result, the core film 1 having the through holes 10 is formed on the conductive substrate 7. FIG. 7B shows this state.
[0063]
Next, the conductive fine particles 4 are grown in the through holes 10 of the core film 1 by electrolytic plating. In this embodiment, by adjusting the current density at the time of electrolytic plating, as shown in FIG. 7C, the conductive fine particles 4 have a height protruding from the core film 1 at the center of the through-hole 10, Moreover, it is grown so that the tip is rounded.
Next, the first adhesive layer 2 is formed on the surface of the core film 1 opposite to the conductive substrate 7 by the same method as the method in which the second adhesive layer 3 is formed by the first method. . Next, the cover film 6 is covered on the first adhesive layer 2. Instead of this, the cover film 6 on which the adhesive layer 2 is formed is heated by placing the cover layer 6 on the core film 1 with the adhesive layer 2 facing the core film 1 side, thereby heating the cover film 6 of FIG. It is good also as a state. However, the heating temperature in this case needs to be a temperature at which the adhesive forming the adhesive layer 2 is not cured.
[0064]
Next, the conductive substrate 7 is removed by an etching method or peeling. FIG. 7D shows this state.
Next, the second adhesive layer 3 is formed on the surface of the core film 1 from which the conductive substrate 7 has been removed, and the cover film 6 is covered on the second adhesive layer 3. Thus, as shown in FIG.7 (e), the electroconductive adhesive sheet with which the cover film 6 was joined on both surfaces is obtained.
[0065]
According to the third method, since the conductive fine particles 4 are grown in the through holes 10 by the electrolytic plating method, the conductive fine particles 4 can be easily arranged in the through holes 10.
[0066]
[Example 1]
[Preparation of conductive adhesive sheet]
In this example, a conductive adhesive sheet is produced by a method corresponding to the example of the first method of the present invention. This embodiment will be described with reference to FIG.
First, a polyethylene terephthalate (PET) film having a thickness of 25 μm was prepared, and the surface of this PET film was coated with polydimethylsiloxane as a release agent to a thickness of about 50 nm. A thermoplastic polyimide solution was applied to the surface of the PET film (support) 5 coated with a release agent using a blade coater. Next, an adhesive layer (first adhesive layer) 2 made of thermoplastic polyimide having a thickness of 10 μm was formed on the PET film 5 by drying and removing the solvent from the coating film.
[0067]
As a thermoplastic polyimide solution, 100 parts by weight of a thermoplastic polyimide solution “UPA-N-111C” manufactured by Ube Industries Co., Ltd. was added in a proportion of 1 part by weight of pentaerythritol trimethacrylate and mixed for 30 minutes. I used it until it disappeared.
On this adhesive layer 2, a liquid negative photosensitive resin was applied using a blade coater to form a photosensitive resin layer 11 having a thickness of 4 μm. A PET film having a thickness of 10 μm was placed on the photosensitive resin layer 11.
[0068]
The photosensitive resin used was an unsaturated polyester prepolymer having a number average molecular weight of 2000: 100 parts by weight, tetraethylene glycol dimethacrylate: 10.7 parts by weight, diethylene glycol dimethacrylate: 4.3 parts by weight, pentaerythritol tris Methacrylate: 15 parts by weight, phosphoric acid (monomethacryloyloxyethyl): 3.6 parts by weight, 2,2-dimethoxy-2-phenylacetophenone: 2 parts by weight, 2,6-di-tert-butyl-4-methylphenol : 0.04 parts by weight, and “OPLAS Yellow 140” manufactured by Orient Chemical Co., Ltd .: 0.11 parts by weight were added and mixed by stirring.
[0069]
The unsaturated polyester prepolymer having a number average molecular weight of 2,000 was obtained by dehydration polycondensation reaction by adjusting the charging ratio of adipic acid, isophthalic acid, itaconic acid, fumaric acid and diethylene glycol. The number average molecular weight was measured using a gel permeation chromatography apparatus manufactured by Shimadzu Corporation and calibrated with a polystyrene standard product.
[0070]
This photosensitive resin does not contain a solvent, but can be applied as it is with the above-mentioned film thickness. However, when coating with a film thickness of 2 μm or less, it is preferable to add a solvent to lower the viscosity. In that case, the photosensitive resin layer is obtained by drying the solvent after coating.
Next, as an exposure mask M, circular chrome patterns with a diameter of 8 μm are regularly arranged with the same arrangement as the arrangement of the through holes 10 shown in FIG. A glass photomask was prepared. This exposure mask M was placed on the photosensitive resin layer 11, and the light from the ultrahigh pressure mercury lamp was irradiated on the exposure mask M. This irradiation light is a parallel light beam obtained by collimating the light from the light source by the optical system. FIG. 2A shows this state. However, in this figure, a PET cover film having a thickness of 10 μm is omitted.
[0071]
Next, the PET cover film was peeled off and developed. As a result, the portion of the photosensitive resin layer 11 that was not exposed to light was removed, and as shown in FIG. 2B, the core film 1 having a large number of through holes 10 became a thermoplastic polyimide adhesive layer (first layer). 1 adhesive layer) 2. In the core film 1, circular through holes 10 having a diameter of 8 μm are regularly arranged at a pitch of 15 μm (lattice point spacing) in the arrangement shown in FIG.
[0072]
After the powder composed of a large number of conductive fine particles 4 is dispersed on the core film 1, the conductive fine particles 4 are put in all the through holes 10 by applying vibration to the entire sheet using an ultrasonic vibration device. It was. Next, the adhesive film “SPV-363” manufactured by Nitto Denko Corporation is attached to the surface of the core film 1 using a roller, and then peeled off, so that it does not enter the through-hole 10 and the upper surface of the core film 1. The existing conductive fine particles 4a were removed.
[0073]
As the powder composed of the conductive fine particles 4, the composition described in JP-A-6-223633 is Ag. _x Cu _(1-x) (0.008 ≦ x ≦ 0.4), the silver concentration on the particle surface is higher than 2.2 times the average silver concentration, and a spherical shape having a region in which the silver concentration increases toward the particle surface in the vicinity of the surface A powder made of conductive particles having an average particle size of 6 μm and a standard deviation of the particle size distribution of 0.6 μm was used.
[0074]
Next, as shown in FIG. 2 (d), a PET film 6 having an adhesive layer (second adhesive layer) 3 made of an epoxy adhesive on one surface is used, and the adhesive layer 3 is used as a core. The film 1 was placed on the core film 1 and heated by heating toward the film 1 side.
The PET film 6 in which the adhesive layer 3 made of an epoxy adhesive is formed on one surface was produced as follows. First, a polyethylene terephthalate (PET) film having a thickness of 25 μm was prepared, and the surface of this PET film was coated with polydimethylsiloxane as a release agent to a thickness of about 50 nm. An epoxy adhesive solution was applied to the surface of the PET film (cover film) 6 coated with a release agent using a blade coater. Next, a layer 3 made of an epoxy adhesive having a thickness of 10 μm was formed on the PET film 6 by drying and removing the solvent from the coating film.
[0075]
The composition of the epoxy adhesive solution used is as follows: bisphenol A type liquid epoxy resin: 10 parts by weight, phenoxy resin: 10 parts by weight, latent hardener comprising imidazole derivative epoxy compound of microcapsule type: 4.5 parts by weight Toluene / ethyl acetate mixture: 5 parts by weight.
As described above, the adhesive layer 2 made of thermoplastic polyimide is arranged on one surface of the core film 1 made of unsaturated polyester resin, and the adhesive layer 3 made of epoxy adhesive is arranged on the other surface, In the core film 1, circular through holes 10 having a diameter of 8 μm are regularly formed at a pitch of 15 μm (lattice interval) in the arrangement shown in FIG. 1B, and one copper- A conductive adhesive sheet in which conductive fine particles 4 made of silver alloy were arranged was obtained. PET films 5 and 6 are bonded to both surfaces of the conductive adhesive sheet.
[Performance evaluation]
Test substrates 30, 40, and 50 shown in FIGS. 8 and 9 were prepared.
[0076]
FIG. 8A is a plan view showing a part of the test substrate 30, and FIG. 8B is a cross-sectional view taken along the line aa in FIG. 8A.
The test substrate 30 has 200 wirings 32 and an inspection pad 35 connected independently for each wiring 32 on the insulating substrate 31. The wiring 32 has a width W of 15 μm, an arrangement pitch p of 30 μm, and a thickness h of 15 μm.
[0077]
9A is a plan view showing a part of the test substrates 40 and 50, FIG. 9B is a cross-sectional view of the test substrate 40, and FIG. 9C is a cross-section of the test substrate 50. FIG. FIG. 9B and FIG. 9C correspond to the cross-sectional view taken along the line bb in FIG. 9A.
The test substrate 40 has a linear wiring pattern 42, a circular dummy pattern 43, and an inspection pad 44 on a glass substrate 41. 200 dummy patterns 43 are arranged in the length direction of the wiring pattern 42 in accordance with the wiring 32 of the test substrate 30. These patterns are formed by forming a thin chromium layer on the glass substrate 41, applying copper plating thereon, and patterning the copper plating layer and the chromium layer.
[0078]
The width W1 of the wiring pattern 42 is 15 μm, the diameter W2 of the dummy pattern 43 is 15 μm, and the arrangement pitch p10 is 30 μm. The thickness of the wiring pattern 42 and the dummy pattern 43 (the total thickness of the copper plating layer and the chromium layer) is 15 μm.
When these test substrates 30 and 40 are used, a portion where all the wirings 32 of the test substrate 30 are formed and a portion where the wiring pattern 42 and the dummy pattern 43 of the test substrate 40 are formed are overlapped. The wiring 32 and the wiring pattern 42 are arranged so as to be orthogonal to each other.
[0079]
The test substrate 50 is formed by forming, on one surface of a glass substrate 51, a convex portion 52 having the same pattern as the wiring pattern 42 and the dummy pattern 43 of the test substrate 40 by excimer laser processing.
When the test substrate 30 and the test substrate 50 are used, a portion of the test substrate 30 where the wirings 32 are formed and a portion of the test substrate 50 where the convex portions 52 are formed are overlapped to form a wiring pattern. The protrusions 52 corresponding to 42 and the wirings 32 are arranged so as to be orthogonal to each other.
[0080]
Using these test substrates 30, 40, and 50, the performance of the conductive adhesive sheet was evaluated by the following method.
First, the PET films 5 and 6 were peeled from both sides of the conductive adhesive sheet obtained by the above-described method, and the conductive adhesive sheet was sandwiched between the test substrates 30 and 40 arranged as described above, and a pressure of 50 MPa was applied. The state was heated to 230 ° C. and held for 5 minutes. As a result, the test substrate 30 and the test substrate 40 were bonded by the conductive adhesive sheet.
[0081]
10A and 10B are cross-sectional views showing this state. FIG. 10A is a cross-sectional view of the wiring pattern 42 and FIG. 10B is a cross-sectional view of the dummy pattern 43. These drawings are cross-sectional views taken along a line parallel to the wiring pattern 42. At the time of bonding, the core film 1 of the conductive adhesive sheet and the adhesive layers 2 and 3 on both sides thereof are deformed, and therefore, these are collectively denoted by reference numeral 23 in FIG.
[0082]
A connection confirmation test using the conductive adhesive sheet of Example 1 was performed using the two test pieces thus obtained. That is, for each test piece, the resistance between the 200 test pads 35 of the test substrate 30 and the test pads 44 of the test substrate 40 was measured. As a result, it was found that there is no one that is not electrically connected to the wiring pattern 42 of the test substrate 40 among the total of 400 wirings 32 of the test substrate 30 of the two test pieces.
[0083]
Next, the PET films 5 and 6 are peeled off from both sides of the conductive adhesive sheet obtained by the above-described method, the conductive adhesive sheet is sandwiched between the test substrates 30 and 50 arranged as described above, and a pressure of 50 MPa is applied. In this state, it was heated to 230 ° C. and held for 5 minutes. As a result, the test substrate 30 and the test substrate 50 were bonded by the conductive adhesive sheet.
[0084]
Using the two test pieces thus obtained, the insulation resistance between the adjacent test pads 35 was measured. As a result, the total insulation resistance is 10% between the total of 398 test pads of the two test pieces. ¹² It was more than Ω. As a result, it was found that no short circuit occurred between all the adjacent wirings 32 with respect to all 400 wirings 32 in total of the two test pieces.
[0085]
From these test results, as shown in FIG. 10 (a), the conductive adhesive sheet of this example causes the wiring 32 of the test substrate 30 and the wiring pattern 42 of the test substrate 40 to be a conductive adhesive sheet. As shown in FIGS. 10A and 10B, it can be seen that the adjacent wirings 32 are not connected by the conductive fine particles 4 and are connected by the conductive fine particles 4.
[0086]
[Example 2]
[Preparation of conductive adhesive sheet]
In this example, a conductive adhesive sheet is produced by a method corresponding to the example of the second method of the present invention. This embodiment will be described with reference to FIGS.
First, a polyethylene terephthalate (PET) film having a thickness of 25 μm was prepared, and the surface of this PET film was coated with polydimethylsiloxane as a release agent to a thickness of about 50 nm. An epoxy adhesive solution was applied to the surface of the PET film coated with the release agent using a blade coater. Next, the solvent was dried and removed from the coating film to form an adhesive layer made of an epoxy adhesive having a thickness of 12 μm on the PET film. Two sheets comprising this PET film and an adhesive layer were prepared.
[0087]
The composition of the epoxy adhesive solution used is as follows: bisphenol A type liquid epoxy resin: 10 parts by weight, phenoxy resin: 10 parts by weight, latent hardener comprising imidazole derivative epoxy compound of microcapsule type: 4.5 parts by weight Toluene / ethyl acetate mixture: 5 parts by weight.
On the other hand, the surface of the same PET film as described above was coated with polydimethylsiloxane as a release agent in a film thickness of about 50 nm. A polyimide resin solution (“UPA-N-111C” manufactured by Ube Industries, Ltd.) was applied to the surface of the PET film coated with the release agent using a blade coater. Next, by removing the solvent from the coating film by drying, a core film 1 made of polyimide resin was formed on the PET film (support) 5 with a thickness of 4 μm as shown in FIG.
[0088]
Next, a nickel metal mask K having an opening K1 corresponding to the through-hole 10 formed in the core film 1 is prepared, and the metal mask K is disposed above the core film 1. Excimer laser was irradiated from above. FIG. 4A shows this state. In the metal mask K, circular holes having a diameter of 8 μm are regularly formed at a pitch of 15 μm (lattice interval) with the same arrangement as the arrangement of the through holes shown in FIG.
[0089]
Excimer laser irradiation was performed using an excimer laser processing apparatus including an excimer laser “INDEX800” manufactured by LUMONICS and a transport system “SIL300H” manufactured by Sumitomo Heavy Industries, Ltd. The wavelength of the laser was 248 nm (krypton fluoride gas), the size of the laser beam was 8 mm × 25 mm, and the oscillation frequency was 200 Hz.
[0090]
As a result, the portion of the core film 1 irradiated with the excimer laser (the lower portion of the opening K1) was removed, and the through hole 10 was formed at a predetermined position of the core film 1. In the core film 1, circular through holes 10 having a diameter of 8 μm are regularly arranged at a pitch of 15 μm (lattice point spacing) in the arrangement shown in FIG. FIG. 4B shows this state. Next, the PET film (support) 5 is peeled from the core film 1.
[0091]
Next, the sheet made of the PET film and the adhesive layer prepared in advance by the above-described method is directed upward with the adhesive layer (first adhesive layer) 2 side upward as shown in FIG. The core film 1 having the through hole 10 was placed thereon and joined by heating. This state is shown in FIG.
After the powder composed of a large number of conductive fine particles 4 is dispersed on the core film 1, the conductive fine particles 4 are put in all the through holes 10 by applying vibration to the entire sheet using an ultrasonic vibration device. It was. This state is shown in FIG. Next, the adhesive film “SPV-363” manufactured by Nitto Denko Corporation is attached to the surface of the core film 1 using a roller, and then peeled off, so that it does not enter the through-hole 10 and the upper surface of the core film 1. The existing conductive fine particles 4a were removed.
[0092]
As the powder composed of the conductive fine particles 4, the composition described in JP-A-6-223633 is Ag. _x Cu _(1-x) (0.008 ≦ x ≦ 0.4), the silver concentration on the particle surface is higher than 2.2 times the average silver concentration, and a spherical shape having a region in which the silver concentration increases toward the particle surface in the vicinity of the surface A powder made of conductive particles having an average particle size of 6 μm and a standard deviation of the particle size distribution of 0.6 μm was used.
[0093]
Next, as shown in FIG. 3 (e), an adhesive layer (second adhesive layer) prepared in advance by the above-mentioned method and having an adhesive layer made of an epoxy adhesive formed on a PET film is formed. ) It was placed on the core film 1 with the 3 side facing down and joined by heating.
Thus, adhesive layers 2 and 3 made of 12 μm thick epoxy adhesive are arranged on both surfaces of the core film 1 made of polyimide resin and having a thickness of 4 μm. The core film 1 has a circular through hole 10 having a diameter of 8 μm. However, in the arrangement shown in FIG. 1B, the conductive film is regularly formed at a pitch of 15 μm (interval between lattice points), and one conductive fine particle 4 made of copper-silver alloy is arranged in each through hole 10. An adhesive sheet was obtained. PET films 5 and 6 are bonded to both surfaces of the conductive adhesive sheet.
[Performance evaluation]
Using the conductive adhesive sheet prepared in Example 2 and the same test substrates 30, 40, and 50 as in Example 1, two test pieces were prepared in the same manner as in Example 1 and performed. A connection confirmation test and a short confirmation test were performed in the same manner as in Example 1.
[0094]
As a result, in the connection confirmation test, it is confirmed that there is no one that is not electrically connected to the wiring pattern 42 of the test substrate 40 among the total of 400 wirings 32 of the test substrate 30 of the two test pieces. It was done.
Further, in the short check test, all the insulation resistances are 10 between the total of 398 test pads of the two test pieces. ¹² It was more than Ω. As a result, it was confirmed that no short circuit occurred between all adjacent wirings 32 with respect to all 400 wirings 32 in total of two test pieces.
[0095]
[Example 3]
[Preparation of conductive adhesive sheet]
In this example, a conductive adhesive sheet is produced by a method corresponding to the example of the second method of the present invention. This embodiment will be described with reference to FIGS. 3, 5, and 6. FIG.
[0096]
In the same manner as in Example 2, a core film 1 made of polyimide resin was formed on a PET film (support) 5. However, the thickness was 7 μm. Next, the PET film (support) 5 was peeled from the core film 1.
Next, as shown in FIG. 5, the core film 1 is sandwiched between pressing dies (pressing surface: 2.5 cm square) composed of a male mold 90 and a female mold 170, and punched with a press. A through hole 10 was opened in the film 1. A flip chip bonder was used as the pressing device, and the alignment of the male mold 90 and the female mold 170 was performed by a method using a CCD camera. The press pressure was 3 MPa.
[0097]
The male mold 90 and the female mold 170 were produced by the method described with reference to FIG. 6 in the above-described embodiment.
Specifically, an aluminum plate having a thickness of 200 μm was prepared as the conductive substrate 7, and the surface thereof was subjected to zinc substitution plating. The photosensitive resin layer 8 was formed with a thickness of 100 μm by the same method using the same photosensitive resin solution as in Example 1. As the exposure mask M, a glass photomask in which circular chrome patterns having a diameter of 10 μm are arranged in the same manner as the arrangement of the through holes 10 shown in FIG. Prepared. The exposure method was the same as the method for the photosensitive resin layer 11 of Example 1.
[0098]
Reactive ion etching of the plating pretreatment was performed using “PC-1000-5030” manufactured by Yamato Kagaku while introducing oxygen gas into the system. The thickness of the plating layer 9 formed by nickel plating was 5 mm. The conductive substrate 7 was removed by wet etching using hydrochloric acid. Moreover, the copper type | mold 15 was produced by the electrolytic copper plating process which uses copper sulfate. The thickness of the plating layer 17 by nickel plating was 5 mm. The copper mold 15 was removed by wet etching using an aqueous ammonium persulfate solution and concentrated nitric acid.
[0099]
In this way, a core film 1 was obtained in which circular through holes 10 having a diameter of 10 μm were regularly arranged at a pitch of 20 μm (lattice point spacing) in the arrangement shown in FIG. An adhesive layer was formed on both surfaces of the core film 1 by the following method.
First, as shown in FIG. 3A, an adhesive layer (first adhesive layer) 2 prepared from a PET film and an adhesive layer (10 μm) prepared in advance by the same method as in Example 2 was used. Placed side up. Next, the core film 1 having the obtained through holes 10 was placed on the adhesive layer 2 and joined by heating. This state is shown in FIG.
[0100]
Thereafter, the conductive fine particles 4 were arranged in the through holes 10 and the second adhesive layer 3 and the cover film 6 were joined in the same manner as in Example 2. However, the powder made of the conductive fine particles 4 was made of the same material but had an average particle diameter of 8 μm and a standard deviation of particle diameter distribution of 0.8 μm.
As a result, the adhesive layers 2 and 3 made of 10 μm epoxy adhesive are arranged on both surfaces of the core film 1 made of polyimide resin and having a thickness of 10 μm. The core film 1 has circular through holes 10 having a diameter of 10 μm, Conductive adhesion, which is regularly formed with a pitch of 20 μm (lattice spacing) in the arrangement shown in FIG. 1B, and each conductive fine particle 4 made of copper-silver alloy is arranged in each through hole 10. A sheet was obtained. PET films 5 and 6 are bonded to both surfaces of the conductive adhesive sheet.
[Performance evaluation]
The width W of the wiring 32 of the test substrate 30 was 20 μm, and the arrangement pitch p was 40 μm. The width of the wiring pattern 42 of the test substrate 40 was 20 μm, the diameter W2 of the dummy pattern 43 was 20 μm, and the arrangement pitch p10 was 40 μm. The pattern of the convex part 52 of the test substrate 50 was matched with this. Except for this point, test substrates 30, 40, and 50, which are the same as those in Example 1, were prepared.
[0101]
Using the test substrates 30, 40, 50 and the conductive adhesive sheet prepared in Example 3, two test pieces were prepared in the same manner as in Example 1, and the same as in Example 1 The connection confirmation test and the short confirmation test were conducted by the above method.
As a result, in the connection confirmation test, it is confirmed that there is no one that is not electrically connected to the wiring pattern 42 of the test substrate 40 among the total of 400 wirings 32 of the test substrate 30 of the two test pieces. It was done.
[0102]
Further, in the short check test, all the insulation resistances are 10 between the total of 398 test pads of the two test pieces. ¹² It was more than Ω. As a result, it was confirmed that no short circuit occurred between all adjacent wirings 32 with respect to all 400 wirings 32 in total of two test pieces.
[0103]
[Example 4]
[Preparation of conductive adhesive sheet]
In this example, a conductive adhesive sheet is produced by a method corresponding to the example of the second method of the present invention. This embodiment will be described with reference to FIG.
First, a thermal release sheet (“Riva Alpha” manufactured by Nitto Denko Corporation) 400 is prepared in which a release layer (resin layer in which foaming is generated by heat and the adhesive strength is extremely reduced) 46 is formed on the surface of the plastic film 45. did. Next, on the release layer 46 of this sheet 400, the same negative photosensitive resin solution as in Example 1 was applied by using a blade coater to form the photosensitive resin layer 11 with a thickness of 4 μm. . A PET film 47 having a thickness of 10 μm was placed on the photosensitive resin layer 11.
[0104]
Next, as an exposure mask M, a circular chrome pattern having a diameter of 8 μm is regularly arranged at a pitch of 15 μm with the same arrangement as that of the through holes 10 shown in FIG. A glass photomask was prepared. This exposure mask M was placed on the photosensitive resin layer 11, and the light from the ultrahigh pressure mercury lamp was irradiated on the exposure mask M. This irradiation light is a parallel light beam obtained by collimating the light from the light source by the optical system. FIG. 11A shows this state.
[0105]
Next, after the PET film 47 was peeled off, development processing was performed. As a result, the portion of the photosensitive resin layer 11 that was not exposed to light was removed, and the core film 1 having a large number of through-holes 10 passed through the release layer 46 as shown in FIG. Formed on top. In the core film 1, circular through holes 10 having a diameter of 8 μm are regularly arranged at a pitch of 15 μm (lattice point spacing) in the arrangement shown in FIG.
[0106]
An adhesive layer was formed on both surfaces of the core film 1 having the through-holes 10 thus obtained by the following method.
First, in the state of FIG. 11B, foaming was caused in the release layer 46 of the sheet 400 by heating the laminated sheet composed of the core film 1 and the sheet 400. Thereby, the film 45 of the sheet 400 can be easily peeled from the core film 1.
[0107]
Next, the sheet 300 made of the PET film 5 and the adhesive layer (10 μm) 2 prepared in advance by the same method as in Example 2 is placed with the adhesive layer (first adhesive layer) 2 side facing up. The laminated sheet in the state of FIG. 11B was placed on the core film 1 with the core film 1 side facing the adhesive layer 2 side, and joined by heating. This state is shown in FIG. Next, the film 45 was peeled from the core film 1. This state is shown in FIG. This state is the same as the state shown in FIG.
[0108]
Thereafter, as shown in FIGS. 3D and 3E, the conductive fine particles 4 are disposed in the through holes 10 and the second adhesive layer 3 and the cover film 6 are joined in the same manner as in Example 2. went. The same powder as in Example 2 was used for the powder composed of conductive fine particles 4.
Thereby, the adhesive layers 2 and 3 made of 10 μm epoxy adhesive are arranged on both surfaces of the core film 1 made of unsaturated polyester resin and having a thickness of 4 μm. The core film 1 has a circular through hole 10 having a diameter of 8 μm. However, in the arrangement shown in FIG. 1B, the conductive film is regularly formed at a pitch of 15 μm (interval between lattice points), and one conductive fine particle 4 made of copper-silver alloy is arranged in each through hole 10. An adhesive sheet was obtained. PET films 5 and 6 are bonded to both surfaces of the conductive adhesive sheet.
[Performance evaluation]
Using the conductive adhesive sheet produced in Example 4 and the same test substrates 30, 40, and 50 as in Example 1, two test pieces were produced in the same manner as in Example 1 and carried out. A connection confirmation test and a short confirmation test were performed in the same manner as in Example 1.
[0109]
As a result, in the connection confirmation test, it is confirmed that there is no one that is not electrically connected to the wiring pattern 42 of the test substrate 40 among the total of 400 wirings 32 of the test substrate 30 of the two test pieces. It was done.
Further, in the short check test, all the insulation resistances are 10 between the total of 398 test pads of the two test pieces. ¹² It was more than Ω. As a result, it was confirmed that no short circuit occurred between all adjacent wirings 32 with respect to all 400 wirings 32 in total of two test pieces.
[0110]
[Example 5]
[Preparation of conductive adhesive sheet]
In this example, a conductive adhesive sheet is produced by a method corresponding to the example of the third method of the present invention. This embodiment will be described with reference to FIG.
First, an aluminum plate (conductive substrate) 7 having a thickness of 100 μm was prepared, and the surface was subjected to zinc substitution plating. A negative photosensitive resin layer 11 having a thickness of 10 μm is formed on the plated surface of the aluminum plate 7 by applying the same negative photosensitive resin solution as in Example 1 using a blade coater and drying. did. A PET film having a thickness of 10 μm was placed on the photosensitive resin layer 11. FIG. 7A shows this state. However, in this figure, the PET film on the photosensitive resin layer 11 is omitted.
[0111]
Next, as an exposure mask M, circular chrome patterns having a diameter of 5 μm are regularly arranged at a pitch of 10 μm with the same arrangement as the arrangement of the through holes 10 shown in FIG. A glass photomask was prepared. This exposure mask M was placed on the photosensitive resin layer 11, and the light from the ultrahigh pressure mercury lamp was irradiated on the exposure mask M. This irradiation light is a parallel light beam obtained by collimating the light from the light source by the optical system.
[0112]
Next, after the PET film was peeled off, development processing was performed. As a result, the portion of the photosensitive resin layer 11 that was not exposed to light was removed, and the core film 1 having a large number of through holes 10 was formed on the aluminum plate 7 as shown in FIG. . In the core film 1, circular through holes 10 having a diameter of 5 μm are regularly arranged at a pitch of 10 μm (lattice point spacing) in the arrangement shown in FIG.
[0113]
Next, as a pretreatment for plating, the surface of the plate-like material composed of the conductive substrate 7 and the photosensitive resin layer 11 is subjected to reactive ion etching treatment, and the development residue remaining on the plate-like material after development is removed. Completely removed.
Next, this plate product was put in a copper pyrophosphate plating bath and energized to the aluminum plate 7 to grow copper conductive fine particles 4 in the through holes 10 of the core film 1 by electrolytic plating. By setting the current density at the time of plating as high as 3 A / dm @ 2, the copper grew until it protruded upward from the through hole 10 and the tip was rounded. As a result, conductive fine particles 4 made of a columnar body made of copper and having a rounded tip were formed in all the through holes 10 of the core film 1. The height of the columnar material forming the conductive fine particles 4 was 12 μm, which was higher than the thickness of 10 μm of the core film 1 at the highest central portion.
[0114]
Next, a sheet made of a PET film and an adhesive layer (10 μm) prepared in advance by the same method as in Example 2 is used, as shown in FIG. 7C, an adhesive layer (first adhesive layer). 2 was put on the core film 1 with the core film 1 side facing and joined by heating.
Next, in order to prevent liquid from entering the adhesive layer 2, the four end surfaces of the adhesive layer 2 were closed. Next, the aluminum plate 7 was completely removed by wet etching by spraying hydrochloric acid onto the aluminum plate 7. FIG. 7D shows this state.
[0115]
Next, a sheet made of a PET film and an adhesive layer (10 μm) prepared in advance by the same method as in Example 2, with the adhesive layer (second adhesive layer) 3 facing the core film 1 side, It put on the core film 1 and joined by heating. This state is shown in FIG.
Thereby, the adhesive layers 2 and 3 made of 10 μm epoxy adhesive are arranged on both surfaces of the core film 1 made of unsaturated polyester resin and having a thickness of 10 μm, and the circular through-hole 10 having a diameter of 5 μm is formed in the core film 1. A conductive adhesive sheet is obtained which is regularly formed at a pitch of 10 μm (lattice point spacing) in the arrangement shown in FIG. 1 (b), and each copper fine particle 4 is arranged in each through hole 10. It was. PET films 5 and 6 are bonded to both surfaces of the conductive adhesive sheet.
[Performance evaluation]
Using the conductive adhesive sheet produced in Example 5 and the same test substrates 30, 40, and 50 as in Example 1, two test pieces were produced in the same manner as in Example 1 and carried out. A connection confirmation test and a short confirmation test were performed in the same manner as in Example 1.
[0116]
As a result, in the connection confirmation test, it is confirmed that there is no one that is not electrically connected to the wiring pattern 42 of the test substrate 40 among the total of 400 wirings 32 of the test substrate 30 of the two test pieces. It was done.
Further, in the short check test, all the insulation resistances are 10 between the total of 398 test pads of the two test pieces. ¹² It was more than Ω. As a result, it was confirmed that no short circuit occurred between all adjacent wirings 32 with respect to all 400 wirings 32 in total of two test pieces.
[0117]
[Example 6]
[Preparation of conductive adhesive sheet]
In this example, a conductive adhesive sheet is produced by a method corresponding to the example of the fourth method of the present invention. This embodiment will be described with reference to FIG.
First, as shown in FIG. 12 (a), a sheet made of a PET film (support) 5 and an adhesive layer 2 having a thickness of 10 μm made of an epoxy adhesive, prepared in advance by the method shown in Example 1, An adhesive layer (first adhesive layer) 2 side was placed facing upward, and a core film 1 made of polyimide resin having a thickness of 4 μm was formed thereon. The core film 1 was formed by applying the polyimide resin solution used in Example 2 onto the adhesive layer 2 and then drying the solvent from the coating film. This obtained the core film 1 in which the 1st adhesive bond layer was formed in one surface.
[0118]
Next, a 5 μm PET film 6 a was placed on the core film 1, and the same metal mask as in Example 2 was placed thereon, and an excimer laser was irradiated from above the metal mask. This irradiation was performed until the PET film 6a and the core film 1 were removed in the entire thickness direction, and the surface of the adhesive 2 was also removed a little (until a hole having a depth of 12 μm was formed).
[0119]
Thereby, the portions of the PET film 6 a and the core film 1 irradiated with the excimer laser were removed, and the through holes 10 were formed at predetermined positions of the core film 1. In the core film 1, circular through holes 10 having a diameter of 8 μm are regularly arranged at a pitch of 15 μm (lattice point spacing) in the arrangement shown in FIG. FIG. 12B shows this state.
[0120]
Next, the same powder as in Example 1 was sprayed on the PET film 6a, and then the whole sheet was vibrated using an ultrasonic vibration device, whereby the core film 1 was coated. The conductive fine particles 4 were put in all the through holes 10. This state is shown in FIG. Next, the upper surface of the core film 1 was exposed by peeling the PET film 6 a from the core film 1. At this time, the conductive fine particles 4a present on the upper surface of the PET film 6a without removing the through holes 10 were removed.
[0121]
Next, as shown in FIG. 12 (d), a sheet made of a PET film (cover film) 6 and an adhesive layer 3 having a thickness of 10 μm made of an epoxy adhesive prepared in advance by the method shown in Example 1 is used. The adhesive layer (second adhesive layer) 3 was placed on the core film 1 with the side facing downward and joined by heating.
Thus, adhesive layers 2 and 3 made of an epoxy adhesive having a thickness of 10 μm are arranged on both surfaces of the core film 1 made of polyimide resin and having a thickness of 4 μm. The core film 1 has a circular through hole 10 having a diameter of 8 μm. However, in the arrangement shown in FIG. 1B, the conductive film is regularly formed at a pitch of 15 μm (interval between lattice points), and one conductive fine particle 4 made of copper-silver alloy is arranged in each through hole 10. An adhesive sheet was obtained. PET films 5 and 6 are bonded to both surfaces of the conductive adhesive sheet.
[Performance evaluation]
Using the conductive adhesive sheet produced in Example 6 and the same test substrates 30, 40, 50 as in Example 1, two test pieces were produced in the same manner as in Example 1, and the test was carried out. A connection confirmation test and a short confirmation test were performed in the same manner as in Example 1.
[0122]
As a result, in the connection confirmation test, it is confirmed that there is no one that is not electrically connected to the wiring pattern 42 of the test substrate 40 among the total of 400 wirings 32 of the test substrate 30 of the two test pieces. It was done.
Further, in the short check test, all the insulation resistances are 10 between the total of 398 test pads of the two test pieces. ¹² It was more than Ω. As a result, it was confirmed that no short circuit occurred between all adjacent wirings 32 with respect to all 400 wirings 32 in total of two test pieces.
[0123]
[Example 7]
[Preparation of conductive adhesive sheet]
As shown in FIG. 13A, first, an epoxy adhesive layer 510 having a thickness of 6 μm was formed on a PET film 500 having a thickness of 25 μm by the same method as in Example 2. Two sheets comprising the PET film 500 and the epoxy adhesive layer 510 were prepared.
[0124]
Next, as the core film 1, a wholly aromatic polyamide film (“Aramika (trade name)” manufactured by Asahi Kasei Co., Ltd.) having a thickness of 4.5 μm was prepared. Also, 80 parts by weight of a polysulfone resin (“Udel P-1700” manufactured by Amoco Polymer), 20 parts by weight of a cyanate ester resin (“B-30” manufactured by Ciba-Geigy), and 400 parts by weight of tetrahydrofuran are mixed with stirring. As a result, an adhesive solution was obtained. The adhesive solution was applied onto the core film 1 and dried to form a polysulfone / cyanate ester adhesive layer 530 having a thickness of 6 μm on the core film 1. FIG. 13B shows this state.
[0125]
The softening temperature of the adhesive forming each of the adhesive layers 510 and 530 was measured using a rotary “rheometer” which is a viscoelasticity measuring device manufactured by Rheometrics Scientific F.E. The measurement conditions were a rotation speed: 10 rad / sec, a temperature rise start temperature: room temperature, a temperature rise speed: 10 ° C./min, and the first temperature at which the slope of the viscosity curve changed was determined as the softening temperature. As a result, the softening temperature of the epoxy adhesive was about 80 ° C., and the softening temperature of the polysulfone / cyanate ester adhesive was 160 ° C.
[0126]
Next, as shown in FIG. 13C, a sheet made of the PET film 500 and the epoxy adhesive layer 510 and a sheet made of the core film 1 and the polysulfone / cyanate ester adhesive layer 530 are bonded to the adhesive layer 510, 530 were faced to each other and bonded together while heating to 60 ° C. Thereby, the laminated sheet which consists of two types of adhesive bond layers 510 and 530 with which the softening temperature difference is 20 degreeC or more, PET film 500, and the core film 1 was obtained.
[0127]
Next, through holes 10 were formed in the core film 1 of the laminated sheet by an excimer laser in the same manner as in Example 2. FIG. 13D shows this state. The arrangement of the through holes was the same as that shown in FIG. The hole diameter of the through hole 10 was 7.5 μm.
Since the excimer laser irradiation needs to be performed under the condition that the through holes 10 are reliably formed at each position of the core film 1, the surface of the adhesive layer 530 is also irradiated with the excimer laser. However, the removal rate by the excimer laser is higher in the core film 1 made of wholly aromatic polyamide than in the polysulfone / cyanate ester adhesive layer 530. Therefore, even when irradiation is performed under the above conditions, the surface of the adhesive layer 530 is removed. The resulting recess can be suppressed to a depth of less than 1 μm.
[0128]
Next, the same conductive fine particles 4 as in Example 2 were filled in the through holes 10 of the core film 1 by the same method as in Example 2. Next, an adhesive layer 530 made of polysulfone / cyanate ester having a thickness of 6 μm was formed on the core film 1 in this state by applying the above-described adhesive solution and drying it.
Next, on this polysulfone / cyanate ester adhesive layer 530, a sheet comprising the PET film 500 and the epoxy adhesive layer 510 shown in FIG. 13A is placed with the epoxy adhesive layer 510 side facing down. And heated to 60 ° C. for bonding. FIG. 13 (e) shows this state.
[0129]
As a result, an adhesive layer 530 made of polysulfone / cyanate ester having a thickness of 6 μm and an adhesive layer 510 made of epoxy resin having a thickness of 6 μm are formed on both surfaces of the core film 1 made of wholly aromatic polyamide resin and having a thickness of 4.5 μm. Are arranged in this order from the core film 1 side, and circular through holes 10 having a diameter of 7.5 μm are regularly formed in the core film 1 at a pitch of 15 μm (lattice point spacing) in the arrangement shown in FIG. Thus, a conductive adhesive sheet was obtained in which one conductive fine particle 4 made of copper-silver alloy was disposed in each through-hole 10. A PET film 500 is bonded to both surfaces of the conductive adhesive sheet.
[Performance evaluation]
Using the conductive adhesive sheet prepared in Example 7 and the same test substrates 30, 40, and 50 as in Example 1, two test pieces were prepared in the same manner as in Example 1, and the test was performed. A connection confirmation test and a short confirmation test were performed in the same manner as in Example 1.
[0130]
As a result, in the connection confirmation test, it is confirmed that there is no one that is not electrically connected to the wiring pattern 42 of the test substrate 40 among the total of 400 wirings 32 of the test substrate 30 of the two test pieces. It was done.
Further, in the short check test, all the insulation resistances are 10 between the total of 398 test pads of the two test pieces. ¹² It was more than Ω. As a result, it was confirmed that no short circuit occurred between all adjacent wirings 32 with respect to all 400 wirings 32 in total of two test pieces.
[0131]
[Example 8]
[Preparation of conductive adhesive sheet]
As shown in FIG. 14, a conductive adhesive sheet was obtained in the same manner as in Example 7 except that the taper-shaped through hole 10 a was formed in the core film 1.
The taper-shaped through hole 10a uses an excimer laser capable of projecting a mask pattern down to 1/10. In FIG. 4A, laser irradiation is performed while gradually reducing the opening K1 having a hole diameter of 8 μm. It was. Thereby, a tapered through hole 10a having a circular cross section parallel to the film surface, a diameter of the large diameter portion of 8 μm, and a diameter of the small diameter portion of 4 μm was formed.
[0132]
As shown in FIG. 14A, the core film 1 was bonded to the first adhesive layer 2 with the small-diameter portion side of the through hole 10 a facing the first adhesive layer 2. In this state, the large diameter portion side of the through hole 10a is an exposed surface, and the conductive fine particles 4 are filled in the through hole 10a in this state. As the conductive fine particles, those having the same material as in Example 2 and having an average particle diameter of 6 μm and a standard deviation of the particle diameter distribution of 0.6 μm were used.
[0133]
As a result, the conductive fine particles 4 are held in the narrowed portion of the tapered through-hole 10, so that they do not protrude into the lower adhesive layer (first adhesive layer) 2, and the inside of the core film 1 Will definitely exist.
[Performance evaluation]
Using the conductive adhesive sheet produced in Example 8 and the same test substrates 30, 40, and 50 as in Example 1, two test pieces were produced in the same manner as in Example 1 and carried out. A connection confirmation test and a short confirmation test were performed in the same manner as in Example 1.
[0134]
As a result, in the connection confirmation test, it is confirmed that there is no one that is not electrically connected to the wiring pattern 42 of the test substrate 40 among the total of 400 wirings 32 of the test substrate 30 of the two test pieces. It was done.
Further, in the short check test, all the insulation resistances are 10 between the total of 398 test pads of the two test pieces. ¹² It was more than Ω. As a result, it was confirmed that no short circuit occurred between all adjacent wirings 32 with respect to all 400 wirings 32 in total of two test pieces.
[0135]
[Comparative Example 1]
[Preparation of conductive adhesive sheet]
The conductive fine particles 4 used in Example 1 were added to the epoxy adhesive solution used in Example 1 at a ratio of 1.2% by volume and mixed. This liquid was applied to the surface of a PET film coated with polydimethylsiloxane as a release agent using a blade coater. Next, by removing the solvent from the coating film by drying, a conductive adhesive sheet having a thickness of 28 μm was formed on the PET film. This conductive adhesive sheet is used after peeling off the PET film.
[0136]
The addition rate of the conductive fine particles 4 to the epoxy adhesive solution was set so that the content of the conductive fine particles 4 in the conductive adhesive sheet was approximately the same as that in Example 2.
[Performance evaluation]
Using the conductive adhesive sheet produced in Comparative Example 1 and the same test substrates 30, 40, 50 as in Example 1, two test pieces were produced in the same manner as in Example 1, A connection confirmation test and a short confirmation test were performed in the same manner as in Example 1.
[0137]
As a result, in the connection confirmation test, it was confirmed that four of the two test pieces in total of the wiring 32 of the test substrate 30 were not electrically connected to the wiring pattern 42 of the test substrate 40. It was done.
Further, in the short check test, all the insulation resistances are 10 between the total of 398 test pads of the two test pieces. ¹² It was more than Ω. As a result, it was confirmed that no short circuit occurred between all adjacent wirings 32 with respect to all 400 wirings 32 in total of two test pieces.
[0138]
[Comparative Example 2]
A conductive adhesive sheet having the same configuration was produced in the same manner as in Comparative Example 1 except that the addition ratio of the conductive fine particles 4 to the epoxy adhesive solution was 20% by volume.
Using the conductive adhesive sheet prepared in Comparative Example 2 and the same test substrates 30, 40, and 50 as in Example 1, two test pieces were prepared in the same manner as in Example 1 and performed. A connection confirmation test and a short confirmation test were performed in the same manner as in Example 1.
[0139]
As a result, in the connection confirmation test, it was confirmed that all the wirings 32 of the total 400 test substrates 30 of the two test pieces are electrically connected to the wiring pattern 42 of the test substrate 40. .
Further, in the short check test, the insulation resistance is 10 at 10 locations among the total of 398 test pads of 2 test pieces. ⁸ It became below Ω. As a result, it was found that a short circuit occurred between the adjacent wirings 32 at these ten locations.
[0140]
【The invention's effect】
As described above, according to the conductive adhesive sheet of the present invention, a plurality of through holes are formed in a predetermined arrangement in the core film surface, and conductive fine particles are arranged in the through holes. It is possible to set the size and the size corresponding to the arrangement pitch of the pattern to be connected, the wiring width, and the like. In use, the arrangement of the conductive fine particles in the sheet surface is fixed by the core film.
[0141]
Therefore, by setting the pitch and size of the through holes corresponding to the arrangement pitch and wiring width of the pattern to be connected, even when connecting patterns arranged at a fine pitch, short-circuits between adjacent patterns. Can be prevented from occurring. Further, it is possible to eliminate the fear that the pattern to be connected is disposed at a position where no conductive fine particles are present.
[0142]
As a result, according to the conductive adhesive sheet of the present invention, a highly reliable connection can be performed even when the dimension of the pattern to be connected is small or when a pattern arranged at a fine pitch is connected.
Further, according to the method for producing a conductive adhesive sheet of the present invention, the conductive fine particles are regularly and densely arranged in the sheet surface (so that the distance between adjacent conductive fine particles is 20 μm or less). The manufactured conductive adhesive sheet can be easily manufactured.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view (a) and a plan view (b, c) showing an embodiment of a conductive adhesive sheet of the present invention.
FIG. 2 is a diagram for explaining an embodiment of a first method for producing a conductive adhesive sheet of the present invention and Example 1;
FIG. 3 is a diagram illustrating an embodiment of a second method for producing a conductive adhesive sheet of the present invention and Examples 2 to 4.
4 is a diagram for explaining an embodiment of a second method for producing a conductive adhesive sheet of the present invention and Example 2. FIG.
5 is a diagram for explaining an embodiment of a second method for producing a conductive adhesive sheet of the present invention and Example 3. FIG.
6 is a diagram for explaining an embodiment of a second method for producing a conductive adhesive sheet of the present invention and Example 3. FIG.
7 is a diagram for explaining an embodiment of a third method for producing a conductive adhesive sheet of the present invention and Example 7. FIG.
FIGS. 8A and 8B are a plan view and a cross-sectional view showing a test substrate 30 used for performance evaluation in Examples 1 to 8 and Comparative Examples 1 and 2 of the present invention. FIGS.
FIG. 9 is a plan view (a) and sectional views (b) and (c) showing test substrates 40 and 50 used for performance evaluation in Examples 1 to 8 and Comparative Examples 1 and 2 of the present invention. .
FIG. 10 is a cross-sectional view showing a state where the test substrate 30 and the test substrate 40 are bonded by the conductive adhesive sheet, where (a) shows a cross-sectional view of a portion of the wiring pattern 42; ) Shows a cross-sectional view of the dummy pattern 43 portion.
FIG. 11 is a view for explaining Example 4 (second method for producing a conductive adhesive sheet) of the present invention.
FIG. 12 is a diagram illustrating Example 6 (fourth method for producing a conductive adhesive sheet) of the present invention.
FIG. 13 is a diagram illustrating a conductive adhesive sheet of Example 7 of the present invention.
FIG. 14 is a diagram illustrating a conductive adhesive sheet of Example 8 of the present invention.
FIG. 15 is a cross-sectional view (a) and a plan view (b) showing an example of a conventional conductive adhesive sheet.
FIG. 16 is a cross-sectional view for explaining problems of a conventional conductive adhesive sheet.
[Explanation of symbols]
1 Core film
2 Adhesive layer (first adhesive layer)
3 Adhesive layer (second adhesive layer)
4 Conductive fine particles
5 Support
6 Cover film
6a PET film
7 Conductive substrate
8 Photosensitive resin layer
9 Plating layer
10 Through hole
10a Tapered through hole
11 Photosensitive resin layer
15 Copper mold
15a protrusion
17 Plating layer
20 Sheet made of adhesive layer
23 Core film during bonding and adhesive layers on both sides
30 Test substrate
31 Insulating substrate
32 Wiring
35 Inspection pad
40 Test substrate
41 glass substrate
42 Wiring pattern
43 Dummy pattern
44 Inspection pad
45 films
46 Release layer
47 PET film
50 test substrate
51 glass substrate
52 Convex
81 Through hole
90 Male (press mold)
91 protrusion
170 Female (press mold)
171 recess
500 PET film
510 Epoxy adhesive layer (adhesive layer with low softening temperature)
530 Polysulfone / cyanate ester adhesive layer
(Adhesive layer with high softening temperature)
A Position where conductive fine particles do not exist
B1 board
B2 board
h Wiring thickness
K1 opening
K metal mask
M exposure mask
P1 connection pattern
P2 connection pattern
p Connection pitch
p10 Dummy pattern arrangement pitch
W Wiring width
W1 Wiring pattern width
W2 Dummy pattern diameter

Claims (8)

In the adhesive sheet that imparts conductivity only in the thickness direction of the sheet by the conductive fine particles dispersed and arranged in the sheet surface, an adhesive layer is disposed on both surfaces of the core film disposed in the center in the thickness direction, The core film and the adhesive layer are insulative, and a plurality of tapered through holes penetrating in the thickness direction are formed in the film surface in a predetermined arrangement in the core film, and conductive fine particles are arranged in the through holes. The average particle size of the conductive fine particles is 0.5 μm or more and 50 μm or less, the standard deviation of the particle size distribution of the conductive fine particles is 50% or less of the average particle size, and the thickness of the core film is 0.5 μm or more and 50 μm. The thickness of the adhesive layer is 1 μm or more and 50 μm or less, and the diameter of the large diameter portion of the tapered through hole is 1 to 1.5 times the average particle diameter of the conductive fine particles. Through hole The diameter of the small diameter portion, the conductive adhesive sheet having an anisotropic conductive particles and wherein the dimensions der Rukoto held in the small diameter portion side. The conductive fine particles are copper, gold, silver, nickel, palladium, indium, tin, lead, zinc, bismuth, or an alloy of any of these metals, fine particles made of carbon, or fine particles having a metal coating on the surface. The conductive adhesive sheet according to claim 1. At least one of the adhesive layers arranged on both surfaces of the core film is laminated with two types of adhesive layers having a difference in softening temperature of 20 ° C. or more arranged with the higher softening temperature on the core film surface side. conductive adhesive sheet according to claim 1, characterized in that the. The method for producing a conductive adhesive sheet according to claim 1, wherein a photosensitive resin layer forming a core film is formed on the first adhesive layer formed on the support, and then exposed by photolithography. By patterning the conductive resin layer, through holes are formed in a predetermined arrangement in the core film, and conductive fine particles are put in the through holes, and then a second adhesive layer is formed on the core film. A method for producing a conductive adhesive sheet. 2. The method for producing a conductive adhesive sheet according to claim 1 , wherein a first adhesive layer is formed on one surface of a core film having a through hole, and then conductive fine particles are placed in the through hole. A method for producing a conductive adhesive sheet, comprising forming a second adhesive layer on the other surface of the core film . The manufacturing method of the electroconductive adhesive sheet of Claim 5 including the process of forming a through-hole in a core film by laser irradiation . A step of forming a through-hole in the core film by punching with a press using a pressing mold comprising a male mold having a projection corresponding to the arrangement of the through-hole and a female mold having a recess for receiving the projection. The manufacturing method of the electroconductive adhesive sheet of Claim 5 containing this . The method for producing a conductive adhesive sheet according to claim 1, wherein a core film having a first adhesive layer formed on one surface is prepared, and laser irradiation is performed from the other surface side of the core film. And forming a through hole in the core film, and then forming a second adhesive layer on the other surface of the core film after putting conductive fine particles in the through hole . Manufacturing method of adhesive sheet.

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