JP7602866B2 - Circuit board and manufacturing method thereof - Google Patents

Description

The present invention relates to circuit boards, such as flexible printed circuits (FPCs), and their manufacturing methods.

In recent years, the high speed transmission of information has progressed along with the high performance and functionality of electrical and electronic devices. Therefore, the parts and materials used in electrical and electronic devices are also required to be compatible with high speed transmission. For the resin materials used in such applications, attempts are being made to lower the dielectric constant and dielectric loss tangent so that they have electrical properties compatible with high speed transmission.

Polyimide is widely used as a material for circuit boards and other electronic and electrical devices and electronic components due to its characteristics of high insulation, dimensional stability, easy moldability, and light weight. In order to accommodate high-speed transmission, efforts are being made to reduce the dielectric constant and dielectric loss tangent of polyimide by devising the composition of the raw material monomers (for example, Patent Documents 1 and 2).

WO2017/159274 WO2018/061727

As mentioned above, polyimide is a material with excellent properties, but it is prone to hygroscopicity due to the abundance of polar groups such as imide groups in the molecule. Therefore, when a circuit board using polyimide as the material for the insulating resin layer is used, the moisture absorption progresses due to the environmental humidity, causing an increase in the dielectric constant and dielectric loss tangent.
SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a circuit board capable of minimizing the effects of environmental humidity during use and capable of allowing an insulating resin layer to maintain its initial dielectric properties for a long period of time.

As a result of intensive research, the inventors discovered that the above problems could be solved by providing a barrier mechanism that can prevent moisture from penetrating into the insulating resin layer of the circuit board, and thus completed the present invention.

That is, the circuit board of the present invention comprises an insulating resin layer, circuit wiring provided in the insulating resin layer, and a barrier film that covers at least a portion of the exposed surface of the insulating resin layer and suppresses moisture absorption by the insulating resin layer.

The circuit board of the present invention may be formed in a film or plate shape, and the barrier film may be provided so as to cover at least a portion or the entire exposed portion of the insulating resin layer on the side surface of the circuit board in a direction parallel to the direction in which the circuit wiring extends.

The circuit board of the present invention may further have a plurality of terminal portions, and the barrier film may be provided so as to cover at least a portion or the entire exposed portion of the insulating resin layer in the region between any two terminal portions.

In the circuit board of the present invention, the barrier film may be formed from a material having a water vapor permeability, as determined by a method in accordance with JIS K 7129, of 1 g/m ² ·day or less.

The circuit board of the present invention may have a barrier film made of metal or resin.

In the circuit board of the present invention, the material of the barrier film may be at least one selected from the group consisting of silicon carbide, silicon oxide, silicon carbide oxide, silicon carbonitride, aluminum oxide, silicon nitride, and silicon nitride oxide.

In the circuit board of the present invention, the insulating resin layer may include a non-thermoplastic polyimide layer composed of a non-thermoplastic polyimide and a thermoplastic polyimide layer composed of a thermoplastic polyimide. In this case, the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer may contain 60 mol% or more of monomer residues having a biphenyl skeleton among all monomer residues derived from all monomer components,
The thermoplastic polyimide constituting the thermoplastic polyimide layer may contain 30 mol % or more of monomer residues having a biphenyl skeleton among all monomer residues derived from all monomer components.

A method for producing a circuit board according to the present invention is any one of the methods for producing a circuit board described above, comprising the steps of:
forming an insulating resin layer having the circuit wiring;
a barrier film forming step of forming the barrier film;
Contains:

In the method for manufacturing a circuit board of the present invention, a part or all of the step of forming the insulating resin layer may be performed in a dry atmosphere, and the barrier film forming step may be performed while maintaining the dry atmosphere.

The method for producing a circuit board of the present invention may further include, after the step of forming the insulating resin layer, a drying step of drying the insulating resin layer in a state in which the barrier film is not formed,
The barrier film forming step may be performed after the drying step.

The circuit board of the present invention is provided with a barrier film that can prevent moisture from penetrating into the insulating resin layer, and therefore the dielectric properties of the insulating resin layer can be maintained for a long period of time without being affected by the humidity of the environment. As a result, electrical and electronic devices and electronic components using the circuit board of the present invention can accommodate high-speed transmission, and a decrease in transmission loss can be suppressed for a long period of time even in a high-humidity environment.

1 is a schematic cross-sectional view of a circuit board according to an embodiment of the present invention. FIG. 4 is a schematic cross-sectional view of a circuit board according to another embodiment of the present invention. FIG. 11 is a schematic cross-sectional view of a circuit board according to still another embodiment of the present invention. FIG. 11 is a schematic cross-sectional view of a circuit board according to still another embodiment of the present invention. FIG. 11 is a schematic cross-sectional view of a circuit board according to still another embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing one configuration example of an insulating resin layer. 5 is a schematic cross-sectional view showing another example of the configuration of the insulating resin layer. FIG. 1 is a diagram showing an example of a planar shape of a circuit board. 1 is a diagram illustrating the relationship between the moisture absorption rate and the dielectric loss tangent of different types of resin films. 4 is a schematic cross-sectional view showing one configuration example of a wiring support layer. FIG. 13 is a schematic cross-sectional view showing another example of the configuration of the wiring support layer. FIG.

Next, an embodiment of the present invention will be described.
Fig. 1 is a cross-sectional view of a circuit board according to one embodiment of the present invention, while Figs. 2 to 5 are cross-sectional views of a circuit board according to another embodiment of the present invention.
The circuit board 101 of this embodiment includes an insulating resin layer 10, a patterned circuit wiring 21 provided in the insulating resin layer 10, and a barrier film 50 that covers at least a portion of the exposed surface of the insulating resin layer 10 and suppresses moisture absorption by the insulating resin layer 10. The circuit board 101 also includes a metal layer 40 on one or both sides of the insulating resin layer 10. Note that the metal layer 40 is not an essential component.

(Insulating resin layer)
The insulating resin layer 10 may be composed of a plurality of layers. The insulating resin layer 10 may be composed of a laminated structure of resin layers of the same type, and may be composed of laminated structures of resins of different types. In the circuit board 101 illustrated in FIGS. 1 to 5, the insulating resin layer 10 is composed of a wiring support layer 20 that supports the circuit wiring 21, and an adhesive sealing layer 30 that covers the circuit wiring 21 to protect the circuit wiring 21 and has adhesive properties with other layers. The resin that constitutes the adhesive sealing layer 30 is filled between the adjacent circuit wirings 21. In the following description, the portion where the circuit wiring 21 is laminated on the wiring support layer 20 may be referred to as a "wiring portion."

The materials of the wiring support layer 20 and adhesive sealing layer 30 that constitute the insulating resin layer 10 are not particularly limited as long as they are resin materials that can be used as circuit board materials, but for example, polyimide, epoxy resin, liquid crystal polymer (LCP), fluororesin, etc. can be used. Among these, when polyimide and epoxy resin, which are hygroscopic materials, are used, the effect of providing the barrier film 50 is significant.

(Circuit wiring)
The material of the circuit wiring 21 is not particularly limited, but examples thereof include copper, stainless steel, iron, nickel, beryllium, aluminum, zinc, indium, silver, gold, tin, zirconium, tantalum, titanium, lead, magnesium, manganese, and alloys thereof. Among these, copper or a copper alloy is particularly preferred.

(Barrier film)
The barrier film 50 is a film having a function of preventing moisture from penetrating into the insulating resin layer 10. The barrier film 50 may cover at least a part of the exposed surface of the insulating resin layer 10. The barrier film 50 is made of a material having a low moisture permeability, and is preferably made of a material having a water vapor permeability of 1 g/ ^m2 ·day or less obtained by a method conforming to JIS K 7129. The material of the barrier film 50 may be, for example, a metal such as copper, chromium, nickel, or cobalt, or may be, for example, a resin such as LCP. Furthermore, it may be an inorganic material such as silicon carbide, silicon oxide, silicon carbide oxide, silicon carbonitride, aluminum oxide, silicon nitride, or silicon nitride oxide. The barrier film 50 is not limited to a single material, and may be made of a composite material including different materials such as silica-deposited PET and alumina-deposited PET.

The barrier film 50 may cover the entire side of the insulating resin layer 10, which is the exposed surface, as shown in FIG. 1, or may cover a portion of the side of the insulating resin layer 10, which is the exposed surface, as shown in FIG. 2. In the embodiment shown in FIG. 1, both ends of the barrier film 50 are connected to a pair of metal layers 40. This makes it possible to prevent moisture from penetrating the insulating resin layer 10. The pair of metal layers 40 can also prevent moisture absorption from the thickness direction of the insulating resin layer 10.

The embodiment shown in FIG. 2 is, for example, a case in which the wiring support layer 20 is made of a highly hygroscopic polyimide and the adhesive sealing layer 30 is made of a resin material with low hygroscopicity, and the exposed side surface of the wiring support layer 20 made of highly hygroscopic polyimide is covered with a barrier film 50.

3 and 4 show embodiments in which not only the side portions, which are exposed surfaces, of the insulating resin layer 10 but also the entire surface including the outer surfaces of a pair of metal layers 40 are covered with a barrier film 50. FIG. 3 shows an embodiment in which the barrier film 50 is provided in a state of being in close contact with the outer surfaces of the metal layer 40 and the insulating resin layer 10. In these embodiments, the entire insulating resin layer 10 is sealed by the barrier film 50 and is isolated from the external atmosphere. In the embodiment shown in FIG. 4, for example, a resin film is used as the barrier film 50. As shown in FIG. 4, the barrier film 50 may cover the outer surfaces of the metal layer 40 and the insulating resin layer 10 with a gap therebetween, rather than being in close contact with them.
In the embodiment shown in FIG. 3 and FIG. 4, since moisture absorption by the insulating resin layer 10 can be prevented even without the pair of metal layers 40, the metal layers 40 are not necessarily required.

5 is an embodiment in which an insulating resin layer 10 having patterned circuit wiring 21 provided therein is laminated on a metal layer 40 serving as a base material, and a barrier film 50 is formed so as to cover the upper surface (the surface opposite to the metal layer 40) and side surfaces of the insulating resin layer 10. In this embodiment, the adhesive sealing layer 30 may not be provided.
5 has a structure in which a first barrier layer 51 having adhesiveness and filling properties and a second barrier layer 53 are laminated. If the first barrier layer 51 has a sufficient barrier function against moisture, the second barrier layer 53 does not need to be provided. In addition, in a structure or usage in which moisture is unlikely to penetrate from the side portion of the first barrier layer 51, it is sufficient that the second barrier layer 53 and the metal layer 40 can suppress the penetration of moisture from the thickness direction, and therefore the first barrier layer 51 does not need to have a barrier function against moisture and may be, for example, a layer having adhesiveness and filling properties.

1 to 5, a structure having circuit wiring 21 on one side of a wiring support layer 20 is exemplified as the configuration of the wiring portion in the insulating resin layer 10, but the configuration of the wiring portion is not limited to the configurations in Fig. 1 to 5. For example, as in the insulating resin layer 10 shown in Fig. 6A, a structure may be used in which a wiring portion having circuit wiring 21 on both sides of a wiring support layer 20 is included and an adhesive sealing layer 30 is laminated so as to cover each circuit wiring 21, or as in the insulating resin layer 10 shown in Fig. 6B, a structure in which wiring portions having a wiring support layer 20 and a circuit wiring 21 are laminated in multiple stages with an adhesive sealing layer 30 interposed therebetween.
The insulating resin layer 10 may have any layer other than the wiring support layer 20 and the adhesive sealing layer 30. Examples of such layers include a coverlay, a cover ink, and a bonding sheet.

In the circuit board 101 of the embodiment shown in Figures 1 to 3, if the barrier film 50 is a metal film, it can be formed by methods such as CVD, PVD, plating, sputtering, soldering metal foils together, and sealing by ultrasonic bonding, and if it is a resin film, it can be formed by methods such as coating, spraying, lamination, and inserting a circuit board into a cylindrical resin film.

The circuit board 101 of the embodiment shown in FIG. 4 can be manufactured, for example, by sandwiching a laminate having at least a wiring portion between two resin films and sealing the ends of the resin films by a method such as heat sealing.

The circuit board 101 shown in FIG. 5 can be manufactured by bonding the barrier film 50 to the metal layer 40 from the top side of the insulating resin layer 10 so as to sandwich the insulating resin layer 10 between the metal layer 40 and the barrier film 50.

The circuit board 101 is formed in a film or plate shape as a whole. The cross-sectional structure shown in Figures 1 to 5 is a cross section in a direction perpendicular to the direction in which the circuit wiring 21 extends (hereinafter, sometimes referred to as the "wiring direction"). As shown in Figures 1 to 5, the barrier film 50 is preferably provided so as to cover at least the exposed surface of the insulating resin layer 10 in parallel to the wiring direction. Here, when the circuit board 101 has a simple shape such as a rectangular shape in a plan view, terminal portions are provided at both ends in the longitudinal direction. Therefore, since the longitudinal direction and the wiring direction coincide, the exposed portion of the insulating resin layer 10 becomes a side portion parallel to the wiring direction when the metal layer 40 is provided, and becomes a side portion parallel to the front and back flat portions (outer surfaces) and the wiring direction when the metal layer 40 is not provided.

On the other hand, when the circuit board 101 has a complex shape in plan view, there are multiple wiring directions due to the circuit wiring 21 connecting the multiple terminals 60. For example, in the case of the planar shape shown in FIG. 7, there are two wiring directions, the up-down direction and the diagonal direction, due to the circuit wiring 21 connecting the three terminals 60. In such a case, when the metal layer 40 is provided, the exposed portion of the insulating resin layer 10 becomes a side portion sandwiched between any two terminals 60, and when the metal layer 40 is not provided, it becomes a front and back flat portion sandwiched between any two terminals 60 and a side portion sandwiched between any two terminals 60.

When forming a barrier film 50 in the manner shown in FIG. 1 on a circuit board 101 having a planar shape as shown in FIG. 7, it is sufficient that the cross sections A-A, B-B, C-C, and D-D in FIG. 7 have the cross-sectional structures as shown in FIG. 1 (however, the number of circuit wirings 21 is not limited). When forming a barrier film 50 in the manner shown in FIG. 2 to FIG. 5, it is sufficient that the cross sections A-A, B-B, C-C, and D-D in FIG. 7 have the cross-sectional structures as shown in FIG. 2 to FIG. 5.

For these reasons, it is preferable that the barrier film 50 be provided so as to cover at least a portion of the exposed portion of the insulating resin layer 10, or the entire exposed portion, in the region sandwiched between any two terminal portions 60 of the circuit board 101.

<Action>
Figure 8 shows the relationship between moisture absorption rate and dielectric loss tangent (Df) of resin films of different materials. As shown in Figure 8, LCP film shows almost constant Df regardless of moisture absorption rate. In other words, LCP is a material that shows stable dielectric properties without being affected by environmental humidity.
On the other hand, it can be seen that the Df of the polyimide films represented by PI film A, PI film B, and PI film C in Figure 8 changes depending on the moisture absorption rate, and the higher the moisture absorption rate, the larger the Df becomes, and the worse the dielectric properties become. It can also be seen that there is a difference in Df between PI films A to C when they have the same moisture absorption rate. This is thought to be mainly due to the chemical structure of the polyimide, and when the moisture absorption rate is low (highly dry state), some films, such as PI film C, show a low Df below that of the LCP film. It should be noted that PI films A to C have a structure in which different types of polyimide layers are laminated.

The present invention utilizes the above-mentioned characteristics of the resin film, and even when a part or the whole of the insulating resin layer 10 of the circuit board 101 is formed from a resin material that tends to easily increase Df due to moisture absorption, the following (1) to (3):
(1) If the barrier film 50 is used for sealing in a highly dry state with a low moisture absorption rate, a low Df can be maintained for a long period of time.
(2) Even if the environment is not very dry, sealing with the barrier film 50 allows a constant Df to be maintained for a long period of time without being affected by the environmental humidity.
(3) By selecting the right material and maintaining a high dryness, the dielectric properties can be maintained below those of LCP for a long period of time.
It has been found that the effects of any one of the above or a combination of these can be achieved.

The above-mentioned effects (1) to (3) are believed to be particularly pronounced when a part or the whole of the insulating resin layer 10 of the circuit board 101 is made of a resin having properties similar to those of the PI film C shown in FIG. 8. Below, a representative structure of such a resin material will be described using a polyimide layer as an example.

[Polyimide layer]
The polyimide layer is used as a layer having various functions in the circuit board 101, but here, an explanation will be given of its application to the wiring support layer 20. The polyimide layer as the wiring support layer 20 preferably has a laminated structure having a non-thermoplastic polyimide layer containing a non-thermoplastic polyimide, and a thermoplastic polyimide layer containing a thermoplastic polyimide laminated on at least one surface of the non-thermoplastic polyimide layer.

As a preferred embodiment of the wiring support layer 20, as illustrated in Fig. 9, a two-layer structure in which a thermoplastic polyimide layer 120A is laminated on one side of a non-thermoplastic polyimide layer 110, and as illustrated in Fig. 10, a three-layer structure in which a thermoplastic polyimide layer 120A is laminated on one side of a non-thermoplastic polyimide layer 110 and a thermoplastic polyimide layer 120B is laminated on the other side can be mentioned. Here, "non-thermoplastic polyimide" means a polyimide having a storage modulus of 1.0 x 10 ⁹ Pa or more at 30°C and a storage modulus of 1.0 x 10 ⁸ Pa or more in a temperature range within a glass transition temperature + 30°C. "Thermoplastic polyimide" means a polyimide having a storage modulus of 1.0 x 10 ⁹ Pa or more at 30°C measured using a dynamic viscoelasticity measuring device (DMA) and a storage modulus of less than 1.0 x 10 ⁸ Pa in a temperature range within a glass transition temperature + 30°C.
The polyimide layer is not limited to the laminated structure illustrated in FIG. 9 and FIG. 10, but may be, for example, one having four or more layers.

The resin component of the non-thermoplastic polyimide layer 110 is preferably made of a non-thermoplastic polyimide, and the resin component of the thermoplastic polyimide layers 120A and 120B is preferably made of a thermoplastic polyimide. When the polyimide layer is directly laminated with the circuit wiring 21, the circuit wiring 21 can be laminated on one side or both sides of the thermoplastic polyimide layers 120A and 120B.

In addition, both the non-thermoplastic polyimide and the thermoplastic polyimide contain an acid dianhydride residue and a diamine residue as a "monomer residue." An "acid dianhydride residue" refers to a tetravalent group derived from a tetracarboxylic dianhydride, and a "diamine residue" refers to a divalent group derived from a diamine compound.

In the polyimide layer, the non-thermoplastic polyimide layer 110 constitutes a polyimide layer with low thermal expansion, and the thermoplastic polyimide layers 120A and 120B constitute polyimide layers with high thermal expansion. The low thermal expansion polyimide layer refers to a polyimide layer having a coefficient of thermal expansion (CTE) preferably in the range of 1 ppm/K to 25 ppm/K, more preferably in the range of 3 ppm/K to 25 ppm/K. The high thermal expansion polyimide layer refers to a polyimide layer having a CTE preferably in the range of 35 ppm/K or more, more preferably in the range of 35 ppm/K to 80 ppm/K, and even more preferably in the range of 35 ppm/K to 70 ppm/K. A polyimide layer having a desired CTE can be obtained by appropriately changing the combination of raw materials used, the thickness, and the drying and curing conditions.

It is preferable that non-thermoplastic polyimides and thermoplastic polyimides contain a large amount of monomer residues having a biphenyl skeleton (hereinafter, sometimes referred to as "biphenyl skeleton-containing residues") relative to all monomer residues derived from all monomer components constituting the polyimides. When the proportion of biphenyl skeleton-containing residues is high, an ordered structure is easily formed throughout the polymer due to the rigid structure derived from the monomer, and the dielectric loss tangent can be reduced by suppressing molecular motion. When the proportion of biphenyl skeleton-containing residues is low, the dielectric loss tangent is not reduced sufficiently.

Here, the biphenyl skeleton is a skeleton in which two phenyl groups are single-bonded, as shown in the following formula (a). Therefore, examples of biphenyl skeleton-containing residues include a biphenyldiyl group and a biphenyltetrayl group. The aromatic rings contained in these residues may have any substituent.
Representative examples of biphenyldiyl groups include those represented by the following formula (b). Representative examples of biphenyltetrayl groups include those represented by the following formula (c). In the biphenyldiyl group and the biphenyltetrayl group, the bonds in the aromatic ring are not limited to the positions shown in formula (b) and formula (c), and as described above, the aromatic rings contained in these residues may have any substituent.

The biphenyl skeleton-containing residue is a structure derived from the raw material monomer, and may be derived from an acid dianhydride or a diamine compound.

Representative examples of acid dianhydride residues having a biphenyl skeleton include residues derived from acid dianhydrides such as 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 2,3',3,4'-biphenyltetracarboxylic dianhydride, and p-biphenylene bis(trimellitate anhydride). Among these, acid dianhydride residues derived from BPDA (hereinafter also referred to as "BPDA residues") are particularly preferred because they are easy to form an ordered polymer structure and can reduce the dielectric tangent and hygroscopicity by suppressing molecular motion. In addition, BPDA residues can impart self-supporting properties to the gel film as a polyamic acid of the polyimide precursor.

Representative examples of diamine compounds having a biphenyl skeleton include diamine compounds having only two aromatic rings, such as 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB), 2,2'-diethyl-4,4'-diaminobiphenyl (m-EB), 2,2'-diethoxy-4,4'-diaminobiphenyl (m-EOB), 2,2'-dipropoxy-4,4'-diaminobiphenyl (m-POB), 2,2'-di-n-propyl-4,4'-diaminobiphenyl (m-NPB), 2,2'-divinyl-4,4'-diaminobiphenyl (VAB), 4,4'-diaminobiphenyl, and 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl (TFMB). Residues derived from these diamine compounds have a rigid structure, and therefore have the effect of imparting an ordered structure to the entire polymer. By containing residues derived from these diamine compounds, polyimides with low oxygen permeability and low moisture absorption can be obtained, and the moisture content inside the molecular chain can be reduced, resulting in a lower dielectric tangent.

Generally, polyimide can be produced by reacting an acid dianhydride with a diamine compound in a solvent to produce polyamic acid, which is then heated to close the ring (imidization). For example, an acid dianhydride and a diamine compound are dissolved in an organic solvent in approximately equal moles, and the mixture is stirred at a temperature in the range of 0 to 100°C for 30 minutes to 24 hours to polymerize, thereby obtaining polyamic acid, which is a precursor of polyimide. In the reaction, the reaction components are dissolved so that the precursor produced is in the range of 5 to 30% by weight, preferably 10 to 20% by weight, in the organic solvent. Examples of organic solvents used in the polymerization reaction include N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N,N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 2-butanone, dimethylsulfoxide (DMSO), hexamethylphosphoramide, N-methylcaprolactam, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diglyme, triglyme, and cresol. Two or more of these solvents can be used in combination, and aromatic hydrocarbons such as xylene and toluene can also be used in combination. There are no particular limitations on the amount of organic solvent used, but it is preferable to adjust the amount so that the concentration of the polyamic acid solution obtained by the polymerization reaction is about 5 to 30% by weight.

The synthesized polyamic acid is usually advantageously used as a reaction solvent solution, but it can be concentrated, diluted, or replaced with another organic solvent if necessary. Polyamic acid is also advantageously used because it generally has excellent solvent solubility. The viscosity of the polyamic acid solution is preferably within the range of 500 cps to 100,000 cps. If it is outside this range, defects such as uneven thickness and streaks are likely to occur in the film during coating operations using a coater or the like. There are no particular restrictions on the method for imidizing polyamic acid, and a heat treatment such as heating in the above-mentioned solvent at a temperature condition within the range of 80 to 400°C for 1 to 24 hours is preferably used.

Next, we will explain non-thermoplastic polyimides and thermoplastic polyimides in more detail.

<Non-thermoplastic polyimide>
In the polyimide layer, the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 110 contains an acid dianhydride residue and a diamine residue. The non-thermoplastic polyimide preferably contains 60 mol % or more, more preferably 70 mol % or more, of biphenyl skeleton-containing residues among all monomer residues derived from all monomer components. By making the biphenyl skeleton-containing residues in the non-thermoplastic polyimide 60 mol % or more, the content ratio of the biphenyl skeleton-containing residues in the entire polyimide constituting the polyimide layer can be increased, and a low dielectric tangent can be achieved.

(Acid dianhydride residue)
The non-thermoplastic polyimide preferably contains 35 mol % or more, more preferably 50 mol % or more, of acid dianhydride residues having a biphenyl skeleton among all acid dianhydride residues, and further preferably contains the above amount of biphenyltetrayl groups represented by formula (c).

In addition to the above-mentioned acid dianhydride residues having a biphenyl skeleton, non-thermoplastic polyimides can contain residues of acid dianhydrides that are generally used as raw materials for polyimides. Examples of such acid dianhydride residues include pyromellitic dianhydride (PMDA), 1,4-phenylenebis(trimellitic acid monoester) dianhydride (TAHQ), 2,3,6,7-naphthalenetetracarboxylic dianhydride (NTCDA), 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 2,2',3,3'-, 2,3,3',4'- or 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,3',3,4'-diphenylethertetracarboxylic dianhydride, bis(2,3-dicarboxyphenoxy)tetracarboxylic dianhydride, and bis(2,3-dicarboxyphenoxy)tetracarboxylic dianhydride. 2,2-bis(2,3- or 3,4-dicarboxyphenyl)-propane dianhydride, bis(2,3- or 3,4-dicarboxyphenyl)methane dianhydride, bis(2,3- or 3,4-dicarboxyphenyl)sulfone dianhydride, 1,1-bis(2,3- or 3,4-dicarboxyphenyl)ethane dianhydride, 1,2,7,8-, 1,2,6,7- or 1,2,9,10-phenanthrene tetracarboxylic acid dianhydride Water, 2,3,6,7-anthracenetetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)tetrafluoropropane dianhydride, 2,3,5,6-cyclohexane dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-1,2,5,6-tetracarboxylic dianhydride, 2,6- or 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7-(or 1,4,5,8-)tetracarboxylic dianhydride Examples of the acid dianhydride residues include those derived from aromatic tetracarboxylic dianhydrides such as tetrachloronaphthalene-1,4,5,8-(or 2,3,6,7-)tetracarboxylic dianhydride, 2,3,8,9-, 3,4,9,10-, 4,5,10,11- or 5,6,11,12-perylene-tetracarboxylic dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, 4,4'-bis(2,3-dicarboxyphenoxy)diphenylmethane dianhydride, and ethylene glycol bisanhydrotrimellitate.

(Diamine residue)
The non-thermoplastic polyimide preferably contains 70 mo1% or more, more preferably 85 mo1% or more, of diamine residues having a biphenyl skeleton among all diamine residues. More preferably, the non-thermoplastic polyimide contains the biphenyldiyl group represented by formula (b) in the above amount. The biphenyldiyl group represented by formula (b) has a rigid structure and has the effect of imparting an ordered structure to the entire polymer, so that it can reduce oxygen permeability and reduce the dielectric loss tangent by suppressing molecular motion.

In addition to the above-mentioned diamine residues having a biphenyl skeleton, the non-thermoplastic polyimide may contain residues of diamine compounds generally used as raw materials for polyimides, to the extent that the effects of the invention are not impaired. Examples of such diamine residues include 1,4-diaminobenzene (p-PDA; paraphenylenediamine), 4-aminophenyl-4'-aminobenzoate (APAB), 3,3'-diaminodiphenylmethane, 3,3'-diaminodiphenylpropane, 3,3'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylpropane, 3,4'-diaminodiphenyl sulfide, 3,3'-diaminobenzophenone, (3,3'-bisamino)diphenylamine, 1,4-bis(3-aminophenoxy)benzene, 3-[4-(4-aminophenoxy)phenoxy]benzenamine, 3-[3-(4-aminophenoxy)phenoxy]benzenamine, 1,3-bis(4-aminophenoxy)benzene (TPE-R), 1,3-bis(3-aminophenoxy)benzene (APB), 4,4'-[2-methyl-(1,3-phenylene)bisoxy]bisaniline, 4,4'-[4-methyl-(1,3-phenylene)bisoxy]bisaniline, 4,4'-[5-methyl-(1,3-phenylene)bisoxy]bisaniline, bis[4,4'-(3-aminophenoxy)]benzanilide, 4-[3-[4-(4-aminophenoxy)phenoxy]phenoxy]aniline, 4,4'-[oxybis(3,1-phenyleneoxy)]bisaniline, bis[4-(4-aminophenoxy)phenyl]ether (BAPE), bis[4-(4-aminophenoxy)phenyl]sulfone (BAPS), bis[4-(4-aminophenoxy)phenyl]ketone (B APK), 2,2-bis-[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)]benzophenone, 9,9-bis[4-(3-aminophenoxy)phenyl]fluorene, 2,2-bis-[4-(4-aminophenoxy)phenyl]hexafluoro 2,2-bis-[4-(3-aminophenoxy)phenyl]hexafluoropropane, 3,3'-dimethyl-4,4'-diaminobiphenyl, 4,4'-methylenedi-o-toluidine, 4,4'-methylenedi-2,6-xylidine, 4,4'-methylene-2,6-diethylaniline, 3,3'-diaminodiphenylethane, 3,3'-diaminobiphenyl, 3,3'-dimethoxybenzidine, 3,3''-diamino-p-terphenyl, 4,4'-[1,4-phenylenebis(1-methylethylidene)]bisaniline, 4,4'- [1,3-phenylenebis(1-methylethylidene)]bisaniline, bis(p-aminocyclohexyl)methane, bis(p-β-amino-t-butylphenyl)ether, bis(p-β-methyl-δ-aminopentyl)benzene, p-bis(2-methyl-4-aminopentyl)benzene, p-bis(1,1-dimethyl-5-aminopentyl)benzene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,4-bis(β-amino-t-butyl)toluene, 2,4-diaminotoluene, m-xylene-2,5-diamine, p-xylene 2,5-diamine, m-xylylenediamine, p-xylylenediamine, 2,6-diaminopyridine, 2,5-diaminopyridine, 2,5-diamino-1,3,4-oxadiazole, piperazine, 2'-methoxy-4,4'-diaminobenzanilide, 4,4'-diaminobenzanilide, 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene, 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene, 1,4-bis(4-aminophenoxy)-2,5-di-tert-butylbenzene, 6-amino-2 Examples of the diamine residues include those derived from aromatic diamine compounds such as -(4-aminophenoxy)benzoxazole, 2,6-diamino-3,5-diethyltoluene, 2,4-diamino-3,5-diethyltoluene, 2,4-diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane, and bis(4-amino-3-ethyl-5-methylphenyl)methane, and those derived from aliphatic diamine compounds such as dimer acid type diamines in which the two terminal carboxylic acid groups of a dimer acid are replaced with primary aminomethyl groups or amino groups.

In non-thermoplastic polyimides, the oxygen permeability, dielectric properties, thermal expansion coefficient, storage modulus, tensile modulus, etc. can be controlled by selecting the types of the above-mentioned acid dianhydride residues and diamine residues, and when two or more types of acid dianhydride residues or diamine residues are used, respectively. In addition, in non-thermoplastic polyimides, when multiple polyimide structural units are present, they may be present as blocks or randomly, but it is preferable that they are present randomly.

The non-thermoplastic polyimide preferably contains an aromatic tetracarboxylic acid residue derived from an aromatic tetracarboxylic dianhydride and an aromatic diamine residue derived from an aromatic diamine. By making both the acid dianhydride residue and the diamine residue contained in the non-thermoplastic polyimide aromatic groups, the dimensional accuracy of the polyimide layer in a high temperature environment can be improved.

The imide group concentration of the non-thermoplastic polyimide is preferably 33% by weight or less. Here, "imide group concentration" means the value obtained by dividing the molecular weight of the imide group (-(CO) ₂ -N-) in the polyimide by the molecular weight of the entire polyimide structure. When the imide group concentration exceeds 33% by weight, the moisture absorption increases due to the increase in polar groups. By selecting the combination of the above-mentioned acid dianhydride and diamine compound, the molecular orientation in the non-thermoplastic polyimide can be controlled, thereby suppressing the increase in CTE associated with the decrease in the imide group concentration and ensuring low moisture absorption.

The weight-average molecular weight of the non-thermoplastic polyimide is preferably, for example, in the range of 10,000 to 400,000, and more preferably in the range of 50,000 to 350,000. If the weight-average molecular weight is less than 10,000, the strength of the film tends to decrease and it tends to become brittle. On the other hand, if the weight-average molecular weight exceeds 400,000, the viscosity increases excessively, and defects such as uneven film thickness and streaks tend to occur during the coating process.

<Thermoplastic polyimide>
In the polyimide layer, the thermoplastic polyimide constituting the thermoplastic polyimide layers 120A and 120B contains an acid dianhydride residue and a diamine residue. The thermoplastic polyimide preferably contains 30 mol % or more, more preferably 40 mol % or more, of the biphenyl skeleton-containing residues among all the monomer residues derived from all the monomer components. By making the biphenyl skeleton-containing residues in the thermoplastic polyimide 30 mol % or more, the content ratio of the biphenyl skeleton-containing residues in the entire polyimide constituting the polyimide layer can be increased, the oxygen permeability can be reduced, and the dielectric loss tangent can be reduced. That is, since an ordered structure is formed in the entire polymer due to the rigid structure derived from the monomer, a polyimide that is thermoplastic yet has low oxygen permeability and moisture absorption, excellent long-term heat-resistant adhesiveness, and a low dielectric loss tangent can be obtained. On the other hand, since it is necessary to improve the flexibility of the polyimide molecular chain and impart thermoplasticity in order to ensure adhesion to the circuit wiring 21, it is preferable to set the upper limit of the content of the biphenyl skeleton-containing residue to 65 mol %. In addition, when the thermoplastic polyimide layers 120A, 120B are provided on both sides of the non-thermoplastic polyimide layer 110, it is sufficient that either one of the thermoplastic polyimide layers 120A, 120B satisfies the above conditions, but it is preferable that both of the thermoplastic polyimide layers 120A, 120B satisfy the above conditions.

(Acid dianhydride residue)
The thermoplastic polyimide preferably contains 60 mol % or more of acid dianhydride residues having a biphenyl skeleton among all acid dianhydride residues, and more preferably contains the biphenyltetrayl group represented by formula (c) in the above amount.

The thermoplastic polyimide may contain, in addition to the above-mentioned residues of dianhydrides having a biphenyl skeleton, residues of dianhydrides that are generally used as raw materials for polyimides, to the extent that the effects of the invention are not impaired. Examples of such dianhydride residues include the residues of dianhydrides exemplified for non-thermoplastic polyimides.

(Diamine residue)
The thermoplastic polyimide preferably contains 1 mo1% or more, more preferably 5 mo1% or more, of diamine residues having a biphenyl skeleton among all diamine residues. More preferably, the biphenyldiyl group represented by formula (b) is contained in the above amount. The biphenyldiyl group represented by formula (b) has a rigid structure and has the effect of imparting an ordered structure to the entire polymer, so that the dielectric tangent and moisture absorption can be reduced by suppressing the movement of the molecules. Furthermore, by using it as a raw material for thermoplastic polyimide, polyimide with low oxygen permeability and excellent long-term heat-resistant adhesion can be obtained.

In addition to the above-mentioned diamine residues having a biphenyl skeleton, the thermoplastic polyimide may contain residues of diamine compounds generally used as raw materials for polyimides, to the extent that the effects of the invention are not impaired. Examples of such diamine residues include residues of diamine compounds exemplified for non-thermoplastic polyimides.

In thermoplastic polyimides, the thermal expansion coefficient, tensile modulus, glass transition temperature, etc. can be controlled by selecting the types of the above-mentioned acid dianhydride residues and diamine residues, and by selecting the respective molar ratios when two or more types of acid dianhydride residues or diamine residues are used. In addition, in thermoplastic polyimides, when multiple polyimide structural units are present, they may be present as blocks or randomly, but it is preferable that they are present randomly.

The thermoplastic polyimide preferably contains an aromatic tetracarboxylic acid residue derived from an aromatic tetracarboxylic dianhydride and an aromatic diamine residue derived from an aromatic diamine. By making both the acid dianhydride residue and the diamine residue contained in the thermoplastic polyimide aromatic groups, degradation of the polyimide in a high-temperature environment of the polyimide layer can be suppressed.

The imide group concentration of the thermoplastic polyimide is preferably 30% by weight or less. Here, "imide group concentration" means the value obtained by dividing the molecular weight of the imide group (-(CO) ₂ -N-) in the polyimide by the molecular weight of the entire polyimide structure. If the imide group concentration exceeds 30% by weight, it becomes difficult to reduce the elastic modulus at temperatures equal to or higher than the glass transition temperature, and the low moisture absorption property also deteriorates due to an increase in polar groups.

The weight-average molecular weight of the thermoplastic polyimide is preferably, for example, in the range of 10,000 to 400,000, and more preferably in the range of 50,000 to 350,000. If the weight-average molecular weight is less than 10,000, the strength of the film tends to decrease and it tends to become brittle. On the other hand, if the weight-average molecular weight exceeds 400,000, the viscosity increases excessively, and defects such as uneven film thickness and streaks tend to occur during the coating process.

In the polyimide layer, the thermoplastic polyimide layers 120A and 120B function as adhesive layers and can improve adhesion with the circuit wiring 21. Therefore, the thermoplastic polyimide preferably has a glass transition temperature in the range of 200°C or more and 350°C or less, and more preferably in the range of 200°C or more and 320°C or less.

Since the thermoplastic polyimide becomes, for example, an adhesive layer in contact with the circuit wiring 21 of the circuit board 101, a completely imidized structure is most preferable in order to suppress the diffusion of copper. However, a part of the polyimide may be an amic acid. The imidization rate is calculated from the absorbance of the C=O stretch derived from the imide group at 1780 cm ^-1 , based on the benzene ring absorber at about 1015 cm ^-1 , by measuring the infrared absorption spectrum of the polyimide thin film by the single reflection ATR method using a Fourier transform infrared spectrophotometer (commercial product: FT/IR620 manufactured by JASCO Corporation).

If necessary, inorganic fillers or organic fillers may be contained in the non-thermoplastic polyimide layer 110 or the thermoplastic polyimide layers 120A and 120B. Specific examples include inorganic fillers such as silicon dioxide, aluminum oxide, magnesium oxide, beryllium oxide, boron nitride, aluminum nitride, silicon nitride, aluminum fluoride, and calcium fluoride, and organic fillers such as fluorine-based polymer particles and liquid crystal polymer particles. These may be used alone or in combination of two or more. In addition, when an organic filler is contained, the organic filler does not fall under all the monomer components constituting the non-thermoplastic polyimide layer 110 or the thermoplastic polyimide layers 120A and 120B.

[Method of manufacturing circuit board]
The circuit board 101 can be manufactured by the same manufacturing method as a general circuit board, except that it includes a step of forming the barrier film 50. That is, the manufacturing method of the circuit board of the present embodiment includes a step of forming the insulating resin layer 10 having the circuit wiring 21, and a barrier film forming step of forming the barrier film 50. Since there are many different manufacturing methods for general circuit boards depending on the configuration of the circuit board, it is meaningless to give specific examples. However, the timing of the barrier film forming step is preferably either i) immediately after a step performed under drying conditions, or ii) immediately after a drying step that is performed after the insulating resin layer 10 is formed. Here, the drying conditions and the drying step may be performed by any method, such as reduced pressure drying or heat drying.

Regarding i) above, if a part or all of the process of forming the insulating resin layer 10 is performed in a dry atmosphere, the barrier film formation process can be performed while maintaining the dry atmosphere. For example, if the sealing process of sealing the circuit wiring 21 with the adhesive sealing layer 30 is performed in a dry atmosphere, the barrier film formation process can be performed after the sealing process while maintaining the dry atmosphere.

Regarding ii) above, after forming the insulating resin layer 10, a drying process is carried out to dry the insulating resin layer 10 without forming the barrier film 50, and the barrier film formation process can be carried out subsequently to the drying process.

In the above cases of i) and ii), the dry state of the insulating resin layer 10 when the barrier film 50 is formed is a highly dry state, for example with a moisture absorption rate of 0.1% or less, preferably 0%. The barrier film 50 allows the insulating resin layer 10 to be maintained in a highly dry state for a long period of time without being affected by the environmental humidity, so that the dielectric properties of the insulating resin layer 10 can be maintained in an excellent state for a long period of time.

If it is not necessary to keep the insulating resin layer 10 in a highly dry state, the barrier film formation process may be carried out after manufacturing the circuit board using a general manufacturing method. Even in this case, the initial dielectric properties of the insulating resin layer 10 can be maintained for a long period of time without being affected by the environmental humidity.

As described above in detail, the circuit board 101 of the present invention is provided with a barrier film 50 that can suppress the intrusion of moisture into the insulating resin layer 10, and therefore the initial dielectric properties of the insulating resin layer 10 can be maintained for a long period of time without being affected by the environmental humidity. Therefore, in electric/electronic devices and electronic components using the circuit board 101 of the present invention, it becomes possible to accommodate high-speed transmission, and a decrease in transmission loss can be suppressed for a long period of time even in a high-humidity environment.

The following examples are provided to more specifically explain the features of the present invention. However, the scope of the present invention is not limited to these examples. In the following examples, unless otherwise specified, the various measurements and evaluations were performed as follows.

[Measurement of dielectric tangent]
The dielectric tangent of the resin sheet (resin sheet after curing) was measured at a frequency of 10 GHz using a vector network analyzer (product name: E8363C, manufactured by Agilent) and an SPDR resonator. Note that "temperature 23°C, humidity 50%" refers to a value measured after leaving the sheet for 24 hours under conditions of temperature: 24-26°C, humidity: 45-55%, and "when dry" refers to a value measured immediately after drying at 120°C for 60 minutes.

[Measurement of copper foil surface roughness]
Using an AFM (manufactured by Bruker AXS, product name: Dimension Icon type SPM) and a probe (manufactured by Bruker AXS, product name: TESPA (NCHV), tip curvature radius 10 nm, spring constant 42 N/m), measurements were taken in a tapping mode over an area of 80 μm × 80 μm on the copper foil surface to determine the ten-point average roughness (Rz).

[Viscosity measurement]
The viscosity was measured at 25° C. using an E-type viscometer (manufactured by Brookfield, product name: DV-II+Pro). The rotation speed was set so that the torque was 10% to 90%, and the value was read when the viscosity stabilized 2 minutes after the start of the measurement.

[Measurement of weight average molecular weight (Mw)]
The weight average molecular weight was measured by gel permeation chromatography (manufactured by Tosoh Corporation, product name: HLC-8220GPC was used). Polystyrene was used as a standard substance, and tetrahydrofuran was used as a developing solvent.

The abbreviations used in the Examples and Reference Examples represent the following compounds.
BPDA: 3,3',4,4'-diphenyltetracarboxylic dianhydride PMDA: pyromellitic dianhydride m-TB: 2,2'-dimethyl-4,4'-diaminobiphenyl BAPP: 2,2-bis[4-(4-aminophenoxy)phenyl]propane BTDA: 3,3',4,4'-benzophenonetetracarboxylic dianhydride Bisaniline-P: 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene (manufactured by Mitsui Chemicals Fine Co., Ltd., product name: Bisaniline-P)
DDA: aliphatic diamine having 36 carbon atoms (manufactured by Croda Japan Co., Ltd., trade name: PRIAMINE 1075, amine value: 210 mg KOH/g, mixture of dimer diamines having a cyclic structure and a chain structure, dimer component content: 95% by weight or more)
N-12: Dodecanedioic acid dihydrazide OP935: Aluminum salt of phosphinic acid (manufactured by Clariant Japan K.K., trade name: Exolit OP935, phosphorus content: 23%, average particle size: 2 μm)
DMAc: N,N-dimethylacetamide

(Synthesis Example 1)
Under nitrogen flow, 14.02g of m-TB (0.066 mol) and 170g of DMAc were put into a 500ml separable flask and stirred at room temperature to dissolve. Next, 6.72g of BPDA (0.023 mol) and 9.25g of PMDA (0.042 mol) were added, and the mixture was stirred at room temperature for 3 hours to carry out a polymerization reaction, thereby preparing polyamic acid solution a. The solid content concentration in polyamic acid solution a was 15% by weight, and the solution viscosity was 20,600 cps.

(Synthesis Example 2)
Under nitrogen flow, 19.66g of BAPP (0.0479 mol) and 170g of DMAc were put into a 500ml separable flask and stirred at room temperature to dissolve. Next, 10.34g of PMDA (0.0474 mol) was added, and the mixture was stirred at room temperature for 3 hours to carry out a polymerization reaction, thereby preparing polyamic acid solution b. The solid content concentration in polyamic acid solution b was 15% by weight, and the solution viscosity was 4,500 cps.

(Synthesis Example 3)
Under nitrogen flow, 12.06g of m-TB (0.057 mol), 2.20g of bisaniline-P (0.0063 mol) and 171.7g of DMAc were put into a 500ml separable flask and stirred at room temperature to dissolve. Next, 6.824g of BPDA (0.031 mol) and 9.19g of PMDA (0.031 mol) were added, and the mixture was stirred at room temperature for 3 hours to carry out a polymerization reaction, thereby preparing polyamic acid solution c. The solid content concentration in polyamic acid solution c was 15% by weight, and the solution viscosity was 18,300 cps.

(Synthesis Example 4)
Under a nitrogen gas flow, 44.98 g of BTDA (0.139 mol), 75.02 g of DDA (0.140 mol), 168 g of N-methyl-2-pyrrolidone, and 112 g of xylene were charged into a 500 ml separable flask and mixed thoroughly at 40° C. for 30 minutes to prepare a polyamic acid solution. The polyamic acid solution was heated to 190° C., heated and stirred for 4.5 hours, and 112 g of xylene was added to complete the imidization to prepare a polyimide adhesive solution a. The solid content concentration in the polyimide adhesive solution a was 29.1% by weight, and the viscosity was 7,800 cps. The weight average molecular weight (Mw) of the polyimide adhesive solution a was 87,700.

(Synthesis Example 5)
34.4 g (10 g as solid content) of the polyimide adhesive solution a prepared in Synthesis Example 4, 1.25 g of N-12, and 2.5 g of OP935 were mixed, and 1.297 g of N-methyl-2-pyrrolidone and 3.869 g of xylene were added to dilute the mixture, to prepare a polyimide adhesive solution b.

(Preparation Example 1)
<Preparation of coverlay film 1>
The polyimide adhesive solution b prepared in Synthesis Example 5 was applied to one side of a polyimide film 1 (manufactured by DuPont-Toray Co., Ltd., product name: Kapton 50EN-S, thickness: 12 μm) so that the thickness after drying would be approximately 25 μm, and then the film was heated and dried at 80° C. for 15 minutes to prepare a coverlay film 1.

(Preparation Example 2)
<Preparation of bonding sheet 1>
The polyimide adhesive solution b prepared in Synthesis Example 5 was applied to one side of a release-treated PET film so that the thickness after drying would be approximately 25 μm, and then dried at 80° C. for 15 minutes to prepare a bonding sheet 1.

(Preparation Example 3)
<Preparation of Circuit Wiring Board 1c>
On the copper foil 1 (thickness; 12 μm, Rz; 0.35 μm), polyamic acid solution b was uniformly applied so that the thickness after curing was about 2 μm, and then heated and dried at 120 ° C for 1 minute to remove the solvent. Polyamic acid solution a was uniformly applied thereon so that the thickness after curing was about 18 μm, and then heated and dried at 120 ° C for 3 minutes to remove the solvent. Furthermore, polyamic acid solution b was uniformly applied thereon so that the thickness after curing was about 2 μm, and then heated and dried at 120 ° C for 1 minute to remove the solvent. Then, a stepwise heat treatment was performed from 130 ° C to 360 ° C to complete imidization, and a single-sided copper-clad laminate 1a was prepared. Copper foil was superimposed on the polyimide insulating layer side of this single-sided copper-clad laminate 1a, and the copper foil was heat-pressed for 15 minutes under the conditions of temperature; 360 ° C and pressure; 6.7 MPa to prepare a double-sided copper-clad laminate 1b. For the obtained double-sided copper-clad laminate 1b, a predetermined pattern of wiring was formed on one side of the copper foil using an aqueous ferric chloride solution to prepare a circuit wiring board 1c. The polyimide insulating layer in the circuit wiring board 1c had a dielectric loss tangent of 0.052 at a temperature of 23°C and a humidity of 50%, and a dielectric loss tangent of 0.0027 when dry.

(Preparation Example 4)
<Preparation of Circuit Wiring Board 2c>
A single-sided copper-clad laminate 2a, a double-sided copper-clad laminate 2b and a circuit wiring board 2c were prepared in the same manner as in Preparation Example 3, except that polyamic acid solution c was used instead of polyamic acid solution a. The dielectric tangent of the polyimide insulating layer in circuit wiring board 2c was 0.039 at a temperature of 23° C. and a humidity of 50%, and was 0.0017 when dry.

(Preparation Example 5)
<Preparation of Circuit Board 1d>
The coverlay film 1 was laminated so that the adhesive polyimide layer was in contact with the wiring of the circuit wiring board 1c, and then pressure-bonded at 160° C. for 120 minutes under a pressure of 2 MPa to prepare a circuit board 1d.

(Preparation Example 6)
<Preparation of Multilayer Circuit Board 1e>
A bonding sheet 1 was sandwiched between the polyimide insulating layer side of the single-sided copper-clad laminate 2a and the wiring pattern side of the circuit wiring board 2c, and the two were vacuum laminated in a superimposed state, and then heated in an oven at 160°C for 120 minutes to prepare a multilayer circuit board 1e.

[Example 1]
After drying the circuit board 1d at 120°C for 1 hour, a sealing sheet made of a silica-deposited PET film and a thermosetting adhesive and stainless steel foil were layered so as to cover the circuit board 1d except for 1 mm at both ends of the side along the extending direction, and these were laminated together using a roll laminator. After that, a heat treatment was performed in an oven at 80°C for 2 hours to prepare a circuit board 1 sealed with a sealing sheet and stainless steel foil. When the transmission characteristics of the circuit board 1 were evaluated, it was confirmed that there was no difference in the transmission characteristics before and after moisture absorption.

[Example 2]
After drying the multilayer circuit board 1e at 120° C. for 1 hour, a sputtering device was used as dry plating on the side surface of the multilayer circuit board 1e to form a 25 nm thick base metal layer made of an N-Cr alloy containing Cr and a 0.3 μm thick copper layer on the surface of the base metal layer, thereby preparing the circuit board 2. When the transmission characteristics of the circuit board 2 were evaluated, it was confirmed that there was no difference in the transmission characteristics before and after moisture absorption.

The above describes in detail the embodiment of the present invention for illustrative purposes, but the present invention is not limited to the above embodiment and various modifications are possible.

10: insulating resin layer, 20: wiring support layer, 21: circuit wiring, 30: adhesive sealing layer, 40: metal layer, 50: barrier film, 51: first barrier layer, 53: second barrier layer, 60: terminal portion, 101: circuit board, 110: non-thermoplastic polyimide layer, 120A, 120B: thermoplastic polyimide layer

Claims (10)

An insulating resin layer;
A circuit wiring provided in the insulating resin layer;
a barrier film that covers a part of an exposed surface of the insulating resin layer and suppresses moisture absorption of the insulating resin layer;
Equipped with
the insulating resin layer has a wiring support layer that supports the circuit wiring and an adhesive sealing layer that covers and protects the circuit wiring, and the wiring support layer includes a non-thermoplastic polyimide layer made of a non-thermoplastic polyimide and a thermoplastic polyimide layer made of a thermoplastic polyimide,
the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer contains 60 mol% or more of monomer residues having a biphenyl skeleton among all monomer residues derived from all monomer components ;
The circuit board , wherein the barrier film covers at least the exposed surface of the wiring support layer . The circuit board is formed into a film or plate shape,
2. The circuit board according to claim 1, wherein the barrier film is provided so as to cover at least an exposed surface of the wiring support layer on a side surface of the circuit board in a direction parallel to a direction in which the circuit wiring extends. The circuit board further has a plurality of terminal portions,
The circuit board according to claim 1 , wherein the barrier film is provided so as to cover at least an exposed surface of the wiring support layer in a region between any two terminal portions. 2. The circuit board according to claim 1, wherein the barrier film is formed from a material having a water vapor permeability of 1 g/ ^m2 ·day or less, as measured by a method in accordance with JIS K 7129. The circuit board according to claim 4, wherein the barrier film is made of a metal. The circuit board according to claim 4, wherein the barrier film is made of a resin. The circuit board according to claim 4, wherein the material of the barrier film is at least one selected from the group consisting of silicon carbide, silicon oxide, silicon carbide oxide, silicon carbonitride, aluminum oxide, silicon nitride, and silicon nitride oxide. A method for manufacturing a circuit board according to any one of claims 1 to 7 , comprising the steps of:
forming an insulating resin layer having the circuit wiring;
a barrier film forming step of forming the barrier film;
A method for manufacturing a circuit board comprising the steps of: 9. The method for manufacturing a circuit board according to claim 8 , wherein a part or the whole of the step of forming the insulating resin layer is carried out in a dry atmosphere, and the barrier film forming step is carried out in a state in which the dry atmosphere is maintained. The method further includes, after the step of forming the insulating resin layer, a drying step of drying the insulating resin layer in a state in which the barrier film is not formed,
The method for manufacturing a circuit board according to claim 8 , wherein the barrier film forming step is performed after the drying step.

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