JP7344812B2 - double-sided adhesive sheet - Google Patents

Description

The present invention relates to a double-sided adhesive sheet.

In response to the lighter weight, smaller size, and higher precision of electronic products, flexible printed circuit boards (hereinafter abbreviated as FPC boards), which are made by laminating and molding polyimide films and wiring conductors, are being used. There is. Such an FPC board is manufactured by forming a pattern on a film-like base material, performing a lamination process, a solder resist treatment process, and a mounting process.

In manufacturing the above FPC board, a thin and highly flexible film-like base material is used as the base material, so while the film-like base material is transported in a so-called roll-to-roll manner, the photoresist for circuit formation is Many processing steps are performed sequentially, such as coating, drying, exposing, developing, fixing, curing, plating, soldering (including reflow), cleaning and drying between each process, etc. A continuous process is adopted.

In addition, workpieces such as film base materials and semiconductor components are reinforced by being held in a reinforcing material (i.e., a transport jig), and while being transported, the same process as in the conventional manufacturing of single-wafer printed wiring boards is carried out. FPC boards are also manufactured by performing processing in the process. In such construction methods, when holding workpieces such as film-like substrates and semiconductor components on the transport jig, it is necessary to form a pressure-sensitive adhesive organic layer made of silicone resin on the transport jig. (Patent Documents 1, 2, 3).

Furthermore, a double-sided adhesive sheet with pressure-sensitive adhesive organic layers (i.e., adhesive layers) formed from silicone resin on both surfaces of the polyimide film is used to transport workpieces such as film-like substrates and semiconductor components. It is used to hold it in a jig.

Patent No. 4571436 Patent No. 4695349 Patent No. 4695350

Conventional double-sided adhesive sheets use silicone adhesive for the adhesive layers on both surfaces, and by appropriately adjusting the adhesive strength, it is possible to attach workpieces such as film base materials and semiconductor components to conveying jigs. By repeating this process and peeling many times, the film can be used for manufacturing semiconductor devices. However, when the workpiece is peeled off, there is a risk that peeling electrification may occur, and the semiconductor member on the film-like base material or the semiconductor member workpiece itself may be damaged by electrostatic discharge. Further, double-sided pressure-sensitive adhesive sheets that have undergone a reflow process multiple times have a problem in that air bubbles are generated in the pressure-sensitive adhesive, which reduces the holding power of the workpiece and causes the workpiece to peel off from the pressure-sensitive adhesive.

The present invention has been made in view of the above circumstances, and can be used to repeatedly attach, process, and peel a workpiece such as a film base material or a semiconductor member to a conveyance jig many times. It is an object of the present invention to provide a double-sided adhesive sheet that is capable of suppressing peeling electrification, is less likely to generate bubbles in the adhesive even after a plurality of reflow steps, and is less likely to peel off a workpiece from the adhesive.

The present invention has the following aspects.
[1] A double-sided adhesive sheet in which a first conductive adhesive layer, a conductive base material, and a second conductive adhesive layer are laminated,
The first conductive adhesive layer and the second conductive adhesive layer contain a silicone adhesive and a conductive filler,
The adhesive force of the first conductive adhesive layer is greater than the adhesive force of the second conductive adhesive layer,
having conductivity in the thickness direction penetrating the first conductive adhesive layer and the second conductive adhesive layer,
A double-sided pressure-sensitive adhesive sheet, wherein the first conductive pressure-sensitive adhesive layer has a thermal weight loss rate of 2.5 to 6% at 260°C.

[2] The double-sided pressure-sensitive adhesive sheet as described in [1] above, wherein the conductive base material has a thickness of 5 to 100 μm.
[3] The double-sided pressure-sensitive adhesive sheet as described in [1] or [2] above, wherein the conductive base material is copper foil or aluminum foil.
[4] The adhesive force of the first conductive adhesive layer to the stainless steel plate (SUS304, surface finish BA) (peel angle 90°, tensile speed 300 mm/min) is 1.0 N/25 mm or more. The double-sided adhesive sheet according to any one of [1] to [3] above.
[5] The adhesive force of the second conductive adhesive layer to the polyimide film (thickness 25 μm) (peel angle 90°, tensile speed 50 mm/min) is 0.03 to less than 2.0 N/25 mm. The double-sided adhesive sheet according to any one of [1] to [4] above, characterized by:

According to the present invention, it is possible to repeatedly attach, process, and peel off a workpiece such as a film-like base material or a semiconductor member to a conveying jig many times, and it is possible to suppress peeling electrification. It is possible to provide a double-sided adhesive sheet in which air bubbles are less likely to form in the adhesive and a workpiece is less likely to be peeled off from the adhesive even after multiple reflow steps.

FIG. 1 is a schematic cross-sectional view of a double-sided pressure-sensitive adhesive sheet according to the present invention. 1 is a schematic cross-sectional view showing an example of a method of using a double-sided pressure-sensitive adhesive sheet according to the present invention.

Hereinafter, a double-sided pressure-sensitive adhesive sheet according to an embodiment of the present invention will be described. Note that in the drawings used in the following explanation, the dimensional ratios of each component are not necessarily the same as in reality.
It should be noted that this embodiment is specifically explained in order to better understand the gist of the invention, and is not intended to limit the invention unless otherwise specified.

[Double-sided adhesive sheet]
FIG. 1 is a schematic cross-sectional view of a double-sided pressure-sensitive adhesive sheet according to the present invention.
The double-sided adhesive sheet 10 is a double-sided adhesive sheet in which a first conductive adhesive layer 20, a conductive base material 50, and a second conductive adhesive layer 30 are laminated. A release sheet 40 is laminated on the adhesive layer 20 side, and a release sheet 41 is laminated on the second conductive adhesive layer 30 side.
The first conductive adhesive layer 20 and the second conductive adhesive layer 30 contain a silicone adhesive and a conductive filler, and the adhesive strength of the first conductive adhesive layer 20 is equal to that of the second conductive adhesive layer. The adhesive force is greater than the adhesive force of the conductive adhesive layer 30.
When the release sheet 40 is peeled off, the first conductive adhesive layer 20 can fix a workpiece such as a film base material or a semiconductor member to a conveyance jig for a reflow process, and the second conductive adhesive layer 20 After the release sheet 41 is peeled off from the agent layer 30, the double-sided adhesive sheet can be used to temporarily fix a workpiece such as a film-like base material or a semiconductor member to a conveyance jig for a reflow process.
Since the adhesive force of the second conductive adhesive layer 30 is smaller than the adhesive force of the first conductive adhesive layer 20, it is possible to repeatedly attach and peel the workpiece to and from the conveyance jig many times. can.

Since the double-sided adhesive sheet 10 has conductivity in the thickness direction penetrating the first conductive adhesive layer 20, the conductive base material 50, and the second conductive adhesive layer 30, it can be used as a conveying jig for a reflow process. On the other hand, even if the workpiece is repeatedly attached and peeled off many times, it is possible to suppress the peeling electrification. Further, since the double-sided adhesive sheet 10 includes the conductive base material 50, it has excellent processability and handling properties. Specifically, since it has appropriate stiffness, it is easy to reapply, the release sheet is easy to peel off, and it is easy to punch out.

It is preferable that the double-sided adhesive sheet 10 has conductivity in the thickness direction penetrating the first conductive adhesive layer 20, the conductive base material 50, and the second conductive adhesive layer 30 and in the planar direction.

In the first conductive adhesive layer 20 and the second conductive adhesive layer 30, the silicone adhesive contains polyorganosiloxane and a curing agent (crosslinking agent) that crosslinks the polyorganosiloxane and cures the adhesive. It is mainly composed of As the polyorganosiloxane contained in the silicone adhesive, polydimethylsiloxane, polyalkylalkenylsiloxane, and polymethylphenylsiloxane have high heat resistance and are suitable.

In the first conductive adhesive layer 20 and the second conductive adhesive layer 30, silicone-based adhesives are classified into an organic peroxide-curing type using peroxide as a curing agent and a silicone-based adhesive based on the curing reaction mechanism. It is classified as an addition reaction type that uses a curing agent that cures the adhesive by bonding (crosslinking) to organosiloxane through an addition reaction, but when using an organic peroxide-curing silicone adhesive, the curing reaction In the process, low-molecular organic substances, which are residues of radicals, are generated. Therefore, when using an adhesive sheet with an adhesive layer made of an organic peroxide-curable silicone adhesive, in the adhesive sheet pasting process, reflow process, etc., organic peroxide-curable silicone adhesive There is a risk that the curing reaction of the adhesive will proceed and contaminate the workpiece. Therefore, it is more preferable to use an addition reaction type silicone pressure-sensitive adhesive that does not have such a risk.

Specifically, when polydimethylsiloxane is used as the polyorganosiloxane, an organic peroxide curing type that uses peroxide as a curing agent is used because polydimethylsiloxane does not have unsaturated bonds and the addition reaction does not proceed. Only silicone-based adhesives can be obtained. On the other hand, when polyalkylalkenylsiloxane is used as the polyorganosiloxane, since polyalkylalkenylsiloxane has a vinyl group with an unsaturated bond, polyalkylhydrogensiloxane having an active hydrogen group that reacts with the vinyl group, etc. By adding as a curing agent and a platinum catalyst, an addition reaction type silicone adhesive can be obtained. This addition reaction type silicone adhesive is cured by heating at 100 to 250°C for several minutes.

In the first conductive adhesive layer 20 and the second conductive adhesive layer 30, the conductive filler is made of metals such as gold, silver, copper, lead, zinc, iron, and nickel, or alloys thereof. Examples include conductive metals, composites of the conductive metals, and carbon. Examples of the composite include silver-coated copper, silver-coated nickel, gold-coated copper, and gold-coated nickel. Examples of the carbon include carbon black, graphite, graphene, fullerene, carbon nanotubes, and the like. In terms of heat resistance, gold powder, silver powder, and carbon powder are preferred, and carbon powder is more preferred. Examples of the shape include spherical powder, flake-like powder, disk-like powder, dendritic powder, needle-like powder, and irregularly shaped powder. The volume average particle diameter of the conductive filler is preferably 0.01 to 100 μm, more preferably 0.05 to 50 μm, and particularly preferably 0.10 to 20 μm. By being equal to or higher than the lower limit, it is easy to ensure contact points between the conductive fillers, and the volume resistivity of the first conductive adhesive layer 20 and the second conductive adhesive layer 30 can be reduced, By being below the upper limit, the surface of the double-sided pressure-sensitive adhesive sheet can be made smoother.

The volume average particle size of the conductive filler can be measured using a laser diffraction particle size distribution measuring device.

In the present invention, the thermal weight loss rate at 260° C. of the first conductive adhesive layer is 2.5 to 6%, preferably 3.1 to 5%. If the thermogravimetric reduction rate at 260°C of the first conductive adhesive layer is within the above range, bubbles are unlikely to form in the first conductive adhesive layer even after multiple reflow steps, and the first conductive adhesive layer is The work piece is difficult to peel off from the adhesive layer. Therefore, when an FPC board is manufactured using the double-sided adhesive sheet of the present invention, the FPC board can be manufactured with a high yield.

Further, the silicone resin fraction in the first conductive adhesive layer is preferably 20 to 50%, and even more preferably 28 to 42%. If the silicone resin fraction in the first conductive adhesive layer is within the above range, bubbles will not easily form in the first conductive adhesive layer even after multiple reflow steps. The workpiece is difficult to peel off. Therefore, when an FPC board is manufactured using the double-sided adhesive sheet of the present invention, the FPC board can be manufactured with a high yield.

The double-sided adhesive sheet according to the present invention has conductivity in the thickness direction penetrating the first conductive adhesive layer 20, the conductive base material 50, and the second conductive adhesive layer 30, and The volume resistivity in the thickness direction penetrating the adhesive layer 20, the conductive base material 50, and the second conductive adhesive layer 30 is preferably 10 ³ to 10 ¹² Ω·cm, and 10 ⁴ to 10 ¹⁰ Ω.・cm is more preferable, and 10 ⁴ to 10 ⁹ Ω・cm is particularly preferable.

The double-sided adhesive sheet according to the present invention has a volume in the thickness direction that penetrates the first conductive adhesive layer 20, the conductive base material 50, and the second conductive adhesive layer 30 after heat treatment at 260° C. for 5 minutes. The resistivity is preferably 1 to 10,000% of that before heat treatment, more preferably 10 ³ to 10 ¹² Ω·cm, more preferably 10 ⁴ to 10 ¹⁰ Ω·cm, and 10 Ω·cm to 10 Ω·cm. It is particularly preferable that the resistance is ⁴ to 10 ⁹ Ω·cm.

The volume resistivity of the double-sided adhesive sheet 10 is determined by laminating the first conductive adhesive layer 20 and a stainless steel plate (SUS304, surface finish BA) using a laminating roll, and then using a ring-shaped probe (manufactured by Mitsubishi Chemical Corporation). , product name: URS probe, inner electrode outer diameter 5.9 mm, outer electrode inner diameter 11.0 mm, outer electrode outer diameter 17.8 mm) and measurement stage (manufactured by Mitsubishi Chemical Corporation, product name: cashier table UFL). The double-sided adhesive sheet 10 is sandwiched between the ring-shaped probe and the second conductive adhesive layer 30 so that the stainless steel plate and the measurement stage are in contact with each other, and the probe is pressed down with a pressure of approximately 3 kg. A voltage of 10 V was applied between the inner electrode and the measurement stage, and the resistivity was measured using a resistivity measuring device (manufactured by Mitsubishi Chemical Corporation, trade name: Hiresta UX). For details of the volume resistivity measurement method using such a ring electrode method, refer to JIS-K6911.

In the first conductive adhesive layer 20, the content of the conductive filler is preferably 5 to 50% by mass, more preferably 7 to 45% by mass, based on the total amount of the constituent components. Particularly preferred is 10 to 40% by weight. The same applies to the content of the conductive filler in the second conductive adhesive layer 30.
Furthermore, the total amount of the components in the first conductive adhesive layer 20 and the total amount of the components in the second conductive adhesive layer 30 is compared to the total amount of the components in the first conductive adhesive layer 20 . The conductive filler content, which is the sum of the conductive filler content in the layer 20 and the conductive filler content in the second conductive adhesive layer 30, is preferably 5 to 50% by mass, and 7. It is more preferably 10 to 45% by weight, particularly preferably 10 to 40% by weight.

The adhesive strength of the first conductive adhesive layer 20 to the stainless steel plate (SUS304, surface finish BA) (peel angle 90°, tensile speed 300 mm/min) is the same as that of the polyimide film (thickness) of the second conductive adhesive layer 30. The adhesive force of the first conductive adhesive layer 20 to the stainless steel plate is 1.0 N/25 mm or more. is preferable, more preferably 2.0 N/25 mm or more, and particularly preferably 3.0 N/25 mm or more.

In the double-sided adhesive sheet according to the present invention, the adhesive strength of the first conductive adhesive layer 20 to the stainless steel plate after heat treatment at 260° C. for 5 minutes has a rate of change within 30% compared to before the heat treatment. Preferably, it is 1.0 N/25 mm or more, more preferably 2.0 N/25 mm or more, and particularly preferably 3.0 N/25 mm or more.

The adhesive force of the first conductive adhesive layer to the stainless steel plate is determined by laminating the first conductive adhesive layer 20 and the stainless steel plate (SUS304, surface finish BA) using a laminating roll, and then applying double-sided adhesive. The measurement is performed by peeling off the sheet 10 from a stainless steel plate under the conditions of a peeling angle of 90°, a pulling speed of 300 mm/min, and a measurement width of 25 mm. For details of the above-mentioned measuring method, refer to JIS-Z0237.

The adhesion force of the second conductive adhesive layer 30 to the polyimide film (thickness 25 μm) (peel angle 90°, tensile speed 50 mm/min) is preferably from 0.03 to less than 2.0 N/25 mm, It is more preferably 0.03 to 1.5 N/25 mm, and particularly preferably 0.03 to 1.0 N/25 mm.

In the double-sided adhesive sheet according to the present invention, the adhesive strength of the second conductive adhesive layer 30 to the polyimide film after heat treatment at 260° C. for 8 hours is 50% or more and less than 200% of the adhesive strength before heat treatment. It is preferably less than 0.03 to 2.0 N/25 mm, more preferably 0.03 to 1.5 N/25 mm, and more preferably 0.03 to 1.0 N/25 mm. It is particularly preferable that there be.

The adhesion of the second conductive adhesive layer 30 to the polyimide film is determined by laminating the first conductive adhesive layer 20 and a stainless steel plate (SUS304, surface finish BA) using a laminating roll, and then A polyimide film is laminated onto the second conductive adhesive layer 30 by moving a roller with a mass of 3 kg back and forth twice, and then the polyimide film is peeled off from the second conductive adhesive layer 30 at a peeling angle of 90°. It is measured by peeling it off at a pulling speed of 50 mm/min and a measurement width of 25 mm. For details of the above-mentioned measuring method, refer to JIS-Z0237.

The conductive base material 50 is such that the first conductive adhesive layer 20 and the second conductive adhesive layer 30 are in contact with each other, and the first conductive adhesive layer 20, the conductive base material 50, and the second conductive adhesive layer are in contact with each other. Any material that imparts conductivity in the thickness direction penetrating the adhesive layer 30 may be used, and may be a metal foil, plating, vapor deposition, or sputtering film. Further, the conductive base material 50 is preferably in the form of a plate-like base material without holes, but may be a conductive porous base material such as a nonwoven fabric, a mesh, or a punching plate. In particular, it is preferable that the conductive base material 50 is copper foil or aluminum foil.

The thickness of the conductive base material 50 may be 5 to 100 μm in the case of a plate-like base material, more preferably 5 to 50 μm, and particularly preferably 5 to 35 μm. For porous substrates, the thickness may be 10 to 1000 μm, preferably 10 to 500 μm, and particularly preferably 10 to 200 μm.

Conventionally known release sheets can be used as the release sheet 40 on the first conductive adhesive layer 20 side and the release sheet 41 on the second conductive adhesive layer 30 side. Release sheets include polyester film, polyethylene film, polypropylene film, polyimide film, release paper, polyetheretherketone (PEEK), polyethylene naphthalate (PEN), liquid crystal polyarylate, polyamideimide (PAI), polyethersulfone (PES). ), or films obtained by subjecting them to release treatment, etc. can be used. In terms of heat resistance, polyimide film, release paper, polyetheretherketone (PEEK), polyethylene naphthalate (PEN), liquid crystal polyarylate, polyamideimide (PAI), and polyethersulfone (PES) are preferred.

The thickness of the first conductive adhesive layer 20 is preferably 1 to 200 μm, more preferably 10 to 100 μm. The thickness of the second conductive adhesive layer 30 is preferably 1 to 200 μm, more preferably 10 to 100 μm. The thickness of the release sheet 40 is preferably 10 to 200 μm, more preferably 25 to 100 μm. The thickness of the release sheet 41 is preferably 10 to 200 μm, more preferably 25 to 100 μm.
The total thickness of the first conductive adhesive layer 20, the conductive base material 50, and the second conductive adhesive layer 30 is preferably 2 to 500 μm, more preferably 20 to 300 μm. preferable.

[Method for manufacturing double-sided adhesive sheet]
First, by uniformly stirring and mixing the silicone adhesive and conductive filler, which are the raw materials for the first conductive adhesive layer 20 and the second conductive adhesive layer 30, and a solvent as necessary. , a first conductive adhesive composition and a second conductive adhesive composition are prepared. By adjusting the amount of solvent, the formation of the first conductive adhesive layer and the second conductive adhesive layer can be facilitated. Further, a conductive base material 50 is prepared.

The solvent is preferably an organic solvent such as benzene, toluene, xylene, mesitylene, cyclohexanone, n-hexane, or n-heptane.
The stirring and mixing can be carried out using, for example, a stirrer such as Scandex, paint conditioner, sand mill, miller, three-roll mill, or bead mill, or by a combination of these. Further, after stirring and mixing, it is preferable to perform vacuum defoaming in order to remove air bubbles from the first conductive adhesive composition and the second conductive adhesive composition.

As a method for manufacturing a double-sided pressure-sensitive adhesive sheet, for example, a first conductive pressure-sensitive adhesive composition is coated on a release sheet 40, heated and dried as necessary, and a second conductive pressure-sensitive adhesive composition is coated on a release sheet 40. One conductive adhesive layer 20 is formed. Next, the conductive base material 50 is laminated on the first conductive adhesive layer 20 to form the conductive base material 50 on the first conductive adhesive layer 20 . Furthermore, a second conductive adhesive composition is coated on the conductive base material 50, and if necessary, heated and dried to form a second conductive adhesive composition on the conductive base material 50. The agent layer 30 is formed. Furthermore, a release sheet 41 is laminated on the second conductive adhesive layer 30. As a result, the double-sided adhesive shown in FIG. A sheet 10 can be produced.

For example, the second conductive adhesive composition is coated on the release sheet 41, and if necessary, heated and dried to form the second conductive adhesive layer 30 on the release sheet 41. Form. Next, the conductive base material 50 is laminated on the second conductive adhesive layer 30 to form the conductive base material 50 on the second conductive adhesive layer 30 . Furthermore, a first conductive adhesive composition is applied onto the conductive base material 50, and if necessary, heated and dried to coat the conductive base material 50 with the first conductive adhesive composition. An adhesive layer 20 is formed. Furthermore, the exposed surface of the first conductive adhesive layer 20 and the release-treated surface of the release sheet 40 are bonded together. This also results in the double-sided structure shown in FIG. An adhesive sheet 10 can be produced.

For example, the second conductive adhesive composition is coated on the conductive base material 50, heated and dried as necessary, and the second conductive adhesive composition is applied on the conductive base material 50. The agent layer 30 is formed. Next, the exposed surface of the second conductive adhesive layer 30 and the release-treated surface of the release sheet 41 are bonded together. After turning the top and bottom upside down, the first conductive adhesive composition is coated on the conductive base material 50, and if necessary, heated and dried to coat the first conductive adhesive composition on the conductive base material 50. One conductive adhesive layer 20 is formed. Furthermore, the exposed surface of the first conductive adhesive layer 20 and the release-treated surface of the release sheet 40 are bonded together. This also results in the double-sided structure shown in FIG. An adhesive sheet 10 can be produced.

For example, a first conductive adhesive composition is applied onto the conductive base material 50, heated and dried as necessary, and the first conductive adhesive composition is applied onto the conductive base material 50. The agent layer 20 is formed. Next, the exposed surface of the first conductive adhesive layer 20 and the release-treated surface of the release sheet 40 are bonded together. After turning the top and bottom upside down, a second conductive adhesive composition is applied onto the conductive base material 50, and if necessary, heated and dried to coat the second conductive adhesive composition onto the conductive base material 50. A second conductive adhesive layer 30 is formed. Furthermore, the exposed surface of the second conductive adhesive layer 30 and the release-treated surface of the release sheet 41 are bonded together. This also results in the double-sided structure shown in FIG. An adhesive sheet 10 can be produced.

For example, the first conductive adhesive composition is coated on the release sheet 40, and if necessary, heated and dried to form the first conductive adhesive layer 20 on the release sheet 40. Form. In parallel with this, a second conductive adhesive composition is coated on the release sheet 41, and if necessary, heated and dried to form a second conductive adhesive composition on the release sheet 41. The agent layer 30 is formed. Furthermore, the exposed surface of the second conductive adhesive layer 30 and the conductive base material 50 are bonded together. Thereafter, the exposed surface of the first conductive adhesive layer 20 and the conductive base material 50 are bonded together. This also results in the double-sided structure shown in FIG. An adhesive sheet 10 can be produced.

For example, the second conductive adhesive composition is coated on the release sheet 41, and if necessary, heated and dried to form the second conductive adhesive layer 30 on the release sheet 41. Form. In parallel with this, a first conductive adhesive composition is applied onto the release sheet 40, heated and dried as necessary, and the first conductive adhesive composition is applied onto the release sheet 40. The agent layer 20 is formed. Furthermore, the exposed surface of the first conductive adhesive layer 20 and the conductive base material 50 are bonded together. Thereafter, the exposed surface of the second conductive adhesive layer 30 and the conductive base material 50 are bonded together. This also results in the double-sided structure shown in FIG. An adhesive sheet 10 can be produced.

The first conductive adhesive composition and the second conductive adhesive composition can be applied by known methods, such as knife coating, die coating, lip coating, roll coating, and curtain coating. Coating methods such as bar coating, gravure coating, flexo coating, dip coating, spray coating, and spin coating are preferred.

After each coating, if necessary, it is cured by heating at room temperature or at a temperature of 50 to 300°C to prepare a first conductive adhesive layer and a second conductive adhesive layer, respectively. can do. The heating temperature is preferably 200 to 250° C. from the viewpoint of preventing foaming due to outgas generation during reflow.

[How to use double-sided adhesive sheet]
The double-sided adhesive sheet 10 can be suitably used, for example, in the production of printed circuit boards and the like, for temporarily fixing a workpiece to a conveyance jig for a reflow process. An example of how to use the double-sided adhesive sheet 10 will be described below. However, the method of using the double-sided pressure-sensitive adhesive sheet according to the present invention is not limited to the following description.

FIG. 2 is a schematic cross-sectional view showing an example of how to use the double-sided pressure-sensitive adhesive sheet according to the present invention. In FIG. 2, the same components as those shown in the already explained figures are given the same reference numerals as in the already explained figures, and detailed explanation thereof will be omitted.

As shown in FIG. 2(a), a double-sided adhesive sheet consisting of a first conductive adhesive layer 20, a conductive base material 50, and a second conductive adhesive layer 30 is fixed to a conveying jig 72. be able to.

Next, as shown in FIG. 2(b), the transport jig 72 is grounded, and the transport jig 72, the first conductive adhesive layer 20, the conductive base material 50, and the second conductive adhesive A workpiece 74 is attached to the exposed surface of the second conductive adhesive layer 30 of the layer 30 and temporarily fixed.

Examples of the work 74 include FPC boards, rigid boards (aluminum, stainless steel, glass epoxy, ceramic, etc.), semiconductor packages, ceramic parts, and the like.

As shown in FIG. 2(c), it is temporarily fixed to the conveying jig 72 with a double-sided adhesive sheet consisting of a first conductive adhesive layer 20, a conductive base material 50, and a second conductive adhesive layer 30. The processed workpiece 74 can be transported and subjected to, for example, wet processing steps such as resist development, plating, etching, and cleaning, and heat processing steps such as photoresist drying and solder resist drying. Furthermore, it can be subjected to a reflow process.

After each processing step of the workpiece 74, the workpiece 74 is peeled off while the conveyance jig 72 is grounded, as shown in FIG. 2(d). It is important that the workpiece 74 be peeled off cleanly from the second conductive adhesive layer 30. Here, in the double-sided adhesive sheet according to the present invention, since it has conductivity in the thickness direction penetrating the first conductive adhesive layer 20, the conductive base material 50, and the second conductive adhesive layer 30, it can be peeled off. Charging can be suppressed. Further, since the adhesive force of the first conductive adhesive layer 20 is designed to be larger than the adhesive force of the second conductive adhesive layer 30, the first conductive adhesive layer 20 It can be made so that it cannot be easily peeled off from the conveyance jig 72.

As shown in FIG. 2(e), a double-sided adhesive sheet consisting of a first conductive adhesive layer 20, a conductive base material 50, and a second conductive adhesive layer 30 is placed on a grounded conveyance jig 72. can be returned to a fixed state. Again, as shown in FIG. 2(b), another workpiece 74 can be pasted and temporarily fixed on the exposed surface of the second conductive adhesive layer 30, and the workpiece 74 can be repeatedly subjected to each processing step. . Here, before temporarily fixing the workpiece, there is a step of pressing cellophane tape against the exposed surface of the second conductive adhesive layer 30 to remove foreign matter, a step of cleaning with an alcohol-based solvent, and a step of washing the exposed surface of the second conductive adhesive layer 30 with an alcohol-based solvent. A wiping process may also be performed.

Hereinafter, the present invention will be explained in more detail with reference to examples, but the scope of the present invention is not limited to these examples.

[Example 1]
<First conductive adhesive composition A>
50 parts by mass of silicone adhesive main ingredient (SD 4560 PSA, toluene solution with solid content concentration 60% by mass) manufactured by Dow Corning Toray, silicone adhesive main ingredient manufactured by Dow Corning Toray (SD 4587L PSA, solid content concentration 40% by mass) carbon black (specific surface area: 65 m ² /g, oil absorption 190 ml / 100g) was added in an amount of 7.5% by mass based on the total amount (dry weight) of the constituent components, and the mixture was uniformly stirred and mixed to prepare a first conductive adhesive composition A.

<Second conductive adhesive composition B>
100 parts by mass of silicone adhesive base (LTC755 Coating, toluene solution with solid content concentration of 30 mass%) manufactured by Dow Corning Toray, silicone adhesive base (SD 4560 PSA, solid content concentration of 60 mass%) manufactured by Dow Corning Toray, Inc. Graphite powder (volume average particle diameter: 3.5 μm, scaly, conductive) A second conductive adhesive composition B was prepared by adding 20% by mass of the conductive filler) based on the total amount (dry weight) of the components and stirring and mixing them uniformly.

Next, the second conductive adhesive composition B prepared above was applied onto the copper foil (thickness: 35 μm) that would become the conductive base material 50, and heated and dried at 230° C. for 1.5 minutes. Then, a second conductive adhesive layer 30 having a thickness of 120 μm was formed on the copper foil. Next, on the second conductive adhesive layer 30, a polyimide film (thickness 25 μm) coated with a release agent, which will become the release sheet 41, is laminated to form the second conductive adhesive layer 30. A release sheet 41 was formed on top. Furthermore, the first conductive adhesive composition A was coated on the surface of the conductive base material 50 opposite to the surface on which the second conductive adhesive layer 30 was formed, and heated at 230° C. in 1. The first conductive adhesive layer 20 having a thickness of 40 μm was formed on the conductive base material 50 by heating and drying for 5 minutes. Furthermore, the exposed surface of the first conductive adhesive layer 20 and the release-treated surface of a polyethylene terephthalate film (thickness: 38 μm) coated with a release agent to serve as the release sheet 40 were bonded together. As a result, the embodiment shown in FIG. 1 in which the release sheet 41, the second conductive adhesive layer 30, the conductive base material 50, the first conductive adhesive layer 20, and the release sheet 40 are laminated in this order. A double-sided adhesive sheet 10 of No. 1 was prepared.

[Example 2]
In Example 1, 50 parts by mass of silicone adhesive main ingredient (SD 4560 PSA, toluene solution with a solid content concentration of 60% by mass) manufactured by Dow Corning Toray Co., Ltd. of the first conductive adhesive composition A was changed to 25 parts by mass. Figure 1 was prepared in the same manner as in Example 1, except that 75 parts by mass of a silicone adhesive base (SD 4587L PSA, toluene solution with a solid content concentration of 40% by mass) manufactured by Dow Corning Toray Co., Ltd. was changed to 113 parts by mass. A double-sided pressure-sensitive adhesive sheet 10 of Example 2 shown in Example 2 was produced.

[Example 3]
In Example 1, except for the silicone adhesive base (SD 4560 PSA, toluene solution with a solid content concentration of 60% by mass) manufactured by Dow Corning Toray in the first conductive adhesive composition A, Both sides of Example 3 shown in FIG. An adhesive sheet 10 was produced.

[Example 4]
In Example 1, 50 parts by mass of silicone adhesive main ingredient (SD 4560 PSA, toluene solution with a solid content concentration of 60% by mass) manufactured by Dow Corning Toray Co., Ltd. of the first conductive adhesive composition A was changed to 100 parts by mass. The procedure of Example 4 shown in FIG. A double-sided adhesive sheet 10 was produced.

[Example 5]
<First conductive adhesive composition C>
100 parts by mass of silicone adhesive base (SD 4560 PSA, toluene solution with a solid content concentration of 60% by mass) manufactured by Dow Corning Toray, 0.9 parts by mass of platinum catalyst (SRX-212) manufactured by Dow Corning Toray, 100 parts by mass of toluene. Graphite powder (volume average particle diameter: 3.5 μm, scale-like, conductive filler) was added to the mass part in an amount of 17% by mass based on the total amount (dry weight) of the constituent components, and stirred and mixed uniformly. In this manner, a first conductive adhesive composition C was prepared.

Next, the second conductive adhesive composition B prepared above was applied onto the copper foil (thickness: 35 μm) that would become the conductive base material 50, and heated and dried at 230° C. for 1.5 minutes. Then, a second conductive adhesive layer 30 having a thickness of 80 μm was formed on the copper foil. Next, on the second conductive adhesive layer 30, a polyimide film (thickness 25 μm) coated with a release agent, which will become the release sheet 41, is laminated to form the second conductive adhesive layer 30. A release sheet 41 was formed on top. Furthermore, the first conductive adhesive composition C was coated on the surface of the conductive base material 50 opposite to the surface on which the second conductive adhesive layer 30 was formed, and heated at 230° C. in 1. The first conductive adhesive layer 20 having a thickness of 80 μm was formed on the conductive base material 50 by heating and drying for 5 minutes. Furthermore, the exposed surface of the first conductive adhesive layer 20 and the release-treated surface of a polyethylene terephthalate film (thickness: 38 μm) coated with a release agent to serve as the release sheet 40 were bonded together. As a result, the embodiment shown in FIG. 1 in which the release sheet 41, the second conductive adhesive layer 30, the conductive base material 50, the first conductive adhesive layer 20, and the release sheet 40 are laminated in this order. A double-sided adhesive sheet 10 of No. 5 was prepared.

[Comparative example 1]
<First conductive adhesive composition D>
100 parts by mass of conductive silicone adhesive main ingredient manufactured by Shin-Etsu Silicone (viscosity 106 (Pa・s), toluene solution with solid content concentration 60% by mass), 0.5 parts of platinum catalyst manufactured by Shin-Etsu Silicone (CAL-PL-50T) A first conductive adhesive composition D was prepared by uniformly stirring and mixing 50 parts by mass of toluene and 50 parts by mass of toluene.

Next, the second conductive adhesive composition B prepared above was applied onto a copper foil (thickness: 35 μm) serving as a support, and heated and dried at 230° C. for 1.5 min. A second conductive adhesive layer with a thickness of 80 μm was formed on the foil. Next, on the second conductive adhesive layer, a polyimide film (thickness 25 μm) coated with a release agent to serve as a release sheet is pasted, and on the second conductive adhesive layer, A release sheet was formed. Furthermore, the first conductive adhesive composition D was applied to the surface of the support opposite to the surface on which the second conductive adhesive layer was formed, and heated at 230° C. for 1.5 minutes. It was dried to form a first conductive adhesive layer with a thickness of 80 μm on the support. Furthermore, the exposed surface of the first conductive adhesive layer and the release-treated surface of a polyethylene terephthalate film (thickness 38 μm) coated with a release agent to serve as a release sheet were bonded together, and the double-sided adhesive of Comparative Example 1 was A sheet was produced.

[Comparative example 2]
<First conductive adhesive composition E>
100 parts by mass of silicone adhesive main ingredient (LTC755 Coating, toluene solution with a solid content concentration of 30% by mass) manufactured by Dow Corning Toray, 0.4 parts by mass of platinum catalyst (SRX-212) manufactured by Dow Corning Toray, 100 parts by mass of toluene. Add carbon black (specific surface area: 65 m ² /g, oil absorption 190 ml/100 g) to 7.5% by mass based on the total amount (dry weight) of the components, and stir and mix uniformly. In this way, a first conductive adhesive composition E was prepared.
Next, a double-sided adhesive sheet of Comparative Example 2 was prepared in the same manner as in Comparative Example 1 except that the first conductive adhesive composition D was changed to the first conductive adhesive composition E described above.

[Comparative example 3]
The second conductive adhesive composition B obtained in Example 1 was applied to a polyimide film (thickness 25 μm) coated with a release agent to serve as a release sheet, and heated at 230° C. for 1.5 minutes. It was dried to form a second conductive adhesive layer with a thickness of 80 μm on the polyimide film.
Next, the first conductive adhesive composition D obtained in Comparative Example 1 was applied onto the second conductive adhesive layer, and heated and dried at 230° C. for 1.5 min. A first conductive adhesive layer having a thickness of 80 μm was formed on the second conductive adhesive layer. Furthermore, the release-treated side of a polyethylene terephthalate film (38 μm thick) coated with a release agent to serve as a release sheet was pasted onto the first conductive adhesive layer to produce a double-sided adhesive sheet of Comparative Example 3. .

[Comparative example 4]
A double-sided adhesive sheet of Comparative Example 4 was produced in the same manner as in Comparative Example 1, except that the copper foil (thickness: 35 μm) serving as the support was changed to a polyimide film (thickness: 50 μm).

Next, the double-sided pressure-sensitive adhesive sheets of Examples and Comparative Examples obtained above were evaluated as follows.
<Measurement of thermal weight loss rate of first conductive adhesive layer>
Approximately 10 mg of the first conductive adhesive layer was weighed and the weight (W1) was measured, and then differential thermal and thermogravimetric simultaneous measurement (TG-DTA) was performed. In the measurement, the temperature was raised from 25°C to 260°C at a heating rate of 10°C/min under a nitrogen atmosphere, and the temperature was further maintained at 260°C for 100 minutes. The thermogravimetric reduction rate was calculated by substituting the weight (W2) that decreased by 120 minutes from the start of the measurement into the following equation (1). The results are shown in Tables 3 and 4.
Thermogravimetric reduction rate (%) = (W2/W1) x 100 (Formula 1)

<Measurement of silicone resin fraction of first conductive adhesive layer>
After weighing out about 25 mg of the first conductive adhesive layer and measuring the weight (W3), it was immersed in about 90 mL of toluene at room temperature (23° C.±10) for 15 hours. After that, the eluted components were taken out using filter paper (No. 2), and the weight (W4) after drying at 120°C for 45 minutes was measured, and the silicone resin fraction was calculated by substituting it into the following formula (2). did. The results are shown in Tables 3 and 4.
Silicone resin fraction (%) = (W4/W3) x 100 (Formula 2)

<Measurement of adhesive force of first conductive adhesive layer>
(initial)
The first conductive adhesive layer of the double-sided adhesive sheets produced in Examples and Comparative Examples, from which the release sheet was peeled off, and the stainless steel plate (SUS304, surface finish BA) were bonded together by moving a 3 kg roller back and forth twice. Ta. Next, the double-sided adhesive sheet was peeled off from the stainless steel plate at a peeling angle of 90°, a pulling speed of 300 mm/min, and a measurement width of 25 mm, and the adhesive force was measured. For details of the above-mentioned measuring method, refer to JIS-Z0237.

The results are shown in Tables 3 and 4. The evaluation criteria are as follows. If the result is "△", "○", or "◎", it can be used without any practical problems, and "◎" is the most preferable. “x” has a practical problem.
(Evaluation criteria)
◎: 3.0N/25mm or more ○: 2.0N/25mm or more, less than 3.0N/25mm △: 1.0N/25mm or more, less than 2.0N/25mm ×: Less than 1.0N/25mm

<Measurement of adhesive force of second conductive adhesive layer>
(initial)
The first conductive adhesive layer from which the release sheet of the double-sided adhesive sheets prepared in Examples and Comparative Examples had been peeled off was bonded to a stainless steel plate (SUS304, surface finish BA) using a laminating roll. Next, a polyimide film with a thickness of 25 μm (product name: Kapton 100H, manufactured by DuPont-Toray) is pasted on the second conductive adhesive layer from which the release sheet has been peeled off, by moving a roller weighing 3 kg back and forth twice. Combined. Further, the polyimide film was peeled off from the second conductive adhesive layer at a peeling angle of 90°, a pulling speed of 50 mm/min, and a measurement width of 25 mm, and the initial adhesive strength was measured. For details of the above-mentioned measuring method, refer to JIS-Z0237.

(after heating)
In addition, the adhesive strength of the second conductive adhesive layer was measured after heat treatment at 260° C. for 8 hours. In the above method, heat treatment was performed at 260° C. for 8 hours before laminating a polyimide film (trade name: Kapton 100H, manufactured by DuPont-Toray) on the second conductive adhesive layer.

The results are shown in Tables 3 and 4. The evaluation criteria are as follows. If the initial adhesive strength result is either "△", "○", or "◎", it can be used without any practical problems, and "◎" is the most preferable. In addition, as for the adhesive strength after heating, "○" means that it can be used without any practical problems. “x” has a practical problem.
(Evaluation criteria: initial adhesive strength)
◎: 0.03N/25mm or more, less than 1.0N/25mm ○: 1.0N/25mm or more, less than 1.5N/25mm △: 1.5N/25mm or more, less than 2.0N/25mm ×: Other than the above ( Evaluation criteria: adhesive strength after heating/initial adhesive strength)
○: 50% or more, less than 200% ×: Other than above

<Measurement of volume resistivity>
The first conductive adhesive layer from which the release sheet of the double-sided adhesive sheets prepared in Examples and Comparative Examples had been peeled off was bonded to a stainless steel plate (SUS304, surface finish BA) using a laminating roll. Next, a ring-shaped probe (manufactured by Mitsubishi Chemical Corporation, product name: URS probe, inner electrode outer diameter 5.9 mm, outer electrode inner diameter 11.0 mm, outer electrode outer diameter 17.8 mm) and measurement stage (Mitsubishi Chemical Co., Ltd., product name: Cash register table UFL), the double-sided adhesive sheets prepared in the examples and comparative examples are placed between the ring-shaped probe and the second conductive adhesive layer with the release sheet removed. The resistivity measuring device (manufactured by Mitsubishi Chemical Corporation, Product name: Hiresta UX). For details of the volume resistivity measurement method using such a ring electrode method, refer to JIS-K6911.

The results are shown in Tables 3 and 4. The evaluation criteria are as follows. If the result is "△", "○", or "◎", it can be used without any practical problems, and "◎" is the most preferable. “x” has a practical problem.
(Evaluation criteria)
◎: 10 ⁴ to 10 ⁹ Ω・cm
○: 10 ¹⁰ Ω・cm
△: 10 ³ Ω・cm, or 10 ¹¹ to 10 ¹² Ω・cm
×: Other than above

<Scratch test>
The first conductive adhesive layer from which the release sheet of the double-sided adhesive sheets prepared in Examples and Comparative Examples had been peeled off was bonded to a stainless steel plate (SUS304, surface finish BA) using a laminating roll. At this time, the area of the double-sided adhesive sheet was made smaller than the area of the stainless steel plate, and the double-sided adhesive sheet was laminated so as not to protrude from the stainless steel plate. Next, using tweezers, the edges of the double-sided adhesive sheet were scratched and observed.
The results are shown in Tables 3 and 4. The evaluation criteria are as follows. If the result is "○", it can be used practically without any problem. “x” has a practical problem.
(Evaluation criteria)
○: No peeling/lifting ×: Peeling/lifting

<Repeated reflow resistance>
The first conductive adhesive layer from which the release sheet of the double-sided adhesive sheets prepared in Examples and Comparative Examples was removed and an aluminum plate (A5052) were laminated using a laminating roll to form a second conductive adhesive layer. The release sheet was peeled off. Next, heating was repeated under reflow conditions such that the preheat temperature was 150 to 200°C (120 seconds), the time at which the temperature was above 220°C was 55 seconds, and the peak top was 260°C for 10 seconds. The presence or absence of blistering was visually confirmed, and the number of times of heating when blistering occurred was recorded.
The results are shown in Tables 3 and 4. The evaluation criteria are as follows. If the result is "△", "○", or "◎", it can be used without any practical problems, and "◎" is the most preferable. “x” has a practical problem.
◎: 1000 times or more ○: 100 times or more, less than 1000 times △: 10 times or more, less than 100 times ×: Less than 10 times

As is clear from the evaluation results in Table 3, the double-sided adhesive sheets of Examples 1 to 5 all have a thickness that penetrates the first conductive adhesive layer, the conductive base material, and the second conductive adhesive layer. Since it has good conductivity in the direction, it can be used for repeatedly attaching, processing, and peeling a workpiece to a conveying jig many times, and can suppress peeling electrification.
In addition, the second conductive adhesive layer in the double-sided adhesive sheets of Examples 1 to 5 all had an adhesive strength of 50% or more and less than 200% of the initial adhesive strength after 8 hours at 260°C. It was confirmed that the workpiece was successfully peeled off from the second conductive adhesive layer after the soldering process (including the reflow process), and there was no problem in manufacturing the FPC board.
Further, since the double-sided adhesive sheets of Examples 1 to 5 have a conductive base material between the first conductive adhesive layer and the second conductive adhesive layer, the first conductive adhesive layer Changes in adhesive force caused by the transfer of the adhesive component to the second conductive adhesive layer are suppressed. Therefore, there is a difference between the adhesive strength of the first conductive adhesive layer and the adhesive strength of the second conductive adhesive layer, making it difficult for the first conductive adhesive layer to peel off from the conveyance jig. The double-sided adhesive sheet is less likely to peel off when attaching and processing workpieces. In addition, since the adhesive component in the first conductive adhesive layer does not move to the second conductive adhesive layer, the adhesive strength of the first conductive adhesive layer does not increase even after repeated heating during reflow. The removability of the workpiece can be maintained without any problems.
In addition, in the double-sided adhesive sheets of Examples 1 to 5, the adhesive does not easily swell (bubbles) even after undergoing the reflow process multiple times, and the workpiece does not easily peel off from the adhesive.

On the other hand, as is clear from the evaluation results in Table 4, when the double-sided adhesive sheet of Comparative Example 1 undergoes the reflow process multiple times, swelling (bubbles) occurs in the adhesive, and the workpiece peels off from the adhesive.
In addition, the double-sided adhesive sheet of Comparative Example 2 had a problem in that the adhesive force of the first conductive adhesive layer was weak and it peeled off from the stainless steel plate.
Further, in the double-sided adhesive sheet of Comparative Example 3, the adhesive layers are directly bonded to each other without having a conductive base material between the first conductive adhesive layer and the second conductive adhesive layer. Therefore, the adhesive component in the first conductive adhesive layer easily moves to the second conductive adhesive layer. Therefore, in the double-sided adhesive sheet of Comparative Example 3, the adhesive strength of the second conductive adhesive layer after 8 hours at 260°C was greater than 200% of the initial adhesive strength, and the soldering process (reflow process) It was confirmed that the workpiece was difficult to peel off from the second conductive adhesive layer after the test (including the above), which caused problems in the production of FPC boards.
In addition, since the double-sided adhesive sheet of Comparative Example 4 has a large volume resistivity in the thickness direction penetrating the first conductive adhesive layer and the second conductive adhesive layer, it is difficult to peel off the workpiece with respect to the conveying jig. When this is repeated, peel-off charging may occur, and the semiconductor member on the film-like base material or the semiconductor member work itself may be damaged by electrostatic discharge.

10 Double-sided adhesive sheet 20 First conductive adhesive layer 30 Second conductive adhesive layer 40 Release sheet 41 Release sheet 50 Conductive base material 72 Conveyance jig 74 Work

Claims (5)

A double-sided adhesive sheet in which a first conductive adhesive layer, a conductive base material, and a second conductive adhesive layer are laminated,
The first conductive adhesive layer and the second conductive adhesive layer contain a silicone adhesive and a conductive filler,
The adhesive force of the first conductive adhesive layer is greater than the adhesive force of the second conductive adhesive layer,
having conductivity in the thickness direction penetrating the first conductive adhesive layer and the second conductive adhesive layer,
A double-sided pressure-sensitive adhesive sheet, wherein the first conductive pressure-sensitive adhesive layer has a thermal weight loss rate of 2.5 to 6% at 260°C. The double-sided pressure-sensitive adhesive sheet according to claim 1, wherein the conductive base material has a thickness of 5 to 100 μm. The double-sided pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the conductive base material is copper foil or aluminum foil. A claim characterized in that the adhesion force of the first conductive adhesive layer to the stainless steel plate (SUS304, surface finish BA) (peel angle 90°, tensile speed 300 mm/min) is 1.0 N/25 mm or more. The double-sided adhesive sheet according to any one of items 1 to 3. The adhesive force of the second conductive adhesive layer to the polyimide film (thickness 25 μm) (peel angle 90°, tensile speed 50 mm/min) is 0.03 to less than 2.0 N/25 mm. The double-sided adhesive sheet according to any one of claims 1 to 4.

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