JP2016157781A - Conductive adhesive sheet, shield printed wiring board, and electronic equipment - Google Patents

Abstract

An object of the present invention is to provide a conductive adhesive sheet that reliably gives an electromagnetic wave shielding effect to a printed wiring board and simultaneously achieves excellent storage stability, tack-free, low resin flow, and flexibility. To do. The conductive adhesive sheet according to the present invention comprises a polyamide resin, a phenol resin, and a conductive material, wherein the polyamide resin is stored at 160 ° C. The elastic modulus is 0.10 MPa or more. [Selection figure] None

Description

  The present invention relates to a conductive adhesive sheet for bonding a printed wiring board and a reinforcing plate. The printed wiring board here is described in JISC 5603 and refers to a board on which printed wiring is formed. For example, a rigid printed wiring board in which the insulating substrate of the printed wiring board is hard, a flexible flexible printed wiring board, a flex rigid printed wiring board composed of a hard part and a flexible part, and a conductive pattern, There are a single-sided printed wiring board on only one side, a double-sided printed wiring board on both sides, and a multilayer printed wiring board having three or more layers including a surface conductor layer.

  In recent years, electronic devices such as mobile phones, smartphones, tablets, video cameras, and notebook computers, which are rapidly becoming smaller and lighter, have flexible and flexible flexible printed wiring for high-density mounting of electronic components and electronic circuit boards. A board (Flexible Printed Wiring Board, hereinafter abbreviated as FPWB) is often used. On the other hand, there is a concern about malfunction of internal circuits due to electromagnetic noise due to high-density mounting and high frequency operation signals, and attention is being paid to countermeasures against electromagnetic noise.

  Conventionally, as countermeasures against electromagnetic wave noise of FPWB, an electromagnetic wave shielding effect is applied to the reinforcing plate by adhering a reinforcing plate having an electromagnetic wave shielding property with a conductive adhesive sheet and making the FPWB ground circuit (copper foil) and the reinforcing plate conductive. In the case of using a reinforcing plate having low electromagnetic shielding properties (Patent Documents 1 and 2) or a method of exerting an electromagnetic wave shielding effect on the conductive adhesive sheet itself (Patent Documents 3 to 5), etc. are performed. ing. Here, the manufacturing process of a laminate of a reinforcing plate and FPWB (referred to as shield FPWB) will be briefly described. First, a conductive adhesive sheet having a release film laminated on one side and a reinforcing plate are temporarily pressure-bonded (temporary). Crimping process). Then, a peeling film is peeled from a conductive adhesive sheet (peeling process). Then, FPWB is superimposed on the surface of the conductive adhesive sheet of the laminate of the reinforcing plate and the conductive adhesive sheet, and heat-pressed (adhesion process). Finally, the above three-layer laminate is after-cured (after-curing step) in a heated atmosphere, and the shield FPWB is completed.

  In recent years, the conductive adhesive sheet has been required to improve many characteristics such as adhesion, physical strength, heat resistance, and moisture resistance as well as conductivity from the viewpoint of sophistication of required characteristics. As a method for improving these characteristics, it is conceivable to increase the crosslinking density of the film after curing. In order to obtain a resin having a high crosslink density, it is necessary to increase the number of reaction points. From such a viewpoint, it is necessary to use an epoxy resin having a large amount of functional groups. For example, Patent Documents 3 to 5 described above describe a conductive adhesive sheet containing an epoxy resin as a thermosetting resin and an acrylic resin or a polyester resin as a thermoplastic resin.

JP 2000-195899 A JP2003-133684A JP2007-189091 JP 2014-65912 A WO2014 / 003159

However, in the conventional conductive adhesive sheet, there are some problems in the epoxy resin having a large amount of functional groups. For example, since the reactivity is high, refrigerated storage is required. In addition, since the crosslink density of the resin is increased after the after-curing step, if the crosslink density is increased, flexibility is impaired, which is disadvantageous when flexibility is required.
In addition, since the epoxy resin has a small molecular weight, the conductive adhesive sheet is tacked, and it is necessary to protect both surfaces of the conductive adhesive sheet, and it is difficult to adjust the bonding position in the bonding process. Furthermore, the resin flow (the amount of the conductive adhesive sheet component that protrudes from the edge of the bonded portion) increases in the bonding step.
As described above, the problems of the prior art have been shown centering on FPWB, but problems such as frozen storage and resin flow are common not only to FPWB but also to rigid printed wiring boards and flex rigid printed wiring boards.

  Accordingly, an object of the present invention is to provide a conductive adhesive sheet that solves the above-described problems, and to improve the conduction state between the ground circuit of the printed wiring board and the reinforcing plate. The electromagnetic wave shielding effect of the adhesive sheet itself is further enhanced.

The conductive adhesive sheet according to the present invention is a conductive adhesive sheet that bonds a printed wiring board and a reinforcing plate, and includes a polyamide resin, a phenol resin, and a conductive material. The storage elastic modulus at is 0.10 MPa or more. The said subject is solved by using the electroconductive adhesive sheet of this invention.
That is, the polyamide resin having an amide bond contributes to the improvement in adhesion between copper, polyimide, etc., which are typical materials for printed wiring boards, and the conductive adhesive sheet, and more than when using an acrylic resin or a polyester resin. Excellent adhesion can be obtained.
In addition, the phenol resin is generally less reactive at room temperature than the epoxy resin and is solid, so that it gives an excellent shelf life to the conductive adhesive sheet and does not cause tack. Moreover, unlike an epoxy resin, a phenol resin does not hinder the flexibility of a conductive adhesive sheet due to a thermoplastic polyamide resin.
Furthermore, since the storage elastic modulus at 160 ° C. of the polyamide resin is 0.10 MPa or more, the fluidity of the resin component can be controlled in the bonding step of the conductive adhesive sheet, so that the resin flow can be reduced. it can.
By dispersing the conductive material in the conductive adhesive sheet, the conductive material contacts each other after the bonding process, the conductive material and the reinforcing plate, and the conductive material and the ground circuit (copper foil) of the printed wiring board. In order to form a conduction path, the ground circuit (copper foil) of the printed wiring board and the reinforcing plate are brought into a conducting state so that the electromagnetic wave shielding effect is exerted on the reinforcing plate, and the electromagnetic wave shielding effect is also exerted on the conductive adhesive sheet itself. be able to.

  In the conductive adhesive sheet according to the present invention, the phenol resin is preferably a resol type phenol resin. Since the resol type phenol has a self-reactive functional group and is cured after the after-curing, the cohesive force and heat resistance of the conductive adhesive sheet can be increased.

  In the conductive adhesive sheet according to the present invention, the conductive material is preferably silver-coated copper powder or copper powder. Since these have high electrical conductivity, it is possible to improve the electrical connection between the ground circuit (copper foil) of the printed wiring board and the reinforcing plate, and to further improve the electromagnetic shielding effect of the conductive adhesive sheet itself. Can be increased.

  The shield printed wiring board according to the present invention is such that the printed wiring board and the reinforcing plate are bonded by the conductive adhesive sheet.

  An electronic apparatus according to the present invention includes the shield printed wiring board.

  According to the conductive adhesive sheet of the present invention, refrigerated storage is not required, it has flexibility, resin flow hardly occurs in the bonding process, and the conductive state between the printed wiring board and the reinforcing plate is caused by the conductive material. As a result, the electromagnetic wave shielding effect of the conductive sheet itself can be further enhanced.

It is a perspective view for demonstrating the structure before a press regarding the evaluation method of the connection resistance in an Example. It is sectional drawing for demonstrating the evaluation method of the connection resistance in an Example. It is the top view which showed the conductive adhesive sheet with a reinforcement board from the reinforcement board side for demonstrating the evaluation method of the resin flow in an Example, and sectional drawing shown toward the side surface.

  Hereinafter, although the form for implementing this invention is demonstrated, this invention is not restrict | limited unfairly by the specific example shown below.

<Conductive adhesive sheet>
The conductive adhesive sheet of the present invention contains a polyamide resin, a phenol resin, and a conductive material, and the polyamide resin has a storage elastic modulus at 160 ° C. of 0.10 MPa or more.

  The polyamide resin used in the present invention is obtained by dehydrating and condensing a mixture of dicarboxylic acid and diamine, and is limited as long as it has an amide bond in the molecular chain and is soluble in an organic solvent. There is no. For example, as dicarboxylic acid, aliphatic dicarboxylic acid such as adipic acid, succinic acid, glutaric acid, azelaic acid, sebacic acid, dimer acid (dimer of higher unsaturated fatty acid having 11 to 22 carbon atoms), isophthalic acid, Aromatic dicarboxylic acids such as terephthalic acid and phthalic acid. Examples of diamines include aliphatic diamines such as hexamethylene diamine, octamethylene diamine, 1,4-diaminobutane, nonane diamine, diaminodicyclohexyl methane, and isophorone diamine, p-phenylene diamine, m-phenylene diamine, metaxylylene diamine, and diamino. Aromatic diamines such as diphenylmethane can be mentioned. Moreover, what has reactive functional groups, such as an amino group and a carboxyl group, can be used for the terminal or side chain of the polyamide resin obtained by the said component. By using the polyamide resin, excellent adhesion, toughness, and chemical resistance can be obtained.

In the present invention, those containing dimer acid as the acid component of the raw material of the polyamide resin are preferred. Polyamide resins generally have a high water absorption rate, but by using dimer acid, it becomes possible to reduce the water absorption rate and improve solder heat resistance.
Furthermore, the polyamide resin preferably has an amino group. As a result, the solubility of the polyamide resin in the organic solvent is increased, a crosslinked structure with the phenol resin is formed, the crosslinking density is increased, and the heat resistance and cohesive force can be improved. Examples of the index having an amino group include an amine value, and it is preferable to use a polyamide resin having an amine value of 5 mgKOH / g or more, and the upper limit is not particularly limited, but can be set to 500 mgKOH / g, for example.

The polyamide resin used in the present invention has a storage elastic modulus at 160 ° C. of 0.10 MPa or more, more preferably 0.15 MPa or more, further preferably 0.20 MPa or more, and further 0.50 MPa or more. By being the said range, since the fluidity | liquidity of the resin component can be controlled in the adhesion | attachment process of an electroconductive adhesive sheet, a resin flow can be reduced. On the other hand, if it is less than 0.10 MPa, the resin flow becomes large in the bonding step, which may cause a problem in the printed wiring board, the electronic component or electronic device on which the printed wiring board is mounted. The upper limit is not particularly limited, but when the lower limit is less than 0.50 MPa, such as 0.10 MPa or more, for example, 0.5 MPa or less.
Although the upper limit of the storage elastic modulus is not particularly limited, the upper limit of the storage elastic modulus of the polyamide resin at 160 ° C. from the viewpoint of improving the followability to the opening for connecting to the ground circuit (copper foil) of the printed wiring board. Is preferably less than 200 MPa, more preferably less than 150 MPa. By being less than 200 MPa, the followability to the opening for connecting to the ground circuit (copper foil) of FPWB is suitably maintained.

  The phenol resin used in the present invention is obtained by a condensation reaction of phenols and aldehydes in the presence of an acid or base catalyst, and is a novolac type phenol resin or a resol type phenol resin. For example, as phenols, alkylphenol, paraphenylphenol, bisphenol A, resorcinol and the like can be mentioned. Examples of aldehydes include formaldehyde, paraformaldehyde, hexamethylenetetramine, and furfural. Since the phenol resin obtained by the above components generally has a three-dimensional network structure when cured, it is excellent in heat resistance and flame retardancy, and has high oil resistance and chemical resistance. Moreover, since it is solid at room temperature, it makes it hard to produce a tack.

In the present invention, it is more preferable to use a resol type phenol resin. The resol type phenol resin is obtained by making formaldehyde excess with respect to phenols and reacting under a base catalyst. Since the resol type phenolic resin has a self-reactive functional group, the heat resistance is improved by curing, and the physical property change is small at room temperature because it is cured by heating at 130 to 200 ° C.
Furthermore, it is preferable to use a tetrafunctional resol type phenol resin in the present invention. The tetrafunctional resol type phenolic resin is more likely to undergo a self-curing reaction and has a higher crosslink density than the 1 to 3 functional resol type phenolic resin, and thus can improve heat resistance and cohesion.

  In the conductive adhesive sheet of the present invention, the ratio of the polyamide resin and the phenol resin is preferably 95: 5 to 5:95, and more preferably 90:10 to 60:40. By being in the range of the weight ratio, the properties of the polyamide resin and the phenol resin can be extracted in a well-balanced manner.

  The conductive material used in the present invention is metal powder, carbon powder, a mixture containing them, and the like. For example, metal powder such as gold powder, silver powder, copper, nickel powder, aluminum powder, solder powder, carbon black, carbon fiber, graphite powder, carbon nanotube, and the like. These conductive materials, resin beads, glass fiber, A material in which an insulating material such as silica is coated with a metal (for example, silver-coated copper powder, gold-plated glass fiber, or the like) may be used. As the shape of the conductive material, there are a spherical shape, a needle shape, a fiber shape, a flake shape, a tree shape, an indefinite shape, and the like.

  In the present invention, it is preferable to use silver-coated copper powder or copper powder as the conductive material. Silver coated copper powder and copper powder are cheaper than gold powder and silver powder, and have higher conductivity than nickel powder, aluminum powder, carbon powder, etc., and therefore provide a conductive adhesive sheet that is cheaper and has excellent electromagnetic shielding properties. be able to. Silver-coated copper powder or copper powder can be used alone or in combination with other conductive materials.

  Furthermore, the shape of the conductive material is preferably a tree shape or a flake shape (flat shape), and more preferably a tree shape. In use, conductive materials of the same shape may be used, or mixed conductive materials of different shapes are used so that a dendritic conductive material and a flaky conductive material are used in combination. May be. In the case of a shape having a large surface area and high electrical conductivity, such as a dendritic or flaky shape, due to heat shrinkage of the phenolic resin in the bonding process and in the after-curing process, the conductive materials, conductive material and reinforcing plate It becomes easy for the conductive material and the ground circuit (copper foil) of the printed wiring board to come into contact with each other.

  The average particle size of the conductive material is preferably 1 to 50 μm, and more preferably 5 to 20 μm. When it becomes larger than the said range, the surface of a conductive adhesive sheet will become rough, and when it becomes smaller than the said range, it will become difficult for conductive materials to contact.

  In the conductive adhesive sheet of the present invention, the conductive material is preferably 10 to 500 parts by weight with respect to 100 parts by weight of the mixture of polyamide resin and phenol resin, and the conductive material is silver-coated copper powder. In this case, it is more preferably 95 to 345 parts by weight, and more preferably 275 to 430 parts by weight when the conductive material is copper powder. By being the said range, the characteristic of each of the mixture of a polyamide resin and a phenol resin, and electroconductive material can be drawn out with sufficient balance.

  The conductive adhesive sheet of the present invention may further contain an inorganic filler in addition to the conductive material as long as various properties are not impaired. By including an inorganic filler, tackiness can be reduced, resin flow can be reduced, and heat resistance can be improved. Examples of the inorganic filler include, but are not limited to, metal hydroxides such as aluminum hydroxide and magnesium hydroxide, silica, alumina, zirconium oxide, zinc oxide, antimony trioxide, antimony pentoxide, magnesium oxide, titanium oxide, Examples thereof include metal oxides such as iron oxide, cobalt oxide, chromium oxide, and talc, graphite powder, carbon black, and glass. These may be used alone or in combination of two or more.

  Whether the conductive adhesive sheet of the present invention contains a polyamide resin or a phenol resin is determined by gas chromatography (GC), liquid chromatography (LC), infrared spectroscopy (IR), nuclear magnetic resonance spectroscopy (NMR). ), Mass spectrometry (MS) or the like, and can be determined by confirming the peaks peculiar to these resins.

<Method for producing conductive adhesive sheet>
Next, a method for producing the conductive adhesive sheet of the present invention will be described. The method for producing the conductive adhesive sheet of the present invention is not particularly limited. For example, the conductive adhesive sheet can be produced by coating a release film with a composition for a conductive adhesive sheet containing a polyamide resin, a phenol resin, and a conductive material. In addition, it may be subjected to a drying process as necessary after coating. As the release film, a film in which a silicone-based or non-silicone-based release agent is applied to the surface on which the conductive adhesive sheet on the base film such as polyester or polyethylene naphthalate is formed can be used. . In addition, the thickness of a release film is not specifically limited, It determines suitably considering the ease of use.

  The coating method is not particularly limited, and known methods represented by gravure coating, die coating, lip coating, and comma coating can be used. The thickness of the conductive adhesive sheet is preferably 15 to 100 μm. By setting it as the said range, it is preferable at the point from which it deform | transforms into the shape which fills a recessed part by flowing moderately when an unevenness | corrugation exists in a reinforcement board or a printed wiring board, and sufficient adhesiveness is obtained.

<Shield printed wiring board, electronic equipment>
The conductive adhesive sheet according to the present invention is used for the purpose of bonding a printed wiring board and a reinforcing plate. Known printed wiring boards and reinforcing boards can be used. Examples of the printed wiring board include a rigid rigid printed wiring board, a rigid flexible substrate having both a hard part and a flexible part, and a flexible film-like flexible printed wiring board having flexibility. Examples thereof include aluminum, copper, polyimide, glass epoxy, and liquid crystal polymer.

  The shield printed wiring board in which the printed wiring board and the reinforcing plate are bonded by the conductive adhesive sheet according to the present invention is preferably used as a component of an electronic device, and the electronic device according to the present invention is the above shield printed wiring board. Is included. Examples of the electronic device include a smartphone, a tablet, a video camera, and a laptop computer.

  Next, the present invention will be specifically described using examples and comparative examples, but the present invention is not construed as being limited to these specific examples.

<Method for Producing Conductive Adhesive Sheet (Example, Comparative Example)>
First, a method for producing a conductive adhesive sheet in each example and comparative example will be described. A release film made of a polyethylene terephthalate film having a thickness of 38 μm coated with a silicone mold release agent on one side is suitably used as a conductive adhesive sheet composition having the composition shown in Tables 1 and 2 below, and an organic solvent is added. The mixed paint was applied and dried at 130 ° C. for 3 minutes to produce a conductive adhesive sheet having a thickness of 40 ± 10 μm.

<Evaluation method>
Below, the evaluation method of a conductive adhesive sheet is demonstrated. In addition, the laminated body which laminated | stacked the peeling film on the single side | surface of the conductive adhesive sheet was used for evaluation of a conductive adhesive sheet.

(Storage modulus)
The storage elastic modulus of the polyamide resin was measured with a REAKERS RS600 manufactured by HAAKE, which is a dynamic viscoelasticity measuring device.
Sample: cylindrical plate with a diameter of 20 mm and a thickness of 2 mm; parallel plate with a diameter of 20 mm Measurement temperature range: 30 to 200 ° C.
Temperature rising rate: 6 ° C./min Measurement frequency: 1.0 Hz
Shear stress: 50 Pa

(Tackiness)
After placing the laminate with the conductive adhesive sheet as the upper surface on a hot plate heated at 30 ° C., lightly touch the surface of the conductive adhesive sheet with a fingertip washed with ethanol (see JISK 6249). evaluated. If the conductive adhesive sheet does not adhere to the finger at all, it can be used without any problem.
○ ・ ・ ・ The conductive adhesive sheet does not adhere to the finger at all × ・ ・ ・ The conductive adhesive sheet adheres to the finger

(Temporary crimpability)
The configuration of the release film / conductive adhesive sheet / reinforcing plate in which the laminate (release film / conductive adhesive sheet) is bonded to the reinforcing plate is a hot roll (120 ° C., 0.2 MPa, 0.5 m / min). After passing, the release film was peeled in the 90 ° C. direction and evaluated according to the following criteria. The conductive adhesive sheet is attached to the reinforcing plate, and can be used without any problem if it does not peel off from the reinforcing plate.
○ ・ ・ ・ The conductive adhesive sheet does not peel off from the reinforcing plate × ・ ・ ・ There is a part where the conductive adhesive sheet peels off from the reinforcing plate

(Shelf life)
After storing the laminate at 60 ° C. × 168 hours, it was evaluated whether or not the conductive adhesive sheet could be peeled off in the same manner as described above (temporary pressure bonding). Even after storage, if the temporary press bonding property is “◯”, it can be used without any problem.

(Connection resistance)
A method for evaluating the connection resistance will be described with reference to FIGS. For the conductive adhesive sheet with a reinforcing plate (reinforcement plate 1 / conductive adhesive sheet 2 in FIG. 1) prepared as described above (temporary pressure bonding), the configuration of the reinforcing plate 1 / conductive adhesive sheet 2 is connected to the ground circuit. After the opening 6 of the part is thermocompression-bonded (160 ° C., 4 MPa, 30 min) to the configuration of the wiring board 5 (insulating layer 3 / copper foil layer 4: FIG. 1) simulating a diameter of 1 mm, connection is made Resistance (between the reinforcing plate 1 and the copper foil layer 4 in FIG. 2) was measured and evaluated according to the following criteria. If it is less than 0.3Ω, sufficient electromagnetic wave shielding performance and conduction performance are ensured for the reinforcing plate.
○ ・ ・ ・ less than 0.3Ω × ・ ・ ・ 0.3Ω or more

(Resin flow)
About the conductive adhesive sheet with a reinforcing plate (reinforcing plate 1 / conductive adhesive sheet 2 in FIG. 1) prepared in the above (temporary pressure bonding property), the reinforcing plate 1 / conductive adhesive sheet 2 / polyimide film or copper foil 7 After thermocompression bonding (160 ° C., 4 MPa, 30 min) with a vacuum press machine, the longest distance and the shortest distance of resin flow 8 (amount of the conductive adhesive sheet constituent component protruding from the edge of the bonded portion) were measured and averaged. Was calculated. 3 is a plan view illustrating the reinforcing plate 1 / conductive adhesive sheet 2 / polyimide film or copper foil 7 from the reinforcing plate 1 side, and the lower diagram of FIG. 3 is the reinforcing plate 1 / conductive adhesive sheet. 2 is a cross-sectional view showing a polyimide film or copper foil 7. The distance L of the resin flow 8 from the conductive adhesive sheet is the length of the resin flow 8 extending vertically from any side of the reinforcing plate 1 along the surface of the reinforcing plate 1 as shown in FIG. Point to. If the average value of the maximum value and the minimum value of L is less than 1.0 mm, it can be used without any problem.
◎ ・ ・ ・ less than 0.3mm ○ ・ ・ ・ less than 1.0mm × ・ ・ ・ 1.0mm or more

(Adhesive strength)
About the laminated body created by the above (resin flow), the reinforcing plate 1 / conductive adhesive sheet 2 was peeled off while pulling in the vertical direction with respect to the polyimide film and the copper foil using a tensile tester, and the 90 ° peel strength was measured. . If it is 10 N / cm or more, it can be used without problems.
◎ ・ ・ ・ 15N / cm or more ○ ・ ・ ・ 10N / cm or more × ・ ・ ・ less than 10N / cm

(Surface resistivity)
After heating the laminated body with a vacuum press (160 ° C., 4 MPa, 30 min), the surface resistivity of the conductive adhesive sheet was measured by a four-probe method. In general, the electromagnetic shielding effect required for the conductive adhesive sheet itself is 40 dB or more (electromagnetic wave shielding rate of 99% or more) when the electric field shielding performance measured by the KEC method (Kansai Electronics Industry Promotion Center method) is in the range of 10 to 1000 MHz. If the surface resistivity is less than 1.0Ω / □, this can be satisfied.
◎ ・ ・ ・ less than 0.3Ω / □ ○ ・ ・ ・ less than 1.0Ω / □ × ・ ・ ・ 1.0Ω / □ or more

(Solder heat resistance)
The configuration of the release film / conductive adhesive sheet / polyimide film was temporarily pressure-bonded with a hot roll (120 ° C., 0.2 MPa, 0.5 m / min), and the release film was peeled off to obtain a polyimide film / conductive adhesive sheet / polyimide film. The composition was heated and pressed with a vacuum press (160 ° C., 4 MPa, 30 min) and aftercured with an oven (160 ° C., 60 min), then floated in a solder bath heated to 260 ° C., and the test piece was observed. The time until floating occurred was measured. If it is 30 seconds or more, it can be used without problems.
○ ・ ・ ・ 30 seconds or more × ・ ・ ・ less than 30 seconds

  The results are shown in Table 1. First, in Example 1, a polyamide resin (A-1) having a storage elastic modulus at 160 ° C. of 0.22 MPa, a resol type phenol resin (B-1), and a silver-coated copper powder (C-1) are used. In Example 2, instead of the above (A-1), a conductive adhesive sheet was produced using a polyamide resin (A-2) having a storage elastic modulus at 160 ° C. of 0.47 MPa. The evaluation result of temporary press bonding property, shelf life, connection resistance and solder heat resistance is “◯”, and the evaluation result of resin flow, adhesive strength (polyimide, copper), and surface low efficiency is “◎”, which is a good result. Obtained.

  Next, in Examples 3 and 4, when magnesium hydroxide (D-1) and aluminum hydroxide (D-2) were used as inorganic fillers, respectively, these contributed to tackiness and resin flow. Although the amount of silver-coated copper powder used was lower than that in Example 1, the same evaluation results as in Example 1 were obtained.

  In Example 5, when the weight ratio of the silver-coated powder was reduced, the resin ratio increased, so that the resin flow was “◯”, but the other evaluations were as good as in Example 1. . Moreover, when copper powder (C-2) was used in Example 6, the favorable result was obtained similarly to Example 1.

  In Example 7, when the novolak type phenol resin (B-2) was used as the phenol resin, the evaluation results were all “◯”, indicating the superiority of the resol type phenol resin. In Examples 8 and 9, when flat copper powder (C-3) and flat nickel powder (C-4) were used, good results were obtained in the same manner as in Example 1.

  On the other hand, in Comparative Example 1, when the epoxy resin (E-1) was used, the tackiness, shelf life, and resin flow were “x”. In Comparative Examples 2 and 3, when acrylic resin (F-1, F-2) was used instead of polyamide resin, the adhesive strength was both “x”, and important characteristics as a conductive adhesive sheet were satisfied. It has not been.

  Furthermore, in Comparative Examples 4 and 5, when a polyamide resin (A-3) having a low storage elastic modulus at 160 ° C. of 0.01 MPa was used, the evaluation result of the resin flow was “x”, and the storage elastic modulus was The difference with Example 1 using high A-1 was shown notably.

  As described above, by using the conductive adhesive sheet of the present invention, shelf life and resin flow superior to using an epoxy resin as a thermosetting resin can be obtained, and an acrylic resin is used as a thermoplastic resin. It is clear that superior adhesive strength can be obtained.

DESCRIPTION OF SYMBOLS 1 Reinforcement board 2 Conductive adhesive sheet 3 Insulating layer 4 Copper foil layer 5 Wiring board imitating diameter 1mm of diameter of connection part with ground circuit 6 Opening part 1mm in diameter 7 Polyimide film or copper foil 8 Conductive adhesive sheet Resin Flow L from

Claims (5)

A conductive adhesive sheet for bonding a printed wiring board and a reinforcing board,
Containing a polyamide resin, a phenol resin, and a conductive material;
The polyamide resin has a storage elastic modulus at 160 ° C. of 0.10 MPa or more.   The conductive adhesive sheet according to claim 1, wherein the phenol resin is a resol type phenol resin.   The conductive adhesive sheet according to claim 1, wherein the conductive material is silver-coated copper powder or copper powder.   The printed wiring board and the reinforcement board are adhere | attached with the electroconductive adhesive sheet of any one of Claims 1-3, The shield printed wiring board characterized by the above-mentioned.   An electronic device comprising the shield printed wiring board according to claim 4.

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