JP2018039959A - Conductive adhesive composition - Google Patents

Abstract

An object of the present invention is to provide a conductive adhesive composition having excellent conductivity even after reflow. SOLUTION: At least one of a thermoplastic resin and a thermosetting resin, a conductive filler, and inorganic particles are contained, and the inorganic particles have a particle diameter of 5 μm measured using a laser diffraction particle size distribution measuring device. The conductive adhesive composition in which the cumulative frequency is 40% or less and the blending amount of the inorganic particles with respect to the entire conductive adhesive composition is 10 to 30% by mass. [Selection figure] None

Description

  The present invention relates to a conductive adhesive composition used for a printed wiring board.

  Conventionally, in order to affix a reinforcement board and an electromagnetic wave shielding film to a printed wiring board, the conductive adhesive which added the conductive filler in the adhesive resin composition is used. When attaching a reinforcing plate or electromagnetic shielding film to a printed wiring board, an opening is formed in the coverlay of the printed wiring board to expose a circuit made of copper foil, and the opening is filled with a conductive adhesive. The circuit is electrically connected to the reinforcing plate and the electromagnetic shielding film.

  As such a conductive adhesive, for example, an adhesive in which a thermosetting resin is blended with a conductive filler and silica particles having a predetermined specific surface area is disclosed. And it is described by mix | blending such a silica particle that the damage of an insulating layer can be suppressed, without impairing the softness | flexibility of the whole electromagnetic wave shield film (for example, refer patent document 1). Moreover, the electroconductive adhesive agent which consists of an adhesive composition containing the inorganic filler which has a predetermined particle diameter, and a thermosetting resin is disclosed. And it is described by using such a conductive adhesive that the connection reliability in a circuit with a high level of wet heat resistance and through-hole steps is improved (for example, see Patent Document 2).

Japanese Patent Laying-Open No. 2015-53412 Japanese Patent No. 5892282

  Here, in general, when the conductive adhesive is exposed to a reflow process (for example, 270 ° C. for 10 seconds), the conductivity and the adhesion to the printed wiring board are lowered, so that the reflow resistance (withstands the reflow process). High heat resistance and high adhesion between the printed circuit board and the conductivity after the reflow process are required. In recent years, since electronic boards tend to be miniaturized, the hole diameter of the opening provided in the cover lay also tends to be small.

  However, the adhesives described in Patent Documents 1 and 2 have a problem that the connection resistance value increases after exposure to the reflow process when the hole diameter of the opening provided in the cover lay becomes small.

  Then, this invention is made | formed in view of the said problem, and it aims at providing the electroconductive adhesive composition which can ensure the outstanding electroconductivity after reflow.

  In order to achieve the above object, the conductive adhesive composition of the present invention is a conductive adhesive composition containing at least one of a thermoplastic resin and a thermosetting resin, a conductive filler, and inorganic particles. The inorganic particles have a cumulative frequency of 40% or less at a particle diameter of 5 μm measured using a laser diffraction particle size distribution analyzer.

  Another conductive adhesive composition of the present invention is a conductive adhesive composition containing at least one of a thermoplastic resin and a thermosetting resin, a conductive filler, and inorganic particles, and is inorganic. The particles have a cumulative frequency of 80% or less at a particle diameter of 10 μm measured using a laser diffraction particle size distribution analyzer.

  The “cumulative frequency” here refers to the cumulative frequency from the small particle diameter side in the particle size distribution curve (vertical axis is cumulative frequency%, horizontal axis is particle diameter) obtained by a laser diffraction particle size distribution analyzer. Say that.

  According to the present invention, it is possible to provide a conductive adhesive composition having excellent conductivity even after reflow.

It is sectional drawing of the electroconductive adhesive film which concerns on embodiment of this invention. It is sectional drawing of the shield printed wiring board which concerns on embodiment of this invention. It is sectional drawing of the shield printed wiring board which concerns on embodiment of this invention. It is sectional drawing of the shield printed wiring board which concerns on embodiment of this invention. It is sectional drawing of the flexible substrate used in an Example. It is a figure for demonstrating the measuring method of the electrical resistance value in an Example.

  Hereinafter, the conductive adhesive composition of the present invention will be specifically described. In addition, this invention is not limited to the following embodiment, In the range which does not change the summary of this invention, it can change suitably and can apply.

  The conductive adhesive composition of the present invention has a cumulative frequency at a particle size of 5 μm measured using at least one of a thermoplastic resin and a thermosetting resin, a conductive filler, and a laser diffraction particle size distribution measuring device. It is a conductive adhesive composition containing 40% or less inorganic particles.

  Thermosetting resin is not particularly limited, and polyamide resin, polyimide resin, acrylic resin, phenol resin, epoxy resin, polyurethane resin, polyurethane urea resin, melamine resin, alkyd resin, etc. are used. can do. These may be used alone or in combination of two or more.

  Moreover, a thermosetting resin is not specifically limited, A phenol resin composition, an epoxy resin composition, a urethane resin composition, a melamine resin composition, an alkyd resin composition, etc. can be used. These may be used alone or in combination of two or more.

<Conductive filler>
The conductive adhesive film of the present invention contains a conductive filler. The conductive filler is not particularly limited, and for example, a metal filler, a metal-coated resin filler, a carbon filler, and a mixture thereof can be used. Examples of the metal filler include copper powder, silver powder, nickel powder, silver-coated copper powder, gold-coated copper powder, silver-coated nickel powder, and gold-coated nickel powder. These metal powders are electrolyzed, atomized, and reduced. Can be created by law.

  In particular, the average particle diameter of the conductive filler is preferably 3 to 50 μm in order to easily obtain contact between the fillers. In addition, examples of the shape of the conductive filler include a spherical shape, a flake shape, a dendritic shape, and a fibrous shape.

  The conductive filler is preferably at least one selected from the group consisting of silver powder, silver-coated copper powder, and copper powder from the viewpoints of connection resistance and cost.

  It is preferable that the said conductive filler is contained in the ratio of 40-90 mass% with respect to the whole quantity of a conductive adhesive composition.

  For conductive adhesive films, silane coupling agents, antioxidants, pigments, dyes, tackifying resins, plasticizers, UV absorbers, antifoaming agents, leveling regulators are used as long as solder reflow resistance is not deteriorated. , Fillers, flame retardants, etc. may be added.

<Inorganic particles>
The inorganic particles contained in the conductive adhesive composition of the present invention have a cumulative frequency of 40% or less at a particle diameter of 5 μm measured using a laser diffraction particle size distribution analyzer. When the cumulative frequency at a particle diameter of 5 μm exceeds 40%, inorganic particles having a small particle diameter increase, so that it is difficult to fix the conductive filler between the inorganic particles, and the thermoplastic resin (or due to heat during reflow) (or This is because the connection between the conductive fillers may be disconnected due to the flow of the thermosetting resin), and thus the connection resistance may not be sufficiently reduced after reflow.

  Further, the inorganic particles may have a cumulative frequency of 80% or less at a particle diameter of 10 μm measured using a laser diffraction particle size distribution measuring apparatus. When the cumulative frequency at a particle diameter of 10 μm exceeds 80%, inorganic particles having a small particle diameter increase, and as described above, due to the flow of the thermoplastic resin (or thermosetting resin) due to heat during reflow, This is because the connection between the conductive fillers may be cut off, and thus the connection resistance may not be sufficiently reduced after reflow.

  The cumulative frequency at a particle size of 5 μm and 10 μm can be measured with a commercially available laser diffraction particle size distribution analyzer (for example, trade name: MICROTRAC S3500 manufactured by Microtrac).

  The inorganic particles are not particularly limited, but silica, alumina, aluminum hydroxide, magnesium hydroxide, barium sulfate, calcium carbonate, titanium oxide, zinc oxide, antimony trioxide, magnesium oxide, talc, montmorolinite, kaolin, bentonite Inorganic compounds such as Among these, it is preferable to use silica particles from the viewpoint of cost.

  Moreover, it is preferable that an inorganic particle is contained in the ratio of 10-30 mass% with respect to the whole quantity of a conductive adhesive composition, and 10-25 mass% is more preferable. If the content of the inorganic particles is less than 10% by mass, the connection stability after reflow becomes unstable. If the content exceeds 30% by mass, the amount of the inorganic particles increases, so that the peelable substrate and the like. This is because it may be difficult to apply the conductive adhesive composition to the surface of the film or the conductivity of the conductive adhesive composition may be reduced.

  The average particle diameter of the inorganic particles is preferably 1 to 15 μm, and more preferably 2 to 10 μm. When the average particle diameter is less than 1 μm, the film forming property of the conductive adhesive composition is lowered, and it becomes difficult to control the thickness. On the other hand, if the average particle diameter exceeds 15 μm, it is difficult to reduce the thickness.

<Curing agent>
The conductive adhesive film of the present invention may contain a curing agent as necessary. It does not specifically limit as said hardening | curing agent, For example, conventionally well-known hardening | curing agents, such as an isocyanate compound, a block isocyanate compound, a carbodiimide compound, an imidazole compound, an oxazoline compound, a melamine, a metal complex type crosslinking agent, can be used.

  These curing agents are effective in improving heat resistance and the like if they are in appropriate amounts. However, if the amount of the curing agent used is too large, it may cause a decrease in flexibility and adhesion. For this reason, it is preferable that the usage-amount of a hardening | curing agent shall be 0.1-200 mass parts or less with respect to 100 mass parts of resin components of a thermosetting resin, and it is more preferable to set it as 0.2-100 mass parts. More preferably, it is 0.2-50 mass parts.

  The conductive adhesive film of the present invention may be used in combination with an imidazole-based curing accelerator in order to accelerate the curing of the curing agent. The curing accelerator is not particularly limited, and examples thereof include 2-phenyl-4,5-dihydroxymethylimidazole, 2-heptadecylimidazole, 2,4-diamino-6- (2′-undecylimidazolyl) ethyl-S. -Triazine, 1-cyanoethyl-2-phenylimidazole, 2-phenylimidazole, 5-cyano-2-phenylimidazole, 2,4-diamino-6- [2'methylimidazolyl- (1 ')]-ethyl-S- Imidazoles such as triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-methylimidazole isocyanuric acid adduct, 1-cyanoethyl-2-phenyl-4,5-di (2-cyanoethoxy) methylimidazole, etc. An alkyl group, ethylcyano group, hydroxyl group, azine, etc. are attached to the ring. Compounds, and the like. These curing accelerators are effective in improving heat resistance and the like if they are in appropriate amounts. However, when there is too much usage-amount of a hardening accelerator, the fall of a softness | flexibility or adhesiveness may be caused. For this reason, the usage-amount of a hardening accelerator has preferable 0.01-1.0 mass part with respect to 100 mass parts of resin components of a thermosetting resin.

<Conductive adhesive film>
As shown in FIG. 1, the conductive adhesive film 1 of the present invention coats the peelable substrate 2 (release film) and the surface of the peelable substrate 2 with the above-described conductive adhesive composition. The conductive adhesive layer 4 formed by this is provided. The coating method is not particularly limited, and known coating equipment represented by die coating, lip coating, comma coating and the like can be used. In addition, what is necessary is just to set suitably the conditions at the time of coating the mold release base material 2 with a conductive adhesive composition.

  The releasable substrate 2 is formed by applying a silicon-based or non-silicon-based release agent on the surface on which the conductive adhesive layer 4 is formed on a base film such as polyethylene terephthalate or polyethylene naphthalate. Can be used. Note that the thickness of the releasable substrate 2 is not particularly limited, and is appropriately determined in consideration of ease of use.

  Moreover, it is preferable that the thickness of the electroconductive adhesive layer 4 is 15-100 micrometers. If the thickness is less than 15 μm, the embedding property becomes insufficient, and sufficient connection with the ground circuit may not be obtained. If the thickness is more than 100 μm, it is disadvantageous in cost and cannot meet the demand for thinning. By setting to such a thickness, when the substrate has irregularities, it flows appropriately, so that it can be deformed into a shape that fills the recess and can be bonded with good adhesion.

<Anisotropic conductive adhesive layer, isotropic conductive adhesive layer>
The conductive adhesive composition of the present invention can be used as an anisotropic conductive adhesive layer or an isotropic conductive adhesive layer depending on the purpose of use. For example, when the conductive adhesive composition of the present invention is used as a conductive adhesive film for bonding to a reinforcing plate, it can be used as an isotropic conductive adhesive layer.

  In the case of an electromagnetic wave shielding film having a metal layer, it can be used as an isotropic conductive adhesive layer or an anisotropic conductive adhesive layer, but it should be used as an anisotropic conductive adhesive layer. Is preferred.

  In addition, these can be made into any adhesive bond layer with the compounding quantity of an electroconductive filler. In order to obtain an anisotropic conductive adhesive layer, the blending amount of the conductive filler is preferably 5% by mass or more and less than 40% by mass in the total solid content of the conductive adhesive composition. In order to obtain an isotropic conductive adhesive layer, the conductive filler is preferably 40% by mass or more and 90% by mass or less in the total solid content of the conductive adhesive composition.

  In addition, the conductive adhesive film using the conductive adhesive of the present invention is excellent in adhesion to the printed wiring board, and the adhesion to the printed wiring board is to a resin board such as a polyimide film. And adhesion to metal materials such as gold-plated copper foil and conductive reinforcing plate are included.

<Electromagnetic wave shielding film>
As shown in FIG. 2, the electromagnetic wave shielding film 20 using the conductive adhesive composition of the present invention includes a conductive adhesive layer 4 and a protective layer 13 provided on the surface of the conductive adhesive layer 4. Have. The protective layer 13 is not particularly limited as long as it has insulating properties (that is, a layer formed of an insulating resin composition), and a known layer can be used.

  As the insulating resin composition, for example, a thermoplastic resin composition, a thermosetting resin composition, an active energy ray curable composition, or the like can be used. The thermoplastic resin composition is not particularly limited, but polyamide resin, polyimide resin, acrylic resin, polyester resin, urethane resin, polycarbonate resin, polyolefin resin, styrene resin composition, vinyl acetate A resin composition or the like can be used. The thermosetting resin composition is not particularly limited, but a phenolic resin composition, an epoxy resin composition, a urethane resin composition, a melamine resin composition, an alkyd resin composition, or the like is used. Can do. The active energy ray-curable composition is not particularly limited, and for example, a polymerizable compound having at least two (meth) acryloyloxy groups in the molecule can be used.

  Further, as the protective layer 13, the resin component (excluding the conductive filler) used for the conductive adhesive layer 4 described above may be used. Further, the protective layer 13 may be a laminate of two or more layers having different materials or physical properties such as hardness or elastic modulus.

  Further, the thickness of the protective layer 13 is not particularly limited and can be appropriately set as necessary, but is 1 μm or more (preferably 4 μm or more), 20 μm or less (preferably 10 μm or less, more preferably 5 μm or less). It can be.

  Further, the protective layer 13 may include a curing accelerator, a tackifier, an antioxidant, a pigment, a dye, a plasticizer, an ultraviolet absorber, an antifoaming agent, a leveling agent, a filler, a flame retardant, and a viscosity as necessary. A regulator, an antiblocking agent, etc. may be included.

  Moreover, this electromagnetic wave shielding film 20 forms the protective layer 13 by coating the resin composition for protective layers on one side of a peelable film, for example, and drying, Next, on the protective layer 13 There is a method of forming the conductive adhesive layer 4 by coating the above-mentioned conductive adhesive composition and drying it.

  As a method for forming the conductive adhesive layer 4 and the protective layer 13, a conventionally known coating method such as a gravure coating method, a kiss coating method, a die coating method, a lip coating method, a comma coating method, a blade coating method, or a roll coating method. A knife coating method, a spray coating method, a bar coating method, a spin coating method, a dip coating method, or the like can be used.

  The electromagnetic wave shielding film 20 can be adhered on the printed wiring board by hot pressing. The conductive adhesive layer 4 of the electromagnetic wave shielding film 20 is softened by heating, and flows into a ground portion provided on the printed wiring board by pressurization. Thereby, the ground circuit and the conductive adhesive are electrically connected, and the shielding effect can be enhanced.

  Moreover, this electromagnetic wave shielding film 20 can be used for the shield printed wiring board 30 shown in FIG. 2, for example. The shield printed wiring board 30 includes a printed wiring board 40 and an electromagnetic wave shielding film 20.

  The printed wiring board 40 includes a base substrate 41, a printed circuit (ground circuit) 42 formed on the base substrate 41, and an insulating adhesive layer 43 provided on the base substrate 41 adjacent to the printed circuit 42. And an insulating cover lay 44 provided to cover the insulating adhesive layer 43. The insulating adhesive layer 43 and the cover lay 44 constitute an insulating layer of the printed wiring board 40, and the insulating adhesive layer 43 and the cover lay 44 have openings for exposing a part of the printed circuit 42. A portion 45 is formed.

  The base substrate 41, the insulating adhesive layer 43, and the coverlay 44 are not particularly limited, and can be, for example, a resin film. In this case, it can be formed of a resin such as polypropylene, cross-linked polyethylene, polyester, polybenzimidazole, polyimide, polyimide amide, polyether imide, or polyphenylene sulfide. The printed circuit 42 can be, for example, a copper wiring pattern formed on the base substrate 41.

  Next, a method for manufacturing the shield printed wiring board 30 will be described. The electromagnetic wave shielding film 20 is placed on the printed wiring board 40 and pressurized while being heated by a press. A part of the conductive adhesive layer 4 softened by heating flows into the opening 45 by pressurization. Thereby, the electromagnetic wave shielding film 20 is affixed on the printed wiring board 40 through the conductive adhesive layer 4.

<Electromagnetic wave shielding film having a metal layer>
Moreover, the electromagnetic wave shielding film of the present invention may have a metal layer. By having a metal layer, more excellent electromagnetic shielding performance can be obtained.

  More specifically, for example, as shown in FIG. 3, the electromagnetic wave shielding film 21 using the conductive adhesive composition of the present invention includes a metal layer (shield layer) 14 and a first surface of the metal layer 14. The conductive adhesive layer 4 provided on the side and the protective layer 13 provided on the second surface side opposite to the first surface of the metal layer 14 are provided.

  Examples of the metal material for forming the metal layer 14 include nickel, copper, silver, tin, gold, palladium, aluminum, chromium, titanium, zinc, and an alloy containing any one or more of these materials. It can be selected as appropriate according to the required electromagnetic shielding effect and repeated bending / sliding resistance.

  Moreover, the thickness of the metal layer 14 is not specifically limited, For example, it can set to 0.1 micrometer-8 micrometers. In addition, as a formation method of the metal layer 14, there are an electrolytic plating method, an electroless plating method, a sputtering method, an electron beam evaporation method, a vacuum evaporation method, a CVD method, a metal organic, and the like. Further, the metal layer 14 may be a metal foil or metal nanoparticles.

  Moreover, this electromagnetic wave shielding film 21 can be used for the shield printed wiring board 31 shown in FIG. 3, for example. The shield printed wiring board 31 includes the above-described printed wiring board 40 and the electromagnetic wave shielding film 21.

  Next, the manufacturing method of the shield printed wiring board 31 is demonstrated. The electromagnetic wave shielding film 21 is placed on the printed wiring board 40 and pressed while being heated by a press machine. A part of the adhesive layer 4 softened by heating flows into the opening 45 by pressurization. As a result, the electromagnetic wave shielding film 21 is attached to the printed wiring board 40 via the adhesive layer 4, and the metal layer 14 and the printed circuit 42 of the printed wiring board 40 are connected via the conductive adhesive. The metal layer 14 and the printed circuit 42 are connected.

<Shield printed wiring board with reinforcing plate>
Moreover, the electroconductive adhesive composition of this invention can be used for a shield printed wiring board provided with a reinforcement board. More specifically, for example, it can be used for the shield printed wiring board 32 shown in FIG. The shield printed wiring board 32 includes a printed wiring board 47, a conductive adhesive layer 4, and a conductive reinforcing plate 15. The printed wiring board 47 and the conductive reinforcing plate 15 are bonded and electrically connected by the conductive adhesive layer 4 of the present invention.

  In the printed wiring board 47, a plating layer (for example, a gold plating layer) 46 is provided on a part of the surface of the printed circuit 42, and the plating layer 46 is exposed from the opening 45.

  Similar to the shield printed wiring board 30 shown in FIG. 2 described above, the printed circuit 42 and the conductive reinforcing plate 15 are not provided through the conductive adhesive layer 4 flowing into the opening 45 without providing the plating layer 46. May be directly connected to each other.

  In order to prevent the conductive reinforcing plate 15 from being damaged in the printed wiring board on which the electronic component is mounted, the portion where the electronic component is mounted is distorted due to the bending of the printed wiring board. Provided. As the conductive reinforcing plate 15, a conductive metal plate or the like can be used. For example, a stainless plate, an iron plate, a copper plate, an aluminum plate, or the like can be used. Among these, it is more preferable to use a stainless steel plate. By using a stainless steel plate, it has sufficient strength to support electronic components even with a thin plate thickness.

  Moreover, although the thickness of the electroconductive reinforcement board 15 is not specifically limited, 0.025-2 mm is preferable and 0.1-0.5 mm is more preferable. If the thickness of the conductive reinforcing plate 15 is within this range, the circuit board to which the conductive reinforcing plate 15 is bonded can be reasonably built into a small device, and the strength sufficient to support the mounted electronic component. Have Further, a metal layer such as Ni or Au may be formed on the surface of the conductive reinforcing plate 15 by plating or the like. The surface of the conductive reinforcing plate 15 may be provided with an uneven shape by sandblasting, etching, or the like.

  In addition, as an electronic component here, chip components, such as a resistor and a capacitor | condenser, can be mentioned besides a connector and IC.

  Next, a method for manufacturing the shield printed wiring board 32 will be described. First, a conductive adhesive film to be the conductive adhesive layer 4 is placed on the conductive reinforcing plate 15 and is heated and pressed with a press to produce a conductive adhesive film with a reinforcing plate. Next, a conductive adhesive film with a reinforcing plate is placed on the printed wiring board 47 and pressed while being heated by a press. A part of the adhesive layer 4 softened by heating flows into the opening 45 by pressurization. As a result, the conductive reinforcing plate 15 is attached to the printed wiring board 47 via the adhesive layer 4, and the conductive reinforcing plate 15 and the printed circuit 42 of the printed wiring board 47 are connected via the conductive adhesive. As a result, the conductive reinforcing plate 15 and the printed circuit 42 are brought into conduction. Therefore, the electromagnetic wave shielding ability by the conductive reinforcing plate 15 can be obtained.

  In addition, as a to-be-adhered body which can stick the electroconductive adhesive film formed with the electroconductive adhesive composition of this invention, the flexible wiring board which receives a bending repeatedly can be mentioned as a representative example, for example. Needless to say, the present invention can also be applied to rigid printed wiring boards. Furthermore, the present invention can be applied not only to a single-side shielded wiring board but also to a double-sided shielded wiring board.

  Hereinafter, the present invention will be described based on examples. In addition, this invention is not limited to these Examples, These Examples can be changed and changed based on the meaning of this invention, and they are not excluded from the scope of the invention. Absent.

(Examples 1-3, Comparative Examples 1-3)
<Preparation of conductive adhesive composition>
The conductive adhesive compositions of Examples 1 to 3 and Comparative Examples 1 to 5 having the composition (% by mass) shown in Table 1 were produced by the following production method.

  The following materials constituting the resin composition shown in Table 1 are mixed with silver-coated copper powder that is a conductive filler and spherical silica particles that are inorganic particles to produce a paste-like conductive adhesive composition. did.

Thermoplastic resin: Polyamide resin having a complex viscosity at 150 ° C. of 8.2 × 10 ³ Pa · s and a terminal being an anhydrous carboxyl group Thermosetting resin: Glycidylamine epoxy resin (trade name: jER604, manufactured by Mitsubishi Chemical) )
Silane coupling agent: Shin-Etsu Silicone, trade name: KBM-602
Cyanate-based curing agent: Lonza Japan, trade name: PT-30
Imidazole-based curing agent: Shikoku Chemicals, trade name: 2MZ-H

<Measurement of cumulative frequency of inorganic particles>
Moreover, the cumulative frequency of the inorganic particles contained in the conductive adhesive compositions of Examples 1 to 3 and Comparative Examples 1 to 5 was measured. More specifically, using a laser diffraction particle size distribution analyzer (trade name: MICROTRAC S3500, manufactured by Microtrac Co., Ltd.), pure water (refractive index = 1.33) as a solvent, refractive index of inorganic particles = 1.51 was measured in the volume distribution mode. The results are shown in Table 1.

<Manufacture of electromagnetic shielding film>
Next, an electromagnetic wave shielding film was produced using the above-mentioned conductive adhesive composition. More specifically, a PET film having a thickness of 60 μm and a release treatment applied to the surface was used as the support substrate. Next, a protective layer composition (solid content 30% by mass) consisting of bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Co., Ltd., jER1256) and methyl ethyl ketone is applied onto the support substrate and dried by heating. Thus, a supporting substrate with a protective layer having a thickness of 5 μm was produced.

  Next, a shield layer was formed on the surface of the protective layer. More specifically, a rolled copper foil having a thickness of 2 μm was bonded to the protective layer.

  Subsequently, the conductive adhesive composition produced in Examples 1 to 3 and Comparative Examples 1 to 5 was applied to the surface of the shield layer to form an adhesive layer having a thickness of 5 μm, and an electromagnetic shielding film was produced. did.

<Preparation of shield printed wiring board>
Next, the produced electromagnetic wave shielding film and the printed wiring board are overlapped so that the adhesive layer of the electromagnetic wave shielding film and the printed wiring board are opposed to each other, and 1 is used at 170 ° C. and 3.0 MPa using a press machine. After heat-pressing for 5 minutes, heat-pressing was performed for 3 minutes at the same temperature and pressure, and the supporting base material was peeled from the protective layer to produce a shield printed wiring board.

  The printed wiring board has two copper foil patterns extending parallel to each other at an interval, and has an insulating layer (thickness: 25 μm) made of polyimide, covering the copper foil pattern. An opening (diameter: 0.8 mm) for exposing the copper foil pattern was provided. Moreover, the adhesive layer of the electromagnetic wave shielding film and the printed wiring board were overlapped so that the opening was completely covered with the electromagnetic wave shielding film.

  In addition, the printed wiring board which the edge part of the copper foil pattern was not covered with the insulating layer and the edge part of the copper foil pattern was exposed was used.

<Reflow resistance evaluation>
Next, the reflow resistance of the produced shielded printed wiring board was evaluated. As a reflow condition, lead-free solder was assumed, and a temperature profile was set such that the shield film on the shield printed wiring board was exposed to 265 ° C. for 1 second.

  And after exposing each shield printed wiring board of produced Examples 1-3 and Comparative Examples 1-5 1-5 times under the temperature conditions of the said profile, as shown in FIG. The electrical resistance value between the two copper foil patterns 51 formed in 50 was measured with an ohmmeter 52, and the connectivity between the copper foil pattern 51 and the electromagnetic wave shielding film 53 was evaluated.

  And the said reflow process was performed once, twice, three times, and five times, and the change of the resistance value after each reflow was evaluated. The results are shown in Table 2.

  As shown in Table 2, an example using a conductive adhesive composition containing inorganic particles having an accumulation frequency of 40% or less at a particle size of 5 μm (or an accumulation frequency of 80% or less at a particle size of 10 μm). In comparison with Comparative Examples 1 to 3, increase in connection resistance value after the reflow process is effectively suppressed, and it can be said that 1 to 3 can ensure excellent conductivity even after reflow.

  As described above, the present invention is suitable for a conductive adhesive composition used for a printed wiring board.

DESCRIPTION OF SYMBOLS 1 Conductive adhesive film 2 Peelable base material 4 Conductive adhesive layer 13 Protective layer 14 Metal layer
DESCRIPTION OF SYMBOLS 15 Conductive reinforcement board 20 Electromagnetic wave shield film 21 Electromagnetic wave shield film 30 Shield printed wiring board 31 Shield printed wiring board 32 Shield printed wiring board 40 Printed wiring board 41 Base substrate 42 Printed circuit 43 Insulating adhesive layer 44 Coverlay 45 Opening 46 Plating layer 47 Printed wiring board

Claims (5)

A conductive adhesive composition containing at least one of a thermoplastic resin and a thermosetting resin, a conductive filler, and inorganic particles,
The inorganic particles have a cumulative frequency of 40% or less at a particle size of 5 μm measured using a laser diffraction particle size distribution analyzer,
The conductive adhesive composition, wherein a blending amount of the inorganic particles with respect to the entire conductive adhesive composition is 10 to 30% by mass. A conductive adhesive composition containing at least one of a thermoplastic resin and a thermosetting resin, a conductive filler, and inorganic particles,
The inorganic particles have a cumulative frequency of 80% or less at a particle diameter of 10 μm measured using a laser diffraction particle size distribution analyzer,
The conductive adhesive composition, wherein a blending amount of the inorganic particles with respect to the entire conductive adhesive composition is 10 to 30% by mass.   A conductive material comprising: a peelable substrate; and a conductive adhesive layer provided on the surface of the peelable substrate and comprising the conductive adhesive composition according to claim 1 or 2. Adhesive film.   An electromagnetic wave shield comprising: an insulating protective layer; and a conductive adhesive layer provided on a surface of the protective layer and made of the conductive adhesive composition according to claim 1. the film. A base substrate on which a printed circuit is formed, a conductive adhesive layer made of the conductive adhesive composition according to claim 1 or 2, and a conductive reinforcing plate.
The printed wiring board, wherein the base substrate and the conductive reinforcing plate are electrically connected by the conductive adhesive layer.

Images