JP6428716B2 - Conductive adhesives, joints and joints - Google Patents

Description

  The present invention relates to a conductive adhesive including a conductive metal powder, a thermosetting resin, a curing agent, an organic acid and rubber particles, a joined body, and a joint.

  In recent years, a conductive adhesive has been used for connection between an electrode of a solar cell and a wiring member. This is because the conductive adhesive can bond metals at a temperature lower than the melting point of the conductive metal powder contained.

  Generally, a conductive metal powder, a thermosetting resin, a curing agent, a curing accelerator, and the like are mixed with the conductive adhesive. Conventionally, as seen in Patent Document 1, silver powder has been used as a conductive metal powder of a conductive adhesive. In Patent Document 2, scaly or spherical silver powder is used as the conductive metal powder of the conductive adhesive.

  In recent years, conductive metal powder instead of silver powder has also been adopted. Patent Document 3 discloses a conductive adhesive using copper particles, nickel particles, copper plating particles, nickel plating particles and the like as the conductive metal powder.

JP 2012-067274 A JP 2003-147306 A JP 2011-061241 A

  However, conductive adhesives using conductive metal powder having a spherical particle shape instead of scale-like conductive metal powder are printed on a plate-shaped member or the like and heated. Powder and liquid components ooze out. Generation | occurrence | production of the bleeding had the problem of leading to the electrical conductivity defect of the location which adhere | attached the conductive adhesive. In addition, for example, when the conductive adhesive printed on the solar panel bleeds, there is a problem that power generation efficiency decreases because the light receiving area of the solar panel decreases.

  The present invention solves such a problem. On the premise of a conductive adhesive that bonds metals at a temperature lower than the melting point of the conductive metal powder, the conductive adhesive that suppresses bleeding of the conductive adhesive, the conductive An object is to provide a joined body and a joint made of an adhesive.

The technical means of the present invention taken in order to solve the above-mentioned problems are as follows.
(1) A conductive adhesive containing conductive metal powder in an amount of 85% by weight to 92% by weight with the balance being a binder, the binder being a thermosetting resin, a curing agent, an organic acid, and 100 nm to 300 nm. Including rubber particles having the following particle diameter, the thermosetting resin is an epoxy resin, the curing agent is an acid anhydride, and the ratio of the rubber particles is 8% by weight or more and 25% by weight with respect to 100% by weight of the binder. A conductive adhesive, characterized by being no more than wt%.

  (2) The conductive adhesive according to (1), wherein the rubber particles are made of at least one of acrylic rubber, polybutadiene, and silicone.

  (3) The conductive metal powder is one or more of Sn, Ag, Cu, Au, Ni, Bi, Sb, Pd alone or an alloy made of a spherical metal selected from these metal powder groups. The conductive adhesive according to (1) above, comprising a single substance or / and an alloy.

( 4 ) The conductive adhesive as described in ( 1 ) above, which is an epoxy resin having an aliphatic skeleton and imparting flexibility as an epoxy resin.

( 5 ) The conductive adhesive according to (1) above, wherein an organic acid is added in an amount of 2 to 10% by weight.

( 6) The conductive adhesive according to ( 1 ), wherein the acid anhydride is acetic anhydride, propionic anhydride, succinic anhydride, maleic anhydride, or phthalic anhydride.

( 7 ) A bonded body characterized by being adhered by the conductive adhesive described in (1) to ( 6 ) above.

( 8 ) A joint using the conductive adhesive described in (1) to ( 6 ) above.

  The conductive adhesive according to the present invention can suppress bleeding. By suppressing bleeding, a conductive adhesive having high conductivity can be realized. In addition, when the conductive adhesive according to the present invention is printed on a solar panel, it is possible to prevent reduction of the light receiving area of the solar panel due to bleeding, so that it is possible to maintain power generation efficiency and obtain stable generated power it can.

<Composition example of conductive adhesive of this embodiment>
The conductive adhesive of the present invention comprises a conductive metal powder and a binder. The binder includes a thermosetting resin, a curing agent, an organic acid, and rubber particles.

  The curable resin includes a resin that is cured by heat, light, ultraviolet rays, or the like. Epoxy resins, phenolic resins, polyimide resins, silicone resins, polyurethane resins, unsaturated polyester resins, etc. can be considered as curable resins. However, resins that cure with light and ultraviolet rays are resin at the bottom of the component when mounted on electronic components. Can not be cured, thermosetting resin is used. The thermosetting resin is selected from an epoxy resin, a phenol resin (novolak), and the like, and an epoxy resin is an optimal resin.

  Bisphenol type epoxy resin is selected as the epoxy resin, and bisphenol type is bisphenol A type, bisphenol AP type, bisphenol AF type, bisphenol B type, bisphenol BP type, bisphenol C type, bisphenol E type, bisphenol F type, bisphenol G type. Type, bisphenol M type, bisphenol S type, bisphenol P type, bisphenol PH type, bisphenol TMC type, bisphenol Z type and the like.

  Epoxy resins are said to be brittle and have poor drop impact properties, while having good electrical and mechanical bonding properties. This is because when the epoxy resin is cured, peeling occurs at the electrode interface and cracks occur.

  For example, when a flexible resin having an aliphatic skeleton added to an epoxy resin is used, both flexibility and toughness are enhanced, and cracks due to surface peeling can be prevented.

  A curing agent is used to cure the thermosetting resin. An amine or an acid anhydride can be used as the curing agent. Examples of the amine include imidazole, a compound having an imidazole ring, and dicyandiamide. Examples of the acid anhydride include acetic anhydride, propionic anhydride, succinic anhydride, maleic anhydride, and phthalic anhydride.

  In order to cure the thermosetting resin, a curing accelerator may be added. Examples of the curing accelerator include phenol compounds, tertiary amines, quaternary ammonium salts, quaternary phosphonium salts, imidazoles, organic acid metal salts, Lewis acids, and the like.

  As the conductive metal powder, Sn, Ag, Cu, Au, Ni, Bi, Sb, Pd alone or an alloy made of a metal selected from these metal powder groups may be used alone or in combination of two or more. An alloy is mentioned. Preferably, Sn alone or a mixture or alloy containing Sn is used. In order to realize a low-cost conductive adhesive, metal powder excluding Ag and Au is preferably used, but may contain these.

  As the rubber particles, it is preferable to use at least one of acrylic rubber, polybutadiene, and silicone.

  The organic acid may be a general organic acid. Preferably, it is a C8 or less low molecular organic acid, and glutaric acid is used in this embodiment. The organic acid is preferably added in an amount of 2 to 10% by weight.

  Hereinafter, although the specific example at the time of applying this invention to a conductive adhesive in an Example is shown, this invention is not limited to the following specific examples. Moreover, the number without a unit in the following table | surface shows weight%.

  In order to ascertain the combination of the conductive metal powder and the binder (thermosetting resin, curing agent, rubber particles, organic acid, etc.) and the blending amount thereof, the following tests were conducted. Both Examples and Comparative Examples are composed of conductive metal powder, thermosetting resin, curing agent, rubber particles and organic acid.

[Test 1: Verification of rubber particles]
Binders were prepared at the composition ratios shown in Table 1. Example 1 contained Kane Ace (registered trademark) MX-267 (manufactured by Kaneka Corporation). This is a mixture of polybutadiene having a rubber particle size of 200 nm and a bisphenol F type epoxy resin which is a flexible resin. The rubber particles used in Example 1 are referred to as rubber particles A. Bisphenol F-type epoxy resin was further added, and the mixture was formulated so that the rubber particles A were 11% by weight with respect to 100% by weight of the binder. Glutaric acid was used as the organic acid. As the acid anhydride as an example of the curing agent, phthalic anhydride was used. The thixotropic agent is added to maintain the shape of the circuit board coated with the conductive adhesive, and the thixotropic agent may be a compound that imparts thixotropic properties.

  The conductive adhesive of Example 1 was made by mixing 12% by weight of the binder and 88% by weight of Sn as a conductive metal powder. The conductive adhesive of Comparative Example 1 was prepared by mixing 12% by weight of the binder shown in Comparative Example 1 and 88% by weight of Sn having a spherical particle shape as the conductive metal powder. The conductive adhesive of the reference example was made by mixing 12% by weight of the binder shown in the reference example and 88% by weight of flaky Ag as the conductive metal powder.

  Each of the mixed conductive adhesives was printed on a glass plate so as to have a length of 11.5 mm, a width of 1.5 mm, and a thickness of 0.12 mm.

  In the table, ○ indicates that the blur was suppressed, and × indicates that the blur occurred. The conductive adhesives of Example 1 and Reference Example suppressed bleeding. In the conductive adhesive of Comparative Example 1, bleeding occurred. The reason why the bleeding was suppressed by the conductive adhesive of the reference example is considered to be that the Ag particles contained in the conductive adhesive of the reference example have a scaly shape.

  Bleeding was suppressed with the conductive adhesive of Example 1, and bleeding was generated with the conductive adhesive of Comparative Example 1, so that the conductive metal powder containing Sn with a spherical particle shape also contains rubber particles A. In other words, it can be said that blurring is suppressed.

Then, the binder was prepared with the composition ratio shown in Table 2.
The conductive adhesives of Examples 2 to 4 are composed of 88% by weight of Sn and 12% by weight of binder as conductive metal powder with respect to 100% by weight of the conductive adhesive. Rubber particles A were used for the rubber particles of Example 2. A bisphenol F type epoxy resin was used as the epoxy resin. In Example 3, Kane Ace (registered trademark) MX-136 (manufactured by Kaneka Corporation) was contained. This is a mixture of polybutadiene having a rubber particle size of 100 nm and bisphenol F type epoxy resin. The rubber particles used in Example 3 are referred to as rubber particles B. Bisphenol F-type epoxy resin was further added, and the mixture was formulated so that the rubber particles B were 20% by weight with respect to 100% by weight of the binder. In Example 4, Kane Ace (registered trademark) MX-965 (manufactured by Kaneka Corporation) was contained. This is a mixture of silicone having a rubber particle size of 300 nm and a bisphenol F type epoxy resin. The rubber particles used in Example 4 are referred to as rubber particles C. Bisphenol F-type epoxy resin was further added, and the rubber particles C were blended at 15% with respect to 100% by weight of the binder. Phthalic anhydride was used for the acid anhydrides of Examples 2 to 4 used in Examples 2 to 4, and glutaric acid was used for the organic acids.

  The conductive adhesives of Examples 5 and 6 are composed of Sn 88% by weight as the conductive metal powder and 12% by weight of the binder with respect to 100% by weight of the conductive adhesive. As the epoxy resin used in Examples 5 and 6, a bisphenol F type epoxy resin and a trifunctional type epoxy resin were mixed and used. Phthalic anhydride was used for the acid anhydrides of Examples 5 and 6, glutaric acid was used for the organic acid, and carbon nanotubes were used for the thixotropic agent.

  The conductive adhesive of Example 7 is composed of Sn 88% by weight as a conductive metal powder and 12% by weight of a binder with respect to 100% by weight of the conductive adhesive. Example 7 contained Acreset (registered trademark) BPA-328 (manufactured by Nippon Shokubai Co., Ltd.). This is a mixture of an acrylic rubber having a rubber particle size of 300 nm and a bisphenol A type epoxy resin. The rubber particles used in Example 7 are referred to as rubber particles D. Phthalic anhydride was used for the acid anhydride of Example 7, and glutaric acid was used for the organic acid.

  The conductive adhesive of Comparative Example 2 is composed of Sn 88% by weight as a conductive metal powder and 12% by weight of a binder with respect to 100% by weight of the conductive adhesive. As the epoxy resin used in Comparative Example 2, a bisphenol F type epoxy resin and a trifunctional type epoxy resin were mixed and used. As the acid anhydride of Comparative Example 2, phthalic anhydride was used, glutaric acid was used as the organic acid, and carbon nanotubes were used as the thixotropic agent.

  The conductive adhesive of Comparative Example 3 is composed of Sn 88% by weight as a conductive metal powder and 12% by weight of a binder with respect to 100% by weight of the conductive adhesive. The epoxy resin used in Comparative Example 3 was a bisphenol A type epoxy resin. Rubber particles D were used for the rubber particles of Comparative Example 3. Phthalic anhydride was used for the acid anhydride of Comparative Example 3, and glutaric acid was used for the organic acid.

  Each of the mixed conductive adhesives was printed on a glass plate so as to have a length of 11.5 mm, a width of 1.5 mm, and a thickness of 0.12 mm.

  In the table, ○ indicates that the blur was suppressed, and × indicates that the blur occurred. In the conductive adhesives of Examples 2 to 7 containing 8% by weight or more and 25% by weight or less of rubber particles with respect to 100% by weight of the binder, bleeding was suppressed. On the other hand, in the conductive adhesives of Comparative Examples 2 and 3, the amount of rubber particles added was 1 and 5% by weight, respectively, and bleeding occurred.

  From this result, it can be said that the conductive adhesive containing 8% by weight or more and 25% by weight or less of rubber particles with respect to 100% by weight of the binder is effective in suppressing bleeding.

  In Examples 2, 4, and 7, polybutadiene, silicone, and acrylic rubber were used as the rubber particles, but different types of rubber particles were used. In each of Examples 2, 4, and 7, bleeding was suppressed. Therefore, it can be said that the difference in the type of rubber particles does not affect the result of suppressing bleeding, and any rubber particle can obtain a preferable result for suppressing bleeding. The rubber particles are preferably made of at least one of polybutadiene, silicone, and acrylic rubber.

  In Examples 2 to 4, rubber particles having different particle diameters of 200 nm, 100 nm, and 300 nm were used, respectively, but in each of Examples 2 to 4, bleeding was suppressed. From this, it can be said that all the rubber particles having a particle diameter of 100 nm or more and 300 nm or less have an effect of suppressing bleeding.

  In Examples 2 to 6 and Example 7, different epoxy resins were used, but since any example suppressed bleeding, the difference in the type of epoxy resin does not affect the bleeding suppression result. It can be said that any epoxy resin can obtain a preferable result with respect to suppression of bleeding.

Further, using the conductive adhesive of the example, printing was performed on the ceramic plate so that the length was 11.5 mm, the width was 1.5 mm, and the thickness was 0.12 mm, and after curing, the resistance value and the volume resistivity were printed. Asked. The volume resistivity is obtained by (resistance value × cross-sectional area / length). The unit is Ωcm. A conductive adhesive having a volume resistivity lower than 10 ⁻³ Ωcm was suitable for use, and the conductive adhesives of the examples satisfied this.

[Test 2: Selection of conductive metal powder]
In the examples so far, Sn powder has been used as the conductive metal powder, but for example, it is highly possible that bleeding is suppressed even in a metal simple substance or alloy other than Sn simple substance, such as Sn-1Cu alloy.

Therefore, Table 3 shows the results obtained with other than Sn powder. The ratio shown in Table 3 indicates the ratio of each composition with respect to 100% by weight of the binder. In Examples 8 to 11 and Reference Example 2 , 90% by weight of the conductive metal powder shown in Table 3 and 10% by weight of the binder having the composition shown in Table 3 were contained.

In Example 8 and Reference Example 2 , Cu powder was used as the conductive metal powder. In Example 11, Sn-3.4Ag-0.7Cu-2Bi-5Sb-0.04Ni (Alloy 1) was used as the conductive metal powder. Otherwise, conductive metal powder as shown in Table 3 was used. Phthalic anhydride was used for the acid anhydrides of Examples 8-11. For the amine of Reference Example 2 , imidazole was used. As the organic acid in Examples 8 to 11 and Reference Example 2 , glutaric acid was used.

The conductive adhesives of Examples 8 to 11 and Reference Example 2 suppressed bleeding. From this result, it was found that the conductive adhesive using a metal simple substance or alloy other than Sn simple substance as the conductive metal powder also suppresses bleeding by containing rubber particles. In addition, the conductive adhesive which mixed and used several types of conductive metal powder also suppressed the bleeding by containing a rubber particle.

  In particular, the conductive metal powder is Sn, Ag, Cu, Au, Ni, Bi, Sb, Pd alone or an alloy made of a metal selected from these metal powder groups. And an alloy. In order to obtain a conductive adhesive having a viscosity suitable for use, the conductive metal powder is preferably contained in an amount of 85% by weight to 92% by weight with respect to 100% by weight of the conductive adhesive. In addition, although the spherical metal simple substance or the alloy consisting of a spherical metal was used for the conductive metal powder of this Embodiment, the shape of a conductive metal powder is not restricted to a spherical shape. In addition to the spherical shape, the shape of the conductive metal powder may be, for example, a spheroid, an indefinite shape, a polygon, or a scale shape.

In Examples 1-11, phthalic anhydride was used as a curing agent, and in Reference Example 2 , imidazole was used as a curing agent, but this is not a limitation. As the curing agent, acid anhydrides other than phthalic anhydride and amines other than imidazole can be used, for example, acetic anhydride, propionic anhydride, succinic anhydride, maleic anhydride, compounds having an imidazole ring, and dicyandiamide are used. The conductive adhesive to suppress the bleeding by containing rubber particles. Moreover, the conductive adhesive which used the mixture of the acid anhydride and amine mentioned above as a hardening | curing agent also suppressed bleeding by containing a rubber particle.

From the above results, the following is understood.
A conductive adhesive containing 85% by weight or more and 92% by weight or less of a conductive metal powder, the balance being a binder, the binder having an epoxy resin, a curing agent, an organic acid, and a particle size of 100 nm or more and 300 nm or less The conductive adhesive containing rubber particles at a predetermined ratio can suppress bleeding.

  The rubber particle content is preferably 8% by weight to 25% by weight with respect to 100% by weight of the binder.

  The rubber particles preferably contain at least one of acrylic rubber, polybutadiene, and silicone.

  The present invention includes conductive metal powder, thermosetting resin, curing agent, organic acid, and rubber particles, and suppresses bleeding after heating. Therefore, the present invention is not limited to the above-described conductive adhesive, but can be applied to conductive adhesives including conductive metal powder, thermosetting resin, curing agent, and organic acid. Further, the present invention can also be applied to bonding where electrical conductivity is required for purposes other than bonding various electronic circuits to a circuit board. The solar panel printed with the conductive adhesive according to the present invention can combine low cost with improved power generation efficiency.

  The present invention is applied to component joining using a conductive adhesive, soldering using a solder paste containing a thermosetting resin, and a joined body or joint joined using this adhesive.

Claims (8)

A conductive adhesive containing conductive metal powder in an amount of 85% by weight or more and 92% by weight or less, the balance being a binder,
The binder includes a thermosetting resin, a curing agent, an organic acid, and rubber particles having a particle size of 100 nm to 300 nm,
The thermosetting resin is an epoxy resin, the curing agent is an acid anhydride,
The ratio of the said rubber particle is 8 to 25 weight% with respect to 100 weight% of the said binder. The conductive adhesive characterized by the above-mentioned. The conductive adhesive according to claim 1, wherein the rubber particles are made of at least one of acrylic rubber, polybutadiene, and silicone. The conductive metal powder is Sn, Ag, Cu, Au, Ni, Bi, Sb, Pd alone or an alloy made of a spherical metal selected from these metal powder groups, The conductive adhesive according to claim 1, comprising: / and an alloy. The conductive adhesive according to claim 1, wherein the epoxy resin is an epoxy resin having an aliphatic skeleton and imparting flexibility . 2. The conductive adhesive according to claim 1 , wherein the organic acid is added in an amount of 2 wt% to 10 wt% . 2. The conductive adhesive according to claim 1, wherein the acid anhydride is acetic anhydride, propionic anhydride, succinic anhydride, maleic anhydride, or phthalic anhydride . Bonded by the conductive adhesive according to claim 1.
A joined body characterized by that. The conductive adhesive according to claim 1 was used.
A joint characterized by that.