JPH07138549A - Conductive adhesive - Google Patents

Abstract

PURPOSE:To obtain a low-cost conductive adhesive suitable for producing a long-stable ceramic semiconductor device by mixing an epoxy resin with a copper powder plated with a conductive metal (e.g. silver) which has a lower activity than copper. CONSTITUTION:A copper powder made by the atomizing method is plated with 1-20wt.% silver. 75-90 pts.wt. the plated copper powder is mixed with 25-10 pts.wt. epoxy resin contg. 5-20wt.% curative, giving a conductive adhesive. A bisphenol F epoxy resin is suitable for obtaining a low-viscosity adhesive. For multifunctionality and low viscosity, a glycidylamine-type or a m- xylenediaminebased epoxy resin is suitable. The addition of a polyether-type reactive diluent gives the adhesive heat resistance. The adhesive has a desired conductivity, is long stable because of the reduced activity of the copper powder, is free from loss of solder due to silver, and can be used for bonding various electronic and electrical parts at low costs.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive adhesive used for mounting a ceramic semiconductor element mounted on an electric / electronic device on a substrate or mounting a lead wire on the ceramic semiconductor element.

[0002]

2. Description of the Related Art A conventional conductive adhesive of this type is mainly one in which silver powder Ag or carbon C is mixed with an epoxy resin or the like. These adhesives have good long-term conductivity stability, but in the former (Ag), in order to obtain high conductivity (low volume resistivity), the amount of silver powder mixed in is large and the cost is high. Silver migration is likely to occur, and the solder is apt to be eaten by the diffusion of silver during soldering, which makes soldering difficult. The latter (C) has no problem in cost as compared with the former, but since it is inferior in electrical conductivity, it cannot be used when high electrical conductivity is required.

On the other hand, conventionally, a conductive paint containing copper powder has been considered, and an adhesive of this type may also contain copper powder. Since the copper powder is low in cost and has a low volume resistivity, the above problems of silver powder and carbon can be solved.

However, since copper powder is more active than powders of silver powder, carbon, etc., it has the drawbacks of poor long-term stability in environmental resistance test (described later) and large time change.

Therefore, according to the present invention, under the above circumstances, the adhesive made of copper powder has the same level of conductivity (1 × 10 ⁻⁴ to 1 × 10 ⁻³ Ω-m) as the adhesive made of silver powder. However, it is an object to obtain a conductive adhesive that has good long-term properties (environmental resistance) (small change with time) and is sufficiently satisfactory in terms of cost.

[0006]

In order to solve the above problems, in the conductive adhesive of the present invention, 75 to 90 parts by weight of a conductive metal-plated copper powder having a lower activity than copper such as silver,
The composition is composed of 25 to 10 parts by weight of an epoxy resin containing 5 to 20% by weight of a curing agent.

The plated copper powder is preferably prepared by subjecting copper powder prepared by an atomizing method to silver plating of 1 to 20% by weight (silver plating treatment concentration: 1 to 20%).

If the amount of the silver-plated copper powder is less than 75 parts by weight, desired conductive properties cannot be obtained, and if it exceeds 90 parts by weight, the amount of resin is small and desired adhesive properties cannot be obtained.

The amount of plating of silver or the like is 1% by weight based on copper powder.
If less than 20% by weight, the surface of the copper powder may not be sufficiently plated, and sufficient electrical characteristics may not be obtained. If it exceeds 20% by weight, silver migration may occur and the solder may diffuse due to silver during soldering. In some cases, the phenomenon of erosion appears and soldering becomes difficult. Preferably 5
It is 15% by weight.

If the amount of the epoxy resin exceeds 25 parts by weight, the desired conductive property cannot be obtained, and if it is less than 10 parts by weight, the adhesiveness cannot be obtained.

As the epoxy resin, bisphenol F type, bisphenol F type with a dispersant (for rust prevention), bisphenol A type, glycidyl amine type, metaxylene diamine type, amine phenol type and the like are adopted.

Here, the filling rate of the copper powder in the epoxy resin depends on the resin viscosity, the powder dispersibility, the polyfunctionality and the like, and when aiming at lowering the viscosity, bisphenol F is more preferable than bisphenol A type. The type is suitable. However, even when bisphenol A type is used, it is possible to lower the viscosity by blending with a reactive diluent. Also, when trying to increase the crosslink density of the compound by performing polyfunctionalization, and when using the conventional phenol novolac type,
The viscosity rises significantly. Therefore, in the case of being polyfunctional and aiming for low viscosity, glycidylamine type, metaxylenediamine type, and aminophenol type are preferable. Furthermore, even if it does not have a heat-resistant skeleton, heat resistance can be obtained by using the following polyether-type reactive diluent.

The diluent for the epoxy resin is a reactive one, and for example, a glycidyl amine type, a polyether type, a diol modified type, a phenyl ether type, or an alcohol modified type can be adopted.

Incidentally, the powder filling rate of conventional general silver-based conductive adhesives (silver powder) is 75% by weight or less.

If the amount of the curing agent is less than 5% by weight, it will not be cured within a desired time, and if it exceeds 20% by weight, the pot life will be shortened and the composition will be cured in the course of product distribution. Here, in order to prepare a one-pack type conductive adhesive, as a curing agent, dicyandiamide, dicyandiamide modification, guanide series, acid redrazide, imidazoles, boron trifluoride series, melamines, sulfonium salt type, etc. are considered. To be

[0016]

In the conductive adhesive thus constructed, the activity of the copper powder is suppressed by the plating of silver or the like, and the long-term characteristics are not inferior to those of silver powder, carbon, or the like. Further, since the weight of silver is smaller than that of silver powder alone, the cost is low, and the desired conductivity is achieved due to the high conductivity of the copper powder.

[0017]

[Examples] As shown in Table 1, Examples 1 to 6 in which the weight part of the silver-plated copper powder is about 80%, Comparative examples 1 and 2 in which the weight part is 75% or less, or 90% or more, and Comparative Examples 3 and 4 in which the curing agent was 5% by weight or less or 20% by weight or more, respectively, were produced, and after 60 days as a pot life, volume specific resistance ρ (conductivity) and shear strength τ were obtained.
(Adhesive strength) was measured, and the results are shown in the lower column of Table 1.

[0018]

[Table 1]

Here, the volume resistivity ρ is obtained by printing the conductive adhesive of the embodiment or the comparative example on a glass epoxy substrate by a screen printing method to form five rotation patterns, and using a precision grade tester, both ends of each pattern. It is an average value calculated by measuring the resistance between. Moreover, the measurement of the adhesive strength τ is 1
976 JISK 6850 "Adhesive Tensile Shear Bond Strength Test Method".

According to the measurement results, each Example can be screen-printed even after 60 days have passed, the pot life is 60 days or more, and the conductivity is 10 ^-4 to 10 ^-3. [Omega] -cm, which is a level close to that of silver powder, and a shear strength of 100 kg / cm < ² > or more, which can be sufficiently used. This result is considered to be because the epoxy resin firmly holds the silver-plated copper powder and forms the matrix in a well-balanced manner.

On the other hand, Comparative Example 1 has poor conductivity and is far below the level of silver powder alone. In Comparative Example 2, since the amount of resin is small, the resin is easily cured and the powder cannot be sufficiently retained, so that the adhesive strength is extremely low. Comparative Example 9 lacks the curing agent and lacks the adhesive force after the predetermined curing treatment.
Since the amount of the curing agent was excessive, the curing started 50 days after the kneading adjustment, and the measurement with ρ and τ was impossible.

Further, in each of the examples, there was no problem in use even when the following environment resistance characteristic tests (characteristic deterioration acceleration tests) were conducted.

[Moisture resistance test] Temperature: 60 ° C., humidity: 90%, leaving time: 24 hours [Heat cycle test] -40 ° C. for 30 minutes and 85 ° C. for 30 minutes were repeated 1000 times.

Since the organic solvent of the embodiment does not use an organic solvent, it is advantageous in the working environment.

[0025]

EFFECTS OF THE INVENTION Since the conductive adhesive according to the present invention is constructed as described above, the high cost of the silver-based conductive adhesive, the long-term instability of the copper-based conductive adhesive, and the low conductivity of the carbon-based adhesive are achieved. It is to overcome. Therefore, it becomes possible to supply a low-cost, high-quality conductive adhesive to the joints of various electronic / electrical devices.

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[Procedure amendment]

[Submission date] January 12, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0001

[Correction method] Change

[Correction content]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive adhesive used for mounting a ceramic element mounted on an electric / electronic device on a substrate or mounting a lead wire on the ceramic element .

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

Under the above circumstances, therefore, the present invention has the same level of conductivity (1 × 10 ^-4 to 1 × 10 ^-3 Ω- cm ) as the adhesive made of silver powder, as compared with the adhesive made of silver powder. However, it is an object to obtain a conductive adhesive that has good long-term properties (environmental resistance) (small change with time) and is sufficiently satisfactory in terms of cost.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

[0011] Epoxy resins, bisphenol F type, with a bisphenol F type dispersing agent (for rust), bisphenol A type, glycidyl amine type, meta-xylene diamine type, employing an amino phenol type.

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

If the amount of the curing agent is less than 5% by weight, it will not be cured within a desired time, and if it exceeds 20% by weight, the pot life will be shortened and the composition will be cured in the course of product distribution. Here, in order to create a one-conductive adhesive, as a curing agent, dicyandiamide, dicyandiamide modified, guanido-based, acid arsenate Dora <br/> Gide, imidazoles, boron trifluoride-based, melamine, A sulfonium salt type is considered.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction content]

[0019] Here, volume resistivity ρ embodiment or the conductive adhesive of Comparative Example to form 5 Article a circuitry pattern was printed by screen printing on a glass epoxy substrate, a precision grade tester, each It is an average value calculated by measuring the resistance between both ends of the pattern. Also, the measurement of the adhesive strength τ is
1976 JIS K 6850 "Adhesive Tensile Shear Bond Strength Test Method".

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction content]

On the other hand, Comparative Example 1 has poor conductivity and is far below the level of silver powder alone. In Comparative Example 2, since the amount of resin is small, the resin is easily cured and the powder cannot be sufficiently retained, so that the adhesive strength is extremely low. Comparative Example 3 lacks the curing agent and lacks the adhesive force after the predetermined curing treatment, and Comparative Example 4
Since the amount of the curing agent was excessive, the curing started 50 days after the kneading adjustment, and the measurement was impossible together with ρ and τ.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Name of item to be corrected] 0023

[Correction method] Change

[Correction content]

[Moisture resistance test] Temperature: 60 ° C., humidity: 90%, leaving time: 1000 hours [Heat cycle test] -40 ° C. for 30 minutes and 85 ° C. for 30 minutes were repeated 1000 times.

Claims (2)

[Claims] 1. A conductive metal-plated copper powder having a lower activity than copper such as silver of 75 to 90 parts by weight, and an epoxy resin containing 5 to 20% by weight of a curing agent and 25 to 10 parts by weight of an epoxy resin. Conductive adhesive. 2. The conductive adhesive according to claim 1, wherein
The above-mentioned plated copper powder is a copper powder prepared by an atomizing method and plated with 1 to 20% by weight of silver, which is a conductive adhesive.