JPH08253745A - Adhesive - Google Patents

Abstract

PURPOSE: To obtain an adhesive having an improved thermal conductivity, a low coefficient of thermal expansion and a prolonged pot life and being desirable to bond a member to which fine conductance points must be given. CONSTITUTION: The adhesive comprises an adhesive resin 1, a curing agent 2 therefor, an additive 6, and conductive particles 4. The curing agent 2 is microencapsulated by using an insulation resin 5 as the wall material, and the additive 6 comprises alumina or aluminum nitride.

Description

Detailed Description of the Invention

[0001]

This invention relates to adhesives. More specifically, the present invention relates to an adhesive in which conductive particles are dispersed as an adhesive instead of solder. The adhesive is particularly useful for bonding electronic components, for example, bonding components having a fine structure such as bonding between a semiconductor chip and another member.

[0002]

2. Description of the Related Art In electronic parts and the like, soldering, welding or the like is carried out when conductivity of an adhesive portion is required.
However, electronic parts are weak against heat, and relatively high heat is applied by soldering or welding, so that the electronic parts that can be bonded are limited. On the other hand, an adhesive composed of a synthetic resin-based adhesive resin and conductive particles mainly made of metal powder (conductive filler) can be used at a relatively low temperature, so that electronic components are not limited. The above-mentioned adhesive can be used, for example, for conductive adhesion of plastics and glasses having an adhesive part requiring conductivity, and lead wires.

The adhesives that have been reported so far are generally epoxy, polyimide, phenol, polyester or other adhesive resins. On the other hand, as the conductive particles, fine powder of metal such as gold, silver and copper, amorphous carbon, powder of graphite, metal oxide and the like are used. In addition, silver powder is most often used as the conductive particles from the viewpoints of price, reliability, performance and the like.

However, considering the case where the above-mentioned adhesive is used for bonding electronic parts having fine electrodes, for example, it is necessary to ensure that conductive particles are present under the fine electrodes. It is necessary to add a large amount of active particles. However, if a large amount of conductive particles is added,
The insulation resistance becomes low, and there is a possibility that adjacent patterns will be electrically connected to each other.

As a technique for solving such a problem, for example, JP-A-4-96981 and JP-A-6-880 are disclosed.
As described in JP-A-40-36 and JP-A-6-136333, there is a method of using a so-called microcapsule (MC) type conductive filler in which the surface of conductive particles is coated with an insulating resin. If an adhesive containing this MC-type conductive filler is used, after applying it to a desired portion of an electronic component, applying pressure or heat pressure to a portion intended to conduct electricity will destroy the insulating resin of the capsule, thereby achieving conduction. On the other hand, since the capsule is not broken in the other parts, the insulating property can be maintained.

[0006]

However, in an electronic component using a semiconductor, the coefficient of thermal expansion of the chip and that of the substrate are different from each other, and the adhesive interposed between the two cannot alleviate the difference in coefficient of thermal expansion. It was It has also been desired to improve the heat conduction of the adhesive and shorten the curing time of the adhesive.

Further, two types of conventional adhesives are mainly used: a one-component type in which an adhesive resin and a curing agent are mixed, and a two-component type in which an adhesive resin and a curing agent are mixed at the time of use. One-part adhesive has a pot life of about 1 at room temperature.
It is a day, and frozen storage is required to prevent the reaction between the adhesive resin and the curing agent until use (note that the pot life is about a few months even if frozen storage is performed). Therefore, it is necessary to return the temperature to room temperature at the time of use, which causes a problem that workability is deteriorated and the adhesive absorbs moisture to deteriorate the characteristics. On the other hand, the two-component type adhesive has a problem that workability is poor because the adhesive resin and the curing agent must be mixed each time it is used.

[0008]

Thus, according to the present invention, a hardening agent, an additive, and conductive particles are dispersed in an adhesive resin, and the additive is made of a material having high thermal conductivity. An adhesive is provided. The adhesive resin that can be used in the present invention is not particularly limited, epoxy resin, polyimide resin, phenol resin, polyester resin,
It is composed of an initial condensation product (prepolymer) such as an acrylate resin, and in particular, an epoxy resin prepolymer is preferable from the viewpoint of electrical characteristics and moisture resistance.

On the other hand, the curing agent reacts with the adhesive resin,
There is no particular limitation as long as it can be cured. For example, when the adhesive resin is an epoxy resin prepolymer, aliphatic, aromatic and alicyclic amine-based, aliphatic, aromatic and alicyclic polyamine-based, aliphatic, aromatic and alicyclic acid anhydride-based , Phenol-based and silicone-based curing agents. Of these, it is particularly preferable to use an imidazole-based curing agent.

Further, the above curing agent is preferably used in the form of microcapsules coated with a thermoplastic resin.
By coating the curing agent with a thermoplastic resin, it is possible to prevent the reaction between the curing agent and the adhesive resin even if it is stored as a one-pack type adhesive that has been mixed with the adhesive resin in advance, and the pot life is maintained even at room temperature. Since the length can be increased, the workability can be greatly improved. Examples of the thermoplastic resin that can be used include acrylic resins, polyester resins, and polyamide resins. When a thermoplastic resin is used, the curing agent exudes and reacts with the adhesive resin by heating above the melting point of the thermoplastic resin during use, and the adhesive can be easily cured. The melting point of the thermoplastic resin is preferably 50 to 200 ° C. When it is lower than 50 ° C, the pot life becomes short, which is not preferable, and when it is higher than 200 ° C, it is difficult to melt at the time of bonding, which is not preferable.

As the adhesive composed of the adhesive resin and the curing agent, it is preferable to use one having an impurity ion concentration of 50 ppm or less from the viewpoint of preventing a short circuit. The impurity ions are, for example, alkali metal ions such as sodium and potassium, and halogen ions such as chlorine. In the adhesive of the present invention, a material having high thermal conductivity is dispersed as an additive. Examples of the material having high thermal conductivity include alumina and aluminum nitride. By adding the above-mentioned additive, the thermal conductivity of the adhesive can be improved and the curing time of the adhesive can be shortened. Further, the coefficient of thermal expansion of the adhesive can be made close to that of the electronic component, and stable adhesion can be realized.
In other words, the adhesive of the present invention has two different thermal expansion coefficients.
Effective to play a buffering role for two electronic components,
Stronger and more stable adhesion can be realized. The particle size of the additive is at least smaller than the particle size of the conductive particles (conductive filler) described below, and particularly preferably 3 μm or less. If it is larger than 3 μm, conduction is hindered, which is not preferable.

Next, the conductive particles usable in the present invention are preferably used in the form of microcapsules coated with an insulating resin. By covering the conductive particles with an insulating resin, pressure is applied to the desired bonding area during bonding to break the insulating resin and maintain electrical continuity, while the other parts are not broken, so the insulating property is maintained. Can be kept.

The conductive particles that can be used are not particularly limited, and metal fine particles of silver, gold, copper, nickel, palladium, rhodium, etc., alloy fine particles of silver-palladium alloy, etc., powders of amorphous carbon, graphite, etc. Etc. Of these, silver, gold and silver-palladium alloy fine particles are preferable. On the other hand, the insulating resin is not particularly limited, and examples thereof include epoxy resin.

It is preferable that the microencapsulated conductive particles have a particle size of 2 to 12 μm. Two
If it is smaller than μm, it is not preferable because it may not be possible to alleviate the variation in the gap between the bonded portions when there are a plurality of bonded portions, resulting in poor adhesion, and if it is larger than 12 μm, there is a risk of electrical conduction with the adjacent bonded portions, which is preferable. Absent.

The above-mentioned mixing ratio of the curing agent to the adhesive resin is 20 to 70 with respect to 100 parts by weight of the adhesive resin.
Parts by weight, preferably 40 to 60 parts by weight. When the compounding ratio of the curing agent is less than 20 parts by weight, an uncured part is generated and insulation failure occurs, which is not preferable, and when it is more than 70 parts by weight, the curing state is good, but the conductivity contained in the adhesive is large. It is not preferable because the number of the particles is reduced and sufficient conduction cannot be obtained.

The mixing ratio of the conductive particles to the adhesive resin is 10 parts by weight of the curing agent to 100 parts by weight of the adhesive resin.
To 500 parts by weight, preferably 50 to 300 parts by weight, more preferably 20 to 70 parts by weight. If the blending ratio of the conductive particles is less than 10 parts by weight, sufficient conduction cannot be obtained, which is not preferable, and if it is more than 500 parts by weight, the entire conductive particles cannot be wetted with the adhesive, and the appearance is not good. Is inferior, which is not preferable.

Further, the mixing ratio of the additive to the adhesive resin is such that the curing agent is 1 to 150 parts by weight with respect to 100 parts by weight of the adhesive resin.
Parts by weight, preferably 30 to 80 parts by weight. If the compounding ratio of the additive is less than 30 parts by weight, the thermal expansion coefficient cannot be made sufficiently small and stable adhesion cannot be realized, so that it is not preferable. This is not preferable because it causes defects.

The hardener microcapsulated by coating the above thermoplastic resin can be formed, for example, as follows. That is, first, an oil phase composed of a solvent, a raw material of a thermoplastic resin, and a curing agent is formed. The emulsifier is then added to the water to form the aqueous phase. The oil phase is dispersed by dropping the oil phase into the aqueous phase to form a suspension. Then, the microcapsulated curing agent can be obtained by polymerizing the raw material of the thermoplastic resin on the surface of the curing agent by applying heat or a catalyst to the suspension.

The conductive particles microencapsulated by coating with an insulating resin can be formed, for example, as follows. That is, an oil phase composed of a solvent, a raw material of an insulating resin, and conductive particles is formed. The emulsifier is then added to the water to form the aqueous phase. The oil phase is dispersed by dropping the oil phase into the aqueous phase to form a suspension. After that, the microcapsulated conductive particles can be obtained by polymerizing the raw material of the insulating resin on the surface of the conductive particles by applying heat or a catalyst to the suspension.

Further, the suspension in the method for forming the microencapsulated curing agent and the conductive particles is carried out by applying a resin raw material onto the surface of the curing agent or the conductive particles and dispersing this in water. Can also be formed. The adhesive of the present invention can be used in the same manner as known adhesives. For example, when bonding electronic components together,
An adhesive is applied in a thickness of 10 to 150 μm on a region of one of the electronic components where conductivity is desired. Next, place the other electronic component, apply pressure to both electronic components to destroy the insulating resin that coats the conductive particles, and heat to a temperature above the melting point of the thermoplastic resin that coats the curing agent. Then, the adhesive can be adhered by curing the adhesive.

Examples of members that can use the adhesive of the present invention include electronic parts. More specifically, semiconductor chips and lead frames, crystal oscillators and sdc meters and lead wires, bronze and carbon brushes for micromotors, glass for liquid crystal display tubes, plastics that require conductive adhesion, printed wiring boards, etc. Is mentioned.

[0022]

The adhesive of the present invention is characterized in that a curing agent, an additive, and conductive particles are dispersed in an adhesive resin, and the additive is made of a material having high thermal conductivity. Therefore, the heat conductivity is improved by the additive, the curing time is shortened, and the coefficient of thermal expansion of the adhesive can be brought close to the coefficient of thermal expansion of the member, and good adhesion stability can be obtained.

[0023]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. Production Example (1) Production of Microencapsulated Conductive Particles 20 g of polyvinyl alcohol and 2 g of an emulsifier were dissolved in 370 ml of water to form an aqueous phase.

On the other hand, 7 g of bismaleimide (hereinafter BMI) and 4 g of diaminodiphenylmethane (hereinafter DDM) were dissolved in 30 ml of dichloroethane, and the particle size was 7 ± 3.
5 g of μm silver powder and titanate coupling agent (Product name K
0.1 g of R-38S, manufactured by Ajinomoto Co., Inc.) was added to form an oil phase. Next, ultrasonic vibration was applied to the oil phase for 30 minutes to uniformly disperse the aggregated silver powder.

Next, using a homogenizer, the aqueous phase was cooled to 700
The oil phase was gradually added dropwise with stirring at 0 rpm to form a suspension in which the oil phase was present on the surface of the silver powder. While stirring this suspension at 200 rpm with a three-one motor, 1 g of a catalyst (diazabicycloundecene) dissolved in 30 ml of water was added dropwise over 2 hours, and the temperature was raised to 65 ° C and stirred for 4 hours. By continuing the reaction of BMI and DDM on the surface of the silver powder to form a shell having a thickness of about 0.1 μm on the surface of the silver powder, microcapsulated conductive particles were obtained. (2) Production of microencapsulated curing agent 0.01 g of benzoyl peroxide in 30 ml of dichloromethane
Then, 1 g of imidazole and 1 g of methyl methacrylate as a curing agent were added to form an oil phase.

Further, 1 g of an emulsifier was added to 200 ml of water to form an aqueous phase. Next, the aqueous phase was gradually added dropwise while stirring the oil phase at 4000 rpm using a homogenizer to form an emulsion. The emulsion was stirred at 120 rpm with a three-one motor, heated to 66 ° C., polymerized in situ for 7 hours, and dichloroethane and a curing agent were enclosed in polymethylmethacrylate (hereinafter referred to as PMMA). This was followed by removal of dichloroethane to form a microencapsulated curing agent with an average particle size of 3 μm with a shell of about 0.5 μm.

Example 1 An adhesive as shown in FIG. 1 was prepared with the materials and compositions shown below. In FIG. 1, 1 is an adhesive resin, 2 is a curing agent, 3 is a thermoplastic resin, 4 is conductive particles, 5 is an insulating resin, and 6 is an additive. Adhesive resin: Epoxy curing agent: Imidazole coated with thermoplastic resin (acrylic resin, melting point approx. 70 ° C) Conductive particles: Capsule type silver fine particles whose surface is coated with epoxy resin (pseudo spherical shape, particle size 7 ±) 3 μm) Additive: Alumina powder (fine powder having a particle size of 1 μm or less) Adhesive composition: 100 parts by weight of adhesive resin, 50 parts by weight of curing agent, 60 parts by weight of alumina, 80 parts by weight of conductive particles Impurity ion concentration (adhesive resin + Hardener): Na ⁺ ,
K ⁺ , Cl ⁻ <10 ppm An adhesive was prepared by mixing the adhesive materials prepared as described above until they became uniform.

(1) The gelation time at 150 ° C. of the adhesive prepared as described above was measured by the gel time method. The gelling time of this adhesive was 10 seconds at 150 ° C., and it showed fast curing property. (2) Using the above adhesive, on a glass epoxy substrate,
128 glass chips (128 connection points) were thermocompression bonded so that the pitch between adjacent glass chips was 100 μm.
500 substrates similar to this glass epoxy substrate were formed. Thereafter, the substrate is given a temperature of -40 to 125 ° C. for 50 minutes.
A temperature cycle test was conducted by performing 0 cycles.

As a result of the temperature cycle test, no defect (peeling) occurred on 500 glass chips. In addition, at all the connection points (6.4 × 10 ⁴ points), the resistance increase was 10% or less, and good conductive resistance was exhibited. (3) The adhesive was left at room temperature for 1 year, and the change in viscosity diameter with time and the change in the peak area of the epoxy group were examined by IR analysis. Table 1 shows the viscosities at the initial stage and after one year of compounding, and the peak area of the epoxy group / the peak area of the P-position phenylene group.

[0030]

[Table 1]

From Table 1, it was confirmed that the epoxy adhesive resin and imidazole (curing agent) did not react, and the pot life was one year or more at room temperature. (4) An electrolytic corrosion test was carried out using a comb-shaped pattern composed of Al electrodes (7, 8) as shown in FIG. In the comb-shaped pattern of FIG. 2, three comb-shaped electrodes of the electrode 7 and four comb-shaped electrodes of the electrode 8 are arranged alternately. Further, the distance between the comb-shaped electrodes of the electrode 7 and the comb-shaped electrode of the electrode 8 which are adjacent to each other was set to 40 μm.

An adhesive was applied on the comb pattern of FIG. 2 and the adhesive was cured at 175 ° C. for 1 minute. Using this, an electrolytic corrosion test was carried out at 85 ° C., 85% humidity and 5V DC for 200 hours, and the results are shown in Table 2.

[0033]

[Table 2] From Table 2, there was almost no change in insulation resistance and good electrolytic corrosion was exhibited.

Example 2 The additive was changed from alumina powder to aluminum nitride (particle size 1 μm).
An adhesive was made of the same material as in Example 1 except that it was changed to a fine powder of m or less), and the same test as in Example 1 was performed. The same results as in Example 1 were obtained in all of the gelling time, the temperature cycle test, the pot life and the electrolytic corrosion test.

Example 3 Bonding with the same material as in Example 1 except that the additive amount of alumina was 0.1, 0.5, 1, 150 and 160 parts by weight with respect to 100 parts by weight of the adhesive resin. The agent was prepared and the same test as in Example 1 was performed.

In the pot life and electrolytic corrosion tests, the same results as in Example 1 were obtained. Table 3 shows the gelation time, and Table 4 shows the results of the temperature cycle test.

[0037]

[Table 3]

[0038]

[Table 4] From Tables 3 and 4, the amount of the additive is 1 to 15 which shows an appropriate fast curing property and does not cause defects (peeling) on the glass chip.
It has been found that 0 parts by weight is preferred.

Example 4 Example 1 except that an adhesive made of the same material as in Example 1 except that an adhesive resin having an impurity ion concentration of 50 ppm or more was used and a curing agent having an impurity ion concentration of 20 ppm or less was used. An adhesive was prepared using the same material as in Example 1 and the same test as in Example 1 was performed.

The same results as in Example 1 were obtained in the pot life, temperature cycle test and electrolytic corrosion test. In the electrolytic corrosion test, the adhesive using the adhesive resin having the impurity ion concentration of 50 ppm or more was short-circuited after 50 hours, but the adhesive using the curing agent having the impurity ion concentration of 20 ppm or less showed the same results as in Example 1. Was obtained. From this result, it was found that the impurity ion concentration is preferably 50 ppm or less.

Example 5 The amount of the curing agent added was 10, based on 100 parts by weight of the adhesive resin.
Example 1 except 20, 40, 70 and 80 parts by weight
An adhesive was prepared using the same material as in Example 1 and the same test as in Example 1 was performed. The pot life was the same as in Example 1.

Table 5 shows gelation time, temperature cycle test,
The state of the adhesive at the time of curing and the result of the electrolytic corrosion test are shown.

[0043]

[Table 5] From Table 5, it is found that the amount of the curing agent is particularly preferably 20 to 70 parts by weight, which does not change the insulation resistance even after 200 hours have passed in the electrolytic corrosion test and has no defect (peeling) on the glass chip.

Example 6 The same material as in Example 1 was used except that the conductive particles were changed from silver particles to gold particles (particle size 7 ± 3 μm) and silver-palladium alloy particles (particle size 7 ± 3 μm). Example 1
The same test was conducted. The same results as in Example 1 were obtained in all of the gelling time, the temperature cycle test, the pot life and the electrolytic corrosion test.

Example 7 The amount of the conductive particles was 10, based on 100 parts by weight of the adhesive resin,
An adhesive was prepared using the same material as in Example 1 except that the amount was changed to 20, 40, 70 and 80 parts by weight, and the same test as in Example 1 was performed.

In the gelation time, pot life and electrolytic corrosion test, almost the same results as in Example 1 were obtained. Table 6
The results of the adhesive appearance and the temperature cycle test are shown in FIG.

[0047]

[Table 6]

From Table 6, it is found that the amount of the conductive particles is more preferably 20 to 70 parts by weight, where the appearance of the bonded portion is good and the glass chip has no defects (peeling).

[0049]

The adhesive of the present invention comprises an adhesive resin, a curing agent,
The additive and conductive particles are dispersed, and the additive is made of a material having high thermal conductivity. Therefore,
Additive improves thermal conductivity, shortens the curing time, and allows the thermal expansion coefficient of the adhesive to be close to that of the member, resulting in good adhesive stability. it can.

Further, if the curing agent is microencapsulated, it becomes possible to leave it for a long time at room temperature (that is, the pot life can be lengthened), which has been difficult with the conventional one-pack type adhesive, and the pot life can be greatly increased. It is possible to improve the workability. Furthermore, by encapsulating conductive particles in a microcapsule, it can be applied to adhesion of electronic parts having fine electrodes. Further, the additive is 1 to 1 with respect to 100 parts by weight of the adhesive resin.
By adding 50 parts by weight, an adhesive having poor adhesion due to thermal expansion and suitable adhesive strength can be obtained.

Further, since the conductive particles are made of conductive particles selected from silver, gold, and a silver-palladium alloy coated with an insulating resin made of an epoxy resin, the conductive particles are excellent in electrical conductivity when conducting. An adhesive having excellent properties and moisture resistance can be obtained. Furthermore, by adding 10 to 500 parts by weight of conductive particles to 100 parts by weight of the adhesive resin, it is possible to obtain an adhesive having complete conduction and appropriate wettability of the adhesive.

Further, the thermoplastic resin coating the curing agent is
By having a melting point of 50 to 200 ° C., the curing agent can be easily dispersed and cured in the adhesive resin simply by heating it to the melting point or higher at the time of adhesion. Furthermore, when the thermoplastic resin coating the curing agent is an acrylic resin, a polyester resin, or a polyamide resin, it is possible to obtain an adhesive that is easily handled during bonding.

Since the adhesive resin is an epoxy resin type prepolymer, an adhesive having excellent electric characteristics and moisture resistance can be obtained. Furthermore, by adding 20 to 70 parts by weight of the curing agent to 100 parts by weight of the adhesive resin, it is possible to completely cure and to secure good conductivity.

Further, since the adhesive contains impurity ions having a concentration of 50 ppm or less, it is possible to prevent insulation failure such as short circuit caused by the impurity ions.

[Brief description of drawings]

FIG. 1 is a schematic view of an adhesive of the present invention.

2 is a schematic plan view of a comb-shaped pattern used in Example 1. FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Adhesive resin 2 Curing agent 3 Thermoplastic resin 4 Conductive particles 5 Insulating resin 6 Additives 7 and 8 Electrodes

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Eiji Tokuhira 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor Makoto Usui 1015, Kamedotachu, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited

Claims (2)

[Claims] 1. An adhesive characterized in that a hardening agent, an additive, and conductive particles are dispersed in an adhesive resin, and the additive is made of a material having high thermal conductivity. 2. The adhesive according to claim 1, wherein the adhesive contains impurity ions at a concentration of 50 ppm or less.