JP3292437B2 - Conductive bonding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive bonding method for electrically bonding and bonding materials, and more particularly to a conductive bonding method between an electrode material on ceramics of a piezoelectric element and a diaphragm. is there.

[0002]

2. Description of the Related Art Conventionally, an acrylic resin-based or epoxy resin-based adhesive has been widely used to establish electrical continuity between metal materials and to physically or mechanically join them. As the epoxy resin-based adhesive, one obtained by mixing a conductive material such as metal powder with a one-component adhesive or a two-component adhesive has been used.

As an example, a bonding and assembling process of a piezoelectric element when a two-pack type epoxy resin adhesive is used will be described below.
For example, the base agent: the curing agent is 100 ± 5: 33 ± 1 by weight ratio.
After stirring for 5 minutes or more, the mixture is uniformly applied on a silver electrode formed on the surface of the piezoelectric element. Combine permalloy on this adhesive coated surface and apply 5 ± 1kg / c
After heating at 100 ± 5 ° C. for 1.5 hours under a pressure of m ² and curing (first stage curing), heat treatment at 150 ± 5 ° C. higher than the glass transition temperature for 1.5 hours (second stage) By curing, the adhesive was cured.

[0004]

Among the one-component adhesives, the acrylic resin adhesive has a uniform system, is excellent in thin-film moldability, and has no problem in terms of conduction, but has durability such as heat resistance and moisture resistance. The sex was inferior. In the case where a conductive material is mixed with a one-component epoxy resin adhesive, the conductive material itself hinders the formation of a thin film, causing a reduction in adhesive strength. On the other hand, two-part adhesives have excellent thin film moldability, but this also necessitates compounding, and furthermore, pot life (pot life).
There were restrictions. The present invention solves the above-mentioned problems and realizes conductive adhesion having excellent durability such as heat resistance and moisture resistance.

[0005]

SUMMARY OF THE INVENTION According to the present invention, there is provided a conductive bonding method for bonding a one-pack type epoxy resin adhesive containing a latent curing agent having a melting point of 40 to 100.degree . Applying at least one surface, pressing the other material onto the adhesive applied surface of the material,
raising the temperature to a temperature higher than the melting point of the latent curing agent by 10 ° C. or more while applying pressure at a pressure of g / cm ² or more, and curing the adhesive by uniformly melting the latent curing agent; The method further comprises a step of heat-treating the cured adhesive at a temperature equal to or higher than the glass transition temperature.

Further, the melting point acting by the heat of fusion is 40 to
A step of applying a one-pack type epoxy resin adhesive containing a latent curing agent at 100 ° C. to at least one surface of a material to be bonded; / Cm ²
Heating the latent curing agent at a temperature rising rate of 30 ° C./min or higher to a temperature equal to or higher than the melting point of the latent curing agent, and curing the adhesive by uniformly melting the latent curing agent; This includes a step of performing a heat treatment at a temperature equal to or higher than the transfer temperature.

[0007] A so-called one-pack type adhesive contains a latent curing agent in advance together with a main component (for example, bisphenol A). The latent curing agent is stable for a long period of time as long as it is blended with the main component and left at room temperature, but is affected by the action of heat, light, moisture or pressure (for example, the heat of fusion of the latent curing agent). As soon as the latch is removed, the base begins to cure. Of these, by using a latent curing agent that acts by the heat of fusion, a stable curing reaction can be performed in the entire system, and stable conductive adhesion can be obtained. Further, the difficulty of using the two-component adhesive as described above is improved, and at the same time, since it is an epoxy resin, reliability such as heat resistance and moisture resistance can be secured. The classification by the method of removing the latch that suppresses the start of the reaction of the latent curing agent is as follows.

[0008]

[Table 1]

Of these, any latent curing agent that can be heated and melted can be applied in principle, as long as the means for releasing the latch is "heat". It is preferable that the curing initiation mechanism is based on “melting”. As the latent curing agent,
As shown in Table 1, there are dicyandiamide, organic acid hydrazide, melamine derivative, imidazole compound, diaminomaleonitrile, polyamine salt and the like. Conductive adhesion is achieved by uniformly curing a system in which such a fusible latent curing agent is dispersed in a main agent.

The latent curing agent has a melting point of 40 to 100.
C. is preferred. In order to prevent the reaction from starting at room temperature, the melting point is preferably 40 ° C. or higher. Also,
In a high-temperature environment exceeding 100 ° C., the curing reaction is started only with the main agent due to the influence of impurities, moisture and the like. Therefore, in order to make the progress of the reaction of the entire system uniform, the above range is appropriate. Furthermore, the average particle size of the latent curing agent is
Those having a size of 30 μm or less are preferred. By setting the average particle size of the latent curing agent to 30 μm or less, the curing reaction of the main agent can be made uniform throughout the system. Preferably, one of the materials to be bonded is permalloy and the other is silver.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The conductive bonding method of the present invention will be specifically described with reference to examples. The present invention is not limited to these. [Example] One-pack type epoxy resin adhesive (latent curing agent mixed type) Main agent: Bisphenol A "Epicoat 828" (Shell Japan Co., Ltd.) Curing agent: Latent curing agent "Amicure PN-23" ( (Ajinomoto Co., Inc.) Average particle size 10 μm ・ Blending ratio (weight ratio) Main agent 100: curing agent 25

[Comparative Example 1] Two-part epoxy resin adhesive ・ Main agent: bisphenol A “Ecobond 55” (Grace Japan Co., Ltd.) ・ Curing agent: Modified aromatic amine “Catalyst 11J” (Grace Japan Co., Ltd.) -Mixing ratio (weight ratio) Main agent 100: Hardener 33 [Comparative Example 2] One-pack type epoxy resin adhesive (latent hardener mixed type)-Main agent: Bisphenol A "Epicoat 828" (Shell Japan Co., Ltd.)・ Curing agent: Latent curing agent “Amicure MY-24” (Ajinomoto Co., Inc.) Average particle size 10 μm ・ Blending ratio (weight ratio) Main agent 100: Curing agent 25

Each of the adhesives of the embodiment and comparative examples 1 and 2 was sandwiched between two slide glasses (10 mm × 10 mm), and the displacement of the thickness of the adhesive layer (hereinafter referred to as an adhesive layer) was determined by TMA ( According to thermomechanical analysis), the heating rate was 10 ° C / m
in, and measured under a set condition of a compression load of 2.0 g.
The result is shown in FIG. As shown in FIG. 1, in the adhesives of Example and Comparative Example 2, which are one-pack type epoxy resin adhesives, a decrease in the thickness of the adhesive layer can be confirmed at around 70 to 80 ° C. This is because the curing reaction of the main agent was started and the viscosity was lowered by gelation, and it indicates that the curing reaction of the main agent was started by melting of the curing agent around this temperature. Further, these adhesives were sandwiched between JIS K-6850 iron test pieces (area 3.125 cm ² ) and a load of 2.0 k
While pressurizing with g, the temperature was raised under the set conditions of a temperature rising rate of 20 ° C./min, and the change in the resistance value of the adhesive during the curing process was measured. The result is shown in FIG.

As shown in FIGS. 1 and 2, the adhesives of Examples and Comparative Example 2, which are one-pack type epoxy resin adhesives, all have a decrease in the thickness of the adhesive layer and a decrease in the resistance value around 70 to 80 ° C. Can be confirmed. Comparative Example 1
On the other hand, the adhesive of Comparative Example 2 does not have a thin adhesive layer as shown in the TMA result. It is small and does not decrease to the conductive adhesion level (100 mΩ or less). The two-part epoxy resin adhesive used in Comparative Example 1 was:
Conductive adhesion has already been confirmed by the piezoelectric element, and the resistance value (conductivity) of the adhesive layer after curing of the adhesive is 1 at room temperature.
00 mΩ or less.

FIG. 3 shows the DSC obtained when the one-component adhesives of Example and Comparative Example 2 were cured at a heating rate of 5 ° C./min.
(Differential scanning calorimetry) The result is shown. It can be seen that the curing reaction of the adhesive of the example progresses rapidly, while the adhesive of the comparative example 2 progresses slowly. 4 and 5 show the melting points of the curing agents used in the adhesives of Example and Comparative Example 2, respectively. From the DSC results, in the case of the adhesive of Example, after the curing agent was melted at 57.5 ° C. (FIG. 4),
While the base material generates heat of curing as shown in FIG. 3, the curing agent used in Comparative Example 2 has a melting point of 68.3 ° C. and 83.1 ° C.
C. and 136.9 ° C. (FIG. 5), and there is a component that melts even after the curing reaction of the main agent is started. Therefore, it is considered that the curing reaction of the main agent progresses slowly, and the degree of viscosity decrease due to gelation at the time of curing becomes small, thereby preventing the adhesive layer from becoming thinner and conducting.

Using the adhesives of the above Examples and Comparative Example 1, a permalloy was bonded to a piezoelectric ceramic element having a silver electrode on the surface. One-part epoxy resin adhesive of Example 1 is applied to one flat silver electrode of a disc-shaped piezoelectric ceramic having a diameter of 15.8 mm and a central hole of 3.1 mm in diameter, and the coated surface thereof Then, a disk-shaped permalloy was pressed. These were heated to 100 ° C. at a temperature rising rate of 30 ° C./min and a compressive load of 2.0 g / cm ² , kept at that temperature for 1.5 hours, and further heated to a glass transition temperature (135 ° C.).
C.) at 150 ° C. for 1.5 hours. Also,
Piezoelectric ceramics and permalloy were bonded in the same manner as in Example 1 except that the two-component epoxy resin adhesive of Comparative Example 1 was used and the compression load was changed to 5.0 kg / cm ² . Both the piezoelectric elements bonded by the conductive bonding method of Example and Comparative Example 1 were confirmed to be conductive. The adhesive peel strength was measured. Table 2 shows the results.

[0017]

[Table 2]

In the case of the conductive bonding method of the example, the average value of the bonding strength was 7.76 kg / cm ² , which was slightly lower than the value of the conductive bonding method of Comparative Example 1 (8.24 kg / cm ² ). As shown, practically sufficient strength is obtained. Further, it can be seen that the variation (σ) is greatly improved, and a stable adhesive strength can be obtained.

In the above embodiment, the applied pressure is 2 g / cm
^Although it is set to ² , it is preferable that the thickness of the adhesive layer be thin in order to achieve conduction between the adhesive materials, and therefore it is preferable to apply a higher pressure. In order to make the adhesive layer conductive, it is necessary to reduce the thickness of the adhesive layer. For this purpose, it is desirable to make the progress of the curing reaction of the main agent uniform throughout the entire system and to increase the viscosity decrease due to gelation at the start of the reaction. In order to cure the adhesive, it is necessary to raise the temperature to a temperature higher than the melting point of the latent curing agent. To make the progress of the curing reaction of the main agent uniform. Further, if the temperature is raised at a high rate, the temperature distribution in the adhesive becomes non-uniform, and the progress of the curing reaction of the system becomes non-uniform. Therefore, it is preferable to raise the temperature at a temperature of 30 ° C./min or less. On the other hand, if the rate of temperature rise is too slow, the curing reaction proceeds gradually, and the viscosity at the start of the reaction increases, so that the adhesive layer cannot be made thinner. In addition, a rate of temperature increase of at least 5 ° C./min is desirable in order to cause a decrease in adhesive strength and an uneven system.

If the melting point of the curing agent is too low, a curing reaction may be accidentally started at room temperature, and stable conductive adhesion cannot be expected. Therefore, the melting point of the curing agent is preferably 40 ° C. or higher. Further, in a high-temperature environment exceeding 100 ° C., the curing reaction is started only with the main agent due to the influence of impurities, moisture and the like. In this case, the stability of the reaction is lacking, the reaction speed is low, and the viscosity at the start of the reaction is high. Therefore, it is difficult to reduce the thickness of the adhesive layer required for conductive bonding. Further, the adhesiveness with the adhesive material is also reduced.
Therefore, it is preferable that the curing reaction of the main agent starts at 100 ° C. or less, that is, the melting point of the curing agent is 100 ° C. or less. Considering the storage stability at normal temperature and the stability of the reaction at high temperature, the temperature is preferably 50 to 80 ° C. The one-component adhesive is a dispersion of a main agent and a curing agent, and in order to make the progress of the curing reaction uniform, the average particle size of the curing agent is preferably smaller, specifically, 30 μm or less. Is preferred. In particular, as used in the above embodiment, the thickness is preferably 10 μm or less.

[0021]

According to the present invention, conductive bonding using a one-pack type epoxy resin adhesive can be performed. As a result, the conventional problems such as the complicated preparation of the adhesive and the limitation of the pot life can be solved, and the conductive bonding with more excellent durability than the acrylic resin adhesive can be realized.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram (TMA result) showing a change in the thickness of an adhesive layer during the curing process of the adhesives of Example and Comparative Examples 1 and 2.

FIG. 2 is a characteristic diagram showing a resistance value of the adhesive layer.

FIG. 3 is a characteristic diagram (DSC result) showing a thermal behavior in a curing process of the adhesives of Example and Comparative Example 2.

FIG. 4 is a characteristic diagram (DSC result) showing the thermal behavior of the curing agent used in the adhesive of the example in the temperature rising process.

FIG. 5 is a characteristic diagram (DSC result) showing a thermal behavior of a curing agent used for an adhesive of Comparative Example 2 in a temperature rising process.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shogo Asano 4-3-1 Tsunashima Higashi, Kohoku-ku, Yokohama-shi Matsushita Communication Industrial Co., Ltd. (56) References JP-A-5-47212 (JP, A) 555-1123 (JP, A) JP-A-3-29207 (JP, A) JP-A-4-142383 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C09J5 / 00-5/06 C09J 11/06 C09J 163/00-163/10

Claims (4)

(57) [Claims] The melting point acting by the heat of fusion is 40 to 10.
Applying a one-component epoxy resin adhesive containing a latent curing agent at 0 ° C. to at least one surface of the material to be bonded; pressing the other material on the adhesive applied surface of the material; / Cm ² while pressurizing at a pressure of not less than 10 ° C. higher than the melting point of the latent curing agent,
A conductive bonding method comprising: a step of curing the adhesive by uniformly melting the latent curing agent; and a step of heat-treating the cured adhesive at a temperature equal to or higher than a glass transition temperature. 2. The melting point acting by the heat of fusion is 40 to 10.
Applying a one-pack type epoxy resin adhesive containing a latent curing agent at 0 ° C. to at least one surface of the material to be bonded; pressing the other material onto the adhesive applied surface of the material; 5-3 while pressurizing at a pressure of / cm ² or more
Raising the temperature of the latent curing agent to a temperature equal to or higher than the melting point of the latent curing agent at a temperature rising rate of 0 ° C./min, and curing the adhesive by uniformly melting the latent curing agent; A conductive bonding method including a step of performing a heat treatment at a temperature equal to or higher than a transition temperature. 3. The latent curing agent has an average particle size of 30 μm.
The conductive bonding method according to claim 1 or 2, wherein: 4. The conductive bonding method according to claim 1, wherein one of the materials to be bonded is permalloy and the other is silver.