JP2001254067A - Electroconductive adhesive and connecting structure therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a packing technology having an enhanced adhesive strength and improved reliability to bending force by introducing a functional group which is easy to form a coordinate bond with an electrode metal to the molecular chain of a binder resin which comprises main components together with a metal filler. SOLUTION: As a thermoplastic resin, one at least two same or different functional groups selected from the group consisting of a carbonyl group, carboxyl group, amino group, imino group, iminoacetic group, iminopropionate group, hydroxyl group, thiol group, pyridinium group, imide group, azo group, nitrilo group, ammonium group, and imidazole group, are introduced to a resin such as a polyester resin, silicone resin, vinyl resin, and thermoplastic epoxy resin, etc., is used. This enables strong adhesion with an electrode metal. This packed structure is prepared by printing an electroconductive adhesive 3 to an electrode 2 on a substrate 1, and mounting an electrode 5 on a part 4 to it, and then heating it.

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 solder-free mounting in the field of electronic components and a connection structure using the same.

[0002]

2. Description of the Related Art In recent years, with the increasing awareness of environmental harmony, there has been a concrete movement in the electric machinery industry to completely eliminate lead-containing solder used for mounting electronic components.

[0003] As lead-free mounting technology, mounting technology using lead-free solder has been actively developed, and some of them have been put into practical use. Numerous problems remain, such as lead-free component electrodes.

[0004] On the other hand, lead-free mounting using a conductive adhesive has not yet been reported, but has the following advantages in addition to lead-free.

First, the processing temperature is as low as about 150 ° C., which is lower than that of solder, so that low cost and high performance of electronic components can be realized. Second, since the specific gravity of the conductive adhesive is about half that of the solder, it is easier to reduce the weight of the electronic device. Third, since it is not a joint made of metal like solder, metal fatigue does not occur and mounting reliability is excellent.

For this reason, by completing a mounting technique using a conductive adhesive, it is expected that an epoch-making mounting satisfying environmental harmony, low cost and high reliability can be realized.

One of the problems of mounting the conductive adhesive is that the adhesive strength is lower than that of solder. In particular, since the strength against bending stress is about one-tenth that of solder, in a large-area electronic component that is easily subjected to bending stress, peeling may occur at the interface between the electrode and the conductive adhesive, and a connection failure may occur. there were.

[0008] Many attempts have been made to improve the adhesive strength, but none of them has yet reported a technique capable of realizing the same strength as solder. The main examples are shown below.

For example, supervised by Hiroo Miyairi, "Development of functional adhesives and the latest technology" (CMC, edited by June 30, 1997)
As shown in JP, 194), many techniques have been reported to improve the adhesive strength by adding an organic metal called a silane coupling agent, which can chemically bond to both resin and metal, to the adhesive material. ing.

However, since the dehydration reaction or the substitution reaction is used, the reactivity between the coupling agent and the resin or the metal is poor, and the conditions for optimizing the reaction (temperature, hydrogen ion concentration, etc.) ), It was difficult to significantly improve the adhesive strength.

Japanese Patent Application Laid-Open No. 9 (1997) -176285 proposes to use a resin having a phosphate ester group introduced into its skeleton as a binder resin. In this method, since the functional group of the binder resin is adsorbed on the metal,
Although there is some effect of improving the adhesive strength, there is a problem that a remarkable improvement effect cannot be obtained because the adsorptive force is weaker than the covalent bond or the coordinate bond.

[0012] As described above, the improvement of the adhesive strength has been a major key in the practical use of the mounting technique using the conductive adhesive.

[0013]

SUMMARY OF THE INVENTION In order to solve the above-mentioned conventional problems, the present invention provides a conductive adhesive and a connection structure using the same, which have significantly improved adhesive strength and improved reliability against bending force. The purpose is to provide.

[0014]

In order to achieve the above object, the conductive adhesive of the present invention comprises a binder resin and a metal filler as main components, and the cured binder resin has a multidentate coordinate bond with an electrode metal. Is characterized in that the molecular chain contains a functional group that forms

Further, the connection structure of the present invention comprises a binder resin and a metal filler as main components, and the binder resin after curing contains a functional group forming a polydentate bond with an electrode metal in a molecular chain. The adhesive and the electrode are electrically connected using an agent.

Further, in the method of manufacturing a connection structure according to the present invention, the binder resin and the metal filler are main components, and the cured binder resin contains a functional group forming a polydentate bond with an electrode metal in a molecular chain. The adhesive and the electrode are electrically connected by using a conductive adhesive.

[0017]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, a polydentate bond means that a polydentate ligand (a plurality of chelating ligands) is introduced into a binder resin, and the polydentate ligand is an electrode. Forming a coordination bond with a metal. That is, a chemical bond (coordination bond) is formed between the binder resin and the electrode, instead of the adhesion using only the Van der Waals force due to a normal weak hydrogen bond.

A method for introducing a polydentate ligand into a binder resin will be described in the following embodiments.

(Embodiment 1) The first method is to use a resin into which a desired polydentate ligand is introduced as an additive component (a reactive diluent, a curing agent, etc.) in a binder resin. .

For example, a linear epoxy resin having a dicarbonyl group represented by the following formula (Chemical Formula 1) introduced into a molecular chain is mixed with a ring-opening catalyst, applied to the surface of an electrode (Cu foil), and cured by heating. The dicarbonyl group at the center of the molecule forms a coordinate bond with the electrode (Cu foil) as shown in the following formula (Formula 2).
Of course, the epoxy rings at both ends of the molecule open to form cross-links.

[0021]

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[0022]

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At this time, as a main component of the binder resin, a normal epoxy resin having no ligand (bisphenol A, bisphenol F, novolak epoxy resin) is used.
The resin into which the polydentate ligand has been introduced is one in the binder resin.
The mixture is kneaded so as to be 0 to 50% by weight.

In addition to a reactive diluent, a ligand can be introduced into a resin used as a curing agent.

(Embodiment 2) The second method is to use a resin into which a desired polydentate ligand is introduced as a main component (a component having the largest content) in the binder resin.

For example, a bisphenol F epoxy resin having a dicarbonyl group represented by the following formula (Chemical Formula 3) introduced into a molecular chain is mixed with a ring-opening catalyst, applied to the surface of an electrode (Cu foil), and cured by heating. As in the first embodiment, the carbonyl group at the center of the molecule forms a coordination bond with the electrode (Cu foil).

[0027]

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At this time, as a sub-component of the binder resin, an ordinary epoxy resin having no ligand (a reactive diluent, a curing agent, etc.) is used. The resin into which the polydentate ligand is introduced is kneaded and used in the binder resin so as to be 30 to 100% by weight.

In the adhesive and the connection structure of the present invention, the number of polydentate bonds is preferably 2 to 4. Of course, the number may be more than this.

In the adhesive and the connection structure, the amount of the resin containing a functional group capable of forming a polydentate bond in the molecular chain may be in the range of 10 to 100% by weight of the whole resin. preferable.

In the adhesive and the connection structure, when the conductive adhesive is 100% by weight, the binder resin is in the range of 5 to 25% by weight, and the metal filler is 75% by weight.
Preferably, it is in the range of ~ 95% by weight. other than this,
If necessary, a curing agent for the binder resin, a curing catalyst, a cross-linking agent, a ring-opening catalyst, a dispersant for the metal filler, a viscosity modifier, p
An H regulator and the like may be optionally added. Therefore, in the present invention, the "main component" in the "mainly comprising a binder resin and a metal filler" means that the binder resin and the metal filler constitute 90% by weight or more of the conductive adhesive.

In the adhesive and the connection structure, the functional group may be a carbonyl group, a carboxyl group, an amino group, an imino group, an iminoacetic acid group, an iminopropionic acid group, a hydroxyl group, a thiol group, a pyridinium group, an imide group. ,
It is preferable that the functional groups are at least two same or different functional groups selected from an azo group, a nitrile group, an ammonium group and an imidazole group.

In the adhesive and the connection structure, the metal filler is preferably at least one particle selected from silver, silver-plated nickel and silver-plated copper. This is because if the surface of the metal filler is silver, it does not react with the ligand of the binder resin but selectively reacts with the electrode metal. However, when the amount of the ligand in the binder resin is large, even if copper is used as the metal filler, for example, not all ligands react with the metal filler, so that copper may be used as the metal filler. it can.

In the adhesive and the connection structure, it is preferable that the binder resin is at least one resin selected from a thermoplastic resin and a thermosetting resin.

In the adhesive and the connection structure, the thermoplastic resin is a polyester resin, a silicone resin, a vinyl resin, a vinyl chloride resin, an acrylic resin, a polystyrene resin, an ionomer resin, a polymethylpentene resin, a polyimide resin, a polycarbonate resin. , A fluororesin and a thermoplastic epoxy resin.

According to the present invention described above, it is possible to realize a mounting technique using a conductive adhesive whose adhesive strength is greatly improved.

According to the present invention, when the conductive adhesive and the electrode metal come into contact with each other, the ligand of the binder resin is very easily reacted with the metal. Form strong chemical bonds. Since the ligand is bound to the molecular chain of the resin, the bond between the binder resin and the electrode metal and the bond between the conductive adhesive and the electrode metal are also strengthened.

The connection structure of the present invention is obtained by electrically connecting the conductive adhesive of the present invention and an electrode, and has improved adhesive strength as compared with a conventional connection structure. Further, since the thermoplastic resin is superior in flexibility as compared with the thermosetting resin, this conductive adhesive can realize bonding with excellent stress relaxation ability against bending force.

A preferred connection structure of the present invention is one in which a component and a substrate are mounted using the conductive adhesive, and the bonding strength against bending force is further improved.

The present invention can be used as a replacement for conventional solder, for example, as a conductive adhesive between a semiconductor substrate and an electronic component chip. The present invention can also be applied to a conductive paste for conducting electrical conduction in the thickness direction of the electrically insulating base material.

[0041]

Embodiments of the present invention will be described below with reference to the drawings.

(Common Experimental Method) FIG. 1 shows a side view of the mounting structure used for the evaluation. After the conductive adhesive 3 is screen-printed on the electrode 2 of the substrate 1 and the electrode 5 of the component 4 is mounted,
By heating in an oven at 150 ° C. for 30 minutes,
A mounting structure was manufactured. The same material was used for the substrate 1 and the component 4 and for the electrode 2 and the electrode 5.

FIG. 2 shows an evaluation method. The component 4 is pressurized from the back surface of the fabricated mounting structure using the substrate pressing jig 6 to measure the amount of deflection when the connection resistance rises to twice or more the initial value, and to determine the adhesive strength with respect to the bending force. evaluated. The distance between the substrate fixing jigs 7 and 8 was 100 mm.

The details of the board and the components are shown below. (1) Parts: 0 ohm resistance Base material: alumina or glass epoxy substrate (3216 size) Electrode specifications: as shown in Table 1. (2) Substrate Base material: Alumina or glass epoxy substrate (30 × 150 ×
1.6mm) Electrode specifications; as shown in Table 1. (3) Conductive adhesive filler; silver powder (85wt%) (average particle diameter 3-10μ)
m) Binder resin (15 wt%); as shown in Table 1.

The contents of each embodiment will be described below. In the following examples, Examples 1 and 2 are examples of conductive adhesive materials in which a functional group is introduced into a thermosetting resin, and Examples 3 and 4
Is an example of a conductive adhesive material obtained by introducing a functional group into a thermoplastic resin.

Example 1 In this example, as described in the first embodiment, a resin in which a polydentate ligand is introduced is used as an additive component (reactive diluent) of a binder resin. is there.

As a binder resin for the conductive adhesive, 15 parts by weight of a reactive diluent having a dicarbonyl group represented by the following formula (4) introduced into a molecular chain, 75 parts by weight of a bisphenol F epoxy resin, and a curing agent A mixture of 5 parts by weight of (maleic anhydride) and 5 parts by weight of a solvent (butyl carbitol acetate) was used.

[0048]

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As a result, the amount of deflection at the time of NG was higher than that of Comparative Example 1 (conventional conductive adhesive), Comparative Example 5 (containing a silane coupling agent), and Comparative Example 7 (phosphoric ester group-introduced epoxy resin). Thus, the adhesive strength with respect to the bending force was improved.

(Example 2) As the conductive adhesive, a binder resin (the above formula (Formula 4)) in which a dicarbonyl group is bonded to the side chain of the same epoxy resin as in Example 1 was used, and a conventional Cu was used as an electrode. A thick film was used.

As a result, Comparative Example 2 (when a conventional conductive adhesive was used), Comparative Example 6 (with a silane coupling agent added), Comparative Example 8 (a phosphate ester group-introduced epoxy resin)
The amount of deflection at the time of NG was higher than that of NG, and the adhesive strength against bending force was improved.

Example 3 The same procedure as in Example 1 was carried out except that a thermoplastic silicone resin having a dicarbonyl group introduced into a side chain of the silicone represented by the following formula (Formula 5) was used as a reactive diluent. did.

[0053]

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As a result, the amount of deflection at the time of NG was higher than that of Comparative Example 1 (conventional conductive adhesive), Comparative Example 5 (containing a silane coupling agent), and Comparative Example 7 (epoxy resin having a phosphate ester group). Thus, the adhesive strength with respect to the bending force was improved. Further, the adhesive strength was improved as compared with Example 1.

Example 4 As a conductive adhesive, a resin represented by the above formula (Formula 4) in which a dicarbonyl group is bonded to a side chain of a silicone resin is used, and a conventional Cu foil is used for an electrode. Using.

As a result, Comparative Example 2 (when a conventional conductive adhesive was used), Comparative Example 6 (with a silane coupling agent added), Comparative Example 8 (a phosphate ester group-introduced epoxy resin)
The amount of deflection at the time of NG was higher than that of NG, and the adhesive strength against bending force was improved. Further, the adhesive strength was improved as compared with Example 2.

Example 5 The following formula (Chem. 6) in which the ligand of the ligand-introduced resin of Example 1 was changed to an aminocarbonyl group
The procedure was the same as in Example 1 except that the epoxy resin shown in (1) was used.

[0058]

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As a result, the amount of deflection at the time of NG was higher than that of Comparative Example 1 (conventional conductive adhesive), Comparative Example 5 (containing a silane coupling agent), and Comparative Example 7 (phosphoric ester group-introduced epoxy resin). Thus, the adhesive strength with respect to the bending force was improved.

Example 6 The procedure was the same as Example 5 except that the electrode was changed to a thick baked Cu foil.

As a result, Comparative Example 2 (when a conventional conductive adhesive was used), Comparative Example 6 (with a silane coupling agent added), Comparative Example 8 (a phosphate ester group-introduced epoxy resin)
The amount of deflection at the time of NG was higher than that of NG, and the adhesive strength against bending force was improved.

Example 7 The same as Example 1 except that an epoxy resin represented by the following formula (Formula 7) was used in which the ligand of the ligand-introduced resin of Example 1 was changed to a dicarbonyl group. I made it.

[0063]

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As a result, the amount of deflection at the time of NG was higher than that of Comparative Example 1 (conventional conductive adhesive), Comparative Example 5 (containing a silane coupling agent), and Comparative Example 7 (phosphoric ester group-introduced epoxy resin). Thus, the adhesive strength with respect to the bending force was improved.

Example 8 The same operation as in Example 7 was performed except that the electrode was changed to a thick baked Cu foil.

As a result, Comparative Example 2 (when a conventional conductive adhesive was used), Comparative Example 6 (with a silane coupling agent added), Comparative Example 8 (a phosphate ester group-introduced epoxy resin)
The amount of deflection at the time of NG was higher than that of NG, and the adhesive strength against bending force was improved.

Example 9 The same as Example 1 except that an epoxy resin represented by the following formula (Formula 8) was used in which the ligand of the ligand-introduced resin of Example 1 was changed to a dicarbonyl group. I made it.

[0068]

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As a result, the amount of deflection at the time of NG was higher than that of Comparative Example 1 (conventional conductive adhesive), Comparative Example 5 (containing a silane coupling agent), and Comparative Example 7 (phosphoric ester group-introduced epoxy resin). Thus, the adhesive strength with respect to the bending force was improved.

Example 10 The procedure was the same as Example 9 except that the electrode was changed to a thick baked Cu foil.

As a result, Comparative Example 2 (when a conventional conductive adhesive was used), Comparative Example 6 (with a silane coupling agent added), Comparative Example 8 (a phosphate ester group-introduced epoxy resin)
The amount of deflection at the time of NG was higher than that of NG, and the adhesive strength against bending force was improved.

Example 11 The same as Example 1 except that the ligand of the ligand-introduced resin of Example 1 was changed to a dicarbonyl group, and an epoxy resin represented by the following formula (Formula 9) was used. I made it.

[0073]

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As a result, the amount of deflection at the time of NG was higher than that of Comparative Example 1 (conventional conductive adhesive), Comparative Example 5 (containing a silane coupling agent), and Comparative Example 7 (phosphoric ester group-introduced epoxy resin). Thus, the adhesive strength with respect to the bending force was improved.

Example 12 Example 11 was the same as Example 11 except that the electrode was changed to a baked Cu thick foil.

As a result, Comparative Example 2 (when a conventional conductive adhesive was used), Comparative Example 6 (with a silane coupling agent added), Comparative Example 8 (a phosphate ester group-introduced epoxy resin)
The amount of deflection at the time of NG was higher than that of NG, and the adhesive strength against bending force was improved.

(Example 13) The following formula (Chem. 10) in which the ligand of the ligand-introduced resin of Example 1 was changed to a dicarbonyl group.
Here, n indicates the degree of polymerization, and is about 2 on average. )), Except that the epoxy resin shown in (1) was used.

[0078]

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As a result, the amount of deflection at the time of NG was higher than that of Comparative Example 1 (conventional conductive adhesive), Comparative Example 5 (containing a silane coupling agent), and Comparative Example 7 (phosphoric ester group-introduced epoxy resin). Thus, the adhesive strength with respect to the bending force was improved.

Example 14 Example 13 was the same as Example 13 except that the electrode was changed to a thick baked Cu foil.

As a result, Comparative Example 2 (when a conventional conductive adhesive was used), Comparative Example 6 (with a silane coupling agent added), Comparative Example 8 (a phosphate ester group-introduced epoxy resin)
The amount of deflection at the time of NG was higher than that of NG, and the adhesive strength against bending force was improved.

(Comparative Example 1) An experiment was conducted in the same manner as in Example 1 except that the binder resin used in Example 1 was replaced with a conventional conductive adhesive, that is, the following composition was used. -Bisphenol F type epoxy resin 90 parts by weight-Hardener (diethylenetriamine) 5 parts by weight-Solvent (butyl carbitol acetate) 5 parts by weight (Comparative Example 2) A fired Cu thick foil was used in place of the Cu foil of Comparative Example 1. Except for the above, the experiment was performed in the same manner as in Comparative Example 1.

(Comparative Example 3) An experiment was conducted in the same manner as in Example 1, except that the binder resin of Example 3 was replaced with a hydrogen-dimethyldisilicone resin at both ends.

(Comparative Example 4) An experiment was performed in the same manner as in Comparative Example 3 except that a thick baked Cu foil was used instead of the Cu foil of Comparative Example 3.

Comparative Example 5 An experiment was performed in the same manner as in Example 1 except that a silane coupling agent was used instead of the binder resin of Example 1.

(Comparative Example 6) An experiment was performed in the same manner as in Comparative Example 5 except that a thick copper foil was used instead of the Cu foil of Comparative Example 5.

Comparative Example 7 An experiment was conducted in the same manner as in Example 1 except that an epoxy resin having a phosphate group introduced into the molecular skeleton was used instead of the binder resin of Example 1.

Comparative Example 8 An experiment was performed in the same manner as in Comparative Example 7 except that a thick baked Cu foil was used instead of the Cu foil of Comparative Example 7.

The results of Example 1-14 and Comparative Example 1-8 of the present invention are shown in Table 1.

[0090]

[Table 1] In this embodiment, only the epoxy resin and the silicone resin are shown as the binder resin of the conductive adhesive.
It is effective to use another resin as described in the embodiment. Although only a dicarbonyl group is shown as a ligand bonded to a side chain of the binder resin, another ligand as described in the embodiment may be used. Further, only copper is shown as the electrode metal, but other metals generally used for the electrodes as described in the embodiment may be used.

[0091]

According to the present invention, it is possible to easily solve the bonding strength, particularly the strength against bending force, which has been a problem in the mounting of the conductive adhesive, and to commercialize the mounting technique using the conductive adhesive. It greatly contributes to.

[Brief description of the drawings]

FIG. 1 is a sectional view of a mounting structure used for evaluating one embodiment of the present invention.

FIG. 2 is an explanatory sectional view showing an evaluation method according to one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Electrode 3 Conductive adhesive 4 Parts 5 Electrode 6 Substrate pushing jig 7, 8 Substrate fixing jig

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05K 3/32 H05K 3/32 B (72) Inventor Yukihiro Ishimaru 1006 Kazuma Kazuma, Kadoma, Osaka Matsushita Electric Industrial (72) Inventor Riki Mitani 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (10)

[Claims] 1. A conductive adhesive comprising a binder resin and a metal filler as main components, and the binder resin after bonding contains, in a molecular chain, a functional group forming a polydentate bond with an electrode metal. 2. The conductive adhesive according to claim 1, wherein the number of polydentate bonds is 2 to 4. 3. An amount of a resin containing a functional group capable of forming a polydentate bond in a molecular chain is 10 to 100% by weight of the total resin.
The conductive adhesive according to claim 1, wherein 4. The conductive adhesive according to claim 1, wherein the binder resin is in a range of 5 to 25% by weight and the metal filler is in a range of 75 to 95% by weight, when the conductive adhesive is 100% by weight. Agent. 5. The method according to claim 1, wherein the functional group is a carbonyl group, a carboxyl group, an amino group, an imino group, an iminoacetic acid group, an iminopropionic acid group, a hydroxyl group, a thiol group, a pyridinium group,
The conductive adhesive according to claim 1, wherein the conductive adhesive is at least two different functional groups selected from the group consisting of an imide group, an azo group, a nitrile group, an ammonium group, and an imidazole group. 6. The conductive adhesive according to claim 1, wherein the metal filler is at least one particle selected from silver, silver-plated nickel, and silver-plated copper. 7. The conductive adhesive according to claim 1, wherein the binder resin is at least one resin selected from a thermoplastic resin and a thermosetting resin. 8. The thermoplastic resin is selected from polyester resin, silicone resin, vinyl resin, vinyl chloride resin, acrylic resin, polystyrene resin, ionomer resin, methylpentene resin, polyimide resin, polycarbonate resin, fluororesin and thermoplastic epoxy resin. 8. The conductive adhesive according to claim 7, which is at least one resin. 9. A connection structure, wherein the conductive adhesive according to claim 1 is used to electrically connect the adhesive to an electrode. 10. A method for manufacturing a connection structure, comprising: using the conductive adhesive according to claim 1 to electrically connect the adhesive to an electrode.