JPH0570750A - Conductive adhesive - Google Patents

Abstract

PURPOSE:To provide a high-reliability conductive adhesive which is made conductive by dispersing metallic particles in the base of the adhesive and can import a stable electric resistance to the desired area without forming an electrical connection among the adjoining patterns. CONSTITUTION:A microencapsulated conductive adhesive is made by dispersing a microencapsulated conductive filler, prepared by forming a metallic plating 11 on the surface of a resin ball 10 and forming an electrical insulating polymer 12 around the external surface of the metallic plating 11, in a one-pack adhesive.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive adhesive in which metal particles are dispersed in a base material of an adhesive to give conductivity.

[0002]

2. Description of the Related Art Heretofore, regarding the bonding of semiconductor devices and the like in the semiconductor manufacturing process, when conductivity on the bonding surface is required, the bonding is performed by soldering or welding. However, as for the adhesion by soldering or welding, the applicable material is limited due to the problem of heat resistance at the time of joining.

On the other hand, adhesion using a conductive adhesive which is an organic-inorganic composite composed of a binder mainly composed of synthetic resin and a conductive filler mainly composed of metal powder is carried out by a bonding method, It has wide applicability in applied materials and usage. Examples of applicable materials for conductive adhesives and their uses include conductive bonding of epoxy and phenolic resin plastics that could not be soldered conventionally, bonding of Nesa glass used for liquid crystal display tubes, phosphor bronze used for micromotors. Adhesion of carbon brushes and lead wires of crystal oscillators and sdc meters.

Recent developments in the semiconductor industry are particularly remarkable, and ICs and LSIs are successively developed and mass-produced. Conventionally, a method using an Au-Sn eutectic has been used to bond these semiconductor elements (silicon wafers) to the lead frame, but an epoxy resin is used as a main component for the purpose of cost reduction and productivity improvement. In addition, a conductive adhesive obtained by kneading silver powder as a conductive filler has been widely used.

The above-mentioned epoxy resin is often used as the main component of this conductive adhesive.
Phenol-based and polyester-based are also partially used. On the other hand, as the conductive filler, fine powder of metal such as gold, silver and copper, amorphous carbon and graphite powder are used, and in addition, metal oxide is also used, although it is a part.
However, of these, silver powder is most often used because of its price, reliability, and track record.

[0006]

As described above, the conductive adhesive has advantages in various aspects as compared with the conventional soldering and welding. For example, this conductive adhesive is mounted on a semiconductor element and parts. There is a problem when it is used for adhesion between working patterns. FIG. 7 shows the relationship between the amount of conductive fine particles in a conventional conductive adhesive and the insulation resistance and conductivity. In the figure, the solid line shows the relationship between the amount of conductive fine particles and insulation resistance, and the broken line shows the relationship between the amount of conductive fine particles and conductivity.

As is clear from FIG. 7, as the amount of conductive fine particles in the conductive adhesive increases, the insulation resistance decreases,
There is a high possibility that adjacent patterns will be electrically connected to each other. On the contrary, if the amount of the conductive fine particles is reduced, it becomes impossible to secure good conduction between the semiconductor element and the component mounting pattern. That is, there is a problem that the conductive adhesive cannot be used for bonding the semiconductor element and the substrate, which require a strict conduction resistance by using a large amount of the conductive fine particles in the conductive adhesive.

Further, silver, which is generally used as the conductive fine particles, is sandwiched between the bumps on the semiconductor element side and the pads on the substrate side to serve as conduction points. However, as shown in FIG. 8, when the substrate-side pad 1 and the semiconductor element-side bump 2 are bonded with the conductive adhesive 3 having the silver filler 7, the silver filler 7 does not plastically deform when the bonding pressure is low, There is also a problem that good contact cannot be obtained and reliability is lacked due to point contact with the substrate side pad 1 and the semiconductor element side bump 2 at contact points 6 and 5, respectively.

An object of the present invention is to provide a highly reliable conductive adhesive which can obtain a stable conduction resistance in a necessary portion without the adjacent patterns being electrically connected to each other.

[0010]

[Means for Solving the Problems] A conductive adhesive in which a microcapsule-type conductive filler in which the surface of conductive fine particles is coated with an insulating resin is dispersed in a base material of an adhesive has a large size of a semiconductor element or the entire surface of a substrate. After applying it to the semiconductor element, pressure is applied to the part between the semiconductor element and the pattern to be electrically connected to break the coating layer (shell) of the microcapsule to expose the conductive fine particles to establish the electrical connection, and the micropattern is provided between the adjacent patterns. This is solved by allowing the encapsulated conductive fine particles to remain as they are and maintaining the insulating property.

For example, when a conductive adhesive in which microcapsules whose surface is coated with an insulating resin is uniformly dispersed in a base material of an adhesive such as an epoxy resin is used, the conductive fine particles increase. Insulation resistance remains constant, and insulation is maintained between adjacent patterns. However, the particle size of the conductive fine particles is 0.5 μm to 50 μm,
It is desirable to satisfy the two conditions that the thickness of the shell material of the microcapsules is 2 μm or less. This is because if the particle size of the microcapsules is 50 μm or more, the insulation between adjacent patterns may not be maintained when used in a fine pattern, and if the thickness of the shell material is large, the conduction resistance will increase. There is a possibility that it will become higher.

The problem that the contact point between the semiconductor element-side bump 2 and the substrate-side pad 1 is small is that a resin ball is used as a core and the surface of the resin ball is plated with metal as conductive fine particles. Can be solved by The shape of the resin ball is preferably spherical or pseudo-spherical. FIG. 1 shows a bonded state of a conductive adhesive having a microcapsule type conductive filler according to the present invention. Since the core of the conductive fine particles is resin, it is much more easily plastically deformed as compared with metal, and plastically deforms even at a low pressure to allow a large contact area as shown in FIG. Furthermore, since the resin has a small specific gravity, the dispersibility of the conductive fine particles in the base material of the adhesive is also improved.

[0013]

According to the present invention, it is possible to bond a semiconductor element having a stable conduction resistance to a necessary portion without causing conduction between adjacent patterns.

[0014]

FIG. 2 shows a conductive adhesive according to an embodiment of the present invention.
It will be described with reference to FIGS. FIG. 2 is a flowchart of a method for producing a microcapsule type conductive filler used in the conductive adhesive of this example. FIG. 3 is a flowchart of the method for treating the titanate coupling agent.

A method of manufacturing the conductive adhesive of this embodiment will be described below with reference to FIGS. 2 and 3. First, the method of treating the titanate coupling agent will be described with reference to the flowchart of FIG. As the conductive fine particles, those having a surface of polystyrene having a particle diameter of 7.4 μm plated with gold (hereinafter referred to as “polystyrene surface gold plating”) were used.

5 g of this polystyrene surface gold plating was added to 100 ml of ethanol (FIG. 3 (a)) (FIG. 3 (b)), and a titanate coupling agent (manufactured by Ajinomoto Co.) as a dispersant for the polystyrene surface gold plating was added. ．
1 g is added ((c) in the same figure). In this ethanol solution,
After the ultrasonic dispersion treatment (at the same figure (d)) for 15 minutes at a frequency of 45 kHz, the mixture was stirred (at the same figure (e)), and then ethanol was evaporated (at the same figure (f)) to perform titanate coupling. 5 g of polystyrene surface gold plating treated with the agent is produced (FIG. 9 (g)).

Next, a method for producing the microcapsule type conductive filler used in the conductive adhesive of this embodiment will be described with reference to the flow chart of FIG. Dichloroethane 15m
7 g of bisphenol A type epoxy resin (BPA) was dissolved in 1 (FIG. 2 (h)), and 5 g of polystyrene surface gold plating treated with a titanate coupling agent prepared according to the flowchart of FIG. 3 (FIG. 2 (g)). To prepare an oil phase. This oil phase 1 at a frequency of 45 kHz
Ultrasonic dispersion is performed for 5 minutes ((i) in the same figure), and the agglomerated polystyrene surface gold plating is uniformly dispersed in the oil phase.

Then, 20 g of polyvinyl alcohol (PVA), 2 g of an emulsifier and 10 g of tetraethylenepentamine (TEPA) are dissolved in 370 ml of water to prepare an aqueous phase (FIG. 2 (j)). Next, the aqueous phase is 7000
While stirring and emulsifying at rpm, the oil phase is gradually dropped into the water phase to prepare a suspension in which the oil phase is present on the surface of the polystyrene surface gold plating (FIG. 2 (k)). While maintaining this suspension at 60 ° C., the suspension is agitated by a three-one motor (agitation motor) at 180 rpm for 6 hours ((l) in the same figure).

In this manner, a microcapsule type conductive filler having an insulating polymer layer, which is a reaction product of BPA and TEPA, having a thickness of 0.1 μm is formed on the surface of polystyrene surface gold plating. The preparation of the microcapsule-type conductive filler of the present example is completed by separating this from the aqueous phase ((m) in the figure) and drying ((n) in the figure) ((o) in the figure).

FIG. 4 shows the microcapsule type conductive filler manufactured by the above manufacturing method. On the surface of a polystyrene resin ball 10 having a diameter of 7.4 μm, a thickness of 500
A metal plating (polystyrene surface gold plating) layer 11 of 〓 is formed, and BPA and T are formed on the outer surface of the metal plating layer 11.
The insulating polymer layer 12, which is a reaction product of EPA, has a thickness of 0.
It is formed with a thickness of 1 μm.

As described above, the conductive fine particles used in the conductive adhesive of this embodiment are characterized in that the surface of the polystyrene surface gold plating is coated with an insulating organic substance. Next, a one-part adhesive, for example a viscosity of 18000 cps
By mixing 75% by weight ratio (7% by volume ratio) of the microcapsule-type conductive filler produced by the above-mentioned method for producing the microcapsule-type conductive filler into the epoxy adhesive of 1. Is created. The one-pack type adhesive can be used in this example as long as the viscosity is 200,000 cps or less. Further, the content of the microcapsule type conductive filler with respect to the main component may be 1 to 60% or less by volume ratio.

Next, the results of measuring the performance such as insulation of the microcapsule type conductive adhesive according to this embodiment will be described. The prepared microcapsule type conductive adhesive was uniformly applied to a semiconductor substrate with a thickness of 30 μm, and the glass chip prepared for an experiment was bonded by thermocompression bonding at a pressure of 10 g per connection point.

FIG. 5 shows a diagram in which the substrate and the glass chip are bonded using the microcapsule type conductive adhesive of this embodiment. FIG. 3A shows a semiconductor substrate pattern. FIG. 3B shows the pattern of the experimental glass chip.
The number of pads is 32 and the electrode interval is 100 μm. FIG. 3C shows a state in which the semiconductor substrate and the glass chip are bonded together. In order to evaluate the conductivity of the microcapsule type conductive adhesive according to this example, the conduction resistance in the section indicated by A in FIG. Further, in order to evaluate the insulating property of the microcapsule type conductive adhesive according to the present example, the insulation resistance in the section indicated by B in FIG.

The measurement result shows that the filler content is 75 wt.
%, A good insulating property of 10 ¹¹ Ω or more was exhibited between the adjacent patterns despite the large amount of use. Further, the conduction resistance showed a good conductivity of about 0.1Ω or less per one connection point. Next, the bonding state of the glass chip and the substrate bonded with the microcapsule type conductive adhesive according to this example will be described.

By observing the cross sections of the bonded substrate and glass chip, the connection state of the microcapsule type filler to the substrate and glass chip was observed. The observation result is shown in FIG. FIG. 6 is a diagram showing a state of plastic deformation of the microcapsule type filler of this example. It was confirmed that the microcapsule type conductive filler existing between the patterns of the bumps 2 on the glass chip (semiconductor element) side and the pads 1 on the substrate side was plastically deformed and had a sufficient contact area.

It was also confirmed that the insulation between adjacent patterns can be maintained even if the conductive fine particles of this embodiment are changed from gold plating on polystyrene surface to silver plating. [Comparative Example 1] Instead of the microcapsule-type conductive filler used in this example, a conductive adhesive prepared by using only gold plating on a polystyrene surface not coated with an insulating resin was prepared and compared. .. As a result, the conductive filler existing between the chip and the pattern after bonding was plastically deformed to maintain a sufficient contact area, but the adjacent patterns were electrically connected.

Comparative Example 2 An experiment was conducted under the same conditions as in this example except that a silver powder filler was used in place of the microcapsule type conductive filler used in this example, and that between adjacent patterns. Was insulating, but the silver filler existing between the chip and the pattern after bonding was not plastically deformed and could not have a sufficient contact area, confirming that the conductivity is not reliable. ..
In addition, after the conductive adhesive was prepared, the microcapsule type filler was settled when it was left to stand naturally.

[0028]

As described above, according to the present invention, the adjacent patterns can be adhered to each other at a necessary portion so that a stable conduction resistance can be obtained without the adjacent patterns being electrically connected to each other.

[Brief description of drawings]

FIG. 1 is a view showing a bonded state of a conductive adhesive having a microcapsule type conductive filler according to the present invention.

FIG. 2 is a flowchart of a method for producing a microcapsule type conductive filler according to an embodiment of the present invention.

FIG. 3 is a flowchart of a method for treating a titanate coupling agent according to an embodiment of the present invention.

FIG. 4 is a view showing a microcapsule type conductive filler according to an embodiment of the present invention.

FIG. 5 is a diagram in which a substrate and a glass chip are bonded together using the conductive adhesive of this example.

FIG. 6 is a diagram showing a state of plastic deformation of the microcapsule type filler of the present embodiment.

FIG. 7 is a diagram showing a relationship between conductive fine particles of a conventional conductive adhesive, insulation resistance, and conductivity.

FIG. 8 is a diagram showing a bonded state of a conventional conductive adhesive having a silver filler under a low bonding pressure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate side pad 2 ... Semiconductor element side bump 3 ... Conductive adhesive 4 ... Microcapsule type conductive filler 5 ... Contact point 6 ... Contact point 7 ... Silver filler 10 ... Resin ball 11 ... Metal plating layer 12 ... Insulating Polymer layer

Claims (9)

[Claims] 1. A microcapsule-type conductive filler in which a metal-plated plating layer is formed on the surface of a resin ball, and the surface of the plating layer is uniformly coated with an insulating resin layer is dispersed in a main agent. And conductive adhesive. 2. The conductive adhesive according to claim 1, wherein the resin balls are formed of a thermoplastic resin. 3. The conductive adhesive according to claim 1, wherein the plating layer of the microcapsule-type conductive filler has a thickness of 500 angstroms or more. 4. The conductive adhesive according to claim 1, wherein a material of the plating layer of the microcapsule type conductive filler is gold or silver. .. 5. The conductive adhesive according to claim 1, wherein the resin ball has a spherical shape or a pseudo-spherical shape. 6. The conductive adhesive according to claim 1, wherein the resin balls have a particle size of 0.5 to 50 μm. 7. The conductive adhesive according to claim 1, wherein the thickness of the insulating resin layer is 2 μm or less. 8. The conductive adhesive according to claim 1, wherein the base material has a viscosity of 200,000 cps or less. 9. The conductive adhesive according to claim 1, wherein the content of the microcapsule-type conductive filler with respect to the main component is 1 to 60% or less by volume. Conductive adhesive that does.