JPH09255922A - Conductive adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a conductive adhesive having a good spreadability over a protruding electrode and a high adhesion by setting the conductive metal particle contact of a conductive adhesive within a specific rang and the content of specific flaky conductive metal particles in all the conductive metal particles within a specific range. SOLUTION: A transparent electrode 4 formed on a substrate 2 is connected with a protruding electrode 3 formed on a semiconductor device 1 by using a conductive adhesive 5 contg. 50-90wt.% conductive metal particles comprising 50-100wt.% (based on all conductive metal particles) flaky conductive particles of a metal such as gold, nickel, palladium or copper, which have an average interval sandwiched between parallel lines in a given direction thereof. When this conductive adhesive is used, the spreadability thereof over the protruding electrode 3 is good and the adhesion thereof to the connecting surfaces is high with a low resistance, whereby a stable connection can be secured.

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 in a flip chip mounting method for mounting a semiconductor device for driving a liquid crystal display device on a substrate using a conductive adhesive.

[0002]

2. Description of the Related Art In a conventional liquid crystal display device, when a semiconductor device for driving a liquid crystal is mounted on a substrate, a conductive adhesive is used as one of the methods for connecting a protruding electrode of the semiconductor device and an electrode on the substrate. A flip-chip mounting method for direct connection is known. FIG. 5 shows a cross-sectional view of a portion where a semiconductor device and a substrate (two glass substrates in FIG. 5) are bonded to each other in a liquid crystal display device subjected to the flip chip mounting method. A portion where the conductive adhesive is in contact with the electrode (4 transparent electrodes in FIG. 5) is a connection area, and is indicated by S in FIG.

As the conductive adhesive, a mixture of an epoxy adhesive composed of an epoxy resin and a curing agent and conductive particles is generally used.

Bisphenol A as an epoxy resin
In general, a resin such as a resin, a bisphenol F type, a novolac type is used, and the resin is selected in consideration of insulation properties, viscosity, adhesive strength, and the like.

As the curing agent, amines, acid anhydrides, imidazoles, etc. are used.
Considering viscosity, adhesive strength, etc., the optimum addition amount is mixed.

The conductive particles are selected from gold, nickel,
It is selected from metal powder such as silver, palladium and copper, and the shape is generally spherical or flake.

In Japanese Patent Application Laid-Open No. 4-372680, in order to connect a surface mounting type electronic component to a printed wiring board, both are bonded with a printed conductive adhesive and conductive particles contained in the conductive adhesive used at that time. The shape and content of (silver powder) are disclosed.

[0008]

However, the number of protruding electrodes formed on a semiconductor device for driving a liquid crystal is increasing and the pitch thereof is becoming finer. As the number of protruding electrodes formed on the semiconductor device increases, The projecting electrode also becomes small, and when the electrode formed on the substrate and the projecting electrode are connected using a conductive adhesive, the connection area is reduced and the adhesive force and conductivity are reduced.

For example, if the connection area is made very small,
There is a problem that the connection resistance value of the power source portion of the liquid crystal driving semiconductor device increases sharply, a difference in brightness occurs between the liquid crystal driving regions of each semiconductor device, and the image quality deteriorates.

Usually, in order to improve the conductivity of the conductive adhesive, the content of the conductive particles in the conductive adhesive is increased. In that case, however, the amount of the epoxy adhesive is reduced, so that the content of the conductive adhesive itself is reduced. The strength will decrease. That is, when the content of the conductive particles is increased, the contact area between the conductive particles and the adhesive surface is increased, but the contact area between the epoxy adhesive and the adhesive surface is decreased, so that the adhesive strength with the adhesive surface is reduced. Therefore, when the conductive adhesive is thermoset, the conductive adhesive is destroyed by the stress generated due to the difference in thermal expansion coefficient between the semiconductor device and the glass substrate.

Japanese Unexamined Patent Publication (Kokai) No. 4-372689 discloses a method of applying a conductive adhesive by printing. However, the printing area, that is, the bonding area is not mentioned, and the bonding in the flip chip mounting method is not mentioned. No mention is made of the problems associated with the reduction in area.

For the above reason, in the flip chip mounting method in which the electrodes formed on the substrate and the protruding electrodes formed on the semiconductor device are bonded with a conductive adhesive, the bonding area is very small, and the resistance is low and the connection is stable. Had a problem that it was difficult to obtain.

An object of the present invention is to provide a conductive adhesive having a good coating property to the protruding electrode when the protruding electrode formed on the semiconductor device and the electrode formed on the substrate are connected using the conductive adhesive. An object of the present invention is to provide a conductive adhesive that has a high adhesive force between the connection surface and the connection surface and can obtain a stable connection.

[0014]

In order to solve the above problems, the conductive adhesive of the present invention has the following constitution.

The conductive adhesive of the present invention is a conductive adhesive for connecting an electrode provided on a substrate and a protruding electrode provided on a semiconductor device, and the conductive adhesive is a metal conductive particle and an epoxy adhesive. Including the total weight of the conductive adhesive,
The conductive particles of metal are contained in an amount of 50 to 90% by weight, and the total number of the conductive particles of metal is 50 to 50 in the amount of flake-shaped conductive particles of metal having an average distance between parallel lines sandwiched in a fixed direction of 3 to 10 μm. It is characterized by containing 100% by weight.

The conductive adhesive of the present invention is preferably used in such a manner that the connection area between the electrode and the bump electrode is 900 to 20000 μm ² .

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Here, the interval between parallel lines sandwiched in a fixed direction (hereinafter, referred to as a fixed direction diameter) means that a surface having a large surface area of flake-shaped metal particles is an upper surface and the upper surface is an amorphous shape. If it is a circle, put the irregular circle in between 2
The tangent lines (parallel lines) of the book are set and the distance between the tangent lines is shown.

When the transparent electrode formed on the substrate and the projecting electrode formed on the semiconductor device are connected, 50% by weight of flake particles having an average directional diameter of 3 to 10 μm with respect to the conductive particles of all metals. Including the above, by using a conductive adhesive containing conductive particles such as gold, nickel, silver, palladium, and copper in the conductive adhesive in an amount of 50 to 90% by weight, the area in which the conductive particles are overlapped is increased. While improving
The content of conductive particles can be made smaller than before. Therefore, the adhesive strength of the epoxy adhesive is also improved. Further, when the adhesive area decreases, the connection resistance increases, but when this conductive adhesive is used, sufficient connectivity can be obtained, the applicability of the conductive adhesive is not deteriorated, and the increase in connection resistance can be suppressed. .

[0019]

The present invention will be described below in detail with reference to examples.

Bisphenol A type, bisphenol F
Type, novolac type epoxy resin base compound and amines, acid anhydrides, imidazoles and other curing agents are mixed at the optimum ratio in consideration of insulation, viscosity and adhesive strength. Use as an adhesive. In some cases, additives such as a reaction accelerator and a plasticizer may be mixed.

The curing agent was added in an amount of 2 to 50 parts by weight based on 100 parts by weight of the main agent.

The above epoxy adhesive was mixed with 50 to 90% by weight of conductive particles of metal such as gold, nickel, silver, palladium and copper, and kneaded using a three-roll to obtain a conductive adhesive.

The conductive adhesive is used to connect a semiconductor device in which a projection electrode is formed on a silicon substrate having an aluminum film formed on the entire surface with a plating method and a transparent electrode formed on a glass substrate by a sputtering method and patterned. And then Figure 4
The connection resistance was measured by the four-wire resistance measuring method shown in.

As a measuring method, a current is passed through a pair of wiring RA and a wiring RB, and a voltage drop is measured by another pair of wiring RC and a wiring RD. If the current value flowing through the DUT R (conductive adhesive in this case) and the voltage values at both ends are known,
The value of the resistance to be measured (in this case, the connection resistance of the conductive adhesive) can be calculated by Ohm's law.

Next, the present invention will be specifically described. Hereinafter, in this embodiment, the epoxy adhesive used was one containing 100 parts by weight of a bisphenol A type epoxy resin as a main component and 50 parts by weight of polymethylenediamine as a curing agent.
Further, if the metal conductive particles are less than 50 wt% with respect to the total weight of the conductive adhesive, the connection resistance value becomes very high, so that the measurement becomes impossible. Since the content of was reduced, the adhesive strength was significantly deteriorated. Therefore, the conductive particles of metal were adjusted to 50 to 90% by weight with respect to the total weight of the conductive adhesive.

FIG. 1 shows the difference in connection resistance due to the difference in the average value of the unidirectional diameters of the flaky conductive particles contained in the conductive adhesive. The conductive adhesive used at this time uses silver conductive particles having an average unidirectional diameter of 2 to 10 μm as the conductive particles, and the content thereof is 70% by weight based on the total weight of the conductive particles. Further, when conductive particles having an average unidirectional diameter of more than 10 μm were used, the applicability of the conductive adhesive to the fine protruding electrodes was deteriorated and the practicality was reduced.

From the graph of FIG. 1, as compared with the conductive adhesive in which the average directional diameter of the flaky conductive particles is less than 3 μm, the one having the average directional diameter of 3 to 10 μm has a remarkably small connection resistance and the conductive property. The nature is improving. Further, since the content of the conductive particles in the conductive adhesive does not change, the adhesive strength does not change.

FIG. 2 shows the relation between the connection resistance and the ratio of the flaky conductive particles having an average unidirectional diameter of 3 to 10 μm in the total weight of the conductive particles.

As shown in FIG. 2, the average of the unidirectional diameters is 3 to 10 μm.
When 50% by weight or more of the electroconductive particles is contained in the total weight of the electroconductive particles, the connection resistance is reduced and the electroconductivity is remarkably improved.

FIG. 3 is a graph showing the relationship between the connection resistance of the conductive adhesive and the connection area. Connection area of conductive adhesive is 1
A conductive adhesive using a conductive particle having a square of 00 to 20000 μm ² and an average directional diameter of less than 3 μm, and a flaky conductive particle having an average directional diameter of 3 to 10 μm is 70% of the total weight of the conductive particles. The measurement was performed for two kinds of conductive adhesives containing wt%.

A comparison of the connection resistances of the conductive adhesives when the conductive particles whose average directional diameter is less than 3 μm is used and when the conductive particles whose average directional diameter is 3 to 10 μm are used are compared. The conductive adhesive using the conductive particles having an average of 3 to 10 μm has remarkably improved conductivity.

[0032] especially connection area when 900 .mu.m ² larger than in the case where the average of the unidirectional diameter with conductive particles of 3~10μm was able to suppress the connection resistance. Especially when paying attention to the connection area of 20000 μm ² or less,
The difference in the connection resistance of the conductive adhesive between the case where the conductive particles whose average directional diameter is less than 3 μm is used and the case where the conductive particles whose average directional diameter is 3 to 10 μm are used becomes large. When the conductive particles having an average of less than 3 μm are used, the connection resistance is increased. On the other hand, when the conductive adhesive of the present invention is used, the connection area changes at 10Ω or less between 900 and 20000 μm ^2. Therefore, it can be seen that the conductive adhesive of the present invention is suitable for connection in an extremely small connection area.

[0033]

As is apparent from the above description, the conductive adhesive of the present invention has an average directional diameter of 3 to 3 when connecting the electrode formed on the substrate and the protruding electrode formed on the semiconductor device. The conductive particles such as gold, nickel, silver, palladium, and copper, which are flake-shaped metal of 10 μm, are contained in an amount of 50% by weight or more in the total weight of the conductive particles, and the conductive adhesive contains 50 to 90% by weight of the metal conductive particles. % By using the conductive adhesive, the area in which the conductive particles are superposed is significantly increased as compared with the case where a conductive adhesive containing spheres or flake-shaped conductive particles having an average diameter of less than 3 μm is used. The conductivity is improved, and the content of conductive particles can be reduced as compared with the conventional one. Therefore, it is possible to perform the connection having good conductivity and high adhesive force. Also, the average of the unidirectional diameter is 3 to
By using conductive particles of 10 μm, sufficient connectivity can be obtained even when connecting with fine projection electrodes having a small adhesive area, and the coating property of the conductive adhesive is not deteriorated.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the average value of the unidirectional diameters of flaky conductive particles contained in a conductive adhesive and the connection resistance.

FIG. 2 is a graph showing the relationship between the content of flaky conductive particles having an average unidirectional diameter of 3 to 10 μm and the connection resistance in the conductive particles.

FIG. 3 is a graph showing a relationship between a connection resistance of a conductive adhesive and a connection area.

FIG. 4 is a wiring diagram of a four-wire resistance measuring method.

FIG. 5 is a cross-sectional view of a portion where a semiconductor device and a substrate are bonded together.

[Explanation of symbols]

 1 Semiconductor Device 2 Glass Substrate 3 Projection Electrode 4 Transparent Electrode 5 Conductive Adhesive 6 Sealing Resin S Connection Area

Claims (2)

[Claims] 1. A conductive adhesive for connecting an electrode provided on a substrate and a protruding electrode provided on a semiconductor device, the conductive adhesive including conductive particles of metal and an epoxy adhesive, The conductive particles of metal are contained in an amount of 50 to 90% by weight based on the total weight of the adhesive, and the average distance between parallel lines sandwiched in a fixed direction is 3 to 1 based on the total weight of the conductive particles of metal.
0 to 100 μm of flaky metal conductive particles
A conductive adhesive characterized in that it is contained in a weight percentage. 2. The connection area between the electrode and the protruding electrode is 900 to
The conductive adhesive according to claim 1, which is used in a range of 20000 μm ² .