JPS63102110A - Anisotropic conductor and making thereof - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an anisotropic conductor that exhibits electrical conductivity in the direction of pressure but exhibits insulation in other directions.

[Conventional technology]

Conventionally, anisotropic conductors or anisotropic conductive films have been proposed that exhibit conductivity in the direction of pressure but insulate in other directions. (For example, JP-A-60-193353, JP-A-61-7687, 1% JP-A-57-346)
57, Japanese Patent Publication No. 60-140791, Japanese Patent Publication No. 59-2179) 0 For example, an anisotropic conductive film made by uniformly dispersing metal particles of around 30 μm in diameter in a rubber film (for example, Material Vol, 23. Floor 7.
p69-73 (1984)). For example, as shown in FIG. 6(a), this anisotropic conductive film 65 is sandwiched between an electrode pattern 62 on a flexible printed circuit board 61 and an electrode pattern 64 on a glass substrate 63.

Connection between both electrode patterns can be established simply by applying pressure to the electrodes at a temperature of approximately 150°C.

The metal particles M in this anisotropic conductive film include lead-tin (Pb
-Sn) low melting point powder is used, approximately 15
When heated to 0° C., the metal particles melt, and at the same time, the rubber film melts as well. This causes the metal to spread over the electrode patterns on both substrates and establish an electrical connection between them.

On the other hand, the rubber extruded from between the electrodes by pressure fills the space created by the difference in level between each electrode between adjacent electrodes. As a result, as shown in Figure 6(b), the packing density of metal particles relative to the volume of rubber filling this space is as follows:
Connections are made so that conductivity is maintained in the thickness direction of the film between the electrode patterns, and insulation is maintained in other directions. Therefore, the electrode pattern is formed at a density of about 5 electrodes/■ (in this case).

It has been reported that good resolution is shown for electrode width W, = 100 pm) [Problems to be solved by the invention] However, as VLSI (Very Large Scale Integrated Circuits) are increasingly used, , also for this VLSI connection.

It is desired to use such an anisotropic conductive film.

In VLSI, high-definition multi-contact electrodes (10 electrodes/m
If the above) is used, it becomes unusable as is. For example, 20/■ electrode pattern (electrode width W2
= 25μm) when connecting the same.

Uniform conductive particles with a particle size on the order of several μm or less must be uniformly dispersed in the film.

As shown in FIG. 7(a), particles M may aggregate together, short-circuits between adjacent electrodes may occur due to the mixing of large-diameter particles as shown in FIG. 7(b), and short-circuits may occur between adjacent electrodes as shown in FIG. The absence of particles M causes problems such as connection failure due to K, and it is difficult to connect high-definition multi-contact electrodes of 10 or more electrodes with such an anisotropic conductive film. .

Moreover, as shown in FIGS. 8(a) and (b), a predetermined 0
In the case where a large number of conductive particles having a particle size within the range are present between the upper and lower electrode pads 81, 82 or between the electrode patterns.

(1) Connection resistance increases.

(2) Because of the continuous point contact, current concentrates on the point contact portions, resulting in heat generation, leading to deterioration of the resin and destruction of the element.

(3) Electrical characteristics such as resistance value, current capacity, and capacitance are not uniform between pads.

It has the following drawbacks, and has the problem of lacking reliability as an electrical connection material.

Therefore, it has been proposed to insert a ball-shaped spacer 83 to keep the distance between the upper and lower electrode patterns constant, as shown in FIG. 8(e), but the number of conductive particles per pattern varies. However, since the pressurizing force applied to the upper and lower electrodes is not sufficiently applied to the conductive particles, there are problems such as an increase in connection resistance.

In addition, as shown in FIG. 8(C), solder particles 84 are also melted by applying pressure and heating.

As shown in Fig. 8(a), the parallelism between the electrode patterns may vary and the connection resistance may not be uniform due to this.
, has the same problem as (b).

Although it is conceivable to mix the spacer 83 in addition to the solder grains 84, it is clear that this would have the same problems as in FIG. 8(e).

In addition, in the case of using solder, new problems arise in that materials for the upper and lower electrode patterns must be selected or some kind of blocking layer must be formed.

Furthermore, when an IC chip is connected using such an anisotropic conductor, there is a problem that a short circuit may occur at the edge of the IC chip.

In FIG. 8(f), it is assumed that a pad 86 of an IC chip 85 is arranged to face an electrode pattern 82 on a substrate, and both are connected by a conventional anisotropic conductor 87. As shown in the enlarged view, the IC chip 85 sometimes has a contact 85', which short-circuits to the electrode pattern 82.

In order to avoid this problem, it has been proposed to place a spacer 88 as shown in FIG. 8(g), but this method lacks mass productivity and lacks reliability.

New problems such as the inability to increase the yield have arisen.

The present invention has been made in view of the above points, and has high reliability without variations in electrical characteristics between electrode patterns or between electrode pads.

Excellent mass production. Moreover, it is an object of the present invention to provide an anisotropic conductor that does not require the use of spacers.

[Means and effects for solving the problem] In order to solve the above-mentioned problem, in the present invention, the conductive particles are electrically insulated and distributed with an insulator, and the electrical conductive particles are In the anisotropic conductor, the conductive particles have a diameter of 1.0 to 100 μm, and are spherical particles with a particle size distribution within ±5% at a specific diameter, It is characterized in that the conductive particles are dispersed and arranged in a single layer.

According to this, by changing the diameter of the conductive particles according to the desired resolution and adjusting the dispersion ratio of the conductive particles according to the required connection resistance, electrical connections with the desired characteristics can be realized. Furthermore, a highly reliable electrical connection with uniform resistance values of the pads can be achieved.

〔Example〕

The present invention will be described in detail below with reference to the drawings. 1st
The figure shows the structure of an anisotropic conductor according to an embodiment of the present invention. In the figure, spherical conductive particles 1 are dispersed in an insulating resin 2, each independently and as a single layer.

The spherical conductive particles 1 may be made of a conductive metal with appropriate hardness, but in this embodiment, as shown in FIG. Conductive particles consisting of a nickel plating layer 12 are used. The spherical conductive particles 1 are dispersed in a poly-4-methylpentene-1 thermoplastic resin to form a film.

Since the conductive particles 1 are dispersed in a single layer in the insulating resin 2, the thickness of the insulating resin 2! is within twice the diameter R of the conductive particles 1 at that time.

Details of the first embodiment are as follows.

As the core material 11, divinylbenzene was suspension-polymerized and then classified for 1 time to give a particle size of 10.0±0.2 μm. The specific gravity of this core material 11 is 1.19, and the heat resistance is 3.
27℃ (TGA), hardness 1239 volume resistivity 3.6
1014Ω・Ro, coefficient of thermal expansion 9.8 x 10-'aa
/aa @'C. The nickel plating layer 12 was obtained by electroless plating and had a thickness of approximately 900 mm.

Poly-4-methylpentene-1 constituting insulating resin 2
Has a volume resistivity of 101@Ω・Ro or higher, a hardness of 60R1, and a specific gravity of 0.
．． 83, melting point 240℃, water absorption 0.01% (ASTM
D570).

As the film forming method, there are the following two methods. (1) Poly-4-methylpentene-1 in a high specific gravity solvent (
For example, by dissolving a predetermined amount in trichlorethylene, chloroform, etc., and filtering under pressure, remove dust with a size of 0.2 μm or more.
Remove impurities. A predetermined amount of the conductive particles were added to this solution and dispersed with high speed stirring using a homogenizer. A predetermined amount of the dispersion solution is applied onto a predetermined base film and dried to form a film with a desired thickness.

(2) The poly-4-methylpentene-1 at 250°C.

The mixture was melted under Ni, and a predetermined amount of the conductive particles were added thereto, followed by stirring and dispersion. This dispersed molten liquid is rolled with a predetermined roller,
Cool to create a film of desired thickness.

FIG. 5 shows conductive particles (10
This figure shows the relationship between the amount of added microorganisms (μm) and the number of dispersed particles. It was also found that if the amount of conductive particles added was less than about 0.6 (mg/-), a nearly single-layer structure could be obtained, but if it was more than that, some parts would become two layers. .

The electrical characteristics at this time are summarized in Table 1.

In addition, the measurement is 150 μm x 150 for 9 parts of the present invention.
This was done for one piece with an interval of 25 μm.

Regarding commercial product 1.1, conductivity at 150 μm x 150 μm depends on the probability of existence of particles, and it was almost impossible to measure at 0 PEN, so we measured it at 55 μm
It was converted into 50μm×150μmK.

FIG. 3 shows another embodiment of the invention. Figure 3(a)
, 4 is a base film, and conductive particles 3 microencapsulated with an insulating resin are arranged in a row on this base film. The microencapsulated conductive particles 3 are obtained by wrapping the conductive particles 1 with an insulating resin, as shown in FIG. 3(b)K. The conductive particles 3 may have a structure similar to that shown in FIG. 2(b). The insulating resin surrounding the conductive particles 3 may be the same as the insulating resin 2 shown in FIG. 1, such as poly-4-methyl-1-pentene or polybutylene phthalate thermoplastic resin. In this case, it is also necessary to make the particle diameters of the conductive particles 3 that have been encapsulated into nine microcapsules the same. That is, microencapsulated conductive particles 3 (
Microcapsules (hereinafter simply referred to as microcapsules) are made by selecting a specific particle size from 1 μm to 100 μm depending on the required resolution, and keeping the two-particle size distribution within ±5% at that specific particle size. The particle size distribution eliminates the need for a 9% separate spacer.

The microcapsules 3 temporarily fixed to this base film 4 are transferred to the necessary locations such as the electrode parts of the substrate ◇After that, the I
Electronic components such as C are placed and heated and pressurized.

FIG. 4 shows an example in which the IC chip 6 is fixed on the electrode 9 of the substrate 10. Pad portion 7 of IC chip 6 is connected to electrode 9 by conductive particles 1 . At this time, the diameters of the 10 conductive particles are uniform.

Moreover, since the conductive particles 1 are arranged in a line, electrical characteristics such as connection resistance are made uniform.

When using microcapsules, they may be placed directly on the connection portion without using a base film. For example, directly with Heat Row 2, etc., or after dispersing in a specified solvent, using a dispenser or spraying.

It can also be printed in a single layer at the required locations on the board using screen printing, etc.

Note that the materials used for each layer are not limited to those used in the examples.

Various other methods are also available. Below, we list the evaluation criteria that should be considered when making a selection.

The selection criteria for the core material and insulating resin are (1) melting point;
(2) Softening point, (3) Moisture resistance (water absorption), (4) Adhesion to adherend, (5) Volume resistivity, (6) Color, (7)
hardness, and (8) melt viscosity.

For example, when used for connecting IC chips.

Because it can be kept at a relatively high temperature (approximately 300℃),
A material with a high melting point and a high softening point can be selected, and it can be made to have high environmental resistance and reliability. Devices using liquid crystals require materials with low melting and softening points. In particular, characteristics suitable for semiconductor devices include DTA (
In the differential thermal analysis) curve, the rise of the endothermic peak due to melting must be 200°C (at least 150'C or higher) or higher.

No deterioration such as oxidation occurs in the temperature range of 300℃ or less (no exothermic peak is observed) or the melt viscosity is 1,000 poise or less in the temperature range of 300℃ or less L 150'CX 100 hours and that it does not deteriorate. Specific materials that can be used include phenol resin, unsaturated polyester resin, alkyd resin, xylene resin, etc., as well as urea resin, melamine resin, allyl resin, furan resin, polyester resin, epoxy resin, and silicone resin.

Polyamide resin, polyamide-imide resin, polyimide resin, polyurethane resin, Teflon resin.

Thermosetting polymers such as polyolefin resin, benzoguanamine resin, polyethylene resin, polypropylene resin, polybutylene resin, polymethacrylic acid resin, methyl resin,
polystyrene resin, acrylonitrile-styrene resin,
Polystyrene resin, acrylonitrile-styrene-phtazidine W resin, vinyl resin, polyamide resin, polyester resin.

Polycarbonate resin, polyacetal resin, ionomer resin, polyether sulfone resin, polyphenyl oxide resin, polyphenylene sulfide resin, polyphenylene oxide resin, aromatic polyimide resin, fluororesin, chlorinated ether resin, styrene resin, vinylidene chloride resin, vinyl carbazole resin, vinyl butyral resin, vinyl formal resin, vinyl acetal resin,
Polyvinyl alcohol resin, vinyl acetate resin, vinyl chloride resin, polyamic acid resin, polyetherimide resin,
Thermoplastic polymers such as polyolefin resins, polyarylate resins, polysulfone resins, polyethersulfone resins, polyphenylene sulfide resins, polysulfone resins, polyurethane resins, phenol resins, and cellulose resins such as ethyl cellulose resins and cellulose acetate resins. Appropriate selection and combinations are possible.

A commercially available product is Micropearl 5P-Ni manufactured by Sekisui Fine Chemical Co., Ltd., which is divinylbenzene mJIW mixed with nickel.

The conductive plating layer is selected from a material that can be plated electrolessly and that does not damage the electrode pads. Gold is a specific metal.

The upper and lower electrode groups are selected from metal compounds such as platinum, palladium, silver, copper, iron, nickel, aluminum, chromium, and solder, conductive inorganic compounds such as conductive carbon, and conductive organic compounds such as organometallic compounds. It can be selected as appropriate depending on the material etc.

In addition, in the examples, the conductive layer was formed by electroless plating, but the conductive layer could be formed by other methods besides electroless plating.
Electroless Metsky electrolytic plating method, vacuum evaporation method, etc. can be selected as appropriate depending on the conductive material used. Furthermore, the conductive layer is not limited to one layer, but may be multilayer or an alloy of the metals mentioned above, depending on the electrode to be connected. It can be selected as appropriate. It goes without saying that other methods such as an air suspension coating method and an inorganic encapsulation method may also be used.

Here, it is possible to use the same material for the core material and the insulating resin layer, but the degree of complexity etc. is adjusted so that the core material has a slightly higher melting point or softening point than the surface layer. [Effects of the Invention] As described above, according to the present invention, since the anisotropic conductor is composed of conductive particles having a uniform particle size of 9, It is possible to obtain an anisotropic conductor with high resolution and high dimensional accuracy without using a spacer.

Furthermore, since the conductive particles are arranged in a single layer, connection with low connection resistance per pad and without variation is possible.

When a synthetic resin is used as the core material, it is easier to make the particle size distribution uniform than when a spherical substance is formed using a conductive material, and it is also easier to adjust the particle size or film thickness, which results in high resolution. It is possible to obtain an anisotropic conductor of. Furthermore, since the 9 particles themselves have appropriate elasticity, no cracks occur in the bonded parts during thermocompression bonding, and adhesion is improved.

Furthermore, if the film is made in advance, the connection can be easily made by placing or transferring it onto the required part of the board, which allows for highly efficient mounting.

[Brief explanation of the drawing]

Figures 1 and 2 show an embodiment of the invention in which conductive particles are dispersed in an insulating resin, Figure 3 shows an embodiment of the invention using a microphone capsule, and Figure 4. FIG. 5 is a diagram showing the characteristics of the present invention, and FIGS. 6, 7, and 8 are diagrams showing conventional examples. 1...- Spherical conductive particles. 2...Insulating resin. 3...Microcapsule. 4...Base film. 5...Insulating resin film. 6...IC chip. 7... Electrode pad. 8... Patsushibasyo/membrane. 9... Lower electrode pattern. 10...Substrate. 11... Core substance. 12... Conductive plating. 13... Insulating resin 0

Claims (1)

[Scope of Claims] (1) Anisotropic conduction in which conductive particles are electrically insulated from each other by an insulator and distributed in a dispersed manner so that when bonded under pressure, they become electrically good conductors in the direction of pressure. In the body, the conductive particles are spherical particles with a diameter of 1.0 to 100.0 μm and a particle size distribution within ±5% with respect to a specific diameter in the range, and An anisotropic conductor characterized by having particles dispersed in a single layer. (2) The conductive particles are dispersed in a layer of an insulator, and the thickness of the insulator is within twice the diameter of the conductive particles. Anisotropic conductor. (3) The anisotropic conductor according to claim 1, wherein the insulator that insulates the conductive particles wraps each conductive particle to form a microcapsule. (4) The anisotropic conductor according to claim 3, wherein the microencapsulated conductive particles are arranged in a single layer on a sheet. (5) After melting the insulator with a solvent or heating, add conductive particles, stir and disperse, and then roll and cool this conductive particle dispersion with a predetermined roller to obtain a film with a desired thickness. A method for producing a characteristic anisotropic conductor. (6) A method for producing an anisotropic conductor, characterized in that conductive particles are wrapped in an insulator to form microcapsules and then fixed on a sheet.