JPH02306558A - Arrangement of conductive particles on electrode - Google Patents

Abstract

PURPOSE:To correspond to micronization of an electrode by scattering conductive particles having a larger diameter than the layer thickness of a photoresist layer and selectively irradiating light only on an electrode part to be pressure-welded and hardened followed by removing unnecessary conductive particles together with a resin layer. CONSTITUTION:A photoresisting resin layer 8 is applied to the surface of a substrate 1 whereon previously an electrode 2 and a surface protective layer 3 are formed. Next, conductive particles 5 having a larger diameter than the layer thickness of the resin layer 8 are scattered on the substrate 1. Next, a mask plate 9 having a transmitting region 7a and a light-shielding layer 7b corresponding to the electrode 2 is made to oppose to the side of the conductive particles 5 stuck to the substrate 1, and an elastic member 4 is made to closely contact with the rear to the conductive particles 5 of the substrate 1. Later, ultraviolet rays 20 are irradiated on a substrate 7 through the mask plate 9. Prior to hardening of the resin layer 8 due to light irradiation, the conductive particles 5 are pressed on the electrode 2 side by by mask plate 9 in the arrow 18 direction to the elastic member 4. Next, the conductive particles 5 stuck excepting to the electrode 2 are removed together with an unhardened resin layer 8b so that resin layer 8a fixes the conductive particles 5 on the electrode 2.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for connecting electrodes between circuit boards such as semiconductor integrated circuit boards, printed circuit boards, glass boards, flexible boards, or ceramic boards through conductive particles. The present invention relates to a method of arranging conductive particles on an electrode, which is suitably implemented for electrical connection by pressure contact.

2. Description of the Related Art Conventionally, soldering has been commonly used as a method for electrically connecting electrodes of circuit boards.

In the soldering method, a solder layer is formed on the electrodes of at least one circuit board by plating or printing, and this solder layer is heated to a high temperature of about 200 to 250 degrees Celsius to melt and attach to the other circuit board. Connect to the electrode of the board. Therefore, it is necessary to use a parent solder metal such as Au, Cu, or Ni as the electrode material in advance.

In order to avoid the thermal effects on circuit boards caused by the high-temperature process of soldering and the high cost of using parent solder metals, conductive particles have recently been dispersed in adhesives. There is a trend to use anisotropically conductive adhesives.

The anisotropically conductive adhesive exhibits conductivity only in the thickness direction when applied and pressurized, and is non-conductive in other directions. Utilizing this anisotropic conductivity, this anisotropic conductive adhesive is applied to the surface of the electrodes or terminals to be connected, and the anisotropic conductive adhesive layer interposed between the electrodes is pressurized across its thickness. Make electrical and mechanical connections between electrodes.

In particular, ITO (Indium Ti) is used as a wiring material.
The above-mentioned anisotropic conductive adhesive is often used to connect terminals of a liquid crystal display board using a liquid crystal display panel using an anisotropic conductive adhesive, because of its ease of connection and thermal conditions.

Problems to be Solved by the Invention The above-mentioned anisotropically conductive adhesive has a structure in which conductive particles are dispersed in a resin material. Therefore, when the pitch width between adjacent terminals becomes fine, there is a problem that electrical short circuit occurs due to the conductive particles present in the resin, making it difficult to connect with the fine pitch width.

An object of the present invention is to solve the above-mentioned problems so that conductive particles can be placed only on the electrodes to be connected, thereby making it possible to cope with miniaturization of the electrodes and to improve the reliability of the connection. An object of the present invention is to provide a method for arranging conductive particles on an electrode that can improve the conductivity of the electrode.

Means for Solving the Problems The present invention involves coating a circuit board on which electrodes are formed with a photocurable resin material to form a resin layer, and forming a conductive layer with a diameter larger than the layer thickness of the resin layer. particles are sprinkled on the circuit board, and the conductive particles are applied to the resin layer of the circuit board on which the conductive particles are sprinkled, through a selectively transmitting light member in which a light transmitting region and a light blocking region are selectively formed. After the resin layer is cured, the conductive particles are pressed against the electrode side by the selective transmission member, and the conductive particles adhering to areas other than the electrode are removed together with the resin layer. A method for arranging conductive particles on an electrode is characterized in that:

Effect 41 According to the present invention, a photocurable resin material is applied to a circuit board including electrodes to form a resin layer.

Conductive particles having a diameter larger than the thickness of the resin layer are sprinkled on the resin layer, and the particles adhering to areas other than the electrodes are removed together with the resin layer. In order to arrange conductive particles only on the electrodes in this way, first, on the resin layer of the circuit board on which the particles are sprinkled, a light transmitting area and a light blocking area are placed at positions corresponding to the electrodes of the circuit board. Light is irradiated through a selectively transmitting light member formed selectively. Furthermore, before the resin layer is cured by light irradiation, the conductive particles are pressed against the electrode side by the selective transmission member.

As a result, the resin layer cured by light irradiation corresponds to the light transmission area of the selective transmission member.

The conductive particles are embedded and fixed, and the conductive particles are held in the uncured resin layer that is not irradiated with light corresponding to the light blocking area.

Therefore, by removing the particles adhering to areas other than the electrode together with the uncured resin layer, only the conductive particles arranged on the electrode are embedded and fixed in the resin layer, forming a protruding electrode. I can do it.

As a result, protruding electrodes can be formed on the circuit board, and a circuit board that can be connected to other circuit boards with high reliability in response to the miniaturization of the electrodes is constructed.

Further, when forming the protruding electrode on at least one of the circuit boards to be connected and pressing the two circuit boards together, an adhesive that hardens at a relatively low temperature may be filled between the two circuit boards. When this adhesive is cured, the electrical connection portion consisting of the protruding electrode is sealed with the resin,
Connection reliability is greatly improved.

Embodiment FIG. 1 is a cross-sectional view showing the configuration of a semiconductor device 6 which is an example of the present invention, FIG. 2 is a cross-sectional view explaining the manufacturing process of the semiconductor device 6, and FIG. FIG. 6 is a cross-sectional view of a liquid crystal display device 1o in which 6 is mounted.

Referring to FIG. 3, a pair of liquid crystal display plates 11 each have a translucent electrode 13 and a counter electrode 16 formed on their surfaces.
12 are pasted together via a sealing resin 15,
A liquid crystal 17 is sealed between them. Liquid crystal display device 10
, the electrode 1 extends on the liquid crystal display panel 12 to the right in the drawing.
A semiconductor device 6 is connected to 3 via conductive particles 5 to drive the display of the liquid crystal display device 10 . Further, the connection portion between the semiconductor device 6 and the liquid crystal display board 12 is sealed with an adhesive 14.

The semiconductor device 6 has a diffusion layer (not shown) formed on a substrate such as silicon or gallium arsenide, and includes a large number of transistors, diodes, etc., and has the function of driving the display of the liquid crystal display device 1o. This semiconductor device 6 includes a substrate 1, an electrode 2 formed in advance on one surface of the substrate 1, a resin layer 8a, and conductive particles 5.

The electrode 2 of the semiconductor device 6 is usually made by adding 1 part of An to 1 part of St.
A layer of Al-3i is used. Al-3
i forms a very thin insulating oxide film such as alumina on its surface, which tends to increase the resistance during connection. In order to reduce this connection resistance, A1・Si
Cr, Ti, W, Cu, Ni, Au, Ag,
It may be coated with one or more metal layers in advance using any metal such as Pt and Pd, or an alloy of these metals.

As a coating method, the metal layer is deposited on the semiconductor device 6 by a sputtering method or an electron beam method, and then patterned by a photolithography method to selectively coat the electrode 2 with the metal layer. Alternatively, since Ni cannot be electrolessly plated directly on the electrode 2 made of Al/Si, Pd may be selectively electrolessly plated on the electrode 2 first, and then Ni may be electrolessly plated on the Pd. Accordingly, the electrode 2 can be coated with a Ni metal layer.

A surface protective layer 3 is formed on a surface region of the substrate 1 where the electrode 2 is not formed. This surface protection N3 is made of, for example, SiN, 5in2, or polyimide.

A resin layer 8a is formed on the electrode 2 of the substrate 1. This resin layer 8a is cured by the method of the present invention, which will be described later, with one end of the conductive particles 5 in contact with the surface of the electrode 2 and the other end protruding from the resin layer 8a. As the material of the resin layer 8a, various synthetic resin materials such as acrylic resin, polyester resin, urethane resin, epoxy resin, or silicone resin can be used.

As the conductive particles 5, Au, Ag, Pt, cu, Ni
, C1In, Sn, Pb, and Pd, or alloys of two or more of these metals can be used. Further, as illustrated in FIG. 1, the conductive particles 5 may be formed by forming a coating layer 5a made of a conductive material on the surface of an elastic particle 5b made of a polymeric material. This lifting weight, elastic particle 5b
Examples of the polymer material that can be used include molded resins such as polyimide resins, epoxy resins, and acrylic resins, or synthetic rubbers such as silicone rubber and urethane rubber.

The conductive material of the coating layer 5a includes Au, Ag,
Pt, Cu, Ni, C, Irr
, S rr , pb and P d , or these metals can be used as one layer or two or more layers. When forming the covering layer 5a with two or more layers, a metal layer such as Ni, which has excellent adhesion to the elastic particles 5b, is first formed, and in order to prevent oxidation of such metal, Preferably, it is coated with a metal layer such as Au. Coating methods include sputtering method,
A vapor deposition method such as an electron beam method or a method such as electroless plating can be used.

Next, an embodiment of the present invention will be described with reference to FIG. In FIG. 2(1), in a substrate 1 on which electrodes 2 and a surface protection layer 3 have been formed in advance, a photocurable material is applied to the surfaces of the electrodes 2 and a surface protection layer 3 by a method such as spin cord or roll coating. A resin material 8 is applied over the entire surface to form a resin layer 8 having a uniform layer thickness 11. This resin layer 8 has a viscosity of 2000 μm to 1 μm in the applied state.
Preferably, it has a viscosity of 110 centipoise (cP).

In order to apply the resin layer 8 as described above, a photocurable resin material prepared in advance to a predetermined viscosity μ is diluted with an appropriate solvent and applied to the substrate 1 in a state in which the viscosity is reduced. Thereby, the layer thickness 11 of the resin layer 8 during coating can be easily controlled, and the layer thickness p1 of the formed resin layer 8 can be maintained uniformly on the substrate 1.

However, it is generally known that when a photocurable resin is impregnated with a solvent, curing by light irradiation becomes insufficient. Therefore, the substrate 1 on which the resin layer 8 has been formed by coating the photocurable resin is left in a vacuum of, for example, about 1 mrnT or +- for a sufficient period of time, for example, at least 1 hour, and the solvent contained in the resin layer 8 is removed. fully vaporize. As a result, the resin layer 8 in which the solvent has been vaporized becomes a liquid in its natural state, the photocurability is improved, and the viscosity is restored to a predetermined viscosity μ prepared in advance.

The resin layer 8 on such a substrate 1 has a layer thickness of 11
-1 to about 20 μm is preferable. The layer thickness 11 of the resin layer 8 should be determined by considering the flatness, roughness, waviness, warpage, etc. of the substrate 1 and the electrodes 2, and should be determined by considering the fineness of the electrodes, pitch width, etc. Basically, the thinner the electrode is, the better, depending on the electrode spacing. However, the layer thickness 1
If it is thinner than 1, the roughness of the substrate 1 will appear as unevenness of the conductive particles 5 during dispersion of the conductive particles 5, which will be described later, and the pressure applied by the mask 9 will be insufficient, which tends to result in poor electrical connection.

In addition, for sound where the resin layer 8 is larger than the layer thickness 11,
The number of wires of the electrode 2 that can be accommodated decreases, and the pitch width increases.

The material for the resin layer 8 is, for example, a base material made of acrylic or polyester resin material mixed with a photocuring agent, or a photocurable resin made by adding a photoreactive group to the base material. You can use the ones you made.

Next, as shown in FIG. 2(2), the conductive particles 5 are arranged in substantially a single layer on the resin layer 8. As a result, as will be described later, a stable connection state can be achieved when the circuit board is pressed into contact with another circuit board. To arrange the conductive particles 5 in a single layer, a sufficient amount of the conductive particles 5 is uniformly sprinkled over the entire surface of the resin layer 8, which has been adjusted to have a predetermined viscosity μ by the above-described treatment.

At this stage, the conductive particles 5 may be stacked in several stages.

Thereafter, by air blowing or N2 blowing of air or nitrogen gas onto the substrate 1, excess conductive particles that are simply laminated and adhered to the conductive particles 5, etc. that have adhered to the resin layer 8 due to their adhesive properties are removed. Remove particles 5. or,
Excess conductive particles 5 may be washed out by washing with water.

As mentioned above, in order for the conductive particles 5 to reliably adhere as a single layer on the resin layer 8, the resin layer 8 must have a viscosity of 2,000 μm to 2,000 μm.
It is sufficient if it has a viscosity of about 100,000 cP. When the viscosity μ is higher than the above value, on the contrary, the adhesiveness of the conductive particles 5 of the resin layer 81\ decreases. On the other hand, if the resin layer 8 has a viscosity lower than the above value, the adhesion of the conductive particles 5 will be insufficient, and the conductive particles 5 once attached will separate from the resin layer 8 and spread to other conductive particles 5. The conductive particles 5 tend to adhere to each other and form a lump.

Next, as shown in FIG. 2(3), a mask plate 9 in which a light-transmitting region 7a and a light-blocking region 7b are selectively formed corresponding to the electrode 2 is attached to the conductive particles adhered to the substrate 1. The electrode 2 and the light-transmitting region 7a are positioned so as to face each other on the 5 sides. Further, an elastic member 4 made of soft rubber or the like is brought into contact with the back surface of the conductive particles 5 of the substrate 1 . Thereafter, the substrate 1 is irradiated with ultraviolet rays 20 through this mask plate 9. Prior to curing of the resin layer 8 by this light irradiation, an arrow mark 1 is placed on the elastic member 4.
The conductive particles 5 are pressed toward the electrode 2 by the mask plate 9 in eight directions. As a result, the conductive particles 5 are fixed with one end thereof in contact with the electrode 2 as the resin layer 8 hardens.

Furthermore, even if the conductive particles 5 do not come into contact with the electrodes 2 during the pressurization by the mask plate 9, it is possible to prevent the conductive particles 5 from coming into contact with the electrodes 2 by selecting a relatively soft resin material such as urethane or silicone for the photocurable resin layer 8 in advance. , the conductive particles 5 penetrate through the resin layer 8 during pressure contact with another circuit board, which will be described later, and the electrodes 2
can be brought into contact with. That is, such a soft resin material is softer than the hardness of the conductive particles 5 even after photocuring, and has such softness that plastic deformation occurs due to the pressurized particles 5 and the resin layer 8 is pushed apart. It is fine as long as it is something.

The material of the mask plate 9 is preferably one that can uniformly press the conductive particles without warping due to the drag force from the conductive particles 5 during pressurization. As a mask plate used for such exposure and pressurization, for example, a metal layer 91) is formed on the entire surface of the transparent thick glass plate 9a by vapor deposition, and then selectively coated by photolithography or the like. A pattern corresponding to the shape of the electrode 2 on the substrate 1 is formed by etching. As a result, the mask plate 9 has
A mask pattern consisting of the light-transmitting region 7a and the light-shielding region 7b is formed depending on the presence or absence of the metal layer 9b. The layer thickness 12 of such a metal layer 9b is determined to be sufficiently small compared to the particle size (amount) of the conductive particles 5 that contact during pressurization, and to an extent that does not cause unevenness of the pressurizing force, for example, within several hundred nanometers. That's fine.

By exposing the resin layer 8 containing the conductive particles 5 to light through the mask plate 9 and applying pressure, the conductive particles 5 on the electrode 2 form a hardened resin layer 8a, as shown in FIG. 2(4). The conductive particles 5 other than those on the electrodes 2 are embedded and held in the uncured resin layer 8b.

The conductive particles 5 disposed on the substrate 1 have a uniform particle size d- whose particle diameter d is at least twice the layer thickness p1 of the resin layer 8, preferably about 3 to 20 times the layer thickness 11. (3~2
0) XZI is sufficient.

If the particle size of the conductive particles 5 (1 is less than twice the layer thickness 11), when the conductive particles 5 are pressed onto the substrate 1 side through the mask plate 9, the resin layer 8 will adhere to the mask plate 9, causing contamination. In addition, this particle size (1) must correspond to the miniaturization of the electrode 2 and the miniaturization of the pitch width, and increasing it unnecessarily may impair the reliability of the electrical connection. This will lead to a decline.

Further, a translucent resin film 12 made of polyethylene, polycarbonate, Teflon, silicone, or the like, or a translucent member such as a glass plate may be interposed between the mask plate and the conductive particles 5. As a result, the mask plate 9 and the conductive particles 5 do not come into direct contact with each other, and therefore, damage to the mask plate 9 caused by direct contact and mutual pressure can be prevented and protected. .

Next, only the electrode 2 is selectively irradiated with the ultraviolet rays 20, and the exposed resin layer 8 is developed using a solvent. A suitable solvent is methyl ethyl ketone.

Ketones such as methyl isobutyl ketone and acetone, or solvents such as xylene and toluene are used, but
The type of solvent should be appropriately determined depending on the characteristics of the resin layer 8, such as a ketone solvent when the resin layer 8 is made of acrylic. Generally, a cured product of a photocurable resin is difficult to dissolve in a solvent, so it is easy to develop.

That is, the resin layer 8a is cured by being irradiated with ultraviolet rays 20.
In this case, a crosslinking reaction based on ultraviolet rays 20 occurs, and it is insoluble or poorly soluble in solvents. On the other hand, in the uncured resin layer 8b that is not irradiated with the ultraviolet rays 20, the reaction does not occur and is easily eluted and removed by a solvent.

As a result, as shown in FIG. 1, a semiconductor device 6 in which conductive particles 5 are disposed only on the electrode 2 is obtained. In this way, in the semiconductor device 6, the conductive particles 5 are placed on the electrode 2.
The resin layer 8εt fixed on the substrate 1 forms minute electrodes protruding from the substrate 1. Therefore, the semiconductor device 6 can be connected to other circuit boards with high reliability in response to miniaturization of electrodes.

FIG. 4 shows the liquid crystal display device 1o shown in FIG.
5 is a partially sectional view seen from IV, and FIG. 5 is an enlarged sectional view showing the details of FIG. 4 in detail. Referring to FIGS. 4 and 5, semiconductor device 6 has one end of conductive particles 5 disposed on resin layer 8a on electrode 2 in contact with the surface of electrode 2, and the other The end is buried and fixed in a state where it protrudes from the resin layer 8a. On the other hand, the electrodes 13 of the liquid crystal display board 12 are made of ITO (Indium Tin Oxide) on the surface of, for example, soda glass.
, or ITO plated with Ni to reduce contact resistance, and the thickness is usually 50 to 20 mm.
It is about 0nffl.

In order to mount the semiconductor device 6 on the liquid crystal display board 12, the surface of the substrate 1 on which the protruding electrodes made of conductive particles 5 of the semiconductor device 6 are formed is opposed to the surface on which the electrodes 13 of the liquid crystal display board 12 are formed. Then, the conductive particles 5 and the electrodes 13 are aligned. After completing the alignment, apply adhesive 1 between substrates 1 and 12.
4, and place the semiconductor device 6 against the liquid crystal display panel 12 in the direction of arrow 19 via the conductive particles 5 and adhesive 14.
Pressure is applied until a predetermined distance 13 is established between the electrodes 2 and 13.

The adhesive 14 is cured under this pressure, and the semiconductor device 6 is mounted on the liquid crystal display board 12.

When the semiconductor device 6 in which the conductive particles 5 are disposed on the electrode 2 is connected to the liquid crystal display board 12 by pressure contact, the conductive particles are removed by the pressure 19 applied to both the circuit boards 1 and 12. The resin layer 8a may be penetrated and one end thereof may be in contact with the electrode 2.

As the adhesive 14, various types of adhesives such as reactive curable, anaerobic curable, thermosetting, and photocurable adhesives can be used.

Particularly in this embodiment, since the liquid crystal display panel 12 is made of a glass plate which is a light-transmitting material, it is effective to use a photocurable adhesive that can be bonded at high speed as the adhesive 14.

In this way, the corresponding electrodes 2 and 1 are connected via the conductive particles 5.
When connecting the circuit boards 1 and 3, if the adhesive 14 is filled in advance between the two circuit boards 1 and 12 and cured, the electrical connection part will be sealed with the resin, and the removability of the connection will be greatly improved.

Furthermore, if the conductive particles are realized by forming the conductive coating layer 5a on the surface of the elastic particles 5b described above, thermal deformation of the electrical connection portion due to changes in external temperature after connecting the circuit board can be avoided. The conductive particles 5 can follow and respond accordingly. Therefore, the reliability of the connection is further improved.

In this embodiment, the case where the conductive particles 5 are arranged on the semiconductor device 6 has been described, but it is not limited to the semiconductor device, and the case where the conductive particles are arranged on another circuit board and pressure-bonded is explained. The invention can also be practiced in a wide range of ways.

Effects of the Invention As described above, according to the present invention, conductive particles can be arranged only on the electrodes of a circuit board by a simple method. As a result, in response to the miniaturization of electrodes, the reliability of the field 6 for connecting the circuit board on which the electrode protruding from the conductive particles is formed and another circuit board by pressure contact is improved. Therefore, productivity is improved and costs are reduced.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a semiconductor device 6 according to an embodiment of the present invention, FIG. 2 is a cross-sectional view explaining the manufacturing process of the semiconductor device 6 shown in FIG. 1, and FIG. 3 is a liquid crystal display on which the semiconductor device 6 is mounted. 4 is a sectional view of the display device 10, FIG. 4 is a sectional view taken along the section line IY-IV in FIG. 3, and FIG. 5 is a partially enlarged sectional view of FIG. 4. DESCRIPTION OF SYMBOLS 1... Substrate, 2,13.16... Electrode, 5... Conductive particle, 6... Semiconductor device, 7a... Transparent region,
7b... Light-shielding area, 8... Resin layer, 10... Liquid crystal display device, 18.19... Pressurizing direction, 20... Ultraviolet ray agent Patent attorney Number of strokes Keiichi ■ C Tsu\ years old

Claims (1)

[Claims] A resin layer is formed by applying a photocurable resin material to a circuit board on which electrodes are formed, and conductive particles having a diameter larger than the layer thickness of the resin layer are applied to the circuit board. The resin layer of the circuit board on which the conductive particles are scattered is irradiated with light only on the electrode portions through a selectively transmitting light member in which a light transmitting region and a light blocking region are selectively formed. Prior to curing of the resin layer, the conductive particles are pressed against the electrode side by the permselective member, and the conductive particles adhering to areas other than the electrodes are removed together with the resin layer. How to place conductive particles on an electrode.