JPH02180036A - Formation of electrode - Google Patents

Abstract

PURPOSE:To cope with fining of an electrode of a wiring board by fixing an interposed object having elasticity and conductivity onto the electrode by alloy junction. CONSTITUTION:A projecting electrode 13 and an electrode 3 are pressure-welded in opposition with a fixed interval l1 between electrodes 3, 11 and a semiconductor device 1 and a liquid crystal display 5 are joined by hardening adhesive layer 14 which is filled between substrate 5, 10. An elastic conductive particle 15 which is used for the projecting electrode 13 is constituted by applying a conductive coating layer 17 which consists of a metal material onto a surface of an elastic bead 16 which consists of high polymer material. An interposed object which is elastic as well as conductive is used and fixed onto an electrode of a wiring board by alloy junction in this way, thereby forming a projecting electrode on the wiring board. According to this constitution, it is possible to cope with fining of an electrode of a wiring board connected each other.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is for electrically connecting an integrated circuit board on which semiconductor elements are formed, and a circuit board such as a printed circuit board, a flexible board, or a ceramic board. The present invention relates to a method of forming an electrode that is suitably carried out.

2. Description of the Related Art Conventionally, as a method for electrically connecting electrodes of an IC (Integrated Circuit) board on which a semiconductor element is formed and electrodes of another circuit board by pressing them against each other, there is mainly a method disclosed in Japanese Patent Publication No. 59-2179 or A method using an anisotropic conductive sheet disclosed in Japanese Patent Publication No. 62/6652 (hereinafter referred to as "first conventional example")
, a method using metal protruding electrodes disclosed in JP-A-63-13337 (hereinafter referred to as "second fft-conventional example"), as well as JP-A-61-242041 and JP-A-61
259548, and a method using an elastic protrusion electrode disclosed in JP-A-63-150930 (hereinafter referred to as "Third Conventional Example J"), etc. are known.

In the first conventional example, an anisotropic conductive sheet in which conductive fine particles are dispersed in an adhesive made of resin, etc. is used. It utilizes anisotropy, which shows conductivity but is non-conductive in other directions. That is,
This anisotropic conductive sheet is interposed between the electrodes to be connected,
Electrical connection between each electrode is established by applying pressure to a portion of the sheet interposed between the electrodes in the thickness direction of the sheet. However, in this anisotropic conductive sheet, when the pitch width of the connected electrodes is fine pitch of about 150μrl'1 or less, conduction is possible between adjacent electrode terminals due to the conductive fine particles dispersed in the sheet. This caused a short circuit.

In order to solve the problems of the first conventional example described above, in the second conventional example, a protruding electrode made of a metal material is provided on the surface of one electrode of the circuit board to be connected, and the protruding electrode is pressed against the corresponding electrode. This is used to make electrical connections. According to this second conventional example, although it is possible to connect electrodes having a minute pitch width, the uneven height of the protruding electrodes causes non-uniformity in connection resistance during pressure welding, resulting in poor connection reliability. There was a problem that it was inferior.

In the third conventional example, in order to solve the problems of the second conventional example described above, the protruding electrodes are made of a material having elasticity and conductivity, and the uneven height of the protruding electrodes is corrected during pressure welding. This is absorbed by the elastic deformation of the protruding electrode.

Problems to be Solved by the Invention Among the third conventional examples, particularly in JP-A-61-242041 and JP-A-61-259548, printing methods such as screen printing are used to form protruding electrodes. However, with the printing method, it is difficult to form minute protruding electrodes corresponding to electrodes with a minute pitch width.
Electrodes having minute pitch widths cannot be connected to each other without shorting.

In addition, the third conventional example) JP-A-63-150”) 30
In order to selectively cure the conductive ink used in forming the protruding electrodes, the conductive ink is cured by irradiating infrared rays or ultraviolet rays through a mask plate. However, in a method of thermosetting using infrared irradiation or the like, it takes several minutes to several tens of minutes to thermally inscribe the conductive material.

Therefore, the conductive ink around the openings on the mask plate (1) is also heated and hardened by heat conduction from the conductive ink heated by the infrared rays irradiated through the openings, and as a result The pattern formation property is poor and the pattern becomes unclear. Furthermore, in photocuring methods using ultraviolet irradiation, the metal powder, self-metal powder, conductive powder, or metal-plated glass beads added to the ink to make it conductive are opaque. Therefore, the entire conductive ink is not irradiated with the ultraviolet rays, resulting in insufficient photocuring. Therefore, there was a problem that the pattern formation property was poor.

Furthermore, JP-A-61-242041 and JP-A-63
In No. 150930, a conductive resin in which various conductive powders are mixed as a conductive agent into the resin is used as a material for the elastic protruding electrode. In such a conductive resin, in order to maintain sufficient elasticity, it is necessary to suppress the amount of conductive powder to a small amount. However, if the amount of conductive powder is small, the conductivity of the conductive resin will be poor.
There is a problem in that the connection resistance of the protruding electrode using this conductive resin becomes high.

An object of the present invention is to solve the above-mentioned problems, to be able to cope with the miniaturization of the electrodes of wiring boards that are connected to each other, to enable connections with low electrical resistance, and to ensure that the mutual electrodes can be connected with high reliability. It is an object of the present invention to provide a method for forming an electrode that can be used for electrical connection in a semiconductor device.

Means for Solving the Problems The present invention is a method of forming an electrode, characterized in that an intervening body having elasticity and conductivity is fixed onto an electrode of a wiring board by alloy bonding.

Function: In the method for forming an electrode of the present invention, an intervening body having elasticity and conductivity is used. This intervening body is fixed onto the electrode of the wiring board by a joint 6, thereby forming an electrode projecting on the wiring board.

Therefore, for example, when a semiconductor device is mounted on a circuit board, if the protruding electrode is formed on the semiconductor device, the semiconductor device can be connected to the circuit board with high reliability by a method such as pressure bonding.

In addition, when applying pressure using the protruding electrodes, it is possible to bond a wide area at low temperature by using a photo-curing or naturally-curing adhesive to bond the circuit boards together. (Since the electrical connection portion is sealed with resin, the reliability of the electrical connection is further improved.)

Embodiment FIG. 1 is an enlarged view of a semiconductor device 1 in which a protruding electrode 13 (hereinafter simply referred to as "protruding electrode 13") is formed according to the electrode forming method of the present invention is mounted on a liquid crystal display device 2 to be described later. FIG. 2 is a cross-sectional view of a liquid crystal display device 2 on which the semiconductor device 1 is mounted. Referring to FIG. 2, a pair of liquid crystal display plates 5.6 each having an electrode 3 and a counter electrode 4 formed on their surfaces are attached to each other with a sealing resin 7 in between, and a liquid crystal 8 is sealed between them. It has been stopped.

In the liquid crystal display device 2, the electrode 3 extends on the liquid crystal display plate 5 to the right in the drawing, and is connected to the protruding electrode 13 of the semiconductor device 1 mounted to drive the display of the liquid crystal display device 2.

The semiconductor device 1 has a diffusion layer formed on a wafer of silicon, gallium arsenide, or the like, constitutes a large number of transistors, diodes, etc., and has the function of driving the display of the liquid crystal display device 2. Referring to Figure 1,
The semiconductor device 1 includes a substrate 10 which is a wiring board;
For example, an electrode 11 formed on the top layer of SiN, S
Surface protective layer 12 made of iO2 or polyimide, etc.
including. The electrode 11 is made of Al-5t, for example.

A protruding electrode 13 is formed on the electrode 11 of this semiconductor device 1 according to the electrode forming method of the present invention described later.

On the other hand, the electrode 3 of the liquid crystal display panel 5 is made of tin-doped indium oxide (Indium oxide) formed on the surface of soda glass or the like.
It is ITO plated with diu+* Tin Oxide (hereinafter abbreviated as rlTo) or Nilagel, and usually has a thickness of about 100 to 200 rIrr+.

The semiconductor device 1 and the liquid crystal display board 5 are pressed into contact with the protruding mold 13 and the electrode 3 facing each other so that a predetermined distance 11 is maintained between the electrodes 3 and 11, and in this state, the gap between the substrates 5 and 10 is The adhesive layer 14 filled in is cured and bonded. Adhesive layer 14
For example, various adhesives such as reactive curable, anaerobic curable, thermosetting, and photocurable adhesives can be used.

In particular, in this embodiment, since the liquid crystal display panel 5 is made of glass, which is a translucent material, the adhesive layer 14 can be made of a photocurable adhesive that can be attached at high speed.

FIG. 3 shows a cross-sectional view of an example of the elastic conductive particles 15 used in the protruding electrode 13 shown in FIG. 1 above. The elastic conductive particles 15 are constructed by covering the surfaces of elastic beads 16 made of a polymeric material with a conductive coating layer 17 made of a metal material. As the elastic beads 16, resins such as polyimide resins, epoxy resins, and acrylic resins, and rubbers such as silicone rubber and urethane rubber can be used.

As the conductive material for the coating layer 17, Au is preferable from the viewpoint of solderability and ductility, but pt, P (amount, Ni, C
u, In, Sr1. Metals such as Pb and CC01A and their metal plates may be coated on the surface of the elastic beads 16 in one layer or in two or more layers. When covering with two or more layers, use a material with excellent adhesion to the elastic beads 161, such as N
A metal layer such as i is formed first, and then a metal layer such as Au is coated to prevent oxidation of the metal layer. As a coating method, a method such as a sputtering method, an electron beam evaporation method, or an electroless plating method can be used.

FIG. 4 is a cross-sectional view sequentially showing the manufacturing steps when implementing the electrode forming method of the present invention using solder metal.

As the electrode 11 of the semiconductor device 1, Al-3i is usually used. Did you know?) Barrier metal layer 18 for preventing metal diffusion, parent solder, solder layer 1 on lever electrode 11
9 and a solder layer 20 are formed in this order by a well-known method such as vapor deposition, photolithography, or plating to form a connection region having the structure shown in FIG. 4(1) on the electrode 11. do. As the barrier metal layer 18, Ti
, W, Or, and their base metals can be used. As one parent solder layer, Cu, Ni, Au, Ag
, Pt, and their hexagonal gold can be used. As the solder layer 20, p b -S rr having a relatively low melting point is used.
System (melting point m, p arrow 183'' (:, ), I
Group-8n type (IT1.P, "F116°C)" etc. can be used.

7lux 21 is coated on the semiconductor device 1 on which the connection region having the structure shown in FIG. 4(1) is formed by a method such as coating or roll coating.

The purpose of applying this flux is to improve solderability and to adhere the elastic conductive particles 15 onto the substrate 10. Therefore, as this flux 21,
A material that is non-volatile and has a predetermined viscosity is used.

Next, as shown in FIG. 4(2), the elastic conductive particles 15 shown in FIG. 3 are placed on the substrate 10. Therefore, the thickness of the 7 lux 21 is preferably about 1/2 to 115 times the diameter of the elastic conductive particles 15. Thereafter, the substrate 10 is heated to 220 to 250°C to remelt the solder layer 20, and the coating layer 1 formed on the surface of the elastic conductive particles 15 is
7 and solder together.

After the solder bonding, the substrate 10 and the bonded elastic conductive particles 15 are cooled and cleaned with an organic solvent such as A7T to remove the flux 21 applied to the surface and unnecessary elastic conductive particles 15. As a result, as shown in FIG. 4 (3), the protruding electrode 13 made of elastic conductive particles 15
It is possible to obtain a semiconductor device 1 in which is formed. In FIG. 4(3), one elastic conductive particle 15 is arranged for the connection area of one electrode 11, but a plurality of elastic conductive particles 1 are arranged for the connection area of one electrode 11.
5 may be arranged to form the protruding electrode 13.

Elastic conductive particles 1 formed according to the procedure explained above
The semiconductor device 1 having the protruding electrodes 13 consisting of 5 is made by hardening the adhesive filled between the circuit boards in advance while being in pressure contact with another circuit board, like the liquid crystal display device 2 of FIG. 2 described above. The circuit boards can then be bonded together and mounted.

FIG. 5 is a sectional view for explaining another embodiment of the present invention. Note that the same reference numerals are used for parts corresponding to the embodiment shown in FIG. In the method for forming an electrode shown in No. 5121, the two metal layers are heated under pressure, and the metals are mutually diffused in a solid state at the interface of these two metal layers to perform bonding. Take advantage of that. Therefore, in this example, as the elastic conductive particles 15,
The covering layer 17 is in particular Au, 3n or Au-S
It is preferable to use a metal material whose main component is an n-alloy.

FIG. 5(1) shows a semiconductor device 24 used in this embodiment.
This is a cross-sectional view showing the electrode structure of the substrate 10. Substrate 10
On the above electrode 11 made of At-3i, for example, a barrier metal layer 18 and a diffusion metal layer 22 to be bonded by diffusion are formed in advance by a well-known method such as vapor deposition, photolithography, or plating. . As the barrier metal layer 18, metals such as Ti, W, Cr, and alloys thereof can be used. As the diffusion metal layer 22, a coating layer 17 of elastic conductive particles 15 shown in FIG.
Although the same metal material II can be used, preferably A u , S r+ or A u −S
A material whose main component is an n-alloy is used.

As shown in FIG. 5(2), the elastic conductive particles 15 are uniformly arranged and adhered onto the temporary substrate 23 to which the adhesive 26 has been applied in advance. The temporary substrate 23 on which the elastic conductive particles 15 are supported is opposed to the semiconductor device 24 in which the diffusion metal layer 22 is formed on the electrode 11 shown in FIG. 5(1). 1 kg/in the direction indicated by
Pressure is applied to about 300 to 35 mrn'.
Heating is performed at 0°C. As a result, the metals are mutually diffused at the interface between the covering layer 17 made of the metal material of the elastic conductive particles 15 and the diffusion metal layer 22 formed on the electrode 11, and alloy bonding is performed, and the elastic conductive particles 15 and A protruding electrode 13 is formed on the substrate 10 at a position corresponding to the electrode 11. Note that by using a method of applying ultrasonic waves to the bonded portion at the time of the above-mentioned pressurization and heating, the elastic conductive particles 15 are directly coated without providing the barrier metal layer 18 and the diffusion metal layer 22 on the electrode 11. can be in contact with the electrode 11.

As a method for uniformly supporting the elastic conductive particles 15 on the temporary substrate 23, an adhesive 26 is applied onto the temporary substrate 23 by a method such as spin code, roll coat I, or printing, and this adhesive 26 is coated with elastic conductive particles. This can be carried out by attaching particles] 5 to ). Adhesive 26 used
Examples include molded resins such as silicone and polyimide, and sol-like oils and greases with high viscosity. i! ff quality can be used. This temporary board 2
The thickness of the adhesive 26 applied on the elastic conductive particles 15 is preferably about 1772 to 1/1 of the diameter of the elastic conductive particles 15.

If the adhesive 26 is thicker than the above value, the elastic conductive particles 15
If a plurality of particles or more adhere to the temporary substrate 23 in a layered manner and are thin, the adhesiveness is low and it is impossible to form an adhesion layer in which the elastic conductive particles 15 are evenly adhered.

Further, the thickness of the diffusion metal layer 22 formed in advance on the electrode 11 via the barrier metal layer 18 etc. is determined by concentrating the pressure during pressurization and heating, and making the portion I\elastic conductivity in the area other than the connection area on the electrode 11 In order to prevent the particles 15 from being compressed, it is preferable that the diameter of the elastic conductive particles 15 is approximately 17'2. If the diffusion metal layer 22 is thicker than the above value, the value of the sum of the layer thickness and the diameter of the elastic conductive particles 15 will become more uneven. In addition to requiring a large pressing force, the amount of deformation of the elastic conductive particles 15 increases unnecessarily. Also, in thin field 6,
Elastic conductive particles 1 are applied even to unnecessary parts such as the surface protective layer 12.
This leads to an undesirable situation in which the number 5 is damaged. Furthermore, in this embodiment, as in the embodiment shown in FIG. good.

As described above, the semiconductor device 24 in which the protruding electrodes 13 made of elastic conductive particles 15 are formed on the electrodes 11'2 can also be used on other circuit boards such as the liquid crystal display device 2, as shown in FIG. It can be mounted by a method such as pressure welding.

In the above embodiment, the substrate 1 of the semiconductor devices 1 and 24 is
Although the explanation has been given regarding the formation of protruding electrodes 13 on 0, it is not necessary to limit the case to forming electrodes in connection with semiconductor devices, for example, when forming electrodes on other circuit boards. The present invention can also be carried out.

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, as described in detail, it is possible to form finely protruding electrodes on electrodes of a wiring board by a simple method. This protruding electrode is made up of an elastic and conductive intervening body that is fixed onto the electrode of the wiring board by self-bonding. For this reason, the connection has high mechanical strength and low electrical resistance. Further, it becomes possible to cope with miniaturization of electrodes of wiring boards that are connected to each other. However, for example, when the wiring board on which the protruding electrode is formed and another wiring board are electrically connected by pressure contact, the reliability of the connection is significantly improved.

[Brief explanation of the drawing]

FIG. 1 shows that a semiconductor device 1 is a liquid crystal display device 2 according to the present invention.
2 is a sectional view of the liquid crystal display device 2, FIG. 3 is a sectional view of the elastic conductive particles 15, and FIG. 4 is an enlarged sectional view of an electrode according to an embodiment of the present invention. 5121 is a sectional view showing a method of forming an electrode according to another embodiment of the present invention. 1.24...Semiconductor device, 2.1 Liquid crystal display device, 3°4.11-...Electrode, 5,6...Liquid crystal display board, 10.
...Substrate, 12...Surface protective layer, 13...Protruding electrode, 14.Adhesive layer, 15...Elastic conductive particles, 18.-
Barrier metal layer, 1 -- Parent solder layer, 20 Solder layer, 22 -- Diffusion metal layer Agent Patent attorney Keiichi

Claims (1)

[Claims] A method for forming an electrode, characterized in that an intervening body having elasticity and conductivity is fixed onto an electrode of a wiring board by alloy bonding.