JPH0793342B2 - Method of forming electrodes - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is for electrically connecting an integrated circuit board on which a semiconductor element or the like is formed and a circuit board such as a printed board, a flexible board, or a ceramic board. In particular, the present invention relates to a method for forming an electrode.

Conventional technology Conventionally, IC (Integrated Circui
t) As a method for electrically connecting the electrodes of the board and the electrodes of the other circuit board by press-contacting each other, the method described in Japanese Patent Publication No.
-2179 or a method using an anisotropic conductive sheet disclosed in JP-B-62-6652 (hereinafter referred to as "first conventional example"), and a metal special electrode disclosed in JP-A-63-13337. Method (hereinafter referred to as "second conventional example"), as well as JP-A-61-242041, JP-A-61-259548, and JP-A-61-259548.
A method using an elastic projection electrode disclosed in 63-150930 (hereinafter referred to as "third conventional example") and the like are known.

In the first conventional example, an anisotropic conductive sheet in which conductive fine particles are dispersed in an adhesive made of a synthetic resin or the like is used, and the anisotropic conductive sheet is conductive only in the pressure direction applied to this sheet. The anisotropy of exhibiting the property of being non-conductive in the other directions is utilized. That is,
Insert this anisotropic conductive sheet between the electrodes you want to connect,
The sheet portion interposed between the electrodes is pressed in the sheet thickness direction to electrically connect the electrodes. However, in this anisotropic conductive sheet, when the pitch width of the electrodes to be connected is a fine pitch of about 150 μm or less, the conductive fine particles dispersed in the sheet make it possible for the adjacent electrode terminals to become conductive, resulting in a short circuit. Was the cause of.

In the second conventional example, in order to solve the above-mentioned problems of the first conventional example, a protruding electrode made of a metal material is provided on one electrode surface of a circuit board to be connected, and is pressed against a corresponding electrode. It is for electrical connection. According to the second conventional example, although the electrodes having a minute pitch width can be connected, the unevenness of the connection resistance at the time of press contact appears due to the uneven height of the protruding electrodes, and the connection reliability is improved. There was a problem that was inferior.

In the third conventional example, in order to solve the above-mentioned problems of the second conventional example, the protruding electrode is composed of a member having elasticity and conductivity, and the unevenness of the height of the protruding electrode when pressure welding is performed. The protrusion electrodes are elastically deformed so as to be absorbed.

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

In JP-A-63-150930 of the third conventional example, in order to selectively cure the conductive ink used for forming the protruding electrodes, the conductive ink is irradiated with infrared rays or ultraviolet rays through a mask plate. The curing ink is being cured. However, in the method of heat curing using infrared irradiation or the like, it takes several minutes to several tens of minutes to heat cure the conductive ink.
Therefore, the conductive ink around the opening of the mask plate also
The conductive ink heated by the infrared rays radiated through the openings is heated and cured by heat conduction, resulting in poor pattern formability in a minute pitch width and unclearness. In addition, in the method of photo-curing using ultraviolet irradiation, since the metal powder, alloy powder, conductive powder, or metal-plated glass beads added to the ink to obtain conductivity is opaque, irradiation There is a problem in that the entire surface of the conductive ink is not irradiated with the generated ultraviolet rays and the photo-curing is insufficient, and thus the pattern formability is poor.

Further, in JP-A-61-242041 and JP-A-63-150930, a conductive resin in which various conductive powders are mixed as a conductivity-imparting agent into a resin is used as a material for a protruding electrode having elasticity. There is. In such a conductive resin, it is necessary to keep the amount of the conductive powder small in order to maintain sufficient elasticity. However, when the amount of the conductive powder is small, on the contrary, the conductive resin has poor conductivity, and the connection resistance of the protruding electrode using this conductive resin becomes high.

The object of the present invention is to solve the above-mentioned problems and to cope with the miniaturization of electrodes of wiring boards to be connected to each other, and to enable the connection of low electric resistance, thereby making the mutual electrodes highly reliable. It is to provide a method for forming an electrode that can be used for electrical connection with.

Means for Solving the Problems According to the present invention, a plurality of intervening bodies having elasticity and electrokinetic property are arranged on one surface of a temporary substrate, and they are detachably attached in one layer to form electrodes to be connected to the interposing bodies. An electrode characterized in that the wiring board and the temporary board are pressurized and heated in a state in which the interposition body attached to the temporary board opposes the wiring board, thereby performing alloy joining of the interposition body and the electrode. Is a method of forming.

Action In the method for forming an electrode of the present invention, an interposition body having elasticity and conductivity is used. This interposer is fixed on the electrode of the wiring board by alloy bonding, whereby a protruding electrode is formed on the wiring board.

Therefore, for example, when a semiconductor device is mounted on a circuit board, if the protruding electrodes are formed on the semiconductor device, the semiconductor device is connected to the circuit board with high reliability by a method such as press contact.

Further, when pressure-contacting using the above-mentioned special electrode, by using a photo-curable or natural-curable adhesive for bonding the circuit boards to each other, it is possible to bond a wide area at low temperature and Since the electrical connection portion is sealed with resin, the reliability of electrical connection is further improved.

In particular, according to the present invention, a temporary substrate is used, and interposers are arranged on one surface of the temporary substrate so as to be detachably attached in one layer using an adhesive or the like, and the temporary substrate and the wiring substrate are pressed and heated. Since the interposition body and the electrode are fixed by alloying the interposition body and the electrode, when the interposition body is arranged on the electrode of the wiring board, the precision of the wiring board and the individual interposition body There is no need to perform precise alignment, thus improving productivity.

EXAMPLE FIG. 1 shows an electrode which is projected according to the method for forming an electrode of the present invention.
FIG. 2 is an enlarged cross-sectional view of a semiconductor device 1 on which 13 (hereinafter, simply referred to as “protruding electrode 13”) is mounted on a liquid crystal display device 2 described later. FIG. 2 is a liquid crystal on which the semiconductor device 1 is mounted. 3 is a cross-sectional view of the display device 2. FIG. Referring to FIG.
A pair of liquid crystal display plates 5 and 6 each having an electrode 3 and a counter electrode 4 formed on the surface are bonded together via a sealing resin 7, and a liquid crystal 8 is sealed between them. In the liquid crystal display device 2, the electrode 3 extends to the right of the drawing on the liquid crystal display plate 5 and is connected to the protruding electrode 13 of the semiconductor device 1 mounted for driving the display of the liquid crystal display device 2.

The semiconductor device 1 has a diffusion layer formed on a wafer such as silicon or gallium arsenide, and a large number of transistors, diodes, and the like are formed by the diffusion layer, and has a function of driving the display of the liquid crystal display device 2. Referring to FIG.
The semiconductor device 1 includes a substrate 10 which is a wiring substrate, an electrode 11 formed on the uppermost layer of the substrate 10, and a surface protective layer 12 made of, for example, SiN, SiO ₂ , or polyimide. The electrode 11 is made of, for example, Al-Si.

A protruding electrode 13 is formed on the electrode 11 of the 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-containing indium oxide (Indioxide) formed on the surface of, for example, soda glass.
um Tin Oxide (hereinafter abbreviated as “ITO”) or nickel-plated ITO with a typical thickness of 100 to 200 nm
It is a degree.

In the semiconductor device 1 and the liquid crystal display panel 5, the protruding electrodes 13 and the electrodes 3 are pressed and opposed to each other so that the electrodes 3 and 11 have a predetermined distance l1. The filled adhesive layer 14 is cured and bonded. As the adhesive layer 14, for example, various kinds of adhesives having a reaction curability, an anaerobic curability, a heat effect, a photocurability and the like can be used. Particularly, 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 photo-curable adhesive capable of high-speed bonding.

FIG. 3 shows a cross-sectional view of an example of the elastic conductive particles 15 used for the protruding electrode 13 shown in FIG. Elastic conductive particles
The surface 15 of the elastic bead 16 made of a polymer material is formed by coating a conductive coating layer 17 made of a metal material. As the elastic beads 16, synthetic resins such as polyimide resin, epoxy resin and acrylic resin and synthetic rubbers such as silicone rubber and urethane rubber can be used.

As the conductive material of the coating layer 17, although Au is preferable in terms of solderability and ductility, Pt, Pd, Ni, Cu, In, Sn, P
Metals such as b, Co and Ag and alloys thereof may be coated on the surface of the elastic beads 16 in one layer or two or more layers.
In the case of coating with two or more layers, a metal layer having excellent adhesion to the elastic beads 16 such as Ni is formed first, and then a metal layer such as Au is coated to prevent oxidation of those metal layers. . As a coating method, a sputtering method, an electron beam vapor deposition method, electroless plating, or the like can be used.

FIG. 4 is a cross-sectional view sequentially showing the manufacturing process when the method of forming an electrode, which is the premise of the present invention, is carried out by using a solder metal. The electrode 11 of the semiconductor device 1 is usually Al-Si
Is used. Therefore, a barrier metal layer 18, a parent solder layer 19, and a solder layer 20 for preventing metal diffusion on the electrode 11 are formed in this order by a known method such as a vapor deposition method, a photolithography method, and a plating method, A connection region having the structure shown in FIG. 4A is formed on the electrode 11. As the barrier metal layer 18, metals such as Ti, W, Cr and alloys thereof can be used. As the parent solder layer 19, metals such as Cu, Ni, Au, Ag and Pt and alloys thereof can be used. As the solder layer 20, Pb having a relatively low melting point is used.
-Sn system (melting point mp = 183 ° C), In-Sn system (mp = 116 ° C)
Etc. can be used.

The flux 21 is applied onto the semiconductor device 1 in which the connection region having the structure shown in FIG. 4 (1) is formed by a method such as spin coating or roll coating. The purpose of applying this flux is to improve the solderability and to adhere the elastic conductive particles 15 onto the substrate 10. Therefore, as the flux 21, one having a non-volatile property and a predetermined viscosity is used.

Next, as shown in FIG. 4 (2), the elastic conductive particles 15 shown in FIG. 3 are arranged on the substrate 10. Therefore, the thickness of the flux 21 is 1/2 of the diameter of the elastic conductive particles 15.
It is preferably about 1/5. After this, the substrate 10 is 220
Re-melt the solder layer 20 by heating to ~ 250 ° C, elastic conductive particles 15
It is soldered to the coating layer 17 formed on the surface.

After solder bonding, the substrate 10 and the bonded elastic conductive particles 15
Is cooled and washed with an organic solvent such as acetone to remove the flux 21 applied to the surface and unnecessary elastic conductive particles 15. As a result, as shown in FIG. 4C, the semiconductor device 1 having the protruding electrodes 13 made of the elastic conductive particles 15 can be obtained. In FIG. 4 (3), one elastic conductive particle 15 is arranged in the connection area of one electrode 11, but a plurality of elastic conductive particles 15 are arranged in the connection area of one electrode 11. Place the protruding electrode
13 may be formed.

The semiconductor device 1 having the protruding electrodes 13 made of the elastic conductive particles 15 formed according to the procedure described above is previously in a state of being pressed against another circuit board like the liquid crystal display device 2 of FIG. 2 described above. The adhesive filled between the circuit boards can be hardened to bond the circuit boards to each other for mounting.

FIG. 5 is a sectional view for explaining one embodiment of the present invention. The same reference numerals are used for the portions corresponding to those shown in FIG. In the method of forming the electrode shown in FIG. 5, the two metal layers are heated under pressure, and at the interface between the two metal layers, the metals are mutually diffused in the solid phase state to perform alloy joining. To use. Therefore, in this embodiment, as the elastic conductive particles 15, the coating layer
It is particularly preferable to use 17 as a material formed of a metal material containing Au, Sn, or an Au—Sn alloy as a main component.

FIG. 5A is a sectional view showing an electrode structure on the substrate 10 of the semiconductor device 24 used in this embodiment. A barrier metal layer 18 and a diffusion metal layer 22 joined by diffusion are formed in advance on the electrode 11 made of, for example, Al-Si on the substrate 10 by a known method such as a vapor deposition method, a photolithography method, or a plating method. . As the barrier metal layer 18, T
Metals such as i, W, Cr and alloys thereof can be used. As the diffusion metal layer 22, the same metal material as the coating layer 17 of the elastic conductive particles 15 shown in FIG. 3 can be used, but preferably one containing Au, Sn, or an Au—Sn alloy as a main component. Is used.

As shown in FIG. 5 (2), one surface of the temporary substrate 23 coated with the adhesive 26 in advance (that is, the lower surface of FIG. 5 (2)).
The elastic conductive particles 15 are attached to the upper surface of the elastic conductive particles 15 so as to be evenly arranged.
The temporary substrate 23 having the elastic conductive particles 15 carried on the surface is opposed to the semiconductor device 24 having the diffusion metal layer 22 formed on the electrode 11 shown in FIG. In the direction indicated by, pressurization of about 1 kg / mm ² and heating at 300-350 ° C are performed. As a result, the coating layer 17 made of the metal material of the elastic conductive particles 15 and the diffusion metal layer 22 formed on the electrode 11 are formed.
Metals diffuse into each other at the interface with and alloy bonding is performed, and the protruding electrode 13 including the elastic conductive particles 15 is formed on the substrate 10 at a position corresponding to the electrode 11. Note that the elastic conductive particles 15 can be directly applied without providing the barrier metal layer 18 and the diffusion metal layer 22 on the electrode 11 by using a method of applying ultrasonic waves to the joint portion at the time of the above-mentioned pressurization and heating. The electrode
Can be joined to 11.

As a method of uniformly supporting the elastic conductive particles 15 on the temporary substrate 23, a pressure-sensitive adhesive 26 is applied onto the temporary substrate 23 by a method such as spin coating, roll coating, or printing, and the plurality of elasticities are applied to the pressure-sensitive adhesive 26. This can be done by attaching the conductive particles 15 in one layer. As the pressure-sensitive adhesive 26 used, synthetic resins such as silicone type and polyimide type, and sol-like substances having high viscosity such as oil and grease can be used. The thickness of the pressure-sensitive adhesive 26 applied on the additional substrate 23 is 1 / the diameter of the elastic conductive particles 15.
About 2 to 1/10 is preferable. When the pressure-sensitive adhesive 26 is thicker than the above value, the elastic conductive particles 15 are laminated on the temporary substrate 23 in a plurality of layers, and when the pressure-sensitive adhesive 26 is thin, the adhesiveness is low and the elastic conductive particles 15 are low.
However, it is impossible to form an adhesion layer in which the particles are uniformly adhered.

Further, as the layer thickness of the diffusion metal layer 22 formed in advance on the electrode 11 via the barrier metal layer 18 and the like, the pressure is concentrated during heating under pressure, and the elastic layer is applied to a portion other than the contact area on the electrode 11. In order to prevent the conductive particles 15 from being crimped,
The elastic conductive particles 15 are preferably formed to have a diameter of about ½. If the diffusion metal layer 22 is thicker than the above value, the unevenness of the value obtained by adding the diameter of the elastic conductive particles 15 to the layer thickness becomes large. Therefore, a large pressure force is required at the time of continuous pressing, and the amount of deformation of the elastic conductive particles 15 unnecessarily increases. On the other hand, when the thickness is thin, the elastic conductive particles 15 adhere to even unnecessary portions such as the surface protective layer 12, which causes an undesired situation. Further, in the present embodiment as well, similar to the configuration shown in FIG. 4 above, a plurality of elastic conductive particles 15 may be bonded to one electrode 11 to form the protruding electrode 13. .

As described above, the semiconductor device 24 in which the protruding electrode 13 made of the elastic conductive particles 15 is formed on the electrode 11 is also pressed to another circuit board such as the liquid crystal display device 2 as shown in FIG. It can be implemented by a method such as.

In the above embodiments, the case where the protruding electrode 13 is formed on the substrate 10 of the semiconductor device 24 has been described, but it is not necessary to limit the case where the electrode is formed in relation to the semiconductor device, and for example, another circuit board is used. The present invention can be implemented even when the upper electrode is formed.

EFFECTS OF THE INVENTION As described above, according to the present invention, it is possible to finely form the protruding electrodes on the electrodes of the wiring board by a simple method. The protruding electrode is formed by fixing an interposition body having elasticity and conductivity on the electrode of the wiring board by alloy bonding. Because of this, the connection has high mechanical strength and low electrical resistance. Also,
It is possible to cope with the miniaturization of the electrodes of the wiring boards that are mutually connected. Therefore, for example, when electrically connecting the wiring board on which the protruding electrode is formed and another wiring board by pressure contact, the reliability of the connection is significantly improved.

In particular, according to the present invention, a temporary substrate is used, the interposers are arranged on one surface of the temporary substrate, and the temporary substrate is detachably attached by, for example, an adhesive or the like, and the wiring having the electrodes is formed. Since the substrate and the electrode are pressed and heated to perform the composite joining of the interposer and the electrode to fix the interposer and the electrode, when the interposer is placed on the electrode of the wiring substrate, the precise interposition of the electrode and the interposer is required. The excellent effect that the alignment is not necessary and the productivity can be improved is achieved.

[Brief description of drawings]

FIG. 1 shows that the semiconductor device 1 is a liquid crystal display device 2 according to the present invention.
2 is an enlarged cross-sectional view showing the joint portion mounted in FIG. 2, FIG. 2 is a cross-sectional view of the liquid crystal display device 2, and FIG. 3 is a cross-sectional view of the elastic conductive particles 15.
FIG. 4 is a cross-sectional view showing a method of forming an electrode which is a premise of the present invention, and FIG. 5 is a cross-sectional view showing a method of forming an electrode which is one embodiment of the present invention. 1,24 …… Semiconductor device, 2 …… Liquid crystal display device, 3,4,11 ……
Electrodes, 5,6 ... Liquid crystal display board, 10 ... Substrate, 12 ... Surface protection layer, 13 ... Projection electrode, 14 ... Adhesive layer, 15 ... Elastic conductive particles, 18 ... Barrier metal layer, 19 ... Parent solder layer, 20 ...
… Solder layer, 22 …… Diffusion metal layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-266842 (JP, A) JP-A-63-47943 (JP, A) JP-A-63-54796 (JP, A)

Claims (1)

[Claims] 1. A wiring substrate having a plurality of interposers having elasticity and conductivity arranged side by side on one surface of a temporary substrate, detachably attached in one layer, and having electrodes to be connected to the interposers. A method for forming an electrode, comprising: pressing and heating a substrate and an interposer adhered to a temporary substrate so as to face the wiring substrate to perform alloy joining of the interposer and the electrode.