JPS6297340A - Electrical connecting method for ic chip - Google Patents

Abstract

PURPOSE:To improve reliability of dense micro-connection of multi-terminals, by arranging a photomask on a carrier film, positioning a conductive bonding agent surface, which is exposed by the removal of photoresist and water soluble polymer, and a transparent terminal electrode on a glass substrate, performing thermal compression, separating the carrier film, further positioning an IC chip and a pad, and performing thermal compression. CONSTITUTION:On one surface of a carrier film 2, a thermal reactivating conductive bonding agent 2, water soluble polymer 3 and photoresist 4 are formed. A photomask 5 is closely contacted and exposed. Then parts 5a and 5b are formed so that the pattern agrees with the pattern of a transparent terminal electrode 6, which is formed on a glass substrate 7. Then development and washing with water are performed. Then, the conductive bonding agent 2b is exposed. After the transparent terminal electrode 6 and the conductive bonding agent 2 are aligned, thermal compression is performed with thermal rolls 8. When the carrier film 1 is separated, the conductive bonding agent 2b is transferred only on the transparent terminal electrode 6. Then a bare IC chip 9 and an electrode pad 10 and the transparent terminal electrode 6 are aligned with each other. Thereafter, compression and heating are carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an electrical connection method for an IC chip, which connects a chip-shaped electronic component, typified by an IC chip, to a group of terminal electrodes on a substrate.

Conventional technology Traditionally, soldering was used to connect the connection terminals of electronic components and the circuit pattern terminals on the board, but in recent years, with the miniaturization of IC flat packages and the increase in the number of connection terminals, it has become difficult to connect. The so-called pitch between terminals has become progressively narrower, and conventional soldering has become increasingly difficult to handle with technology.In addition, recently, bare soldering has become increasingly difficult for calculators, electronic watches, and LCD devices. There is a movement to directly attach IC chips face-down to electrodes on glass substrates in order to use mounting area more efficiently and streamline wiring.
There is a need for effective and fine electrical connection means to replace soldering. As a method for electrically connecting a bare IC chip to a transparent electrode on a glass substrate, for example, Japanese Patent Publication No. 51-11
As shown in Japanese Patent No. 4439, a conductive adhesive is prepared by uniformly dispersing various metal powders in a thermosetting resin with a particle size and a particle shape with an appropriately adjusted amount. After coating the conductive adhesive all over the glass electrode, the bumps of the IC chip and the glass electrode are placed facing each other, and the IC chip is pressed against the glass electrode to harden the conductive adhesive. A method of developing conductivity has been proposed.

Problems to be Solved by the Invention However, in such a method, as the electrodes become finer and the electrode density becomes higher, current leakage occurs between adjacent transparent electrodes or between electrodes on a chip. It was easy. Another method is to selectively print conductive adhesive on the transparent terminal electrodes using the prior art screen printing method.If possible, there will be no current leakage during connection, but the transparent In the current situation where terminal electrodes are formed finely and densely, selective printing is extremely difficult with conventional printing techniques.

The present invention was invented in view of the above problems, and its purpose is to reliably form a conductive adhesive on a group of terminal electrodes formed finely and densely on a glass substrate. , to make an electrical connection with the electrode pads of the IC chip.

Means for Solving the Problems In order to solve the above problems, the present invention first coats a heat-reactivated conductive adhesive on one side of a carrier film, and then coats a water-soluble polymer and a photoresist on it. 9. Next, a predetermined photomask is placed and exposed, followed by predetermined development and water washing to remove the photoresist and water-soluble polymer. After aligning the conductive adhesive surface exposed by removal with the transparent terminal electrode on the glass substrate, thermocompression bonding is performed.Next, when the carrier film is peeled off, the conductive adhesive is transferred only onto the transparent terminal electrode on the glass substrate. be able to. The method is characterized in that the finally obtained transparent terminal electrodes with conductive adhesive and the pads of the IC chip are aligned and thermocompression bonded to connect each pad of the IC chip and each electrode on the glass substrate.

However, according to the above-described method of the present invention, the conductive adhesive exposed after development and washing with water can be transferred only onto the transparent terminal electrode, and the photoresist is not used as a mask except for clearing the transparent terminal. Since it acts as a material and does not allow conductive adhesive to adhere, there will be no short circuit between adjacent transparent electrodes on the substrate or between electrodes of the IC chip after connection.Furthermore, the portion of the conductive adhesive that is transferred Since it can be made fine by using a photoresist, fine transfer of the conductive adhesive is possible, and the reliability of fine and dense multi-terminal micro-connections is improved.

Example The method of the present invention will be explained in detail below based on the drawings.

1 to 8 are process cross-sectional views illustrating the method for electrically connecting an IC chip of the present invention, in which 1 is a carrier film, 2 is a heat-reactivated conductive adhesive, and 3 is a water-soluble polymer. , 4 is photoresist, 5 is photomask, 6
1 is a transparent terminal electrode, 7 is a glass substrate, 8 is a heat roll, 9 is a bare IC chip, and 10 is an electrode band of the IC chip.

In the present invention, first, as shown in FIG.
It is formed to a thickness of 20 to 30 μm by a method such as roll printing. The heat-reactivated conductive adhesive 2 used at this time is a thermosetting conductive adhesive using epoxy resin, phenol resin, etc. as a binder resin, or an ultraviolet-curable photosensitive adhesive such as an acrylic binder. A conductive adhesive may also be used. In this example, a photosensitive conductive adhesive was used.
100 parts by weight of R-60 (epoxy acrylate), 3 parts by weight of Irgacure 651 (manufactured by Ciba Geigy), and silver, gold, v4. Chromium, lead.

It is prepared by blending an appropriate amount of fine powder of tin, iron, aluminum, or an alloy thereof to obtain the desired conductivity, and dissolving it in an appropriate solvent. Further, when thermosetting is used in combination, for example, a latent epoxy curing agent dimethylbenzylamine or a radical polymerization agent benzyl peroxide may be appropriately added.

Next, as shown in FIG. 2, a water-soluble polymer 3 was coated on the heat-reactivated conductive adhesive 2 using a bar coater and dried to form a 2 μm thick layer. The water-soluble polymer liquid used at this time was a 5% aqueous solution of GOHSENOL 172SS (Nippon Gosei Kaji type polyvinyl alcohol), but it is not limited to this as long as it is a water-soluble polymer. A mold photoresist 4 was applied to a thickness of 2 to 5 μm and dried. The photoresist 4 used was Nagase Microresist #752 (isoprene rubber type manufactured by Seibu Sangyo) 5.
~15% solution. This solution uses a xylene-based solvent, and there is no need to limit the type of photoresist 4 as long as it does not attack the three water-soluble polymer layers.

Next, as shown in FIG. 4, a photomask 5 is brought into close contact with the photoresist 4 and exposed. At this time, the pattern of the photomask 5 is such that it is identical to the pattern of the transparent terminal electrode 6 formed on the glass substrate 7, which will be described later.
b is formed.

The photoresist 5 in the portion corresponding to 5b is cured, and the ultraviolet-curable heat-reactivated conductive adhesive 2 2a is cured and is no longer heat-reactivable, but the portion 2b not irradiated with ultraviolet rays is heat-reactivable. Remains active.

Next, as shown in FIG. 5, when development and washing are performed, the portion 2b is exposed. At this time, photoresist 4 was developed using xylene, but the three underlying water-soluble polymer layers were not attacked at all.When washed with water afterwards, the water-soluble polymer corresponding to the area where photoresist 4 was removed during development was removed. Ru. At this time, the conductive adhesive 2 is not affected by water at all.

Next, as shown in FIG.
A large number of transparent terminal electrodes 6 (ITO electrodes in this case) are formed with a pitch of 200 μm and 50 to 1100 μm, and a fifth
After aligning the exposed surfaces of a large number of heat-reactivated conductive adhesives 2 as shown in the figure so that they collapse once, they are heat-pressed by a means such as a heat roll 8 or a heat-press bonding machine, and then, as shown in FIG. When the carrier film l is peeled off as shown in the figure, the transparent terminal electrode 6
The thermally reactivated conductive adhesive 2b is transferred only to the top, and is not transferred to the other glass substrates.

Next, as shown in FIG. 8, after aligning the electrode pads 10 of the bare IC chip 9 and the transparent terminals; poles 6 (transferred heat-reactivated conductive adhesive 2b) on the glass substrate 7, By applying appropriate pressure and heat, electrical connection and adhesion are achieved simultaneously. At this time, when an ultraviolet curing type conductive adhesive is used, ultraviolet rays are further irradiated from the back side of the glass base Fi7, and when a thermosetting type conductive adhesive is used, it is further heated and cured to create an electrical property. The reliability of connections and adhesion can be improved.

Effects of the Invention As explained above, according to the method for electrically connecting an IC chip of the present invention, a conductive adhesive is formed on a transparent terminal electrode on a substrate by transfer, which was previously impossible by printing. A conductive adhesive for electrical connection can be selectively and accurately formed on a group of ultra-fine and ultra-densely formed terminal electrodes, which is effective in mounting IC chips on a glass substrate, and is also effective in mounting IC chips on glass substrates. It is also effective in making ultra-fine connections in electronic components, so it has extremely high practical value.

[Brief explanation of drawings]

FIGS. 1 to 8 are cross-sectional views showing steps for explaining the method for electrically connecting an RC chip according to the present invention. l...Carrier film, 2...Heat-reactivated conductive adhesive, 3...Water-soluble polymer, 4
... Photoresist, 5 ... Photomask, 6 ... Transparent terminal electrode, 7 ... Glass substrate, 8 ... Heat roll, 9... Bare IC chip, 10... Electrode pad of IC chip.

Claims (1)

[Claims] (1) Coating a heat-reactivated conductive adhesive on one side of a carrier film, coating a water-soluble polymer on the heat-reactivated conductive adhesive, and forming a photoresist layer on the water-soluble polymer. a step of exposing the photoresist surface with a predetermined photomask in close contact with the photoresist surface; a step of developing and removing the photoresist and water-soluble polymer in the unexposed area; and a step of removing the photoresist and the water-soluble polymer by developing the exposed conductive material. After aligning the adhesive part and the transparent terminal electrode on the glass substrate, there is a process of thermocompression bonding and peeling off the carrier film.
A process of transferring the conductive adhesive only onto the transparent terminal electrode, aligning the obtained transparent terminal electrode with the conductive adhesive with the pads of the IC chip, and bonding them by thermocompression to each pad of the IC chip. 1. A method for electrically connecting an IC chip, the method comprising: connecting each electrode of a glass substrate.