JP2511909B2 - Method for micro-forming electrical connection material - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric connection material for connecting a chip-shaped electronic component typified by an IC chip to a terminal electrode group on a substrate. The present invention relates to a micro-forming method of an electrical connection material which is accurately formed only on the top.

Conventional technology Conventionally, soldering was often used to connect the connection terminals of electronic parts to circuit pattern terminals on the board, but in recent years, for example, due to the miniaturization of IC flat packages and the increase of connection terminals, connection has been made. The so-called pitch interval between terminals has become narrower, and it has become increasingly difficult to cope with it with conventional soldering technology. In addition, recently, in calculators, electronic watches, liquid crystal displays, etc., there is a movement to directly attach a bare IC chip to an electrode on a glass substrate in order to use the mounting area efficiently. There is a strong demand for effective and fine electrical connection means. As a method for electrically connecting a bare IC chip to a transparent electrode on a glass substrate, for example, as disclosed in JP-A-51-114439,
Particle size, particle shape, various metal powders appropriately adjusted such as a blending amount to obtain a conductive adhesive by uniformly dispersing in a thermosetting resin, after applying this to the entire electrode surface on a glass substrate,
A method has been proposed in which the bumps of the IC chip and the transparent terminal electrodes are aligned and then pressure-bonded to cure the conductive adhesive, so that the bumps are made conductive and electrical connection is achieved. . Further, as disclosed in JP-A-60-133603, conductive rubber is obtained by including carbon in silicon rubber, and the conductive rubber is applied between the electrode portion of the substrate and the bump of the IC chip. A method of applying pressure to make an electrical connection has been proposed.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the first conventional method, the finer the electrodes and the higher the electrode density, the more the current leakage between adjacent transparent terminal electrodes or between the electrodes on the chip occurs. It was likely to occur. In order to avoid this current leakage, it is possible to selectively print the conductive adhesive on the transparent terminal electrode group only by using the conventional screen printing method, but it is necessary to directly mount the IC chip. To
The transparent terminal electrode group is 100 μm in the shape of the pad of the IC chip.
□, it is considered that it is almost impossible with the conventional printing technology in the present situation that the pitch is 200 μm. Also,
In the second conventional method, since the conductive rubber is used, the connection resistance is large and only a minute current can be passed, and the use is limited. Further, the finer the electrodes are, and the higher the electrode density is, the more difficult it is to miniaturize the conductive rubber interposed between the electrodes.

The present invention has been made in view of the above problems,
The purpose is to finely and closely attach the electrode pads of the electronic component and the electrode group on the substrate with high reliability, only the electrode group on the substrate or the electronic component, for example, the electrode pad of the IC chip. Another problem is to form a conductive connecting material with high reliability.

Means for Solving the Problems In order to solve the above problems, the present invention provides a fine pitch,
After attaching the mask, which is made of a photopolymer that is surface-inactive and peelable, and which has the photopolymer corresponding to the fine terminal electrode group removed by photolithography technology, to the substrate surface on which the fine terminal electrodes are formed Then, the conductive adhesive surface of the separately prepared film with conductive adhesive is thermocompression-bonded to one surface including the fine electrode group on the substrate to transfer the conductive adhesive onto the mask. After that, the mask is peeled off and the conductive adhesive is transferred only onto the fine terminal electrode group, which is intended to realize micro formation of the electrical connection material.

According to the above-described method of the present invention, since the conductive adhesive is thermocompression-bonded and the mask covering the area other than the terminal electrode group on the substrate is peeled off, the area other than the terminal electrode group on the substrate is removed. The conductive adhesive is not transferred. Further, by using a photopolymer for the mask, it is possible to form a fine and dense pattern, which enables fine transfer. In addition, since the transferred conductive adhesives are present independently of each other, it is possible to connect the adjacent electrodes without current leakage.

Example Hereinafter, a micro-forming method of an electrical connecting material according to an example of the present invention will be described in detail with reference to the drawings.

1 to 6 are process cross-sectional views showing the first embodiment of the present invention, and FIGS. 7 to 12 are process cross-sectional views showing the second embodiment of the present invention. Further, FIG. 13 shows a cross-sectional view of the film with a conductive adhesive used in the first and second embodiments. FIG. 14 and FIG. 16 are cross-sectional views when an IC chip is mounted on a substrate by using the method for micro-forming the electrical connection material of the present invention. Further, FIG. 15 is a sectional view of an IC chip cut out from the silicon wafer of the second embodiment.

In the figure, 1 is a glass substrate, 2 is a transparent terminal electrode (ITO
Electrodes), 3 and 9 are surface-inactive and peelable masks,
4 is a conductive adhesive, 5 is a carrier film, 6 is a heat roll, 7 is a silicon wafer, 8 is an electrode pad of an IC chip,
10 is an IC chip.

In the first embodiment of the present invention, first, as shown in FIG. 1, on the surface including the ITO electrode group 2 formed on the glass substrate 1 at a pitch of, for example, 200 μm and 100 μm □, the surface as shown in FIG. Made of an inert, peelable photopolymer, ITO
After the electrode group 2 and the mask 3 on which the reverse pattern is formed are aligned, they are bonded to the glass substrate 1 as shown in FIG.
The mask 3 used at this time is selected such that it is surface-inactive and can be peeled off later, such as a dry film photopolymer. However, it is not necessary to limit to a dry film-shaped photopolymer, and any other mask can be used as long as it is a surface-inactive and peelable mask 3.

Next, as shown in FIG. 4, a sheet with a conductive adhesive having a thickness of 20 to 30 μm formed with a conductive adhesive 4 on a separately prepared carrier film 5 shown in FIG. Then, thermocompression bonding is performed using the heat roll 6. Then, the fifth
When the carrier film 5 is peeled off as shown in the figure, the conductive adhesive 4 is transferred. Further, when the mask 3 is peeled off as shown in FIG. 6, the conductive adhesive is applied only on the ITO electrode 2 of the glass substrate 1. 4 is transcribed.

The conductive adhesive 4 is made by mixing metal powder or carbon having good conductivity into the adhesive. As the metal powder, fine silver powder, copper powder, nickel powder or the like can be used. Although an epoxy resin or the like can be used, in the present embodiment, any conductive adhesive can be used without limitation to its composition.

In the above embodiment, the carrier film 5 and the mask 3 are peeled off separately, but they can be peeled off at the same time without any problem.

In addition, in the second embodiment, a method of micro-transferring the conductive adhesive onto the silicon wafer 7 including a large number of IC chips is shown. As the method, first, on the silicon wafer 7 as shown in FIG. As shown in FIG. 8, similarly to the first embodiment, a mask 9 made of a surface-inactive and peelable photopolymer and having a pattern opposite to the electrode pad 8 is aligned, The silicon wafer 7 is bonded as shown in the figure. Next, as shown in FIG. 10, the separately prepared sheet with conductive adhesive shown in FIG. 13 is thermocompression-bonded using the heat roll 6 so as to face the mask 9 surface. After that, when the carrier film 5 is peeled off as shown in FIG. 11, the conductive adhesive 4 is transferred. Further, when the mask 9 is peeled off as shown in FIG. 12, only the electrode pads 8 of the IC chip are electrically conductive. Adhesive 4 is transferred.

The conductive adhesive 4 formed on the transparent terminal electrode 2 on the glass substrate 1 obtained in the first embodiment and the electrode pad 8 of the IC chip 10 are opposed to each other and thermocompression-bonded to each other, followed by conductive bonding. When the agent 4 is cured, the IC chip and the glass substrate can be connected as shown in FIG.

In addition, the silicon wafer 7 in which the conductive adhesive 4 is micro-formed on the electrode pads 8 of the IC chip obtained in the second embodiment is cut along the dotted line as shown in FIG. And can be connected to a glass substrate as shown in FIG.

EFFECTS OF THE INVENTION As described above, according to the method for micro-forming an electrical connection material of the present invention, a conductive material can be finely formed on a substrate or an electronic component, for example, an electrode portion of an IC chip by a transfer technique. The conductive material for electrical connection can be selectively and accurately formed on the ultra-fine and ultra-densely formed terminal electrode group, which was not possible with conventional printing.
Not only for connecting the chip to the electrode on the glass substrate, but also for electrically connecting various electronic components to various substrates, it is effective for ultrafine connection, which is difficult to connect by soldering, and thus has extremely high practical value.

[Brief description of drawings]

FIGS. 1, 2, 3, 4, 5, and 6 are process sectional views showing the first embodiment, FIG. 7, FIG. 8, and FIG.
FIG. 10, FIG. 11, FIG. 11 and FIG. 12 are process cross-sectional views showing a second embodiment, and FIG. 13 is a film with a conductive adhesive used in the first and second embodiments. 14 and 16 are cross-sectional views when an IC chip having a conductive adhesive micro-formed thereon is mounted on a substrate based on the first and second embodiments, respectively, and FIG. From the silicon wafer
It is sectional drawing which cuts out an IC chip. 1 ... Glass substrate, 2 ... Transparent terminal electrode (ITO electrode),
3,9 …… Surface inactive and peelable mask, 4 …… Conductive adhesive, 5 …… Carrier film, 6 …… Heat roll, 7
...... Silicon wafer, 8 …… IC chip electrode pad, 10
…… IC chip.

Claims (1)

(57) [Claims] 1. A mask, which is made of a photopolymer which is surface-inactive and can be peeled off, and which has a fine pitch and a fine terminal electrode is formed on the surface of a substrate, and which has a photopolymer corresponding to the fine terminal electrode group removed by a photolithography technique. After the alignment, the step of adhering and the separately prepared conductive adhesive film of the conductive adhesive surface is thermocompression-bonded to one surface including the fine terminal electrode group on the substrate to apply the conductive adhesive on the mask. A method for micro-forming an electrical connection material, comprising a step of transferring and a step of peeling off the mask and transferring a conductive adhesive only onto the fine terminal electrode group.