JPH0237734A - Mounting method for ic chip - Google Patents

Abstract

PURPOSE:To improve production yield of product and reduce production cost of the product by allowing an IC bump to contact the signal I/O part of a circuit on a board to perform electrical connection after aligning the height of the signal I/O part of the circuit on the board. CONSTITUTION:A paste with a conductive particle on a board 1 is printed on an electrode or a lead pattern and at least an IC chip 5 of the printed pattern is subject to press treatment for the part to be in contact for aligning the height. Then, heat treatment is performed to the printed pattern, the electrode or the lead is completed, and a pad of the signal I/O part of the lead and the bump of the signal I/O part of the IC chip 5 are allowed to be connected electrically. It allows the height of an electrode pattern 2 formed by the printing method can be made uniform and a complete conduction can be obtained without any improper conductive part on mounting the IC chip 5. Also, resistance of the electrode can be reduced by the press treatment.

Description

[Detailed Description of the Invention] [Field of Application of the Present Invention] This invention provides a method for precisely printing electrical wiring on an insulating substrate such as a printed circuit board or a glass substrate or a substrate having an insulating surface in order to reduce costs. A method of mounting an IC chip using.

"Conventional technology" Conventionally, to form electrical wiring on a printed circuit board, copper foil is pasted on an insulating substrate such as glass epoxy, and electrical wiring is formed by wet etching using a well-known photolithography process. A method was taken to do so.

In addition, in the case of devices such as thermal heads, a conductive metal, mainly Au, is deposited on the entire surface of the substrate by ion blating or the like on a ceramic substrate, which is an insulator.
As in the case of printed circuit boards, a method was adopted in which electrical wiring was formed using photolithography and wet etching.

In printed circuit boards, etc., the pin spacing between the holes for inserting the terminals of semiconductor elements is 0.1 inch (2.45 mm).
During this period, photolithography was used mostly to form patterns for high-density printed wiring boards in which three or more electrical wiring circuits were drawn. A method has been adopted in which a dry film is applied to a printed wiring board, a wiring pattern is drawn on it using a photographic technique of exposure and development, and the unnecessary portions are dissolved with a solvent to form the pattern.

The materials used in this method, such as copper foil, dry film, and developer, are expensive, and the exposure equipment is also expensive, which is one of the causes of increased manufacturing costs.

Furthermore, the photolithography process is complicated and requires a considerable amount of time, leading to high costs.

Furthermore, photolithography processes are similarly used when forming electrode patterns for thermal heads, image sensors, and liquid crystal display devices, increasing the manufacturing cost of each device.

In order to solve this problem, by forming the wiring directly on the substrate using a printing method, we can reduce the cost of materials such as copper foil, photoresist, developer, etc. that are the base of the wiring, and the time and time involved in the process, which were required in the conventional method. You can save on labor costs,
Methods have been proposed to reduce costs.

An insulating layer is formed on an insulating substrate such as glass, glass epoxy, ceramic, etc. or on a substrate already provided with wiring, and then a conductive printing ink containing metal powder or alloy metal powder is applied to a thickness of about 1 to 20 μm by a printing method. The pattern is printed with a film thickness of .

COB (chip-on-board) technology is known for mounting ICs for driving electronic devices on circuits drawn directly on the substrate using this method, and in this COB, conventionally, IC electrode pads and The signal input/output sections of the circuit on the board were connected one by one using thin metal wires.

However, due to demands for productivity and cost, a fly-knob chip method has been developed in which bumps are provided on IC pads and are brought into direct contact with signal input/output sections of circuits on a substrate.

In this case, the IC bump and the signal input/output section of the circuit on the board are not completely contacted, causing a problem of poor conduction and lowering the yield of the product.

The present invention has a structure in which a signal input/output section of a circuit on a substrate is formed by applying a press process to at least a portion of the circuit made of electrodes or leads drawn by a direct printing method or the like on the substrate that contacts the bumps of Ic. After aligning the heights of the ICs, the IC head is brought into contact with the signal input/output section of the circuit on the board to make an electrical connection, which solves the above problem, improves the manufacturing yield of the product, and reduces the manufacturing cost of the product. It has the effect of lowering

The present invention will be explained below with reference to Examples.

"Example" A predetermined electrode or lead pattern (2) was printed on a substrate having an insulating surface using a polymer-type copper paste commercially available as a conductive printing ink by a known screen printing method.

The polymer type copper paste used in this example is manufactured by Mitsui Mining & Co., Ltd. and is commercially available under the trade name S-5000.
It is composed of copper particles having a particle size of approximately I, an epoxy resin, and an organic solvent.

This conductive printing paste is printed in a predetermined pattern (2) using a 2QO to 400 mesh screen. In this case, the width of the printed pattern electrode or lid is at least 4
The width of the screen mesh is about 0 μm and the maximum is about 100 μm, and the gap between the screen meshes is 20 to 40 μm, and naturally there is a difference in height corresponding to the mesh in the printed pattern (2).

Now, if we print 100 linear electrodes with a thickness of 20 μm and a width of 40 μm, the maximum thickness is 27 μm and the minimum thickness is 1
The height difference was 3 μm, and there was a height difference between one electrode as well as between a plurality of electrodes. The situation is shown in FIG. 2(a).

Naturally, it was impossible to obtain complete conduction by bringing an IC chip into contact with an electrode pattern having a height difference of about 15 μm.

Therefore, in this embodiment, first, the electrode or lead pattern (2) shown in FIG. 1 was printed on the substrate (1) having an insulating surface using the above-mentioned conductive paste. Although only a portion of which is shown in FIG. 1, 80 electrode patterns were printed. In this state, as mentioned above, there are height differences in the electrodes or lead patterns; for example, the height of the electrode (33) is 15 μm, the height of the electrode (3) is 29 μm, and the average of the 80 electrodes is 19.5 μm. Met.

Next, this printed pattern is subjected to preliminary heat treatment. That is, heat was applied to the conductive paste to such an extent that it did not completely solidify, and a portion of the organic solvent present in the printed pattern was blown off.

Actually, preliminary heat treatment was performed at 60°C for about 5 minutes.

Next, this electrode was subjected to a press treatment. In the case of this example, the printing pattern subjected to the preliminary heat treatment was subjected to press treatment using a roll press at a surface pressure of 20 kg/c+fl. Thereafter, heat treatment was performed at 180° C. for 30 minutes to completely solidify the electrode pattern. At this time, the height of the electrode (33) is 14 μm, the height of the electrode (3) is 20 μm, and the average height of the 80 electrodes is 18 μm.
．． It was 0 μm. The state of the electrode pattern after pressing is shown in FIG.

This pressing process only needs to be applied to the part of the electrode pattern formed on the substrate (1) that comes into contact with the bumps of the IC chip, but if the entire or almost the entire electrode pattern is subjected to the pressing process, some parts of the electrode pattern formed on the substrate (1) will be present in the pattern formed by the pressing process. Another feature is that the contact area between the copper particles increases and the conductivity of the electrode improves.

Next, the bumps (6) of the IC chip (5) and the signal input/output portion of the pattern (2) on the substrate are aligned and brought into contact with each other.

At this time, apply the ultraviolet light curing adhesive (4) to the IC chip (5) while heating it to about 150°C, and after irradiating it with ultraviolet light to bond it, stop heating and place the IC chip on the substrate. Finish the implementation. The situation at this time is shown in Figure 3.

The adhesive (4) that adheres the IC chip (5) to the substrate expands and contracts in volume as the temperature changes. In this example, the adhesive was cured in a heated state, that is, in a state where the volume expanded, so even if the temperature was lowered, the volume of the adhesive would shrink and the IC chip (
5) It has the characteristic that it can withstand temperature cycle tests, etc. simply by increasing the force that presses it against the board.

For comparison, IC was applied to the printed pattern without press processing.
The table below shows the results of mounting the chip and examining its electrical connection characteristics.

In the method of the present invention in which press processing is performed in this way, all the connected parts show good conductivity, and the yield of the connected parts is 100%.
I was able to do this.

In this example, the difference between the highest and lowest electrode heights after pressing was 6 μm. Originally, it is thought that this height difference of 0 would give the best results, but the inventors have found that connection is possible even with a height difference of 8 μm.

[Effects] According to the method of the present invention, the electrode patterns formed by the printing method could be formed with the same height, and complete conduction was obtained with no defective conduction points during the mounting of the IC chip.

Another feature is that the resistance value of the electrode is reduced by the press treatment.

[Brief explanation of the drawing]

1 and 2 show printed patterns of electrodes according to the method of the invention. FIG. 3 shows how the IC chip is mounted. ■90. Substrate 590. ICC stamp 66. Electrode pattern 40. , Adhesive ＾-One Funeral Picture

Claims (2)

[Claims] 1. a step of printing a paste having conductive particles on a substrate having an insulating surface into a pattern of electrodes or leads by screen printing; and at least I of the printed pattern.
A step of applying press treatment to the part that contacts the C chip to make the height uniform; a step of applying heat treatment to the printed pattern to complete the electrode or lead; and a step of applying a signal input/output part pad of the electrode or lead to the signal of the IC chip. 1. A method for mounting an IC chip, comprising the step of opposing and electrically connecting bumps of an input/output section. 2. Claim 1 is characterized in that the printed pattern is subjected to preliminary heat treatment prior to the step of applying a press treatment to at least a portion of the printed pattern that contacts an IC chip to align the heights of the electrodes or leads. How to mount an IC chip.