JPH0613429A - Bonding method for outer lead using photo-curing resin - Google Patents

Abstract

PURPOSE:To make it possible to join an outer lead without generating a heat effect on an LSI or some other parts, and take off a package from a board in a necessary repairing step, by using a frame-shaped polyethylene-telephthalate sheet coated with a photo-curing resin, and by swelling a resin with a solvent in the repairing step. CONSTITUTION:After an LSI-chip package 1 is mounted on a board 3, which has a wiring pattern 4 for an electric circuit, an outer-lead leg 2 of the package 1 is aligned with the wiring pattern 4. A frame-shaped polyethylene-telephthalate sheet 6 that is coated with an photo-curing resin 5 is so placed that the coated side thereof is put in contact with the outer-lead leg 2. Then, while the polyethylene-telephthalate sheet 6 is pressed downward by the bonding tool 7, an ultraviolet ray is cast through the bonding tool 7 so that the photo-curing resin 5 is hardened in shrinking, and thereby the outer-lead leg 2 and the wiring pattern 4 are joined electrically.

Description

Detailed Description of the Invention

[0001]

2. Description of the Related Art Conventionally, ICs or Ls used in electronic equipment
The soldering method is most widely used as the outer lead bonding method for mounting the SI package on the printed circuit board or the flexible circuit board on which the electronic circuit pattern is arranged. As one of the methods, for example, reflow bonding in which a solder paste is supplied on a wiring pattern of a printed circuit board by solder screen printing, an LSI chip is mounted on the printed circuit board, heated and joined in a reflow furnace, and then washed to complete the process. There is a law. Also, as another one, solder plating is performed by electrolytic plating or super plating on the wiring pattern of the printed circuit board, the LSI chip is mounted, and the LS is mounted.
After positioning the outer lead legs of the I-chip on the wiring pattern, press and heat with a bonding tool to join,
After that, there is a tool bonding method of cleaning and completing the process.

As another mounting method, an anisotropic conductive film is placed on a printed circuit board on which a wiring pattern is arranged, and an LSI chip is positioned and mounted on the anisotropic conductive film, and then a bonding tool is used. There is a method of using an anisotropic conductive film to complete the treatment by bonding under pressure and heating. This anisotropic conductive film has a fibrous conductor mixed in an insulative adhesive, and reacts with pressure and heat to conduct only between the outer lead leg of the LSI chip and the wiring pattern of the printed circuit board. It is a thing.

[0003]

The disadvantages of the above-mentioned conventional soldering method are that, in the case of the reflow bonding method, it is difficult to form a fine pitch due to screen printing, and the forming of the outer lead leg of the tape carrier package is difficult. The shape needs to be tightly controlled. Further, in the case of the tool bonding method, it is necessary to devise a solder plating method. For example, in electroplating, a special method such as arranging plating leads, and in the case of electroless plating, a super solder is required. A flux applying step is also required.

Further, as a problem of the soldering method itself, the flux must be removed by washing after bonding. In this process, washing with chlorofluorocarbon is the mainstream, and there is a demand for an immediate response from the trend of complete elimination of chlorofluorocarbon.

In the method using the anisotropic conductive film, a pattern is formed by placing an opaque anisotropic conductive film on a printed board and pressing the anisotropic conductive film with a bonding tool. There was a problem that it was difficult to align the positions.

[0006]

In order to solve the above problems, the outer lead bonding method using a photo-curable resin of the present invention mounts an LSI chip package on a substrate on which a wiring pattern of an electric circuit is arranged. Then, the outer lead legs of the package are aligned with the wiring pattern, and a frame-shaped polyethylene terephthalate sheet coated with a photocurable resin corresponding to the outer lead legs of the LSI chip is attached to the photocurable resin side. On the polyethylene terephthalate sheet by pressing with a bonding tool, and irradiating ultraviolet light through the bonding tool to shrink and cure the photocurable resin. And the wiring pattern are electrically connected to each other.

[0007]

The outer lead bonding method of the present invention is
The outer lead leg of the SI chip and the wiring pattern of the substrate can be directly aligned and aligned with each other, and since heat treatment is not performed for bonding, no dimensional change occurs in the printed circuit board.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The outer lead bonding method of the present invention will be described below with reference to the drawings.
FIG. 3 is an exploded perspective view when mounting an SI chip package and performing a bonding process, FIG. 2 is a process diagram of an outer lead bonding method of the present invention, and FIG. 3 is a principle diagram of the outer lead bonding method of the present invention.

First, the rectangular package 1 of the IC or LSI chip shown in FIG. 1 is provided with a plurality of outer lead legs 2, 2 ... The wiring patterns 4, 4 ... Are adhered and formed on a substrate 3 such as a printed circuit board or a flexible substrate corresponding to the lead legs 2, 2 of the package 1.

Next, a polyethylene terephthalate sheet 6 coated with a frame-shaped photocurable resin 5 corresponding to the outer lead legs 2, 2, ... Of the package 1 is provided. The outer dimensions of the sheet 6 are the outer lead legs 2 extending from the opposite sides of the package 1 in both the vertical and horizontal directions.
The length from the tip to the tip of 2 is a little longer or slightly longer, and the cut internal dimension is equivalent to the length of the package 1 in the lengthwise direction and the length in the widthwise direction, and can be inserted into the package 1. .

A bonding tool 7 made of transparent quartz glass and having a cross section equivalent to that of the frame-shaped sheet 6 is prepared.

In the LSI chip package 1, the substrate 3, the photo-curable resin-coated polyethylene terephthalate sheet 6 and the bonding tool 7 having the above-described structure, as shown in FIG. Package 1 is mounted on 3. When mounting the package 1, in the case of a quad flat package (QFP), mount it as it is, and
In the case of CP), the polyimide in the bonding portion is removed and the outer lead legs are left in a peeled state. The outer lead legs 2, 2 ... Of the package 1 and the wiring patterns 4, 4 ...

Next, as shown in FIG. 2B, a frame-shaped transparent polyethylene terephthalate sheet coated with a photocurable resin 5 corresponding to the outer lead legs 2, 2 ... Of the LSI chip. 6 so that the photocurable resin 5 side is in contact with the outer lead legs 2, 2 ...
Insert into and place.

Next, as shown in FIG. 2C, the transparent bonding tool 7 presses the sheet 2 from above the sheet 2, and at the same time, ultraviolet light (UV) L is emitted through the bonding tool 7. Irradiation is performed to shrink and cure the photocurable resin 5 attached to the tool 7.

Due to the shrinkage forces of the photocurable resin 5 and the polyethylene terephthalate sheet 6, the photocurable resin 5 causes the outer lead legs 2, 2 ...
.. Shrinkage and cure to fill the gap and complete the bonding process. Therefore, as a result, as shown in FIG. 3, the outer lead legs 2 and the wiring patterns 4 at the required locations are physically closely attached and electrically connected, and the outer lead legs 2, 2 ... Are cured. It is electrically insulated by the resin 5'and the polyethylene terephthalate sheet 6.

[0016]

Since the outer lead bonding method according to the present invention performs the above-described processing, it does not affect the IC or LSI or the peripheral components due to heat, and the dimension of the substrate does not change.

When repairing is required after bonding, the package 1 can be peeled from the substrate 3 by swelling the resin cured by a solvent, and rebonding can be performed only by replacing the fixing sheet. . Since the fixing sheet required for bonding is also a polyethylene terephthalate tape only coated with a photocurable resin, it has advantages such as being inexpensive.

[Brief description of drawings]

FIG. 1 is an exploded perspective view when processing by an outer lead bonding method of the present invention.

FIG. 2 is a process drawing of an outer lead bonding method of the present invention.

FIG. 3 is a principle diagram of an outer lead bonding method of the present invention.

[Explanation of symbols]

 1 Package of LSI chip 2 Outer lead leg of LSI chip 3 Printed circuit board 4 Wiring pattern 5 Photocurable resin 6 Polyethylene terephthalate sheet 7 Bonding tool

Claims (1)

[Claims] 1. A frame corresponding to an outer lead leg of an LSI chip, wherein a package of an LSI chip is mounted on a substrate on which a wiring pattern of an electric circuit is arranged and an outer lead leg of the package is aligned with the wiring pattern. A polyethylene terephthalate sheet coated with a photo-curable resin is placed so that the photo-curable resin side is in contact with the outer lead leg, and pressure is applied from above the polyethylene terephthalate sheet by a bonding tool, and the bonding tool is attached. An outer lead bonding method using a photo-curable resin, characterized in that the photo-curable resin is shrunk and cured by irradiating ultraviolet light therethrough to electrically connect the outer lead legs and the wiring pattern.