JPH08274454A - Sheet solder and its manufacture - Google Patents

Abstract

PURPOSE: To prevent solder paste coated on a printed board from sticking to unnecessary parts by fixing the periphery of form solder of constant thickness with heat-resistant high-molecule resin of the same thickness to where it meets an electronic part of lead. CONSTITUTION: A solder washer in a circular shape of 0.01 to 1mm in thickness with a hole 5 in its center is provided at a position meeting a PGA lead. The solder washer is fixed by a heat-resistant high-molecule resin 6 to obtain sheet solder 7. The PGA is mounted in a manner of inserting the lead into the hole 5 of the solder washer and a through hole on the printed board. The PGA- mounted printed board is heated in a reflow furnace to melt the solder paste and the solder washer, thereby soldering the PGA lead to the printed board mount. This makes it impossible for the solder paste on the printed board to stick to unnecessary parts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet-like foam solder which can be supplied in a batch to a large number of soldering spots for rational soldering and a method for manufacturing the same.

[0002]

2. Description of the Related Art Recently, highly integrated electronic components, which have become smaller and have more functions, have come to be used in many electronic devices. An example of such a highly integrated electronic component is PG
There is A (Pin Grid Alley). The PGA has a narrow lead interval and is provided with hundreds of leads.

Soldering of PGA and printed circuit board is done by P
This is done by inserting the GA leads into the through holes of the printed circuit board and joining the leads to the through holes and the mounts around the through holes with solder. Conventionally, only solder paste has been used for soldering PGA, but solder paste alone does not provide sound soldering because the amount of solder is insufficient and voids are formed between the through holes and the leads.

It is possible to increase the amount of the solder paste applied during soldering of PGA using the solder paste. However, if the amount of the solder paste applied increases,
A large amount of solder paste cannot be used because the solder paste will drip and spread during reflow and form a bridge that is integrated with the adjacent soldering part.

The applicant of the present invention, in PGA soldering, when it is necessary to secure a certain amount of solder in the soldering portion, a reliable soldering can be achieved by using a solder paste and a sheet-form foam solder together. He found what he could do and proposed an invention for this method. (Japanese Patent Application No. 4-29081) The sheet-form foam solder used in this method is one sheet-form in which a large number of solder washers are partially connected.

[0006]

By the way, in the above-mentioned sheet-form foam solder, a solder connecting portion is provided between the adjacent solder washers, and the adjacent solder washers hold each other at this connecting portion. Is. However, if the sheet-form foam solder has a connecting portion, even if it is heated during soldering, the connecting portion may be melted as it is without being separated, or may be solidified as it is to form a bridge.

Therefore, it is possible to make the connecting portion of the sheet-form foam solder thin so that it can be easily cut. However, if this connecting portion is made thin, it is possible to carry a heavy sheet-form foam solder or install it in the soldering portion. There was a case where the joint was bent or broken during the handling.

If the sheet-form foam solder having the connecting portions is heated uniformly during soldering, all the connecting portions are melted at the same time and the respective foam solders are separated. However, in this sheet-shaped foam solder, if the heating is non-uniform and there is a time lag in melting of the connection part, or if unmelting occurs, the previously melted foam solder will be drawn to the unmelted portion. However, there may be a problem that the amount of solder in the unmelted portion is increased.

In order to solve these drawbacks, it is sufficient to eliminate the connecting portion between the adjacent solder washers. As a sheet-form foam solder without a connecting portion, there is a paper-type sheet-form foam solder in which a large number of solder washers are fitted to paper having holes.
(Reference: Jitsukai Sho 58-49473)

However, in this paper-type sheet-form foam solder, the foam solder is fitted to the paper, so that the foam solder projects on both sides of the paper which is the holder. If the form solder protrudes above the holder in this way, when the sheet-shaped form solder is installed after applying the solder paste, the form solder will immerse in the solder paste, pushing the solder paste and pushing the solder paste. The paste is missing from the soldered area. As a result, there is a problem in that the solder paste melted during soldering does not adhere to the soldering portion, the amount of solder is insufficient, and the solder paste adheres to unnecessary portions.

It is an object of the present invention to provide a sheet-form foam solder in which the solder paste applied to a printed circuit board does not adhere to unnecessary places, and a method for producing the same.

[0012]

Means for Solving the Problems As a result of intensive studies made by the present inventors, when the sheet-form foam solder and the solder paste are used together, the solder paste is prevented from adhering to unnecessary portions. The present invention has been completed by focusing on the fact that it is optimal to use a sheet-shaped foam solder having a special shape, and that it is optimal to use a polymer resin that can be easily supplied as a manufacturing method thereof.

According to the present invention, the foam solder having a thickness of 0.01 to 1 mm is located at the position corresponding to the lead of the electronic component mounted on the printed circuit board, and these foam solders have the same heat resistance around the periphery. Sheet-like foam solder characterized by being fixed with a water-soluble polymer resin, or a step of pasting a masking film on one side of the solder foil; forming a predetermined form solder shape on the other side of the solder foil. Step of drawing with etching resist; Step of dissolving and removing solder foil other than the part where etching resist is drawn with etching solution; Step of removing etching resist on solder foil surface with solvent after cleaning the above etching solution; and Form solder A process of supplying heat-resistant polymer resin around the resin and fixing the foam solder with polymer resin. ; A method for producing a sheet-like form solder, characterized in that it consists of.

The sheet-form foam solder of the present invention has a thickness of the foam solder and the heat resistant resin of 0.01 mm.
If it is thinner, the strength of the heat-resistant polymer resin will be weaker even if it is elastic, and it will be bent or damaged during handling. On the other hand, if the thickness is more than 1 mm, when the sheet-shaped foam solder is installed between the printed circuit board and the electronic component, the space between them becomes wide, and when the foam solder or the solder paste melts,
This space cannot be connected by the molten solder, resulting in poor conduction.

The foam solder of the sheet-form foam solder of the present invention is a solder washer having a hole in the center of a disk, a disk-shaped solder disk without a hole, a rectangular solder disk and the like. Solder washers are suitable for soldering electronic components with relatively long leads, such as PGA, solder discs are QF
It is suitable for soldering electronic parts with short leads such as P, SOP, PLCC.

As the heat-resistant polymer resin for fixing the sheet-form foam solder of the present invention, any resin can be used as long as it does not soften or scorched at the solder melting temperature of about 200.degree.

As the heat-resistant polymer resin, for example, epoxy resin (trade name: PR-220, manufactured by Asahi Kaken Co., Ltd.) and the like are suitable, but polyvinyl alcohol (PVA, trade name:
When a water-soluble material such as Gohsenol NL-05) is used, it is possible to easily remove unnecessary polymer resin by washing with water after soldering.

Further, in the case where cleaning cannot be performed after soldering, the polymer resin is made urethane with isocyanate so as to have a function of a solder resist which is insoluble in water, and this is removed even after soldering. It is not necessary and electrical insulation is secured.

As the masking film used in the method for producing the sheet-form foam solder of the present invention, a polymer resin having water resistance such as polyethylene, polypropylene, polyester and the like, which is coated with an adhesive on one side, is suitable. There is.

Next, a method for manufacturing the sheet-form foam solder of the present invention will be described with reference to the drawings.

1A to 1E are respective steps of the method for producing the sheet-like foam solder of the present invention. A: A long solder foil having a thickness of 200 μm and a width of 65 mm (6
A 50 μm thick masking film 2 is attached to one surface of the 3Sn-Pb) 1. B: A large number of washer shapes with a diameter of 2 mm and a central hole system of 1 mm are drawn with the etching resist 3 on the other surface of the solder foil (the surface on which the masking film is not attached). A large number of washer shapes to be drawn are at positions corresponding to the leads of PGA. A liquid photoresist is used as the etching resist, and the etching resist is applied by a roll coater method.
If this is exposed and developed, accurate drawing can be performed. C: An etching solution of a sulfonic acid-based solder stripping solution is sprayed onto the drawn washer shape to dissolve and remove the solder in a portion other than the etching resist.
Then, the etching resist portion remains as the solder washer 4 on the masking film. The solder washer is disk-shaped and has a hole 5 in the center. D: The solder stripping solution attached to the masking film or the etching resist is washed with water, and the etching resist on the surface of the solder foil is removed with a solvent. E: Heat-resistant polymer resin 6 around the solder washer
(PVA) is supplied by a printing method using a silk screen, heat-cured at 70 to 100 ° C., and a solder washer is fixed with a heat-resistant polymer resin to obtain a sheet-form foam solder 7. The masking film 2 may be peeled off immediately after fixing the solder washer with the heat-resistant polymer resin, or immediately before soldering.

Next, a method of soldering PGA and a printed circuit board using the sheet-form foam solder of the present invention will be described. 2A to 2D show the soldering process.

A: A solder paste 10 is applied to the mount 9 which is a soldering portion of the printed circuit board 8 by a printing method. Through holes 11 are formed in the mount 9. b: Sheet-shaped foam solder 7 in which solder paste 10 is applied and a solder washer is fixed with PVA
Is placed. At this time, the hole 5 of the solder washer 4 and the through hole 11 of the printed board 8 are completely aligned. c: PGA by inserting the lead 12 into the hole 5 of the solder washer and the through hole 11 of the printed circuit board 8.
Equipped with 13. d: The printed circuit board 8 on which the PGA 13 is mounted is heated in a reflow furnace to melt the solder paste and the solder washer to mount the PGA lead 12 and the printed circuit board mount 9.
Solder and. The printed circuit board after soldering is washed with water to dissolve and remove the flux residue and PVA.

In the soldering of the PGA and the printed circuit board, when the sheet-form foam solder is handled, the sheet-form foam solder is not bent or damaged at all, and the bridge, the unsoldered or the unnecessary portion of the solder is not soldered. There was no adhesion.

[0025]

As described above, the sheet-form foam solder of the present invention does not push the solder paste to a place other than the soldering portion when it is used together with the solder paste in the soldering of the electronic component and the printed circuit board. Therefore, not only will solder not be attached to unnecessary parts or soldering will be insufficient due to insufficient solder amount, but also since the foam solder is connected with a high-strength polymer resin, it may bend during use. It has an excellent effect of not being damaged.

Further, in the method for manufacturing a sheet-like foam solder of the present invention, a large number of foam solders can be accurately installed at predetermined positions, and a thin foam solder is firmly supported by a support. Is something that can be done.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of each step of a method for producing a sheet-shaped foam solder of the present invention.

FIG. 2 is a schematic view of P using the sheet-form foam solder of the present invention.
It is explanatory drawing of the method of soldering GA and a printed circuit board.

[Explanation of symbols]

 1 Solder Foil 2 Masking Film 3 Etching Resist 4 Solder Washer 5 Solder Washer Hole 6 Heat Resistant Polymer Resin 7 Sheet Foam Solder 8 Printed Circuit Board 9 Mount 10 Solder Paste 11 Through Hole 12 Lead 13 PGA

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[Procedure amendment]

[Submission date] December 10, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is an explanatory diagram of each step of a method for producing a sheet-shaped foam solder of the present invention.

FIG. 2 is a schematic view of P using the sheet-form foam solder of the present invention.
It is explanatory drawing of the method of soldering GA and a printed circuit board.

[Explanation of symbols] 1 Solder foil 2 Masking film 3 Etching resist 4 Solder washer 5 Solder washer hole 6 Heat resistant polymer resin 7 Sheet-form foam solder 8 Printed circuit board 9 Mount 10 Solder paste 11 Through hole 12 Lead 13 PGA

Front page continuation (72) Inventor Toshihisa Sudo 1 Matsuyama-cho, Moka-shi, Tochigi Senju Metal Industry Co., Ltd. Tochigi Plant (72) Inventor Osamu Sogata 405 Yatsuka-cho, Soka-shi, Saitama Senju Metal Industry Co., Ltd. In-house

Claims (3)

[Claims] 1. A foam solder having a thickness of 0.01 to 1 mm is located at a position corresponding to a lead of an electronic component mounted on a printed circuit board, and these foam solders have high heat resistance with the same thickness around the periphery. Sheet-shaped foam solder, which is fixed with molecular resin. 2. The sheet-shaped foam solder according to claim 1, wherein the foam solder is a solder washer, a solder disk, or a solder pellet. 3. A step of attaching a masking film to one surface of the solder foil; a step of drawing a predetermined form solder shape on the other surface of the solder foil with an etching resist; a solder foil other than the part where the etching resist is drawn. To remove the etching resist on the surface of the solder foil with a solvent after cleaning the above etching liquid; and to supply a heat-resistant polymer resin around the foam solder to form a polymer for the foam solder. A step of fixing with a resin;