JPH06268359A - Soldering method - Google Patents

Abstract

PURPOSE:To improve solderability of a printed board by removing moisture stuck to and absorbed into the printed board in conveyance before flux is applied thereto. CONSTITUTION:A printed board 1 with electronic parts temporarily mounted on is conveyed with the conveyance tans 12 of a soldering device 11A, and moisture stuck to and absorbed into the printed board 1 is removed by drying with a drying device 16 such as drying furnace. Next, the printed board 1 from which moisture is removed is immediately coated with flux by a spraying fluxer 13, and then after preliminarily heated by a preheater 14, it is soldered in a solder bath 15. Thereby, the moisture stuck to and absorbed into the printed board 1 is removed, and even when a small amount of flux is applied thereto, the melted solder is satisfactorily spread over within the through-hole of the printed board, so that the occurrence of soldering defective may be eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soldering method for improving the solderability of a printed circuit board.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing a structure of a soldering apparatus for explaining a conventional soldering process. A printed circuit board 1 on which electronic parts are temporarily attached is a soldering apparatus 11.
The flux was applied by the transport means 12, the flux was applied by the flux 13 and preheated by the preheater 14, and then soldered by the solder bath 15.

The printed circuit board 1 is generally made of glass fiber reinforced synthetic resin or paper phenol, and the like. The synthetic resin printed circuit board 1 has moisture in the atmosphere or moisture caused by a solvent during the production of the printed circuit board. Although (hereinafter simply referred to as "moisture") only adheres to the surface, in particular, the printed circuit board 1 made of paper phenol not only adheres to the surface, but also adheres the moisture to the inside of the printed circuit board 1 easily. There is a property.

[0004]

By the way, in the above-mentioned conventional soldering method, since the printed circuit board 1 on which water is adhered or absorbed can remove the excess flux by the cleaning process using the fluorocarbon solution in the subsequent process. If the flux 13 is a foam type when applying the flux, even if a large amount of the flux is applied to the printed circuit board 1 and the water attached or absorbed on the printed circuit board 1 exudes and mixes into the flux, Since the ratio of the flux to was large, it had almost no effect on the application of the flux. However, in recent years, printed circuit boards 1
Since the cleaning of the flux has been omitted, the amount of flux used is small and the spray type fluxer 1 is effective for applying flux.
I started to use 3. Therefore, the printed circuit board 1
Since the ratio of the flux applied to is smaller than that of water, there is a problem that solderability is deteriorated.

Further, when soldering, if moisture adheres to or is absorbed by the printed circuit board 1, the preheating time must be lengthened. Therefore, the through holes and the resist of the printed circuit board 1 must be removed. Since the water oozes out, the adhesion of the solder melt is hindered, and the solder melt rises to only about half the height of the through hole,
There was a problem that complete soldering was not possible.

The present invention has been made in order to solve the above-mentioned problems, and it is intended to improve the quality of soldering by removing moisture adhering to or absorbed by a printed circuit board before applying flux. Aim to get a way.

[0007]

In the soldering method according to the present invention, the moisture adhering to or absorbed by the printed circuit board during transportation is removed before the flux is applied.

[0008]

In the present invention, the flux is applied immediately after removing the moisture while the printed board is being carried by the carrying means.

[0009]

1 is a block diagram showing the structure of a soldering apparatus for carrying out the present invention. 11A shows the entire soldering apparatus according to the present invention, and 12 to 15 are the same as those shown in FIG. is there. Reference numeral 16 represents a drying device.

Next, the operation will be described. The printed circuit board 1 on which the electronic components are temporarily attached is carried by the carrying means 12 of the soldering device 11A, and the drier 16 such as a drying oven dries and removes the moisture adhered to or absorbed by the printed circuit board 1. Next, the printed circuit board 1 from which the moisture has been removed is immediately fluxed by the spray type fluxer 13,
Next, after preheating with the preheater 14, the solder bath 1
Soldered at 5.

Thus, the soldering method of the present invention is
The printed circuit board 1 is dried immediately before the flux processing.

Further, as the drying device 16 for the printed circuit board 1, a drying furnace by heating a heater, or a dehumidifier for blowing air dehumidified through a dehumidifying agent such as silica gel with a blower to dry it is used. Note that the electronic components temporarily attached to the printed circuit board 1 may be thermally destroyed when exposed to high temperature for a predetermined time or longer. Therefore, in order to prevent this, a cooling device (Fig. (Not shown) may be provided.

Next, experimental results of an embodiment of the present invention, that is, the case where the printed circuit board 1 was dried immediately before applying the flux, and a conventional method, that is, the case where the printed circuit board 1 containing water was used, were used. Will be described.

The printed circuit board 1 is made of paper phenol and has a size of 200 mm × 200 mm, and the number of through holes is about 300. The atmosphere of the drying device 16 is 80 to 110 ° C. in the drying process. As a result of performing the soldering for about 3 minutes, the defective rate of soldering was 36% in the conventional method, but was reduced to 1% in this embodiment.

[0015]

As described above, according to the present invention, the moisture adhering to or absorbed by the printed circuit board is removed before the flux is applied to the printed circuit board being conveyed. The moisture that has adhered to or absorbed in the solder is removed, and even if a small amount of flux is applied, the solder melt will spread sufficiently into the through holes of the printed circuit board, resulting in unsoldered parts or solder balls. This has the advantage that the occurrence of defective soldering can be eliminated and the soldering quality can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a soldering device for carrying out the present invention.

FIG. 2 is a block diagram showing a configuration of a soldering device for explaining a conventional soldering process.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printed circuit board 11A Soldering device 12 Conveying means 13 Fluxer 14 Preheater 15 Solder tank 16 Drying device

Claims (1)

[Claims] 1. A soldering method for a printed circuit board, wherein a printed circuit board on which an electronic component is temporarily attached is applied with flux while being transported by a transportation means, and then preheated and then soldered. A soldering method, characterized in that the moisture adhering to or absorbed in is removed before the application of the flux.