JPS6297763A - Soldering method and device - Google Patents

Abstract

PURPOSE:To remove a bridge solder with suction by capillary phenomenon and to realize good soldering simply by dipping a soldering part in a molten solder together with the brush which is composed of numerous fine metallic wires and by separating it from the brush after the ascent. CONSTITUTION:The lead L of the connector C which is fitted to a print board P is pushed down against the spring 5 energizing to the upper part together with the brush 2 which is composed of numerous fine metallic wires and dipped into the upwash molten metal of a solder tank 1. The lead L is ascended with the brush 2, thereafter the lead part L is separated from the brush 2. The bridge generation is completely prevented with very simple method because of the solder formed by the bridge being sucked to the fine wire side with capillary phenomenon due to the fine wire gap of the brush 2 being narrower than the gap of the lead L.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a soldering method and apparatus suitable for soldering electronic devices, particularly printed circuit boards and electronic components in which adjacent soldering areas are very narrow.

[Conventional technology]

Modern electronic devices have become extremely compact, so the printed circuit boards used for them are wired with high-density circuits, and the electronic components are also smaller and the distance between them is narrower.

For example, in a connector for taking out a large number of leads from a printed standard, many are installed in a comb shape, and the spacing is 1 mm or less.Furthermore, in a brush I/pack IC that has leads on all sides, the lead spacing is It is a very narrow object with a diameter of 0.5 mm or less.

When soldering various electronic components, if the soldered parts are simply dipped in molten solder and soldered, a so-called bridge occurs where molten solder crosses and adheres to adjacent solder joints. There is. Figure 6 shows the connector (C
), solder (S) adheres between a large number of leads (L) to form a bridge.

To prevent bridging, conventional methods include the air knife method, in which compressed air is blown onto the soldered area immediately after soldering to blow away the excess solder, and the printed circuit board, which has just been soldered, is struck against another object. A striking method has been used that uses impact to shake off excess solder. However, in the air knife method, the solder blown away by the compressed air may nick other circuits or electronic components, forming a short circuit or damaging the function of the electronic components.

In addition, the impact method sometimes causes undesirable phenomena such as the soldered parts coming off due to impact and adversely affecting electronic components. Therefore, neither the air knife method nor the impact method are used much these days.

Another method for preventing bridging is to solder so that only the soldered portion is slightly contacted with molten solder. In this method, the soldering part must be immersed into the molten solder with an accuracy of approximately ±0.5 mm, and for this reason, the positional accuracy of the printed circuit board transfer device of the automatic soldering machine and the solder bath must be adjusted. It needs to be good. However, trying to improve the accuracy of automatic soldering equipment requires a large amount of effort. Moreover, no matter how accurate this is, the printed circuit board will warp due to thermal expansion when it comes into contact with molten solder, so the center and edges must be immersed in molten solder. The ease of soldering would change, and it would be completely meaningless to improve the accuracy of the automatic soldering device.

Therefore, today, when soldering printed circuit boards with high-density wiring or electronic components with narrow spacing, the occurrence of bridges is unavoidable, and workers often touch them up with a trowel after soldering. Since this requires a lot of time and effort, the industry has been eagerly awaiting a soldering method that does not cause bridges and the emergence of Ha.

[Purpose of the invention]

The present invention has no adverse effect on other circuits or electronic components, and does not require much concern about the positional accuracy of the conveyor or solder bath of an automatic soldering machine; soldering that does not generate bridges at the soldering part. An object of the present invention is to provide a method and apparatus.

[Structure of the invention]

The present inventors completed the present invention by paying attention to the fact that solder in a liquid state progresses in wetting due to capillary action. In other words, a bridge is also a state in which solder is spread over narrow spaces due to capillary action, but if you apply something wet to the molten solder to the soldering area that is even narrower than the space that causes the bridge, the molten solder will spread out. Narrower spacing ζ
It takes advantage of this transition.

A feature of the present invention is that a number of thin metal wires are applied to the soldering part immersed in molten solder, and the object to be soldered is pulled up from the molten solder, and then the object to be soldered is placed on the surface of the molten solder. This is a method in which an object and a large number of thin metal wires are separated and soldered together, and the object on which a large number of thin metal wires are installed can be immersed in molten solder, and the object can be raised to a certain height while being applied to the object to be soldered. Once completed, the solder is separated from the reed soldering object (the dimensions are the equipment).

〔Example〕

The present invention will be explained below based on the drawings.

2 to 5 explain the soldering method of the present invention, and show an example in which a connector having a large number of leads is soldered to a printed circuit board.

First, attach the connector (C) to the specified location on the printed circuit board (P), aligning the connector lead (L) with the soldering location on the printed circuit board (P), and then attaching the connector (C) to the top and bottom of the connector. This is done by sandwiching the printed circuit board between the leads placed opposite each other. Pudding is the soldering part!・Pre-process the board and connector lead by applying flux or preheating, and transport them to the top of the solder bath (1) using a transport device (not shown) (Figure 2).
. At this point, the drive of the transport device is stopped and the printed circuit board is lowered. At this time, a brush (2
), immerse the soldered part together with the brush into the molten solder (Figure 3).

Once the molten solder has adhered to the soldering area, the printed circuit board is pulled upward together with the brush (FIG. 4).

Then, the printed circuit board is further pulled upward to separate the soldering part and the brush, and the soldering is completed (FIG. 5).

Here, the effects of the above soldering method will be explained.

When the soldered part is immersed in molten solder with many thin metal wires applied to it and pulled up,
Excess molten solder that adheres to the soldered part and causes bridging is absorbed by capillary action between the many thin metal wires. Therefore, if the soldered part and the thin metal wire are then separated, a large amount of solder will not adhere to the soldered part and no bridge will be formed.

Next, the soldering device of the present invention will be explained.

As shown in FIG. 1, the soldering device of the present invention has a brush (2) in which a large number of thin metal wires are implanted above a jet soldering bath (1).
) is installed so that it can be moved up and down. The brush (2) is attached to a concave-shaped shaft (3), and both ends of the shaft are inserted into sliding cylinders (4) on both sides of the solder bath (1). has a compression spring (5) of a certain length,
The lower end of the shaft (3) is placed on it. Therefore, when the brush (2) is pushed from above, the shaft (3) moves downward against the compression spring (5) in the sliding cylinder, and when the pressing force of the brush is removed, the shaft returns to its original position due to the force of the spring. Return to position.

In the soldering apparatus of the present invention, when an object to be soldered, for example, a printed circuit board (P) on which a connector (C) is attached as shown in FIG. 1, is placed on the brush and pushed downward, the brush is placed on a compression spring, so the object to be soldered can be immersed in the molten solder together with the brush. After the solder adheres to the soldering area, when the object to be soldered is pulled upward, the brush will be soldered by the spring force. It is pulled up while touching the area. The brush, which leaves the soldering bath in contact with the soldered part in this manner, absorbs excess molten solder from the soldered part into the thin metal wire of the brush. Even if the soldering object rises further, the compression spring on which the brush mounting shaft is placed has a constant length, so it no longer follows the soldering object and separates midway. Therefore, the object to be soldered can be soldered without a bridge.

In the embodiment, the brush is shown as a large number of thin metal wires, but any shape can be used as long as it can absorb excess solder from the soldered portion by capillary action. For example, steel wool coated with thin metal wires has the same effect as a brush.

〔Effect of the invention〕

According to the present invention, it is possible to completely prevent the occurrence of bridging even when the spacing between solder chips is narrow, which was previously thought to be impossible to prevent. Moreover, the device does not need to be used for field feeding equipment or solder baths as in the past. It has the advantage of being inexpensive because there is no need to worry about accuracy.

[Brief explanation of drawings]

FIG. 1 is a perspective view of the soldering apparatus of the present invention, FIGS. 2 to 4 are central sectional views illustrating the soldering method of the present invention, and FIG. 6 is a diagram illustrating the bridging phenomenon in a connector.

Claims (4)

[Claims] (1) With many thin metal wires applied to the soldering part immersed in molten solder, the object to be soldered is pulled up from the molten solder, and then the object to be soldered and the many thin metal wires are placed on the surface of the molten solder. A soldering method characterized by separating the two. (2) It is characterized by a structure in which an object on which a large number of thin metal wires are installed can be immersed in molten solder, and can be raised to a certain height while it is in contact with the object to be soldered, and then separated from the object to be soldered. Soldering equipment. (3) Claim No. 2, characterized in that the object on which the thin metal wire is installed is a brush on which the thin metal wire is implanted.
) Soldering equipment described in section 2. (4) The soldering device according to claim (2), wherein the object on which the thin metal wire is installed is steel wool.