JPS588944B2 - How to solder electrical parts - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of soldering electrical components, and more particularly to a method of soldering electrical components such as chip components to a predetermined steel foil portion of a printed wiring board.

In conventional immersion soldering methods using static soldering baths and jet soldering baths, when soldering leadless electrical components such as chip components to printed wiring boards, flux gas generated during soldering and gas generated from the board itself are generated. remains in the solder joints and becomes a hindrance to good solder joints.

To solve this problem, as a countermeasure using a solder tank, a stationary solder tank that generates little solder gas is used and gas is introduced into the tank (a liquid that vaporizes at the solder melting temperature may also be introduced).

), a bubble-introducing solder bath has been proposed that generates bubbles to remove the flux gas generated at the solder joint and also ripples the surface of the solder solution to ensure soldering.

However, with this method, the swelling caused by air bubbles on the surface of the solder solution may pop out or scatter through the through holes of the printed wiring board (for example, holes for passing lead wires of discrete components, ICs, etc.) onto the board surface opposite to the solder joint surface. Therefore, especially in printed wiring boards that use both sides, this can cause short circuits or cause wiring paths that should not be connected to each other to connect, causing malfunctions.

The present invention solves the above-mentioned drawbacks of the prior art. After pre-soldering electrical components, including chip components, to a printed wiring board in a bubble-introducing solder tank, a static solder tank or a jet-type solder tank is used. To provide a soldering method in which finish soldering is performed and soldering is performed at a raised part of the surface of the solder solution generated by air bubbles in the bubble introduction type soldering tank.

The present invention will be explained below based on illustrated embodiments.

Fig. 1 shows a no-soldering process using the soldering method of the present invention, in which (I) is a preliminary soldering process using a bubble-introducing solder bath; Gas (for example, an inert gas such as nitrogen (N2), or air) is introduced into the tank 1 from the discharge holes 3, 3' through the introduction pipe 2 to generate bubbles.

In addition, instead of a gas, a liquid or flux that vaporizes at the solder melting temperature may be used (particularly when flux is used, the flux application process, which is a pre-soldering process, can be omitted).

When introducing the printed wiring board 4 into the step (I), the solder joint surface 5 of the printed wiring board 4 is slightly separated from the surface of the solder solution, and the chip element 6 is placed near the top of the bulge on the surface of the solder solution due to air bubbles. The electrode 7 is connected to the copper foil part 8
to enable soldering.

This prevents solder from jumping out or scattering to the surface opposite to the solder joint surface 5 through the through hole 9 (for example, a hole through which a lead wire of a discrete component, IC, etc. is passed) provided in the printed wiring board 4.

Also, since there is no directionality in the flow of solder like in a jet soldering tank, uniform soldering can be achieved.

However, in this preliminary soldering process, the solder joint surface is not sufficiently immersed in solder, so the soldering is not good, and the bursting of the bubbles causes solder droplets to scatter, which adhere to the solder joint surface 5. It may cause a short circuit or adhere to parts that do not require soldering, causing malfunction.

Therefore, in the finishing step shown in (]I), normal soldering is performed in a static solder bath 10.

In this case, since preliminary soldering has already been done, the above-mentioned disadvantages of the static soldering tank (failure of solder joints due to accumulation of flux gas, etc.) are hardly a problem, and sufficient soldering is performed and the solder joint surface Adhering solder droplets can be removed.

Further, in this final soldering process, the same effect can be obtained by using a normal jet type solder tank instead of a stationary type solder tank, and the drawbacks of the jet type solder tank do not pose any problems.

In the embodiment shown in FIG. 1, each solder tank is independent, but as shown in FIG.
The step (II) may also be performed.

That is, the printed wiring board 13 to be soldered is gradually brought closer to the surface of the solder solution, and when it approaches a predetermined distance, gas is introduced into the tank 11 through the discharge hole 12 to generate bubbles, thereby performing preliminary soldering. Let's do it.

Then, the introduction of gas is stopped just before the bulge on the surface of the solder solution generated by air bubbles approaches the distance from which it pops out from the through hole of the printed wiring board 130, and the solder tank is made into a stationary type solder tank. 11 for final soldering.

In this case, the soldering process can be automated by controlling the start and stop of gas introduction using a detection signal from a device that detects the distance between the printed wiring board and the surface of the solder solution.

In addition, as another example of the method of performing steps (I) and (II) in the same solder tank, the first half of one solder tank is used as the bubble-introducing solder tank of step (I), and the second half is (II
) process may be a static type soldering bath or a jet type soldering bath.

However, if a jet solder bath is used in the second half, a barrier may be provided at the boundary between the first half and the second half to prevent the effect of the jet solder from reaching the bubble introduction type solder bath in the first half. good.

As described above, the present invention is designed to solder electrical components such as chip components to a predetermined copper foil portion of a printed wiring board using the raised portion of the solder solution surface generated by bubbles in a bubble-introducing solder bath, and then stand still. Finish soldering is performed by immersing the solder in a type solder tank or a jet type solder tank, and the solder flows out or scatters to the surface of the board opposite to the solder joint surface through the through hole provided in the printed wiring board. This has the excellent effect of preventing short circuits and malfunctions caused by connections between circuits that should not be connected, as it can prevent solder droplets from adhering to the solder joint surface due to the bursting of air bubbles. has.

[Brief explanation of the drawing]

1 and 2 both show embodiments of the present invention. Explanation of symbols, 1... Bubble introduction type solder tank, 2.
...Introduction pipe, 3...Discharge hole, 4...
...Printed wiring board, 5...Solder joint surface,
6... Chip element, 7... Electrode, 8...
...Copper foil part, 9...Through hole, 10...
...Static solder tank.

Claims (1)

[Claims] 1. After soldering electrical components such as chip components to a designated copper foil part of a printed wiring board using the raised area on the surface of the solder solution generated by air bubbles in a bubble-introducing solder tank, solder them to a static solder tank or a jet-type solder tank. A method for soldering electrical parts, characterized by performing final soldering by dipping.