JPS6250220B2 - - Google Patents

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Application Field) The present invention relates to discrete electronic components having lead wires such as resistors, capacitors, transistors, etc. on printed wiring boards, or leadless electronic components. The present invention relates to a method of soldering a printed wiring board for soldering components.

(Prior Art) In general, in order to solder electronic components to a printed wiring board, first, discrete electronic components or leadless electronic components are mounted on the printed wiring board, and then the lower surface of the printed wiring board, that is, A liquid flux is applied to the soldering side using a foaming method or a spray method, and after preheating, soldering is performed using a jet method or an immersion method.

In this case, when the flux is applied by the foaming method, the alcoholic solvent normally contained in the liquid flux evaporates during foaming application, increasing the concentration of the flux. However, there is the trouble of having to dilute the flux by adding an alcoholic solvent. In addition, flux applied to the bottom surface of a printed wiring board, the lead wires of electronic components, or the electrodes of leadless electronic components by a foaming method or a spray method is preheated and transferred to the solder bath before being applied to the printed wiring board. The lead wires penetrate through the lead wire insertion holes formed in the top surface of the printed wiring board, that is, the insertion side of discrete electronic components, and go around to the electrical contact parts of switch components, relay components, semi-fixed resistors, etc. They tend to adhere and cause these parts to malfunction.
Eliminating this is extremely difficult.

Therefore, in order to prevent such accidents, switch parts, relay parts, semi-fixed resistors, etc., where flux adhesion is a problem, are sometimes installed after the normal printed wiring board soldering process. Such a method is extremely inefficient and significantly reduces productivity.

In addition, in a soldering bath, an oxide film tends to form on the surface of molten solder, and it is well known that this oxide film hinders good soldering, but it is difficult to completely remove the oxide film. Have difficulty.

(Problems to be Solved by the Invention) As described above, in the method of foaming and applying flux to a printed wiring board, concentration control must be carried out by diluting the flux by adding an alcoholic solvent during the work, and However, there is a problem in that the flux applied by a foaming method or a spray method in a previous process wraps around the upper surface of the printed wiring board through the lead wire insertion hole and adheres to electronic components, causing malfunctions. Furthermore, during soldering, there is a problem in that an oxide film on the surface of the molten solder causes soldering defects.

The present invention is an attempt to solve the above-mentioned problem, and aims to effectively apply flux when soldering a printed wiring board on which electronic components are mounted.
It does not require flux concentration control during work, prevents flux from going around to the top surface of the printed wiring board, and effectively removes the oxide film of molten solder from the soldering area to ensure good soldering. The purpose is to obtain.

[Structure of the invention]

(Means for Solving the Problems) The present invention includes mounting an electronic component on a printed wiring board, and moving the printed wiring board with the electronic component mounted thereon and bringing the lower surface of the printed wiring board into contact with molten solder. In the method of soldering a printed wiring board to be attached, immediately before the bottom surface of the printed wiring board and the lead wires of electronic components or the electrodes of leadless electronic components come into contact with molten solder, flux is atomized to solder the printed wiring board. The molten solder is simultaneously sprayed onto the lower surface of the molten solder and the lead wire or electrode section.

Moreover, in addition to the above configuration, the present invention further includes:
Immediately before the printed wiring board is soldered in contact with the molten solder and separated from the molten solder, a fluid such as a mist of flux, a heat-resistant oil, a high-boiling solvent, or an inert gas is applied to the underside of the printed wiring board. It is sprayed.

(Function) The present invention sprays flux in the form of a mist just before the soldering area on the bottom surface of the printed wiring board comes into contact with molten solder, thereby efficiently applying flux to the soldering area and applying the flux to the soldering area before application. By eliminating the evaporation of the alcohol-based solvent in the flux and simultaneously spraying the flux onto the molten solder surface, the oxide film on the surface of the molten solder is removed to improve soldering.

Furthermore, just before the printed wiring board is separated from the molten solder, the molten solder that hangs down from the soldered portion in the form of icicles or bridges is removed by spraying a fluid consisting of, for example, atomized flux.

(Example) An example of the present invention will be described below with reference to FIGS. 1 and 2.

Reference numeral 1 denotes a solder tank, and a nozzle 2 for a solder jet is provided at the top of the solder tank 1. A long and narrow rectangular jet port 3 is formed at the upper end of the nozzle 2, and solder receiving plates are provided on both sides of the jet port 3. 4 is displayed. Further, a pump 5 for circulating solder is provided at an intermediate portion of one end of the solder bath 1, and a motor 6 is connected to this pump 5 via pulleys 7, 8 and a belt 9. Further, a plurality of sheathed heaters 10 are provided at the bottom of the solder bath 1.

Then, the pump 5 is driven by the motor 6 via the pulleys 7 and 8 and the belt 9, and the molten solder a in the solder bath 1 is circulated under pressure, and the molten solder a is jetted upward from the jet port 3 of the nozzle 2. , so as to form a jet wave b over the receiving plates 4 on both sides.

Further, a plurality of flux jetting nozzles 11 are arranged at the upper part of one side of the solder bath 1, and each flux jetting nozzle 11 is connected to a flux tank 12. And flux tank 12
The flux c inside each flux jetting nozzle 11
It is now sprayed out in the form of a mist.

Reference numeral 21 denotes a printed wiring board, and a plurality of electronic components 22 are mounted on this printed wiring board 21 by passing lead wires 23 therethrough.

Then, when soldering the printed wiring board 21, the jet port 3 of the nozzle 2 of the solder bath 1 is
After preheating the printed wiring board 21 on which the electronic components 22 are mounted by jetting the molten solder a,
This printed wiring board 21 is moved substantially horizontally in the direction P in FIG. 1 toward the upper surface of the jet wave b of the molten solder a.

Immediately before the printed wiring board 21 comes into contact with the jet wave b, each flux is applied to the lower surface of the printed wiring board 21, the portion of the lead wire 23 of the electronic component 22 exposed to the lower surface of the printed wiring board 21, and the molten solder surface. The flux c is sprayed in the form of a mist from the jet nozzle 11.

Next, the printed wiring board 21 is brought into contact with the jet wave b, and the lead wires 23 of the electronic component 22 are soldered.

In this way, an appropriate amount of flux can be efficiently applied to the lower surface of the printed wiring board 21 and the lead wires 23 of the electronic components 22 just before soldering, and the flux can be applied to the flux tank 12 before soldering.
There is no evaporation of the alcohol-based solvent in the flux, which eliminates the need to manage flux concentration during work, simplifying the soldering process, and the flux is sprayed just before soldering. Since it is used immediately for soldering, the flux is prevented from getting around to the upper surface of the printed wiring board 21, and good soldering can be achieved.

Further, when the flux c is ejected from the flux ejection nozzle 11, the spray is applied to the lower surface of the printed wiring board 21 and the electronic components 22, as described above.
This spray of flux c is also sprayed onto the surface of the jet wave b of the molten solder a, that is, onto the jet wave b on the receiving plate 4,
As a result, the oxide film on the surface of the jet wave b can be removed by the flux c sprayed onto this portion, and the oxide film of the molten solder can be removed by spraying the flux from the printed wiring board 21. This is done immediately before the soldering part comes into contact with the molten solder, so the soldering part can come into contact with the molten solder free of surface oxides, resulting in good soldering.

In this method, the flux jetting nozzle 11
It is desirable to provide the flux jetting nozzle 11 at a position close to the jet wave b of the molten solder a, and the flux jetting nozzle 11 may be installed horizontally or slightly upwardly at any position shown in FIG. The atomized flux c ejected from the flux ejection nozzle 11 may be scattered around the printed wiring board 2.
In order to prevent it from adhering to the top surface of 1, it is desirable to spray it in a fan-like flat shape, and
It is desirable that the vertical spread of the spray be as narrow as possible. More preferably, the pressure of the flux jetting nozzle 11 can be adjusted to enable atomization of a small amount of flux.

In order to apply the mist flux uniformly, the lower surface of the printed wiring board 21 must be heated to about 100°C for paper-based or glass epoxy-based boards before soldering, and to about 100°C for ceramic-based boards before soldering. It is desirable to preheat to about 150°C.

Next, FIGS. 3 and 4 show the second embodiment of the present invention.
This is an embodiment of the flux ejection nozzle 1 shown in FIGS. 1 and 2.
A heating tube 13 is installed as a heating device in the flux tank 12 connected to the flux c, and a heating medium is passed through the heating tube 13 to heat it, and the heated flux c is atomized from the flux jetting nozzle 11 to form a fine atomization of the printed wiring board 21. It is designed to be applied to the lower surface and the lead wires 23 of the electronic component 22.

In this way, when the flux c is heated and applied, the molten solder a caused by the spray application of the flux c is
This prevents a drop in the surface temperature of the jet wave b, and also prevents a drop in the surface temperature of the lead wire 23 of the electronic component 22, making it possible to improve soldering. A flux with a high resin concentration containing a small amount of an organic solvent, such as an alcoholic solvent, or a solvent-free flux containing almost no organic solvent can also be reduced in viscosity by heating and sprayed for application.

As a heating device for the flux tank 12, a heating tube, a sheathed heater, or the like may be provided inside the flux tank 12.

Next, FIGS. 5 and 6 show a third embodiment of the present invention, which is the same as that shown in FIGS. 1 and 2, or that shown in FIGS. 3 and 4. , a plurality of fluid blowing nozzles 14 are arranged at the upper part of the other side of the soldering bath 1, and the fluid blowing nozzles 14 are connected to a fluid tank 15, and a heating pipe 16 is surrounded by this fluid tank 15. heating tube 1
The printed wiring board 2 is heated by passing a heat medium through it.
Immediately before 1 leaves the molten solder, the printed wiring board 21 is injected with heated fluid from the fluid blowing nozzle 14, either by atomizing flux, heat-resistant oil, high boiling point solvent, or inert gas.
It is sprayed onto the underside of the

That is, the printed wiring board 21 is moved toward the upper surface of the jet wave b of the molten solder a, the lead wires 23 of the electronic components 22 are soldered to the printed wiring board 21, and immediately before the printed wiring board 21 is separated from the molten solder. , fluid blowout nozzle 1
By spraying the fluid d, which is any one of atomized flux, heat-resistant oil, high boiling point solvent, or inert gas, from step 4, the molten solder hanging down in the form of icicles or bridges on the lower surface of the printed wiring board 21 is separated from the air. It is possible to prevent surface oxidation due to contact, prevent increase in solder surface tension due to oxidation, and eliminate icicle-like or bridge-like soldering defects.

When this method is used in combination with the spraying of flux c shown in FIGS.
Even when the lead wire 23 is exposed for a longer period of time, the icicle-like or bridge-like solder hanging from the tip of the lead wire 23 can be removed, and a better solder finish can be obtained. When the flux, heat-resistant oil, high boiling point solvent, or inert gas blown from the fluid blowing nozzle 14 is blown onto the lower surface of the printed wiring board 21, the temperature of the molten solder a at that part suddenly increases. In order to prevent excessive solder from decreasing and remaining on the lead wires 23 of the electronic component 22, it is desirable to heat it in advance. In this way, a solvent-free flux can also be used as the fluid.

Next, FIGS. 7 and 8 show the fourth embodiment of the present invention.
5 and 6, an exhaust pipe 17 is provided at both ends of the jet nozzle 2, and a large number of suction ports 18 are formed in the exhaust pipe 17. When the finely sprayed flux from the flux jetting nozzle 11 and the atomized flux from the fluid jetting nozzle 14 are jetted, the excess amount scattered around is forcibly discharged through the exhaust pipe 17. By doing so, the soldering work can be carried out smoothly without contaminating the working environment.

In each of the above embodiments, a jet soldering apparatus has been described, but as shown in FIGS. 9 and 10, the printed wiring board 21 is lowered relative to the molten solder a in the solder bath 1, It can also be directly applied to an immersion soldering device that performs soldering and ascends.

Also in this case, as shown in FIGS. 11 and 12, it is desirable to provide an exhaust pipe 17 to remove excess flux.

In each of the above embodiments, electronic components having lead wires have been described, but the electronic components mounted on the printed wiring board are leadless electronic components.
Even when this is mounted on the lower surface of a printed wiring board, by applying flux to the electrode portion in the form of a mist, the flux can be applied efficiently and good soldering can be achieved.

〔Effect of the invention〕

According to the present invention, when electronic components are mounted on a printed wiring board and soldered, immediately before the printed wiring board comes into contact with molten solder, a room temperature or heated flux is atomized to form a mist on the bottom surface of the printed wiring board. The flux is simultaneously sprayed onto the molten solder surface together with the lead wire of the electronic component or the electrode part of the leadless electronic component, and the flux application and soldering are completed almost simultaneously, so that the flux is applied effectively without waste. There is no evaporation of the alcohol-based solvent in the flux before application, and there is no need to control the concentration of the flux during work, so the soldering process is simplified, and the flux is sprayed immediately before soldering. Since it is used for soldering, it prevents the flux from getting around to the top surface of the printed wiring board, and by spraying the flux onto the molten solder surface, it is possible to remove the oxide film on the surface of the molten solder. The oxide film on the molten solder is removed by spraying this flux immediately before the soldered part of the printed wiring board comes into contact with the molten solder, so the soldered part is completely covered with molten solder with no surface oxide. contact is possible and good soldering is achieved.

In addition, atomized flux is sprayed just before the printed wiring board comes into contact with the molten solder, and the flux, heat-resistant oil, high boiling point solvent, or inert By spraying a room temperature or heated fluid such as gas onto the underside of the printed wiring board, the surface oxidation of the molten solder hanging down in the form of icicles or bridges on the underside of the printed wiring board due to contact with air is prevented. It prevents the increase in surface tension of the solder due to oxidation and eliminates icicle-like or bridge-like soldering defects. Therefore, when the lead wires of electronic components are long, the icicle-like or bridge-like soldering defects that tend to occur at the tips of the lead wires can be prevented. Bridge-shaped solder can be almost completely eliminated.

[Brief explanation of the drawing]

The figures show embodiments of the present invention, FIG. 1 is a sectional view showing the first embodiment, FIG. 2 is a plan view thereof,
FIG. 3 is a sectional view showing the second embodiment, FIG. 4 is a plan view thereof, and FIG. 5 is a sectional view showing the third embodiment.
Fig. 6 is a plan view thereof, Fig. 7 is a sectional view showing the fourth embodiment, Fig. 8 is a plan view thereof, Fig. 9 is a sectional view showing the fifth embodiment, and Fig. 10 is a plan view thereof. 11 are cross-sectional views showing the sixth embodiment, and FIG. 12 is a plan view thereof. DESCRIPTION OF SYMBOLS 1...Solder bath, 11...Flux jetting nozzle, 14...Fluid blowing nozzle, 21...Printed wiring board, 22...Electronic component, 23...Lead wire, a...Melted solder, c...Flux, d...
…fluid.

Claims (1)

[Claims] 1. Soldering of a printed wiring board, in which an electronic component is mounted on a printed wiring board, and the printed wiring board with the electronic component mounted thereon is moved while bringing the lower surface of the printed wiring board into contact with molten solder for soldering. In the attachment method, immediately before the lower surface of the printed wiring board and the lead wires of the electronic components or the electrodes of the leadless electronic components come into contact with the molten solder, flux is atomized to the lower surface of the printed wiring board and the lead wires or electrodes. A method for soldering a printed wiring board, characterized by simultaneously spraying molten solder onto the surface of the printed wiring board. 2. Claim 1, characterized in that the flux that is sprayed in the form of a mist is heated.
How to solder a printed wiring board as described in section. 3. In a printed wiring board soldering method in which electronic components are mounted on a printed wiring board, and the printed wiring board with the electronic components mounted thereon is moved and soldered by bringing the bottom surface of the printed wiring board into contact with molten solder, Immediately before the bottom surface of the printed wiring board and the lead wires of electronic components or the electrodes of leadless electronic components come into contact with the molten solder, flux is atomized and applied to the molten solder surface together with the bottom surface of the printed wiring board and the lead wires or electrodes. At the same time, the printed wiring board is soldered in contact with the molten solder, and just before it is separated from the molten solder, a mist of flux, heat-resistant oil, high boiling point solvent or inert gas is sprayed on the underside of the printed wiring board. A method for soldering printed wiring boards, characterized by spraying any of the following fluids. 4. The printed wiring board soldering method according to claim 3, characterized in that a heated fluid such as atomized flux, heat-resistant oil, high boiling point solvent, or inert gas is used. .