JPH0270377A - Method and device for automatic soldering - Google Patents

Abstract

PURPOSE:To realize satisfactory soldering by decreasing flow velocity and without washing away a fillet by allowing molten solder jetted from a nozzle to flow temporarily into a solder receiving tank disposed on the upper part than a solder tank, and allowing it to flow out of a hole of the bottom part. CONSTITUTION:Molten solder 5 of a solder tank 2 is brought to pressure feed to a nozzle 3, and jetted from a jet port 6. A substrate 8 on which electronic parts 18 are mounted on a position brought into contact with the top face 16 of jet solder 12 moves in A direction. A lead wire 19 is soldered to the substrate 8, and the remaining solder 5 flows into solder receiving tanks 9, 10, stored temporarily, and thereafter, flows into the solder tank 2 from outflow holes 9b, 14c and 15a. The position of a liquid level 21 of the molten solder 5 stored in a solder receiving tank 4 is a much higher position than a liquid level 13 of the molten solder of the solder tank 2, therefore, a head becomes remarkably small. Therefore, flow velocity becomes remarkably slow, and satisfactory soldering can be realized without washing away the fillet of solder.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method and apparatus for automatic soldering, and in particular, a solder receiver disposed at a position one step higher than a solder tank is capable of directing molten solder spouted from a nozzle into the tank. Once the solder flows into the solder tank, the solder receiver raises the liquid level of the molten solder in the tank one step higher than the liquid level of the molten solder in the solder tank, thereby increasing the surface tension of the molten solder. The present invention relates to a method and apparatus for automatic soldering in which the surface flow velocity of the molten solder to the lower surface of the board is significantly slowed down by utilizing the method, and a good fillet can be formed in the lead wire portion of the electronic component of the board.

Conventional technology Conventional automatic soldering equipment involves pumping molten solder stored in a solder tank with a pressure pump and ejecting it from a nozzle.
Generally, after soldering electronic components to a board, the excess molten solder is dropped directly into a solder bath and collected for reuse. The molten solder spouted from the nozzle falls freely under the action of gravity to the liquid level of the solder tank, so the flow speed becomes faster and the solder fillet formed on the lead wire of the electronic component is washed away and the solder becomes good. This method has the disadvantage that it may not be possible to obtain a fillet with a certain shape. In addition, the molten solder spouted from the nozzle is exposed to the air for a long distance until it flows into the molten solder in the solder tank, so it is easily oxidized, making it difficult to obtain a solder joint with sufficient strength. This method has the disadvantage that it is necessary to perform oxide removal work frequently, which reduces work efficiency.

Purpose The present invention has been made in order to eliminate the drawbacks of the prior art described above, and its purpose is to provide a solder receiver having an opening in the upper part and an outlet hole for molten solder in the lower part. After arranging a tank near a nozzle through which the molten solder flows out and allowing the molten solder spouted from the nozzle to flow in from the opening,
By configuring the solder socket to flow out into the molten solder stored in the solder tank without coming into contact with the outside air through the outflow hole, the solder receiver can raise the liquid level of the molten solder in the tank one step higher than the liquid level of the molten solder in the solder tank. By using the extremely large surface tension of molten solder, the flow velocity of molten solder against the bottom surface of the board is significantly slowed down, and by this, the molten solder adhering to the lead wires of electronic components mounted on the board is washed away. To form a solder fillet with a good shape by preventing this, and to perform soldering with sufficient strength.

Another purpose is to prevent oxidation of the molten solder by minimizing the time the molten solder ejected from the nozzle is in contact with air, and to prevent incomplete soldering caused by oxidized molten solder, etc. It is to eliminate.

Another purpose is to improve work efficiency by reducing the work required to remove oxides from molten solder.

Configuration In short, the present invention (claim 1) provides that the solder receiver, which is disposed near the spout of the nozzle and above the solder tank in which the molten solder is stored, allows the molten solder spouted from the nozzle to flow once into the tank. , the solder receiver is made to flow into the solder tank from an outflow hole formed at the bottom of the tank, and the solder receiver is arranged so that the liquid level of the molten solder in the tank is one step higher than the liquid level of the molten solder in the solder tank. This method is characterized by significantly slowing down the surface flow velocity of the molten solder to the lower surface of the substrate.

Further, the present invention (claim 2) provides an automatic soldering device comprising a solder tank for storing molten solder, a pressure pump for pumping the molten solder, and a nozzle for spouting the molten solder. A solder receiver is disposed near the spout of the nozzle and above the liquid level of the molten solder in the solder tank,
The solder receiver has an opening formed at the top of the tank at a drop position for the molten solder spouted from the nozzle, and the solder receiver has an outflow hole formed at the bottom of the tank so that the solder is stored in the solder tank. The solder receiver is disposed at a position below the liquid level of the molten solder, and the solder receiver causes the molten solder spouted from the nozzle to flow into the tank once, and then flows into the solder tank through the outflow hole without being exposed to outside air; The solder receiver is characterized in that the liquid level of the molten solder in the tank is made one step higher than the liquid level of the molten solder in the solder tank, thereby significantly slowing down the surface flow velocity of the molten solder to the lower surface of the substrate. It is.

The present invention will be explained below based on embodiments shown in the drawings. The automatic soldering device 1 according to the present invention includes a solder bath 2 and a nozzle 3.
The solder light is equipped with a tank 4.

The solder tank 2 is a box-shaped container, and contains therein molten solder 5 heated and melted by a heater (not shown).

The nozzle 3 is disposed in the solder tank 2, and the nozzle 3 is arranged in the solder tank 2, and the nozzle 3
It is connected to a pressure pump (not shown) that pumps the water.

Further, the spout 6 of the nozzle 3 is usually formed with a short cross-section, and is arranged near the center of the solder bath 2, facing upward.
Molten solder 5, which is pumped from a pressure pump, is spouted upward.

A soldering light tank 4 is adjacent to the nozzle 3, and normally consists of a soldering light tank 9 on the upstream side with respect to the conveyance direction of the substrate 8 (direction of arrow A), and a soldering light tank 10 on the downstream side. . The solder light tank 9 on the upstream side is disposed near the top of the solder tank 2, and is connected to the nozzle 3 by a rectifier plate 11, and guides the jet of solder 12 ejected from the spout 6 of the nozzle 3 to the upstream side. The side soldering light is made to flow in from an opening 9a formed above the tank 9. Further, a hole 9b for the upstream solder light is formed at the bottom of the tank 9 at a position below the liquid level 13 of the molten solder 5 stored in the solder tank 2.

The solder light tank 10 on the downstream side differs only in size between the two paths.
It is constructed by stacking two box-shaped containers 14 and 15,
The solder light on the downstream side is transmitted to the upper end 14 of the upper opening 14a of the tank 10.
b is located above the upper end 2a of the solder tank 2, and the outflow holes 14c and 15a formed at the bottom are located below the liquid level 13 of the molten solder 5 in the solder tank 2.

Further, the substrate 8 is transported at a constant speed in the direction of arrow A at an upward slope of about 6° by a substrate transport device (not shown).

Function The present invention is constructed as described above, and its function will be explained below. Referring to FIGS. 1 and 2, the molten solder 5 stored in the solder tank 2 is pumped by a pressure pump (not shown).
The liquid is fed under pressure to the nozzle 3 and is ejected upward from the ejection port 6. - Since the board 8 on which the electronic component 18 is mounted at a position connected to the top surface 16 of the solder jet 12 is being transported at a constant speed in the direction of arrow A by a transport device (not shown), the lead wire 19 of the electronic component 18 is connected to the board. 8, and the remaining molten solder 5 is exposed to the openings 9a of the tanks 9 and 10, respectively.
The solder light flows into the tank from 14a, and the solder receiver enters the tank 9.
, 10, flows into the molten solder 5 of the solder tank 2 through the respective outflow holes 9b, 14c, and 15a, is collected, is pumped again by the pressure pump, and is ejected from the nozzle 3 to perform soldering. is repeated.

Here, the operation from when the molten solder 5 is ejected from the nozzle 3 until it is collected into the solder bath 2 will be explained in detail with reference to FIGS. 3 and 5. In the conventional automatic soldering apparatus 1, as shown in FIG. Free fall down a large head H1 until (
Figure 5). At this time, since there is no obstacle to the flow velocity of the solder jet 12, the flow velocity vector 20a of the surface side portion of the jet solder 12 is almost the same as the η velocity vector 20b of the intermediate portion and the flow velocity vector 20c of the inner portion. The flow velocity is quite high.

On the other hand, in the automatic soldering apparatus 1 of the present invention, the jet solder 12 ejected from the nozzle flows into the solder tank 4, which is disposed above the solder tank 2, and is stored therein. It flows into the solder tank 2 through the holes 9b and 15a and is collected. The position of the liquid level 21 of the molten solder 5 stored in the tank 4 corresponds to the position of the molten solder 5 flowing from the openings 9a and 14a.
This is the position when the amount of molten solder 5 flowing into the solder tank 2 from the outflow holes 9b and 15a is the same, and the amount of molten solder 5 spouted from the nozzle 3 or the amount of molten solder 5 flowing into the solder tank 2 from the outflow holes 9b and 15a is the same.
By adjusting the cross-sectional area of 5a, it is possible to set it at a position much higher than the liquid level 13 of molten solder 5 in solder tank 2.

Therefore, the solder light from the nozzle 3 is transmitted to the liquid level 2 of the molten solder 5 in the tank 4.
The head difference 1!2 from 1 to 1 becomes significantly smaller. Furthermore, since the molten solder 5, which is an alloy of tin and lead, has a very high specific gravity of 9 to 10, its surface tension is also extremely high, 9 to 10 times that of water. The surface side on which it acts becomes almost solid, and acts as if pushed up by the liquid level 21 of the molten solder 5 in the solder receiving tank 4.
The flow velocity vector 22a becomes significantly slower. However, since the flow velocity on the inner side is less affected by surface tension, the flow velocity vector 22b is larger than that on the surface side.

A jet of solder 1 ejected from the nozzle 3 is placed on the lower surface 23 of the substrate 8, which is transported in the direction of arrow A by a transport device (not shown).
2 comes into contact with the lead wire 19 of the electronic component 18 and the molten solder 5
When the solder is attached and soldered, and the board 8 is further conveyed in the direction of arrow A, the solder jet 12 and the board 8 are separated, but the flow velocity vector 22a on the surface side of the solder jet 12 at this time is as described above. Because it is extremely slow, the state is the same as if the board 8 were gently released from the stationary molten solder 5, and the molten solder 24 adhering to the leads yA19 of the electronic component 18 is not washed away by the flow of the jet solder 12, and the fourth As shown in the figure, a sufficient amount of solder remains attached, and as the board 8 is transported, it is cooled to obtain a strong solder fillet 25 with a good shape, and the solder has good soldering performance. be able to.

In addition, since the drop from the top surface 16 of the solder jet 12 to the liquid level 21 of the molten solder 5 in the tank 4 is small, the time in which the solder light comes into contact with the air is short. Since the solder 5 flows into the solder tank 2 from the outflow holes 9b and 15a without being exposed to air, the degree of oxidation is greatly reduced.

Effects As described above, the present invention has an opening in the upper part and an outflow hole in the lower part for allowing the molten solder to flow into the solder tank.The solder light is provided with a tank near the nozzle to collect the molten solder spouted from the nozzle. The structure is such that the solder light flows into the solder tank from the opening, and after the solder receiver is stored in the tank, it flows into the molten solder stored in the solder tank from the outflow hole without coming into contact with air. Since the liquid level is one step higher than the liquid level of the molten solder in the solder tank, the flow rate of the molten solder to the bottom surface of the board can be significantly slowed down, and the solder fillet formed on the lead wire of the electronic component will not be washed away. The shape can be made into a good shape, and extremely good soldering is effective in obtaining performance.

Additionally, since the time period during which the molten solder spouted from the nozzle is in contact with air can be shortened, oxidation of the molten solder can be significantly reduced, and incomplete soldering due to oxidized molten solder can be prevented. effective. It also has the effect of reducing the work required to remove oxides and improving work efficiency.

[Brief explanation of the drawing]

1 to 4 relate to embodiments of the present invention; FIG. 1 is a vertical sectional view showing the operating state of the automatic soldering device; FIG. 2 is an enlarged vertical sectional view of the main part of FIG. 1; Figure 3 is an enlarged vertical cross-sectional view showing and explaining the flow velocity of molten solder in each part using vectors, Figure 4 is a vertical cross-sectional view showing the shape of solder fillets formed at the points where electronic components need to be soldered, FIG. 5 is a longitudinal sectional view similar to FIG. 2, showing the flow of molten solder ejected from a conventional nozzle. ① is the device for automatic soldering, 2 is the solder bath, 3 is the nozzle, 4.
9.10 is a tank for soldering light, 5 is molten solder, 6 is a nozzle spout, 8 is a substrate, 9a, 14a are openings, 9b, 14b
, 15a is the outflow hole, 13 is the liquid level of molten solder in the solder tank, 2
1 is the solder light on the surface of the molten solder in the tank, and 23 is the bottom surface of the substrate.

Claims (1)

[Scope of Claims] 1. Molten solder spouted from a nozzle is once flowed into a solder receiving tank disposed near the spouting port of the nozzle and above a solder tank that stores the molten solder, and then the solder receiving tank is The molten solder flows into the solder tank from an outflow hole formed at the bottom, and the level of the molten solder in the solder receiving tank is made higher than the level of the molten solder in the solder tank, thereby reducing the amount of the molten solder against the bottom surface of the substrate. An automatic soldering method characterized by significantly slowing down the surface flow velocity. 2. In an automatic soldering device equipped with a solder tank that stores molten solder, a pressure pump that pumps the molten solder, and a nozzle that spouts out the molten solder, the solder tank is located near the spout of the nozzle and the solder tank is located near the spout of the nozzle. A solder receiving tank is disposed above the liquid level of the molten solder in the solder receiving tank, and an opening formed in the upper part of the solder receiving tank is arranged at a position where the molten solder spouted from the nozzle falls, and the solder receiving tank is arranged above the liquid level of the molten solder. An outflow hole formed at the bottom of the tank is placed below the level of the molten solder stored in the solder tank, and after the molten solder spouted from the nozzle once flows into the solder receiving tank, Allowing the solder to flow into the solder tank from the outflow hole without coming into contact with outside air,
The automatic apparatus is characterized in that the liquid level of the molten solder in the solder receiving tank is made one step higher than the liquid level of the molten solder in the solder tank, thereby significantly slowing down the surface flow velocity of the molten solder to the lower surface of the substrate. Soldering equipment.