JPH0832223A - Solder jet system - Google Patents

Abstract

PURPOSE:To facilitate the control of the atmosphere within a cover and the temperature of a solder bath while enhancing the soldering quality by passing a nitrogen supply pipe above a preheater for an object to be soldered thereby minimizing the effect of temperature variation due to nitrogen gas. CONSTITUTION:A nitrogen supply pipe 17 from a nitrogen generator, installed at the lower part of a soldering system A, passes upward between a fluxer 3 and a temperature heater 4 and reaches a solder bath 11 through a space above a preheater 5. The nitrogen supply pipe 17 is snaked above the preheater 5.Nitrogen gas jetted from the supply pipe 17 through jet holes is heated by means of the preheater 5 to produce a nitrogen atmosphere having elevated temperature. Consequently, the temperature drop of fused solder in the solder bath 11 can be suppressed by the nitrogen atmosphere.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a jet type soldering apparatus in which at least a soldering step is performed in a nitrogen atmosphere.

[0002]

2. Description of the Related Art Conventionally, a printed circuit board is generally soldered by a jet type (automatic) soldering device. FIG. 1 shows an example of a jet type soldering device.
In this soldering apparatus 1, reference numeral 2 is a conveyor for conveying an article to be soldered (for example, a printed circuit board) to be soldered. The transfer conveyor 2 is composed of two tracks 2a and 2b provided in parallel and facing each other. The printed circuit board has these tracks 2a,
It is conveyed in a state of being installed between 2b. Below the transport conveyor 2, the fluxer 3, the warm air heater 4, the preheater 5, the solder bath 6, the cooling from the inlet side (front side in the drawing) toward the outlet side along the extending direction of the transport conveyor 2. The fan 7 and the like are sequentially arranged.

With this structure, the printed circuit board carried into the soldering device 1 from the entrance side of the conveyor 2 is first fluxed by the fluxer 3 and then applied to the warm air heater 4. After the flux is dried and preheated by the preheater 5,
After being soldered in the solder bath 6 and further cooled by the cooling fan 7, it is carried out and moved to the next step.

By the way, in the soldering apparatus (process) as described above, conventionally, a flux containing pine resin (rosin) or a halide is used as the flux adhered by the fluxer 3. If this flux remains on the printed circuit board, it may cause corrosion or a decrease in insulation resistance. Therefore, cleaning with chlorofluorocarbon or trichloroethane was performed after the soldering process. However, in recent years, it has been determined that these fluorocarbons and trichloroethane are internationally regulated as ozone-depleting substances.

Under these circumstances, recently, a soldering apparatus which does not require cleaning of flux in the soldering process of a printed circuit board has begun to be provided. In such a soldering apparatus, a flux having a small reducing action is used in order to eliminate the need for cleaning the flux. When such a flux is used, there is a concern that the terminals and copper foil will be oxidized before reaching the soldering part, so soldering should be performed in an inert gas (nitrogen gas) atmosphere. I have to.

For example, ELECTRONIC PACKING & PRODUCTIO
In N magazine, April 1990 issue, P64-P66, a jet-type soldering machine covers the entire transport system from fluxers to cooling machines in a tunnel shape, and nitrogen gas is supplied to almost the entire area inside the cover. A nitrogen-enclosed jet-type soldering device in which a mouth is arranged and the entire inside of the cover is made into a nitrogen atmosphere is disclosed. In this case, the oxygen concentration inside the cover that covers the entire transport system is set to about 50 ppm or less. According to such a nitrogen-filled jet-type soldering device, it is possible to perform good soldering even if a flux having a small reducing action is used.

Further, the nitrogen gas supply port is not provided over almost the entire area of the transfer system as described above, but the nitrogen gas supply port is provided only in the upper part of the solder bath, and the nitrogen gas is directly blown to the lower surface of the printed board. Therefore, a jet-type soldering device is also used in which only a portion corresponding to the solder bath has a nitrogen atmosphere. The same effect can be obtained by such a nitrogen spray type jet soldering device.

[0008]

However, the conventional jet-type soldering apparatus as described above has the following problems. In a nitrogen-filled jet-type soldering device, the temperature of the atmosphere is reduced by the nitrogen gas supplied into the cover, and the temperature of the molten solder in the solder bath is also reduced accordingly. Also, there is a problem that it becomes difficult to control the temperature of the solder bath. Further, in the nitrogen spray type jet soldering apparatus, there is a problem that the back surface of the printed circuit board is rapidly cooled by the sprayed nitrogen gas, which deteriorates the soldering quality. The present invention has been made in consideration of the above points, and facilitates temperature control of the atmosphere in the cover and the solder bath by improving the soldering quality by minimizing the influence of temperature change due to nitrogen gas. It is an object of the present invention to provide a jet-type soldering device that can be used.

[0009]

The invention according to claim 1 is
A conveyor for conveying the article to be soldered, a solder tank provided below the conveyor, and a preheater provided upstream of the conveyor for preheating the article to be soldered conveyed by the conveyor. And a nitrogen supply pipe for supplying nitrogen gas from a nitrogen gas supply source so that at least soldering of the article to be soldered in the solder bath is performed in a nitrogen atmosphere. The nitrogen supply pipe is arranged so as to pass above the preheater.

According to a second aspect of the present invention, in the jet type soldering apparatus according to the first aspect, the nitrogen supply pipe is arranged in a meandering manner above the preheater.

[0011]

According to the first aspect of the invention, the nitrogen supply pipe is arranged to pass above the preheater for preheating the article to be soldered. As a result, the nitrogen supply pipe is heated, so that the temperature of the nitrogen gas supplied from the nitrogen gas supply port can be increased, and it is formed between the lower surface of the article to be soldered and the molten solder surface of the solder bath. It is possible to raise the temperature of the nitrogen atmosphere created in the space.

According to the second aspect of the invention, the nitrogen supply pipe is arranged so as to meander above the preheater. As a result, the length of the heated portion of the nitrogen supply pipe becomes longer, and the temperature of the supplied nitrogen gas, that is, the nitrogen atmosphere can be further increased.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to an embodiment shown in the drawings. Here, the present invention will be described using an example in which the present invention is applied to, for example, a device for soldering a printed circuit board. FIG. 1 shows a schematic structure of a jet type soldering apparatus A according to the present invention. This jet type soldering device (hereinafter abbreviated as "soldering device") A
Has almost the same configuration as the conventional jet type soldering apparatus 1, and the same reference numerals are given to the common configurations.
The description is omitted.

As shown in FIG. 1, the soldering apparatus A is
A conveyer conveyor 2 is provided for conveying a printed circuit board (soldered product) to be soldered in the longitudinal direction of the soldering apparatus A. Below the conveyer conveyor 2, a conveyer conveyor 2 is provided along the extending direction of the conveyer conveyor 2. From the inlet side (front side in the drawing) toward the outlet side, the fluxer 3, the warm air heater 4, the preheater 5, the solder tank 11, and the cooling fan 7 are sequentially arranged.

As shown in FIGS. 1 and 2, the transfer conveyor 2 has two tracks 2a and 2b provided in parallel.
It is configured to have. As shown in FIG. 2, each of the tracks 2a and 2b has a plurality of conveying pawls 12, which are circularly driven.
.. are provided, and the printed circuit board P is directly gripped and conveyed between the opposed conveying claws 12, 12. The distance between the tracks 2a and 2b, that is, the conveyance width, can be changed / adjusted by a track width adjusting mechanism (not shown) according to the width of the printed circuit board P to be conveyed. Frames 13 and 13 are provided on both outer sides of the tracks 2a and 2b in parallel with each other at substantially the same height as the tracks 2a and 2b. The tracks 2a and 2b are supported by the frames 13 and 13, and by changing the angles of the frames 13 and 13, the transfer angle of the transfer conveyor 2 can be changed.

As shown in FIG. 1, the fluxer 3,
Devices other than the solder bath 11 such as the warm air heater 4, the preheater 5, and the cooling fan 7 are supported by the frames 13 and 13.

As shown in FIG. 3, the solder tank 11 is divided into two tanks by a partition plate 14 in the extending direction of the conveyor 2, and each tank has a first nozzle 15 and a second nozzle 15. A nozzle 16 is provided.

In the vicinity of the upper end of the solder bath 11 as described above,
Further, at positions below the carrying line L of the printed circuit board P, supply parts 17a, 17a, ... Of a nitrogen supply pipe 17 having ejection holes (not shown) are arranged. The nitrogen supply pipe 17 is made of a metal pipe, and supplies the nitrogen gas generated by a nitrogen generator (not shown) such as a nitrogen generator using membrane separation through a path as shown below.
It is designed to be ejected from an ejection hole (not shown) after being led to a.

As shown in FIG. 4, this nitrogen supply pipe 17
Extends upward from a nitrogen generator (not shown) installed in the lower part of the soldering device A through a space between the fluxer 3 and the warm air heater 4 and through a space above the preheater 5 to the solder bath. It is piped to reach 11. And
Above the preheater 5, the nitrogen supply pipe 17 is bent so as to meander.

As shown in FIGS. 3 and 4, the nitrogen supply pipe 17 is branched into supply parts 17a, 17a, ... Near the solder bath 11, and each supply part 17a is connected to the solder bath 11. It is designed to extend in the width direction. A large number of ejection holes (not shown) are formed along the longitudinal direction of each supply portion 17a.

Further, above the solder bath 11, a shield 21 for enclosing the nitrogen gas supplied from the nitrogen supply pipe 17 in an upper space substantially corresponding to the solder bath 11 to form a shielded space is provided. Is provided. This shield 2
1 is formed so as to be sufficiently longer in the front-back direction than the length of the solder bath 11 with respect to the extending direction of the frames 13 and 13, and between the frames 13 and 13 as shown in FIG. It is formed to have the same width as the width.

Next, the soldering device A having the above structure
The operation of will be described. However, here, the flux used in the soldering apparatus A is a special one having a small reducing action, and does not require cleaning after soldering. Further, the fluxer 3 for applying this flux to the soldering surface of the printed circuit board is of a type in which the flux is sprayed and sprayed.

In the operating state of the soldering device A, the nitrogen generating device (not shown) is operated to eject nitrogen gas from the ejection holes (not shown) of each supply portion 17a of the nitrogen supply pipe 17 to shield the nitrogen gas. The inside of the body 21 is made a nitrogen atmosphere.
Other operations are the same as the operation of the conventional jet-type automatic soldering device.

The printed circuit boards P to be soldered are sequentially conveyed by a conveyor 2, and first, a flux having a low reducing action is applied to a soldering surface (rear surface) in a spray type fluxer 3 (not shown), and then the preheater 5 is used. It passes over and approaches the solder bath 11. Then, the printed board P enters the shield 21 in a nitrogen atmosphere and is soldered in the solder bath 11.

At this time, as shown in FIG. 5, when the printed circuit board P to be soldered reaches the upper portion of the solder bath 11, an extremely narrow space sandwiched between the lower surface of the printed circuit board P and the molten solder M. C is formed. By the way, below the carrying line L of the printed circuit board P on the upper surface of the solder bath 11, supply parts 17a, 17a, ... Of the nitrogen supply pipe 17 are provided. Therefore, the space C becomes a nitrogen atmosphere in which the oxygen concentration is close to 0 (zero) and the nitrogen gas concentration is extremely high even with a small amount of nitrogen gas. As a result, it is possible to effectively prevent oxidation of terminals, copper foils, etc. on the printed circuit board P, use flux with a low reducing action, and eliminate the flux cleaning step.

Moreover, the nitrogen supply pipe 17 for creating a nitrogen atmosphere is arranged so as to pass above the preheater 5. Therefore, the nitrogen gas ejected from the ejection holes (not shown) through these nitrogen supply pipes 17 is heated by the preheater 5, and the nitrogen atmosphere created by this gas has an increased temperature. There is. This makes it possible to suppress the temperature decrease of the molten solder M in the solder bath 11 due to the nitrogen gas, and it becomes possible to easily control the atmosphere in the shield 21 and the temperature of the solder bath 11. At this time, since the pre-heater 5 is used as a heating source when heating the nitrogen gas, it is not necessary to provide a new heating source, the thermal energy can be effectively used, and the above effect can be obtained at low cost. You can

The printed circuit board P soldered by passing over the solder bath 11 in this manner is then covered with the shield 2.
The process of the next step is performed by going out of the outside of 1.

In the above embodiment, the nitrogen atmosphere is formed in the upper part of the solder bath 11 where soldering is actually performed, but the nitrogen atmosphere is restricted from being formed in other portions. is not. Therefore,
The above-mentioned shielded space may be formed so as to make a wide space above the solder bath 11 a nitrogen atmosphere. Further, in order to increase the nitrogen concentration of the shielded space in the shielded space, it is different from the above. The jet holes may be provided in the nitrogen supply pipe 17. In the above embodiment, the present invention is applied to the nitrogen-filled jet type soldering device A,
Of course, this may be applied to a spray-type jet-type soldering device that directly sprays nitrogen gas onto the lower surface of the printed board P. This also increases the temperature of the nitrogen gas blown onto the printed circuit board P, so that the back surface temperature of the printed circuit board P can be prevented from being rapidly cooled, and the quality of soldering can be stabilized. .

[0029]

As described above, according to the jet type soldering device of the first aspect, the nitrogen supply pipe for supplying the nitrogen gas is arranged to pass above the preheater. As a result, the nitrogen supply pipe is heated, so that the temperature of the nitrogen gas supplied from the nitrogen gas supply port can be increased. Therefore, in the nitrogen-filled jet-type soldering device, the temperature of the nitrogen atmosphere can be significantly increased as compared with the conventional one, thereby preventing the temperature drop of the molten solder in the solder tank, and preventing the temperature of the nitrogen atmosphere and the solder tank from increasing. It becomes possible to facilitate management. Also, in the nitrogen spray type jet soldering machine, the temperature of the sprayed nitrogen gas is raised, so it is possible to prevent the backside temperature of the soldered product from being rapidly cooled, and the soldering quality is stabilized. It becomes possible. Moreover, since the existing pre-heater is used as a heat source when heating the nitrogen gas, it is not necessary to provide a new heating source, the heat energy can be effectively used, and the above effect can be achieved at low cost. it can.

According to the jet type soldering device of the second aspect, the nitrogen supply pipe is arranged so as to meander above the preheater. As a result, the length of the heated portion of the nitrogen supply pipe becomes longer, and the temperature of the supplied nitrogen gas can be further increased. Thereby, the effect described in claim 1 can be made more remarkable.

[Brief description of drawings]

FIG. 1 is a perspective view showing the appearance of an example of a jet type soldering device according to the present invention and an example of a conventional jet type soldering device.

FIG. 2 is a side sectional view showing a solder tank portion of the jet type soldering device according to the present invention.

FIG. 3 is a front sectional view of the solder bath section.

FIG. 4 is a plan view showing a pipeline of a nitrogen supply pipe of the jet type soldering device.

FIG. 5 is a partial front cross-sectional view showing a state in which an article to be soldered is soldered in the solder bath.

[Explanation of symbols]

 2 Conveyor conveyor 5 Preheater 11 Solder tank 17 Nitrogen supply pipe A Soldering device P Printed circuit board (soldered product)

Claims (2)

[Claims] 1. A transfer conveyor for transferring an article to be soldered, a solder tank provided below the transfer conveyor, and an article to be soldered provided upstream of the solder tank and transferred by the transfer conveyor. And a nitrogen supply pipe for supplying nitrogen gas from a nitrogen gas supply source so that at least the soldering object to be soldered in the solder bath is soldered in a nitrogen atmosphere. A jet type soldering device, wherein the nitrogen supply pipe is arranged so as to pass above the preheater. 2. The jet soldering apparatus according to claim 1, wherein the nitrogen supply pipe is arranged in a meandering manner above the preheater.