JP3008061B2 - Apparatus and method for suppressing convection in solder bath in low oxygen atmosphere - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for soldering low-melting-point metal solder in an inert gas atmosphere, and more particularly to an apparatus and method for soldering wiring of a printed wiring board.

[0002]

2. Description of the Related Art Conventionally, a jet soldering apparatus has been used for soldering an object to be soldered, particularly wiring of a printed wiring board. At that time, Sn, Pb, Bi, In, S
In order to prevent oxidation when soldering a low melting point metal such as b and a molten solder in which these alloys are melted, soldering is performed in an inert atmosphere.

A soldering apparatus of this kind is disclosed in
FIG. 3 shows a conventional apparatus disclosed in Japanese Patent Application Laid-Open No. 124,264. FIG. 3 illustrates a conventional method of providing an inert gas filling material tank, and shows a mode in which wiring of a printed wiring board is soldered with jet solder. In this apparatus, an inert gas injection hole 6 is formed in the upper portion of a tunnel structure container 10, and the injection hole 6 is connected to an inert gas supply source 7 via a gas heater 15. It has a gas exhaust port 17 in the lower part of 10 as a basic configuration.

In order to solder the wiring of the printed wiring board, a flux coating device 13, a preheating device 14,
A jet-type solder bath 1, a cooling fan 18, a transfer device 5, and the like are added. The preheating device 14 and the jet solder bath 1 are installed on a trapezoidal table 19, and are located higher than the flux coating device 13 and the cooling fan 18. The container 10 having the tunnel structure is installed so as to cover the preheating device 14, the jet solder bath 1, and the table 19, and the outlet of the conveyor 5 formed between the container 10 and the table 19 serves as the discharge port 17. . FIG. 3 shows a case in which a low oxygen atmosphere is used in which a metal is not oxidized in a container by utilizing a specific gravity difference due to a temperature difference of a gas.
A warm inert gas is gently filled from above to obtain a low oxygen atmosphere. As another method, there is a method in which a shutter is provided at the entrance of the printed wiring board to shut off the inside and outside of the solder tank to maintain a low oxygen atmosphere.

[0005] The problems which cannot be solved by the above-mentioned conventional technology are as follows. (1) In the apparatus shown in FIG. 4, high-quality soldering cannot be performed because the conveyor at the portion to be soldered is horizontal. Therefore, if the conveyor is given an inclination angle, the heated gas rises and an airflow that flows in a fixed direction in the tunnel is generated, and air enters one after another and the low oxygen atmosphere is broken, so the equipment becomes huge, There was a disadvantage. To solve this problem, it was necessary to inject a large amount of inert gas. (2) A solder tank having a shutter mechanism requires a structure for controlling and detecting the position of the substrate for opening and closing the shutter, and the equipment is more expensive than the conventional method.

[0006]

SUMMARY OF THE INVENTION The present invention relates to an apparatus and a method for suppressing convection in a solder bath in a low-oxygen atmosphere of a printed circuit board, which makes it possible to reduce the size and cost of the apparatus, improve the quality of soldering, and reduce the amount of solder consumed. The purpose is to provide.

[0007]

According to a first aspect of the present invention, there is provided an apparatus for soldering low melting point metal solder in an inert gas atmosphere, comprising: a device for transferring an object to be soldered; A soldering device for a container having a mountain-shaped tunnel structure having a size to cover and house a soldering device having a jet part, wherein an injection hole connected to an inert gas supply source is formed in the soldering device, Further, a plurality of convection suppression plates provided with openings through which the object to be soldered can be provided at regular intervals inside the soldering device having the tunnel structure, and the convection suppression plate excludes a portion through which the object to be soldered passes. According to the present invention, there is provided a convection suppressing device in a low-oxygen atmosphere solder bath in which movement including convection of gas inside the device is suppressed. According to a second aspect of the present invention, there is provided a convection suppressing device in a low-oxygen atmosphere solder bath in which an opening area of an opening of a convection suppressing plate is adjustable. Further, a third means of the present invention is a method of soldering low melting point metal solder in an inert gas atmosphere, comprising: a device for transferring an object to be soldered;
A soldering device for a container having a mountain-shaped tunnel structure having a size to cover and house a soldering device having a jet part, wherein an injection hole connected to an inert gas supply source is formed in the soldering device, Through the injection hole, an inert gas is introduced into the inside of the soldering apparatus, and a plurality of convection suppression plates provided inside the apparatus and having openings through which the article to be soldered can pass, a portion through which the article to be soldered passes. Except for this, a method for suppressing convection in a low-oxygen atmosphere solder bath characterized in that movement including convection of gas inside the apparatus is suppressed.

[0008]

According to the present invention, the soldering device is constituted by a mountain-shaped tunnel-shaped container provided with entrances at both ends, and a plurality of openings having an opening through which an object to be soldered can be provided in the tunnel-structured container. Convection suppression plates are provided at regular intervals so as to suppress movement including convection of gas inside the apparatus except for a portion through which a soldering object passes. The above-mentioned container having the mountain-shaped tunnel structure prevents oxygen in the atmosphere from entering the container, and the convection and movement of the gas inside are almost completely achieved by the plurality of convection suppressing plates surrounding the object to be soldered. And the atmosphere of the inert gas inside the tunnel is secured with high accuracy. Therefore, there is no need for a restricting means such as a shutter, a curtain or a long tunnel for restricting the entrance of outside air, and it is possible to suppress the consumption of the inert gas. In addition, the size of the soldering apparatus can be reduced, and soldering in an inert gas atmosphere with low cost and high purity can be performed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention in which a soldered object is a printed wiring board will be described below in detail. FIG. 1 is an explanatory view of an embodiment of the present invention, and FIG.
It is sectional explanatory drawing of the tunnel part of a part. In the figure, 1
Is a solder bath, 2 is a primary jet for soldering, 3 is a secondary jet for finishing, 4 is molten solder, 5 is a conveyor for transporting a printed circuit board, and 6 is an inert gas injection. Nozzle, 7 is an inert gas supply source, 8 is a printed wiring board, 9 is a compressed air blowing port, 10 is a container with a tunnel structure, 11 is a convection suppression plate, 13 is a spray type flux coating device, and 14 is a printed circuit board spare The heating device 16 is a compressor.

As shown in FIG. 1, the container 10 having a tunnel structure is formed in a gentle mountain shape having a gentle uphill ascending portion 10a and a steeply descending descending portion 10b. And a conveyor 5 for transporting the printed wiring board 8
Is covered in a tunnel shape, and the contact with the outside air is limited to the entrances provided at the lowest portions on both right and left ends. A spray type flux coating device 13 is provided outside the entrance side of the container 10 having the tunnel structure, and a printed board preheating device 14 and a jet type solder bath 1 are provided below the conveyor 5 in the rising portion 10a. In addition, an inert gas inlet 6 and a compressed air blowing port 9 are attached near the top and outlet of the container 10 having a tunnel structure, and are connected to the inert gas supply source 7 and the compressor 16 by piping, respectively.

When the printed wiring board 8 placed on the conveyor 5 first passes over the spray type flux coating device 13, a certain amount of liquid flux is applied to the lower surface (soldering surface) of the printed wiring board 8. Applied. When further transported, it is heated to a temperature suitable for soldering on the printed board preheating device 14 in the container 10 having the tunnel structure,
Then, the primary jet 2 and the secondary jet 3 on the solder tank 1
Then, the terminal portion on the lower surface of the printed wiring board 8 is soldered. The molten solder 4 is easily oxidized in the air, and if a large amount of flux does not exist on the soldering surface of the printed wiring board 8, the lead wires may be short-circuited by solder oxide, or the soldering may be incomplete and loose contact may occur. Therefore, high quality soldering cannot be performed. Therefore, an inert gas (for example, nitrogen) is injected into the atmosphere around the solder bath 1 to reduce the oxygen atmosphere (oxygen concentration: 1).
000 ppm or less) so that high-quality soldering can be performed with a small amount of flux.

Conventionally, as means for maintaining a low oxygen atmosphere in the apparatus, as described above, a method of providing a shutter at the entrance and exit to seal the apparatus except when passing through a printed wiring board, and a method of providing a height difference and utilizing a specific gravity difference According to the present invention, the shutter mechanism is abolished in order to reduce the apparatus cost.
The equipment was downsized. With this alone, the internal atmosphere cannot be ensured. Therefore, as shown in FIG. 1, the low-oxygen atmosphere was maintained by attaching the convection suppressing plate 11 for the internal gas.

In the tunnel of the container 10 having such a mountain-shaped tunnel structure, a large number of convection suppressing plates 11 are provided at regular intervals (for example, about 40 to 200 mm). As shown in FIG. 2, the convection suppressing plate 11 is formed so as to protrude in a direction perpendicular to the inside of the container 10 and surround the periphery of the container 10 except for a portion through which the printed circuit board 8 passes. Therefore, the convection suppressing plate 11 eliminates convection and movement of the gas inside the container 10. In addition, even when the compressed air is blown out from the blow-in port 9, the outflow of the inert gas is suppressed, and the inflow of outside air sucked from the tunnel entrance following the conveyor 5 is prevented. Therefore, the consumption of the inert gas injected from the injection port 6 can be further reduced. Further, when the size of the printed wiring board 8 to be soldered is changed, the opening area of the convection suppressing plate 11 is adjusted to be minimized according to the changed size, so that the inert gas consumption is further reduced. It can be reduced. Although the embodiment of the present invention has been described with reference to the example of the printed wiring board as the object to be soldered, it is needless to say that the present invention can also be applied to other objects to be soldered. However, it goes without saying that it can be applied to other methods.

[0014]

According to a first aspect of the present invention, there is provided an apparatus for soldering low-melting-point metal solder in an inert gas atmosphere, comprising an apparatus for transferring an object to be soldered, a heating and melting portion of a molten solder, and a jet section. A soldering device for a container with a mountain-shaped tunnel structure having a size to cover and house the soldering device, wherein the soldering device is provided with an injection hole connected to an inert gas supply source, and further has a tunnel structure. A plurality of convection suppression plates provided with openings through which the object to be soldered can be provided at regular intervals inside the soldering device, and the gas inside the device except for the portion through which the object to be soldered passes by the convection suppression plate. A convection suppressing device in a low-oxygen atmosphere solder bath in which movement including convection was suppressed was constructed. Further, a second means of the present invention comprises a convection suppressing device in a low-oxygen atmosphere solder bath in which the opening area of the opening of the convection suppressing plate is adjustable. Furthermore, the third aspect of the present invention
Means for soldering a low melting metal solder in an inert gas atmosphere, wherein the size is such that the transfer device for the object to be soldered, the heating and melting of the molten solder, and the soldering device having the jet part are covered. A soldering device for a container with a mountain-shaped tunnel structure having a hole, an injection hole connected to an inert gas supply source is formed in the soldering device, and an inert gas is introduced into the soldering device through the injection hole. The plurality of convection suppression plates provided inside the apparatus and having openings through which the object to be soldered can pass, thereby suppressing movement including convection of gas inside the apparatus except for a portion through which the object to be soldered passes. A method for suppressing convection in a solder bath in a low-oxygen atmosphere, which is characterized in that, is adopted. As a result, in the means 1 and 3, the oxygen in the atmosphere does not easily enter the inside of the container having the mountain-shaped tunnel structure having a low entrance and exit, and the internal atmosphere can be maintained in a low oxygen state. in addition,
The convection of the gas inside the container can be almost completely suppressed by the plurality of convection suppression plates which are provided with openings through which the objects to be soldered can pass and project from the periphery in a direction perpendicular to the surroundings. Therefore, it is possible to perform soldering in an atmosphere in which the consumption of the inert gas is much smaller than in the past and the component ratio of the inert gas is high. Further, in a container for soldering a printed wiring board in a low oxygen atmosphere, it is possible to omit means for restricting the entrance of outside air, such as a narrow entrance / exit, a long tunnel, or an air curtain. For this reason, a small and inexpensive solder tank or the like can be installed, the occurrence of loose contact and the like can be prevented, and high quality soldering can be achieved. In particular,
According to the device of Means 2, since the opening area through which the object to be soldered passes in the convection suppressing plate is configured to be adjustable, it is adjusted to the minimum opening area regardless of the size of the shape of the object to be soldered. Can be applied. Therefore, according to the present invention, it is possible to provide a device and a method for suppressing convection in a vessel in a low oxygen atmosphere having various features such as maintaining an atmosphere of an inert gas with high purity and widening an application range. .

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory cross-sectional view taken along line AA ′ of FIG. 1;

FIG. 3 is an explanatory view of a conventional soldering device using a specific gravity difference.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Solder tank 2 Primary jet port 3 Secondary jet port 4 Melt solder 5 Conveyor 6 Inert gas injection nozzle 7 Inert gas supply source 8 Printed wiring board 9 Compressed air inlet 10 Tunnel structure container 11 Convection suppression plate 13 Flux coating device 14 Preheating device 15 Gas heater 16 Compressor 17 Gas outlet 18 Cooling fan 19 units

Continuation of the front page (51) Int.Cl. ⁷ Identification code FI H05K 3/34 506 H05K 3/34 506F 506G (72) Inventor Masahito Nozue 7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd. (72) Inventor Kanazawa Hide 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd. (72) Inventor Shunichi Yasuoka 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industrial Co., Ltd. In-company (56) References JP-A-6-29655 (JP, A) JP-A-63-174778 (JP, A) JP-A-6-85443 (JP, A) JP-A-6-207261 (JP, A) Japanese Patent Application Laid-Open No. Sho 60-124664 (JP, A) Japanese Translation of PCT International Publication No. 5-503664 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 31/02 310 B23K 1/08 H05K 3 / 34 560

Claims (3)

(57) [Claims] 1. A device for soldering in an inert gas atmosphere a solder having a low melting point metal, accommodating I dissolution by heating solder melting and transfer device of the soldering material, a solder device having a jet portion covering Mountain with size
In soldering device of the container in the form of a tunnel structure, the device with solder injection hole which is connected to the inert gas supply source is bored, further inside the soldering apparatus of the tunnel structure, the object
A plurality of convection suppressing plates provided with openings through which a soldering object can pass are provided at regular intervals, and the convection suppressing plates serve to
A convection suppressing device in a low-oxygen atmosphere solder bath, wherein movement including convection of a gas inside the device is suppressed except for a portion through which an attachment passes . 2. An opening area of an opening of the convection suppressing plate is adjusted.
The low acid according to claim 1, wherein the low acid is configured to be adjustable.
A convection suppressor in a solder bath under a bare atmosphere. 3. A low melting point metal solder in an inert gas atmosphere.
In the method of soldering by using, the transfer device of the soldering object and the heating and melting of the molten solder, the jet part
Having a size to cover and accommodate a soldering device having
Soldering device for a container having a tunnel-shaped structure,
Has an injection hole connected to the inert gas supply.
And an inert gas is introduced into the soldering device through the injection hole.
Introduced, installed inside the device and the soldered object passes
A plurality of convection suppressing plates having possible openings are provided.
Except for the area through which the solder passes,
Low oxygen atmosphere characterized by suppressing movement including flow
A method for suppressing convection in the solder bath.