JP5825326B2 - Solder bath and method for heating solder contained in solder bath - Google Patents

Description

  The present invention relates to a solder bath and a method for heating solder contained in the solder bath, and specifically to a solder bath and a heating method for heating and melting solder contained in a solder bath body.

  As is well known, when soldering a printed circuit board using a solder bath, for example, the solder bath body of the solder bath is heated in order to strictly control the temperature of the solder.

  For example, paragraph No. 0005 and FIG. 7 of Patent Document 1 disclose an invention in which solder contained in a solder bath is heated using a sheathed heater in which a heater is embedded in a metal pipe passed through the solder bath. However, the heating of the solder bath body is often performed by fixing a sheathed heater or the like to the outer surface of the solder bath body. This is because the method in which the heater is fixed to the outer surface of the solder bath body and heated is more economical than a throwing heater in which the heater is directly cast into molten solder, because there is no fear of the heater being damaged by solder erosion.

  In Patent Document 2, a heater is mounted on the outer surface of the solder bath body in which the inner wall of the solder bath body is covered with aluminum nitride, which is a substance with poor solder wettability, so that the solder can be replaced without remelting the solder. In addition, an invention in which a heat insulating material covers the outer surface of the heater is disclosed, and Patent Documents 3 to 5 also disclose an invention in which the heater is disposed so as to surround the solder bath body.

JP 2003-136233 A Japanese Utility Model Publication No. 6-41965 Japanese Utility Model Publication No. 5-18756 JP-A-3-254362 JP-A-52-127449 JP 2005-7405 A

  However, in the inventions disclosed in Patent Documents 2 to 5 in which the heater is fixed to the outer surface of the solder tank body and heated, the outer surface of the solder tank body in contact with the heater is strongly heated and the temperature rises. The outer surface of the solder bath main body at a portion away from the heater does not increase in temperature excessively, the temperature of the solder bath main body is likely to vary, and the temperature of the solder contained in the solder bath main body is also likely to vary partially. If the temperature of the solder varies, the temperature of the solder flowing out from the jet nozzle installed inside the solder bath body is likely to fluctuate, and a solder failure is likely to occur.

  In the conventional Sn-Pb solder, even if the temperature of the solder varies somewhat by heating with the heater, the melting temperature of the solder alloy is 183 ° C, whereas the set temperature of the molten solder is usually around 245 ° C, Since there was a margin of about 60 ° C., it was not a problem.

  However, since lead-free solder has a melting temperature of about 220 ° C., the set temperature of the solder is about 250 ° C., which is only about 30 ° C., which is half of the margin of conventional Sn-Pb solder. . For this reason, in the case of lead-free solder, there is a problem that if the temperature of the solder varies due to heating by a heater, it is likely to cause bridges and unsoldering.

  Furthermore, in the inventions disclosed in Patent Documents 2 to 5, the solder bath body in the vicinity where the heater is installed is locally heated and partially thermally expanded, so that the life of the solder bath body is shortened and heating is performed. There is also a problem that heat for heat is dissipated into the air from the outer surface of the solder bath body, and the operating cost increases.

  This invention is made in view of the subject which such a prior art has, The solder tank and the heating method which can heat and melt the solder accommodated in the solder tank main body of a solder tank as uniformly as possible The purpose is to provide.

As a result of intensive investigations to solve the above problems, the present inventors have (a) not directly heating the solder bath body with a heater, but with the heater against the outer surface of the bottom surface and the side surface of the solder bath body. Heating a flat plate-shaped heat diffusion plate made of stainless steel that is mounted in contact, and heating the solder bath body by heat conduction from the heat diffusion plate; and (b) Heating of the heat diffusion plate is a heat diffusion. Solder contained in the solder bath body of the solder bath is made as uniform as possible by using a heating resistor embedded away from the heat diffusion plate inside the heat insulating body made of foamed ceramic that is mounted in contact with the plate. Knowing that it can be melted by heating, the present invention has been completed.

The present invention provides a solder feed chamber having an inlet located below the liquid level of the solder to be accommodated and an outlet located above the liquid level, and solder from the inlet to the inside of the solder feed chamber. A solder bath comprising a solder bath main body provided with an internal pump and a heating member for heating the solder mounted on the outer surface of the bottom surface and the side surface of the solder bath main body, the heating member being stainless steel The heat diffusion plate and the heat insulator are embedded in the order of the heat diffusion plate and the heat insulator, and the heat diffusion plate is disposed on the bottom surface of the solder bath body. The heat insulator is made of a porous body having a three-dimensional network structure and has a groove formed at a predetermined depth from the surface on the side in contact with the heat diffusion plate. In the groove A solder bath, characterized in that the serial heating resistor is embedded spaced apart from the heat diffusion plate.

  In the solder bath according to the present invention, the solder is lead-free solder.

  From another point of view, the present invention uses the solder tank according to the present invention described above, heats the heat diffusion plate by the heat generated by the heating resistor, and makes the solder bath main body substantially uniform by heat conduction from the heat diffusion plate. It is a heating method of the solder accommodated in the solder tub characterized by heating to the inside.

  According to the present invention, the solder accommodated in the solder bath body of the solder bath can be heated and melted as uniformly as possible. For this reason, it is possible to suppress the occurrence of solder defects such as bridges and unsoldering and the decrease in the life of the solder bath main body, and it is possible to suppress an increase in operating cost.

1A and 1B are explanatory views showing a configuration of a solder bath according to the present invention, in which FIG. 1A is a sectional view and FIG. 1B is a bottom view. FIG. 2 is a three-sided view showing an example of the state in which the heating resistor 11 is embedded. FIG. 2 (b) is a cross-sectional view taken along the line aa 'shown in FIG. 2 (a), and FIG. It is a figure which shows the bb 'cross section shown in FIG. FIG. 3 is a view showing a state of the surface of the heat diffusion plate 9 removed from the solder bath main body 2 after the solder bath 1 according to the present invention has been used for a predetermined period, and FIG. FIG. 3B is a diagram showing the state of the surface on the side in contact with the solder tank body 2, and FIG. 3B is the state of the surface on the heating resistor 11 side of the thermal diffusion plate 9.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings. 1A and 1B are explanatory views showing a configuration of a solder bath 1 according to the present invention, in which FIG. 1A is a cross-sectional view and FIG. 1B is a bottom view.

  As shown to Fig.1 (a) and FIG.1 (b), since the solder tank 1 which concerns on this invention is equipped with the solder tank main body 2 and the heating member 3, these are demonstrated sequentially.

[Solder tank body 2]
The solder tank body 2 is a rectangular container that opens upward to accommodate the solder 4, and may be any well-known and commonly used solder tank body of this type. For example, it is desirable to be made of stainless steel and further to nitride the inner surface in order to prevent erosion by solder.

As shown in FIG. 1A, a solder feed chamber 5 and a pump 6 having a substantially L-shaped cross section are disposed inside the solder bath body 2.
The solder feed chamber 5 has an inlet 5a on the left side in the longitudinal direction (left and right direction in the drawing) and an outlet 5b on the right side. The inlet 5 a is provided so as to be positioned below the liquid level L of the solder 4 accommodated in the solder bath main body 2. Further, the outlet 5b is provided so as to be positioned above the liquid level. The outlet 5b forms a so-called jet nozzle, and as shown in FIG. 1 (a), soldering is performed on the printed circuit board (not shown) from which the molten solder jets upward and is conveyed above the outlet 5b. I do.

  The pump 6 is disposed in the casing 6d. The rotary shaft 6a of the pump 6 extends to the upper part of the solder tank body 2, and is rotationally driven by a drive source 6c having a drive motor 6b. Thereby, the pump 6 is driven to rotate, and the solder 4 accommodated in the solder bath main body 2 is sent from the inlet 5a to the inside of the solder feeding chamber 5 and jetted from the outlet 5b. As the pump 6, in order to suppress the pulsation of the solder to be sent, it is desirable to use a screw pump having spiral blades. In particular, the screw pump having four spiral blades is used only for suppressing pulsation during constant speed rotation. Rather, it is desirable because it has rapid convergence when changing the rotational speed. As an example, FIG. 1 shows a case where a screw pump is used. However, since the screw is rotated in the casing 5, the solder is fed along the penetration direction of the casing 6d without flowing out of the screw, As a result, the pressure applied to the solder feed chamber 5 is the same at any position according to Pascal's principle, so that the solder flowing out from the outlet is hardly waved. The solder bath according to the present invention can be applied regardless of the solder jet method, such as a solder bath using the screw pump shown in this example, a solder bath using an impeller pump and a duct (not shown) other than this example.

  Reinforcing ribs 7 are provided on the outer surface of the bottom surface of the solder bath body 2, and support plates 8 are provided on the upper and lower sides and the left and right sides of the solder bath body 2. A heat insulator 10 including the plate 9 and the heating resistor 11 is fixed between the support plates 8 and 8 by a rod 8a.

[Heating member 3]
As shown in FIG. 1A and FIG. 1B, the heating member 3 is attached to the outer surface of the bottom surface of the solder bath body 2 and the outer surface of the side surface, and the solder 4 accommodated in the solder bath body 2 is accommodated. It is for heating.

The heating member 3 includes a heat diffusion plate 9, a heat insulator 10, and a heating resistor 11.
The heat diffusion plate 9 is attached to the solder tank body 2 by the rod 8a between the support plates 8 and 8 together with the heat insulator 10 including the heating resistor 11 on the outer surface of the bottom surface and the side surface of the solder tank body 2. Further, it is a flat plate material that is attached to the solder bath main body 2 by appropriate means such as latching, fastening, or welding (not shown), and is made of stainless steel. As will be described later, the heat diffusing plate 9 absorbs heat from the heating resistor 11 and makes it uniform over the entire area, and heats the bottom surface and side surfaces of the solder tank body 2 to be in contact with. Is preferably 5 to 10 mm, but may be appropriately changed according to the heat generation capacity of the heating resistor 11.

  Further, the heat diffusion plate 9 does not necessarily have to be attached to the entire bottom surface and side surfaces of the solder bath main body 2, and in the case of Sn-Pb solder, the temperature management range is large as described above. The solder may be mounted downward from a predetermined position below the substantially liquid level L of the solder. However, in the case of lead-free solder, since the temperature control range is small as described above, it is desirable that the solder is mounted on the outer surface corresponding to at least the entire region below the substantially liquid level L of the contained solder.

  The heat diffusing plate 9 is made of the same material as that of the solder bath main body 2 so that temperature unevenness hardly occurs. Therefore, in the present invention, the heat diffusion plate 2 is made of stainless steel, which is frequently used as the material of the solder bath body 2, and temperature unevenness generated between the heat diffusion plate 9 and the solder bath body 2 is eliminated. The heat diffusing plate 9 is disposed in the vicinity of the heat generating resistor 11 that generates heat, and thus is susceptible to thermal damage such as local expansion, but is less expensive than the solder bath body 2 and is therefore damaged. In this case, only the heat diffusing plate 9 needs to be replaced, so that the cost and man-hour required for the replacement can be reduced.

  The heat insulator 10 is mounted in contact with the outer surface of the heat diffusion plate 9. The heat insulator 10 is made of ceramic foam. The foamed ceramic is a porous body having a three-dimensional network structure such as foamed polyurethane having alumina as a basic material.

  As will be described later, since the heat generating resistor 11 is covered with the heat insulating body 10, the heat from the heat generating resistor 11 is efficiently propagated to the heat diffusion plate 9, so that the cost can be reduced and the driving operator can Even if it touches the heat insulator 10 of the solder bath main body 2, there is no fear of a burn and the safety is high.

A heating resistor 11 is embedded in the heat insulator 10. FIG. 2 is a three-sided view showing an example of the state in which the heating resistor 11 is embedded. FIG. 2B is a cross-sectional view taken along the line aa ′ shown in FIG. Bb ′ cross section shown in FIG.
The heating resistor 11 generates Joule heat when energized to generate heat, and a nichrome wire is used in the present embodiment.

  As shown in FIG. 2, the heating resistor 11 is insulated by being housed in a groove 10 a formed at a predetermined depth from the surface of the heat insulating body 10 made of foamed ceramic that is in contact with the heat diffusion plate 9. Embedded in the body 10.

  Furthermore, since the depth of the groove portion 10a is provided about 5 to 10 mm deeper than the outer diameter of the heat generating resistor 11, the heat generating resistor 11 is in a separated state where it does not directly contact the heat diffusing plate 9. 11 is buried. This distance may be changed as appropriate according to the thickness of the heat diffusion plate 9 and the heat capacity of the heating resistor 11.

  The solder tank 1 according to the present invention is configured as described above. Using the solder tub 1 according to the present invention, the heat generating resistor 11 is energized to heat the heat diffusing plate 9 by the heat generated by the heat generating resistor 11, and the solder tub main body 2 is moved by the heat conduction from the heat diffusing plate 9. When heated, the heating resistor 11 is in contact with the solder bath body directly in a state close to point contact or line contact as in the inventions disclosed in Patent Documents 2 to 5 described above, and the solder bath body is heated. (A) Heating by the heat generating resistor 11 and heating by the heat diffusion plate 9 in surface contact with the solder bath body 2; (b) Heat generated by the heat generating resistor 11 is a porous body. The heat spreader 9 is uniformly distributed inside the heat insulator 10 and the temperature inside the heat insulator 10 is uniformly increased, and the heat diffusion plate 9 in surface contact with the heat insulator 10 is heated uniformly, and (c) the heating resistor 11 is provided. The heat diffusing plate 9 is not spaced from the heat diffusion plate 9 Are three Rukoto together, dispersion unevenness of heat is suppressed, the mounting portion of the heat diffusion plate 9 in a solder bath main body 2, it is possible to heat a very evenly uniform temperature.

  FIG. 3 shows the state of the surface of the heat diffusion plate 9 removed from the solder bath main body 2 after the solder bath 1 according to the present invention has been used for a predetermined period, and FIG. FIG. 3B shows the state of the surface on the side of the heating resistor 11 of the thermal diffusion plate 9. As shown in the figure, on the surface on the side of the heating resistor 11, a heating trace along the nichrome wire constituting the heating resistor 11 can be seen (FIG. 3B). On the other hand, a diffused heating trace is observed on the surface in contact with the solder bath main body 2 (FIG. 3A).

  As described above, according to the present invention, the solder 4 accommodated in the solder bath body 2 of the solder bath 1 is made as uniform as possible by interposing the heat diffusion plate between the heating resistor 11 and the solder bath body 2. It can be melted by heating. For this reason, it is possible to suppress the occurrence of solder defects such as bridges and unsoldering and the decrease in the life of the solder bath main body, and it is possible to suppress an increase in operating cost.

DESCRIPTION OF SYMBOLS 1 Solder tank 2 Solder tank main body 3 Heating member 4 Solder 5 Solder feed chamber 5a Inlet 5b Outlet 6 Pump 6a Rotating shaft 6b Drive motor 6c Drive source 6d Casing 7 Rib 8 Support plate 8a Rod 9 Heat diffusion plate 10 Heat insulator 10a Groove 11 Heating resistor

Claims (3)

A solder feed chamber having an inlet positioned below the liquid level of the solder to be accommodated and an outlet positioned above the liquid level, and a pump for sending solder from the inlet to the inside of the solder feed chamber A solder bath body provided therein, and a heating bath mounted on the outer surface of the bottom surface and the side surface of the solder bath body to heat the solder,
The heating member is a flat plate-shaped heat diffusion plate made of stainless steel that is mounted in direct contact with the outer surface of the bottom surface of the solder bath body and the outer surface of the side surface ;
A heat insulating body comprising a porous body having a three-dimensional network structure and having a groove formed at a predetermined depth from the surface on the side in contact with the heat diffusion plate ;
It consists of a heating resistor embedded in the heat insulating material apart from the heat diffusion plate in the groove ,
A solder bath, wherein a heat diffusion plate and a heat insulator are arranged in this order with respect to the solder bath body.   The solder bath according to claim 1, wherein the solder is lead-free solder.   Using the solder bath according to claim 1 or 2, the heat diffusion plate is heated by heat generation of the heating resistor, and the solder bath main body is substantially reduced by heat diffusion from the heat diffusion plate. A method for heating solder contained in a solder bath, characterized by heating uniformly.