JP2013141668A - Solder bath - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the leakage of solder and to strengthen the support of a solder bath, in the solder bath having a double structure consisting of an inner bath and an outer bath.SOLUTION: The solder bath includes: the inner bath made of conductive members, in which molten solder is housed; the outer bath made of the conductive members, which holds the inner bath with a predetermined gap; and a detection electrode which is projected from the outer bath in the gap and electrically isolated from the outer bath. Continuity between at least one of the inner bath and the outer bath, and the detection electrode is detected. Furthermore, the inner bath and the outer bath are fixed by members made of metal.

Description

  The present disclosure relates to a solder bath.

  For soldering a printed circuit board, flow soldering in which the printed circuit board is immersed in a solder bath containing molten solder is widely used. However, the solder bath is eroded by solder during continuous use. In recent years, in the case of lead-free solder, which has become widespread, there has been a problem that erosion of a stainless steel solder bath is likely to proceed due to various causes as compared with conventional tin-lead eutectic solder. Measures are taken to delay the time of erosion and to reduce the rate of erosion. However, fundamental measures have not yet been found.

  In order to prevent the solder tank from being eroded and flowing out of the solder, a solder tank having a double structure of an inner tank and an outer tank is used. In order to detect solder leakage in such a solder bath, the present applicant has proposed a solder leakage detection device described in Patent Document 1. The solder tank described in Patent Document 1 includes a conductive inner tank in which molten solder is stored, and a conductive outer tank provided outside the inner tank with a predetermined interval. An electrical insulator portion having electrical insulation is provided between the inner tank and the outer tank to form a predetermined interval. And the leak detection part which detects that the electroconductivity between an internal tank and an external tank changes with the leaked solder is provided.

JP 2010-99676 A

  In Patent Document 1, it is detected that the inner tank and the outer tank are short-circuited by the leaked solder. Therefore, when the inner tub and the outer tub are formed of a conductive metal material, it is necessary to insulate them with an insulating member therebetween. When a relatively inexpensive glass fiber is used as the insulating member, it is difficult to firmly support the inner tank having a weight of several hundred kilograms with respect to the outer tank, and there is a problem of poor stability. On the other hand, if a strong insulating member such as an insulator or ceramic is used, the inner tank can be supported relatively stably. However, insulators, ceramics, and the like are difficult materials to handle and have a high cost.

  Accordingly, an object of the present disclosure is to provide a solder bath that can detect solder leakage and can firmly support the inner bath with respect to the outer bath.

In order to solve the above-described problem, the present disclosure includes an inner tank of a conductive member that contains molten solder;
An outer tank of a conductive member that holds the inner tank with a predetermined gap;
A detection electrode that protrudes into the gap from the outer tank and is electrically insulated from the outer tank;
This is a solder tank that detects conduction between at least one of the inner tank and the outer tank and the detection electrode.
Preferably, in the present disclosure, the inner tank and the outer tank are fixed by a metal member.

  According to the present disclosure, since solder leakage is detected by conduction between at least one of the inner tank and the outer tank and the detection electrode, the inner tank can be supported on the outer tank by the metal member.

It is a cross-sectional schematic diagram of the solder tank by this indication. It is sectional drawing of the solder tank main body by this indication. It is a partial assembly figure for demonstrating the fixing member which fixes the inner tank and outer tank of the solder tank by this indication. It is an expanded sectional view of an example of a detection electrode of a solder tub by this indication. It is a basic diagram explaining the detection part of the solder tank by this indication.

  The embodiment described below is a preferable specific example of the present disclosure, and various technically preferable limitations are given. However, the scope of the present disclosure is not limited to these embodiments unless otherwise specified in the following description.

"Structure of solder bath"
An embodiment of the present disclosure will be described. FIG. 1 is a schematic cross-sectional view of a soldering apparatus 1 having a solder bath according to an embodiment of the present disclosure. The soldering apparatus 1 includes a solder bath 2, a board transfer unit (not shown), a throwing heater (not shown in FIG. 1), a pump 3, and a detection unit 4.

  The solder tank 2 has a double structure of an inner tank 11 and an outer tank 16. The inner tank 11 accommodates the molten solder 5. The molten solder 5 is accommodated near the upper part of the inner tank 11 and shows a molten solder liquid level 5a.

  Inside the inner tank 11, a duct 12, a jet duct 13, and an ejection nozzle 14 are provided. The duct 12, the jet duct 13, and the ejection nozzle 14 are connected to form an integral structure. The integral structure is a flow path of the molten solder 5 that penetrates from near the bottom surface of the inner tank 11 to near the molten solder liquid surface 5a. The integral structure is substantially L-shaped when viewed from the side. The duct 12 extends in a direction parallel to the molten solder liquid surface 5a. The duct 12 has an opening 12a on the bottom surface. The jet duct 13 extends in a direction perpendicular to the duct 12. The jet nozzle 14 is provided on the jet duct 13 extending in the vertical direction.

  The pump 3 that creates a flow of the molten solder 5 includes a motor (not shown), a shaft 31, and an impeller 32. The impeller 32 is disposed in the duct 12. The rotation of the motor is transmitted to the impeller 32 through the shaft 31 and converted into kinetic energy through which the molten solder 5 flows. When the impeller 32 rotates, a molten solder flow F1 indicated by an arrow in the figure is generated, and the molten solder 5 is introduced into the duct 12 from the opening 12a of the duct. The molten solder 5 introduced into the duct 12 becomes a molten solder flow F2 and proceeds along the duct 12 in the horizontal direction. The molten solder 5 that has become the molten solder flow F3 in the vertical direction by the jet duct 13 further proceeds to the molten solder flow F4 and is ejected from the ejection nozzle 14. The ejected molten solder 5 forms a jet solder liquid surface 5b. A workpiece (substrate) W transported by a substrate transport unit (not shown) comes into contact with the ejected molten solder 5 and is soldered. Thereafter, the molten solder 5 flows to the outside of the jet duct 13 as molten solder flows F5 and F6 and stays in the inner tank 2.

  The inner tank 2 that accommodates the molten solder 5 is formed of a metal member. The inner tank 2 has a predetermined gap 15 and is held by a metal member fixing member (not shown) with respect to the outer tank 16. The inner tank 2 is made of a metal having good corrosion resistance, such as titanium. The outer tub 16 is made of metal such as stainless steel. In addition, you may perform the surface treatment of a tank with metals with high corrosion resistance, such as titanium. A drain (not shown) is provided for the inner tank 16 so that the molten solder 5 in the inner tank 16 can be extracted. The gap 15 may be filled with a heat insulating material having electrical insulation. The outer tank 16 is provided with at least one detection unit 4 for detecting the molten solder 5 leaking from the inner tank 2. The detection part 4 is provided in several places suitably. Preferably, the impeller 32 is installed, and the detection unit 4 is provided in the vicinity where corrosion of the inner tank 2 is likely to occur, such as a portion where the flow of the molten solder 5 is fast. Details of the detection unit 4 will be described later.

  FIG. 2 shows a cross section of a solder bath 2 according to an embodiment of the present disclosure. 2 is a cross section obtained by rotating the solder bath 2 by 90 degrees in the horizontal direction from the cross section of FIG. The outer tub 16 of the solder tub 2 is further covered with a side plate 17 around the periphery. A heat insulating material 18 is embedded between the outer tub 16 and the side plate 17 to enhance the heat retention of the molten solder 5.

  A heater 19 is provided near the bottom surface of the inner tank 11. This heater 19 is a so-called throw-in type. The heater 19 is configured such that a heating wire (such as a nichrome wire) is enclosed inside a metal pipe material such as titanium or stainless steel via an insulating powder (MgO: magnesium oxide, magnesia, etc.). Since the temperature of the molten solder 5 becomes high around the heater 19, the inner tank 2 in the vicinity thereof is one of the places where corrosion easily occurs. Therefore, the detection unit 4 is also preferably provided in the vicinity of the heater 19.

`` Fixing member ''
A fixing member 20 is provided between the lower side of the bottom surface of the inner tank 11 and the upper side of the bottom surface of the outer tank 16. The fixing member 20 is made of metal. The inner tank 11 and the outer tank 16 are fixed by the fixing member 20, and the solder tank 2 is firmly supported.

  As shown in FIG. 3, the inner tank 11 of the soldering apparatus 1 is fixed to the outer tank 16 by a fixing member 20. On the bottom surface of the inner tank 11, a leg portion 21 that protrudes in a direction facing the outer tank 16 is provided. The leg 21 is fixed to the inner tank 11 by welding, for example. A screw hole 22 is processed in the leg portion 21 from the outer tub 16 side toward the inner tub 11. The outer tub 16 is provided with an opening 23 corresponding to the screw hole 22. And the inner tank 11 and the outer tank 16 are joined by the metal volt | bolt 24. FIG. The bolt 24 penetrates the opening 23 of the outer tub 16 and enters the screw hole 22 of the inner tub 11, and fastens and fixes the inner tub 11 and the outer tub 16. The fixing member 20 is provided at a plurality of locations on the bottom surface of the solder tank 2.

  By using the metal fixing member 20, the inner tank 11 can be firmly supported by the outer tank 16. The inner tank 11 needs to support the molten solder 5 which is high temperature and heavy. Furthermore, by using a metal member for all of the fixing member 20, the cost of the fixing member 20 can be reduced compared to using insulators, ceramics, or the like.

"Detector"
Next, the detection unit 4 will be described in detail with reference to FIGS. 4 and 5. The detection unit 4 has a detector provided in a part of the outer tub 16 and an electric circuit unit connected to the detector.

  The detector of the detection unit 4 includes a boss 40, an insulating bush 41, a detection rod 42, and a terminal 43. A boss 40 is provided on the bottom surface of the outer tub 16 so as to protrude in the direction opposite to the gap 15 (vertically below). The boss 40 is made of metal. The boss 40 is fixed to the outer tub 16 by welding, for example. The boss 40 is formed with a hole penetrating in the vertical direction. The hole is threaded.

  An insulating bush 41 is screwed into the hole of the screwed boss 40 from below. An electrical insulating member (non-conductor) is used for the insulating bush 41. The insulating bush 41 is formed such that its tip end surface, which is screwed, has substantially the same height as the surface of the outer tub 16 on the gap 15 side. As described above, the insulating bush 41 has a diameter that fits the hole of the boss 40 on the tip side, whereas the base side has a larger diameter. That is, when the insulating bush 41 is viewed from the side, the form thereof is substantially inverted T-shaped. With this configuration, when the insulating bush 41 is screwed into the hole of the boss 40, the base portion becomes a stopper. The insulating bush 41 is also formed with a hole penetrating in the vertical direction. The hole is also threaded.

  A detection rod 42 as a detection electrode is screwed from below into the hole of the insulating bush 41 where the thread has been cut. An electric conductor (conductor) is used for the detection rod 42. The detection rod 42 is formed so that its screwed tip surface protrudes beyond the tip surface of the insulating bush 41 (the inner surface of the outer tub 16). The width of the gap 15 between the inner tank 11 and the outer tank 16 is made as small as possible. Preferably, the width of the gap 15 is about 10 mm. The detection rod 42 is electrically insulated from the outer tank 16 and the inner tank 11. For the detection rod 42, for example, a metal bolt is preferably used. Here, although the form in which the bolt is screwed in is illustrated, for example, a form in which the push pin of the conductor is used without cutting the screw may be used.

  A terminal 43 is connected to the detection rod 42. For the terminal 43, for example, a crimp terminal is used. In the figure, the terminal 43 is not connected to the detection rod 42 yet. From this state, the tip of the terminal 43 is screwed between the head of the detection rod 42 and the screw portion.

  In the detector of the detection unit 4 provided in this way, the members are fitted to block the movement of the substance between the gap 15 and the outside. Note that the detection unit 4 may be provided in the gap 15 at, for example, a plurality of locations on the bottom surface of the outer tub 16. Further, when the detection rod 42 is removed, the gap 15 is connected to the outside through the hole of the insulating bush 41. You may make it take out the solder in the gap | interval 15 through this hole.

  Next, the configuration on the electric circuit side will be described with reference to FIG. The electric circuit of the detection unit 4 includes a switch 44, electric wires 45, 47 and 49, a direct current power supply 46, and a lamp 48. The electric wire extending from the terminal 43 described above is connected to one end of the switch 44. The other end of the switch 44 is connected to a power source 46 by an electric wire 45. The other end of the power source 46 is connected to the lamp 48 by an electric wire 47. The other end of the lamp 48 is connected to the outer tub 15 by an electric wire 49. The connection destination of the electric wire 49 may be the inner tank 11. In the embodiment of the present disclosure, the inner tub 11 and the outer tub 16 are coupled by the conductive fixing member 20, so that the connection destination is substantially one of the inner tub 11 and the outer tub 16. Connection with both will be ensured. When the solder leakage is detected by the electrical circuit thus connected, the switch 44 is set to the closed state.

  In the configuration described above, when solder leakage occurs, the inner tank 11 or the outer tank 15 and the detection rod 42 are short-circuited by the leaked solder, and a current flows through the lamp 48. Therefore, the lamp 48 lights up when a solder leak is detected. For example, an LED or a miniature bulb is used for the lamp 48. The solder leak notification is not limited to the exemplified light notification, and may be a notification by sound from a buzzer, a speaker, or the like. Further, an amplification circuit using a transistor, an amplifier, or the like, or a comparison circuit may be incorporated in the electric circuit depending on the application.

"Modification"
As mentioned above, although embodiment of this indication was described concretely, it is not limited to each above-mentioned embodiment, and various modification based on the technical idea of this indication is possible. For example, the detection sensitivity may be increased by inclining the bottom of the outer tub 16 in the height direction and providing a detector on the low-inclination side. The configurations, methods, steps, shapes, materials, numerical values, and the like given in the above-described embodiments are merely examples, and different configurations, methods, steps, shapes, materials, numerical values, and the like may be used as necessary. .

  The configurations, methods, processes, shapes, materials, numerical values, and the like of the above-described embodiments can be combined with each other without departing from the gist of the present disclosure.

DESCRIPTION OF SYMBOLS 1 Soldering apparatus 2 Solder tank 4 Detection part 5 Molten solder 11 Inner tank 15 Gap 16 Outer tank 19 Heater 20 Fixing member 40 Boss 41 Insulation bush 42 Detection rod 43 Terminal 48 Lamp W Workpiece

Claims (5)

An inner tank of a conductive member containing molten solder;
An outer tank of a conductive member that holds the inner tank with a predetermined gap;
A detection electrode protruding from the outer tank into the gap and electrically insulated from the outer tank;
A solder bath configured to detect conduction between at least one of the inner bath and the outer bath and the detection electrode.   The solder tank according to claim 1, wherein the inner tank and the outer tank are fixed by a metal member. An insulating member for electrically insulating between the detection electrode and the outer tank is provided,
The solder tank according to claim 1, wherein the insulating member is formed at substantially the same height as the inner surface of the outer tank.   The solder tank according to claim 1, wherein a bottom portion of the outer tank is inclined in a height direction, and the detection electrode is provided on a lower side of the outer tank. An insulating member for electrically insulating between the detection electrode and the outer tank is provided,
The detection electrode can be freely inserted into and removed from the insulating member,
The solder tank according to claim 1, wherein the gap is opened through a hole after the detection electrode is detached.

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