JP2006114556A - Wave solder bath - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wave solder bath where a jet stream height of a primary jet stream nozzle can be made sufficiently high. <P>SOLUTION: In the wave solder bath, a clearance between a screw pump and a casing becomes 0.1 to 1 mm. The shaft of the screw pump is pivoted by a bearing cylinder where a bearing hole is vertically pierced. The bearing cylinder and the casing are connected by a plurality of struts. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a jet solder bath installed in an automatic soldering apparatus for soldering printed circuit boards.

  Generally, soldering of a printed circuit board is performed by an automatic soldering apparatus. In this automatic soldering apparatus, a processing apparatus for soldering such as a fluxer, a pre-heater, a jet solder bath, a cooler, etc. is installed in the apparatus main body. Further, a pair of transport rails are installed on these processing apparatuses, and an endless transport chain is installed on the transport rails so as to rotate. The printed circuit board is transported by a number of claws attached to opposite transport chains, flux applied by a fluxer, pre-heated by a pre-heater, solder deposited in a jet solder bath, cooled by a cooler, and soldered. Is made.

  A jet solder bath used in an automatic soldering apparatus is provided with a primary jet nozzle that jets a rough wave and a secondary jet nozzle that produces a gentle jet. Since the molten solder jetted from the primary jet nozzle is rough, it penetrates well into the through holes of the printed circuit board and the corners of the chip parts to eliminate unsolder. However, the rough wave causes a soldering failure such as a wig or a bridge when it adheres to the soldered portion.

  Therefore, these poor soldering caused by soldering with the primary jet nozzle are corrected with the secondary jet nozzle. A gentle molten solder is jetted from the secondary jet nozzle, and the adhered solder is remelted by soldering with the primary jet nozzle. At this time, the molten solder jetted from the secondary jet nozzle remelts the tsura and bridges, so that these soldering defects are eliminated and a large amount of solder is reduced so that the solder is uniformly attached. .

  In a jet solder bath, the removal of unsolder with the primary jet nozzle, the correction of the tsura and bridge with the secondary jet solder nozzle, and the uniform attachment of molten solder are greatly affected by the characteristics of the jet pump.

  As a jet pump used for a jet solder bath, an impeller pump has become the mainstream. A jet solder bath using an impeller pump will be briefly described. FIG. 6 is a cross-sectional view cut at a primary jet nozzle portion of a jet solder bath, and FIG. 7 is a perspective view with a part broken away. In a jet solder bath using an impeller pump, a duct 31 is always installed in the jet solder bath 30. The duct 31 is formed with a nozzle port 32 standing upward, and a jet nozzle 33 is attached to the nozzle port. The jet nozzles shown in FIGS. 6 and 7 are primary jet nozzles, and a large number of holes 34 are formed in the jet port, and a rough wave is formed when molten solder is jetted from the holes 34. This rough wave penetrates through holes and corners of chip parts to eliminate unsoldering.

  Inside the jet nozzle 33, a rectifying plate 36 having a large number of holes 35 is laid horizontally. A storage portion 38 for the impeller pump 37 is formed at the end of the duct 31. The storage portion has a slightly larger diameter than the diameter of the impeller pump and has an approximately 3/4 arc.

  A shaft 39 is fixed to the impeller pump 37, and a pulley 40 is attached to the upper end of the shaft, and the pulley is interlocked with a pulley 42 of a motor 41 and a belt 43.

  An impeller pump is a jet pump in which a large number of plate-like blades are fixed radially around a shaft, and is most often used in today's jet solder baths. This impeller pump feeds molten solder by flying the molten solder present between the plate-shaped blades when the shaft rotates to the outside with the force of rotation of the plate-shaped blades. Therefore, when using an impeller pump, a duct is always necessary. That is, in the impeller pump, a guide that reaches from the impeller pump to the jet nozzle is necessary in order to flow the molten solder between the blades and flow in the direction of the jet nozzle, and the guide is a duct.

  By the way, since the impeller pump blows the molten solder with a large number of blades, the molten solder is blown with one blade and then is blown with the next blade, while the molten solder is intermittently fed. Therefore, in a jet solder bath using an impeller pump, a so-called “pulsating flow” in which the top of the molten solder jetted from the jet nozzle moves up and down easily occurs, and the contact with the printed circuit board becomes non-uniform and unsoldered or printed There was a case where it was deposited on the surface of the substrate.

  As a means for preventing this pulsating flow, as shown by reference numeral 36 in FIG. 6 and FIG. Although the installation of the current plate is effective in preventing pulsating flow, there is a problem that when the current plate is installed, a solder oxide adheres to the current plate. The problem of oxide adhesion is that fine oxides adhere to the rectifying plate while the jet solder bath is used for a long time, which accumulates into large lumps. And the lump blocks the hole of the current plate, or jets together with the molten solder and adheres to the printed circuit board, resulting in a short circuit or poor appearance. Thus, although the impeller pump has problems such as pulsation and oxide adhesion, the structure is simple and can be manufactured at a low cost.

As described above, the impeller pump is the mainstream as the jet pump used in the jet solder bath, but a screw pump is also proposed in the literature. (Reference: Patent Documents 1 to 3) This screw pump is one in which spiral blades are attached around a shaft.
Japanese Utility Model Publication No. 48-55025 Japanese Utility Model Publication No. 53-34345 JP-A-62-259665

  The screw pump is a pump that has been used in various fields for a long time, and the spiral blade has a structure that does not cause clogging, and thus is suitable for the transfer of particulate matter, semi-solid matter, and the like. As described above, it has been proposed in the literature to use a screw pump for a jet solder bath, but it has never been used for a jet solder bath. The reason is that the height of the molten solder jetted from the jet nozzle, particularly the height of the jet at the primary jet nozzle, could not be sufficiently increased in the jet solder bath using the screw pump. It is an object of the present invention to provide a jet solder bath capable of sufficiently increasing the jet height at the primary jet nozzle.

  As a result of intensive studies on the reason why the jet height cannot be sufficiently increased in the jet solder bath using the screw pump, the present inventors have found that the clearance between the screw pump blade and the casing housing the screw pump is appropriate. Turned out not to be. Accordingly, the present inventor has found that the jet height can be sufficiently increased if the clearance is appropriate, thereby completing the present invention.

  In the jet solder bath in which the shaft of the screw pump housed in the casing protrudes upward and the upper end of the shaft is interlocked with the motor, the clearance between the screw pump and the casing is 0.1 to 1 mm. It is a jet solder bath characterized by being.

  Another aspect of the present invention is a jet solder bath in which a shaft of a screw pump housed in a casing protrudes upward, and an upper end of the shaft is interlocked with a motor. The bearing cylinder is pivotally supported by a bearing cylinder having a hole formed therein, and the bearing cylinder is connected to a casing housing the screw pump by a plurality of columns, and the clearance between the screw pump and the casing is 0.1 to 1 mm. It is a jet solder bath characterized by becoming.

  In the jet solder bath of the present invention, since no pulsating flow occurs at all like the conventional jet solder bath, the molten solder can be brought into uniform contact with the printed circuit board. In addition, since the jet solder bath of the present invention does not require the installation of a rectifying plate, solder oxide does not adhere, and short-circuiting and appearance defects due to oxide do not occur at all.

  The reason why pulsation occurs in the jet solder bath is that the molten solder flows intermittently. In the intermittent flow of the molten solder, the flow of the molten solder stops for a moment and then becomes a vigorous flow. As a result, the pulsation causes the top of the molten solder jetted from the jet nozzle to move up and down, making it impossible to make uniform contact with the printed circuit board, resulting in poor soldering.

  The present inventor has found that in a jet solder bath using a screw pump, the clearance between the screw pump and the casing may be 0.1 to 1 mm in order to eliminate intermittent feeding. In the jet solder bath using a screw pump, the smaller the clearance is, the more intermittent feeding is not. However, when the clearance is smaller than 0.1 mm, the screw pump and the casing are slightly deformed by the components constituting the jet pump. Will come in contact and hurt. In other words, even if the components constituting the jet pump are finished with high accuracy, thermal distortion due to thermal expansion / contraction occurs in the case of being subjected to repeated high and low temperatures during use and non-use, such as a jet solder bath. This thermal strain varies depending on the thickness and size of the component parts, but in a jet solder bath, it may be distorted to near 0.1 mm. Therefore, in the present invention, the clearance is set to 0.1 mm or more in consideration of thermal distortion.

  On the other hand, when the clearance exceeds 1 mm, the screw pump intermittently feeds and generates pulsation. Therefore, in the jet solder bath of the present invention, the clearance between the screw pump and the casing is set to 0.1 to 1 mm.

  In order to maintain the clearance between the screw pump and the casing at 0.1 to 1 mm, the shaft should not be shaken. In order to prevent the shaft from moving, the shaft is supported at two or more places when the screw pump is housed in the casing. Therefore, in the present invention, in order to support the shaft at two places, a bearing cylinder having bearing holes in the upper and lower portions is used. Also, the screw pump must always be concentric with the casing hole when the shaft fixed to the screw pump rotates. In order to make the screw pump concentric with the casing, the position of the shaft support or the casing is adjusted. The position of the shaft support part and the casing may be adjusted by connecting the shaft support part and the casing with a plurality of support columns and inserting a washer having an appropriate thickness between the support column and the hole.

  Hereinafter, the jet solder bath of the present invention will be described with reference to the drawings. FIG. 1 is an enlarged cross-sectional view of a main part of the jet solder bath of the present invention, FIG. 2 is an enlarged perspective view in which a main portion of the jet solder bath of the present invention is partially broken, FIG. 3 is a plan view of the jet solder bath of the present invention, and FIG. 3 is a cross-sectional view taken along line AA in FIG. 3, and FIG.

  As shown in FIGS. 3 and 4, the jet solder bath 1 is a box-like shape with an open lid, in which solder 2 is put, and the solder is melted by an electric heater (not shown) and kept at a predetermined temperature. In the jet solder tank 1, a primary jet nozzle 3 and a secondary jet nozzle 4 are installed. A large number of jet holes 5 are formed in the jet port of the primary jet nozzle 3, and the molten solder jetted therefrom becomes rough waves with irregularities. This rough wave penetrates into the through hole of the printed circuit board and the corner of the chip component and eliminates unsolder. However, rough waves can cause poor soldering such as wigs and bridges. Therefore, these soldering defects are corrected with molten solder flowing out from the secondary jet nozzle. Since the secondary jet nozzle 4 has a wide jet port and no obstacles, the secondary jet nozzle 4 is in a gentle jet state. When the printed circuit board on which the tsura or bridge is formed is brought into contact with this gently flowing molten solder, the tsura or bridge is remelted and corrected, and an excessively large amount of solder is removed to an appropriate amount. .

  A partition plate 6 is installed horizontally in the lower part of the jet solder bath 1. A nozzle port 7 is erected on the partition plate, and a primary jet nozzle 3 and a secondary jet nozzle 4 are attached to the nozzle port. The partition plate 6 is provided with a jet pump 8. The jet pump 8 includes a shaft 9, a bearing cylinder 10, a casing 11, and a screw pump 12.

  A pulley 13 is attached to the upper end of the shaft 9, and the pulley is interlocked with a pulley 15 and a belt 16 of a motor 14 installed outside the jet solder bath 1. A screw pump 12 is attached to the lower end of the shaft 9.

  The bearing cylinder 10 has a hollow cylindrical shape, and holes 17 and 18 through which a shaft can be inserted are formed in an upper part and a lower part. The lower hole 18 has a size that does not hinder the rotation of the shaft 9 and does not allow molten solder to easily enter. A rectangular flange 19 is formed in the lower portion of the bearing cylinder 10 and holes 20 are formed at four corners.

  The casing 11 has a large hole 21 at the center, and a rectangular flange 22 is formed at the top. In the flange 22, holes... 23 are formed at positions corresponding to the holes 20 in the flange 19 of the bearing cylinder 10. The bearing cylinder 10 and the casing 11 are connected by four columns 24. A hexagon head 25 is formed at the lower part of the support column 24, and a male screw 26 having a smaller diameter than the support body is screwed at the upper part. The support 24 is inserted through the hole 23 formed in the flange 22 of the casing 11, and the lower hexagon head 25 is brought into contact with the lower surface of the hole 23. The male screw 26 on the upper side of the column 24 is inserted through the hole 20 formed in the flange 19 of the bearing cylinder 10, and the step formed by the column main body and the small male screw is brought into contact with the lower surface of the hole 20. . A nut 27 is screwed into a male screw 26 protruding from the hole 20 of the flange 19 of the bearing cylinder 10, thereby connecting the bearing cylinder 10 and the casing 11.

  The screw pump 12 is attached to a shaft 9, and a plurality of (four) spiral blades 28 are attached around the lower portion of the shaft. The screw pump 12 is accommodated in the hole 21 of the casing 11, and the clearance (C) between the blade 28 and the hole 21 is 0.1 to 1 mm. As described above, if the clearance between the blade and the hole in the casing is not 0.1 to 1 mm in the screw pump, a jet flow without pulsation cannot be achieved. In order to set the clearance between the screw pump and the casing to a predetermined value, the screw pump and the casing must naturally be concentric. When these are not concentric, the tightening degree of the nut 27 is adjusted, or a washer having an appropriate thickness is sandwiched between the lower surface of the hole 20 of the flange 19 of the bearing cylinder 10 and the stepped portion of the column 24, and adjusted. To do.

  The shaft 9 to which the screw pump 12 is attached is inserted from below the casing 11 and is inserted through the lower hole 18 and the upper hole 17 of the bearing cylinder 10 to protrude upward. Since the vertical position of the screw pump in the casing is important, the shaft 9 is positioned by fixing the ring 29 to the shaft.

  In the jet solder bath of the present invention, when the clearance between the screw pump and the casing was 0.5 mm, the top of the molten solder jetted from the jet nozzle did not move up and down, and no pulsation occurred. On the other hand, in the jet solder bath having the clearance of 2 mm, the height of the molten solder jetted from the jet nozzle cannot be made sufficiently high. .

  In the embodiment, the jet solder bath for soldering the entire back surface of the printed circuit board has been described. However, it goes without saying that the present invention can also be applied to a so-called “partial dip solder bath” for soldering only a necessary portion of the printed circuit board. .

It is a principal part expanded sectional view of this invention jet soldering tank. It is the expansion perspective view which fractured | ruptured the principal part of this invention jet solder tank partially. It is a top view of this invention jet soldering bath. FIG. 4 is a sectional view taken along line AA in FIG. 3. It is a fracture perspective view of the present invention jet solder bath. It is sectional drawing of the jet solder tank using an impeller pump. It is the perspective view which fractured | ruptured the principal part of the jet solder tank using an impeller pump.

Explanation of symbols

8 Jet pump 9 Shaft 10 Bearing cylinder 11 Casing 12 Screw pump 24 Strut 26 Male screw

Claims (3)

In the jet solder bath in which the shaft of the screw pump housed in the casing protrudes upward and the upper end of the shaft is interlocked with the motor, the clearance between the screw pump and the casing is 0.1 to 1 mm. A jet solder bath. In a jet solder bath in which the shaft of the screw pump housed in the casing protrudes upward and the upper end of the shaft is interlocked with the motor, the shaft of the screw pump has a bearing cylinder with holes for bearings in the upper and lower portions. And the bearing cylinder is connected to a casing containing a screw pump by a plurality of support columns, and the clearance between the screw pump and the casing is 0.1 to 1 mm. A jet solder bath. A male screw is screwed to the upper end of the support column connecting the bearing cylinder and the casing, and the male screw is inserted into a connection hole of the bearing cylinder. 3. A jet solder bath according to claim 2, wherein the bearing cylinders are concentric.

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