JP2006093281A - Flow soldering apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent an oxide film from occurring on the surface of a jet wave of molten solder, attaching to the printed wiring board of a work to be soldered, and generating solder bridges, at the time of flow soldering of the printed wiring board. <P>SOLUTION: By forming a wavy end 71 in an end in the flowing direction of a guide board 70 which guides the flowing down of each jet wave generated by molten solder inside a solder bath, a distribution sequence can be formed wherein a flow portion of rapid fluid velocity and a flow portion of relatively slow fluid velocity are alternately formed, on the downstream portion of each jet wave. Thereby, force which tends to run and push down an oxide film extended filmily on the surface of the jet wave running down on the guide board 70 is distributed in the shape of comb teeth and unevenly applied. Therefore, the oxide film which tends to run up on the jet wave is cut off and pushed down by the portion of jet wave of rapid fluid velocity, and consequently the oxide film can hardly develop. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is a flow in which a molten lead-free solder that is jetted is brought into contact with a printed wiring board on which electronic components are mounted, and the lead-free solder is supplied to a soldered portion of the printed wiring board to perform soldering. The present invention relates to a soldering apparatus.

  Flow soldering equipment supplies solder to the soldered part of the printed wiring board by bringing the printed wiring board on which the electronic components are mounted into contact with lead-free solder that is jetted in a molten state (this is called a jet wave). This is a mechanism for soldering.

  FIG. 1 is a view for explaining a main part of a flow soldering apparatus, and is a view showing a longitudinal section thereof. In addition, in the same figure, the conveyance conveyor 20 is shown with the dashed-dotted line. That is, a solder (molten solder) 2 that is heated by a heater and a temperature control device (not shown) and held at a target temperature is accommodated in the solder tank 1 and is blown by the pumps 3 and 4. It is configured to be supplied to the ports 5 and 6 to flow down the guide plate 7 to form a jet wave.

  Then, the printed wiring board 30 on which electronic components to be soldered are mounted is conveyed in the direction of the arrow A at the elevation angle θ by the conveying conveyor 20 and brought into contact with the jet wave of the molten solder 2 so that the soldered portion is soldered. Is supplied and soldering is performed.

  The flow soldering apparatus shown in FIG. 1 has a first pump 3, a second pump 4, and a first pump to form two jet waves, ie, a first jet wave 8 and a second jet wave 9. The blower body 10 and the second blower body 11 are provided, and the solder after jetting each flows down the guide plate 7 and returns to the solder tank 1 in the course of the first jet wave 8 and the second jet body 10. The jet wave 9 is formed.

  In addition, the structure of the 1st blower body 10 and its blower opening (1st blower opening) 5, and the structure of the 2nd blower body 11 and its blower opening (2nd blower opening) 6 differ, and were different. It is configured so that a jet wave of the nature is formed. In the example of FIG. 1, the second blowing body 11 is provided with a tray portion 12 for stabilizing the flow of the molten solder 2.

  Further, the guide plate 7 is fixed by a screw 13 passing through the long hole, and is configured so that the position can be adjusted in the direction of the arrow B in the figure, that is, in the vertical direction, thereby adjusting the nature of the jet wave. It is a mechanism that can do.

  On the other hand, the solder used for soldering the printed wiring board 30 is replaced with a conventionally used solder, for example, 63 wt% tin-37 wt% lead solder (hereinafter referred to as tin-37 lead solder). Therefore, a lead-free solder, that is, a lead-free solder has been used. In other words, this is to eliminate the lead poisoning of the natural environment and human body. And most of this lead-free solder is mainly composed of tin.

  Representative examples of lead-free solder include, for example, tin-silver-copper lead-free solder (tin-3.5 silver-0.75 copper solder, etc.), tin-copper lead-free solder (tin- 0.7 copper solder, etc.), tin-silver lead-free solder (tin-4 silver solder, etc.), tin-zinc lead-free solder (tin-9 zinc solder, etc.), etc. Many of these solders have further improved various characteristics of the solder by adding trace amounts of elements. As described above, most of the lead-free solder is tin-rich lead-free solder having a tin content of 85 wt% or more.

  When performing flow soldering of a printed wiring board, a solder oxide film is generated on the surface of the jet wave of molten solder, and this oxide film adheres to the printed wiring board that is the work to be soldered, resulting in a bridge. That is a problem. In particular, this problem has become apparent since it has become a lead-free solder with a high tin content, and dealing with it has become an urgent issue.

  When this oxide film is seen with the naked eye, it is a whitish thin fluffy form, and has a hardness that covers the surface against the flow of the jet, and when this oxide film is fixed by touching a rod-shaped member, this oxide film Is fixed and held on the flow of solder, and has such a property that a jet of solder flows under this oxide film. The existence of such an oxide film is disclosed in Patent Document 1 and Patent Document 2.

  As shown in FIG. 1, the surfaces of the first and second jet waves 8 and 9 are covered with an oxide film 2a, and the upper part where the molten solder 2 jets is the part where the oxide film starts to be generated. Although the presence of the film 2a is negligible, the film thickness increases as it flows down the guide plate 7 and below provided on the side of the air outlet, and its presence can be clearly recognized. Then, such an oxide film 2a is accumulated on the liquid surface of the molten solder 2 in the solder bath 1, and floats as an oxide (dross).

  Thus, since the oxide film 2a has such a property that its surface can be covered statically against the flow of the jet waves 8, 9, the oxide film 2a flows on the surface of the jet waves 8, 9. The oxide film 2a to be lowered is accumulated on the upstream side of the jet waves 8, 9 from the liquid surface side of the molten solder 2 in the solder bath 1, that is, on the upper part of the jet waves 8, 9, as a whole. Since it flows down at a speed much slower than the flow of the waves 8 and 9, it behaves as if the oxide film 2a covers the surfaces of the jet waves 8 and 9 while ascending.

  Further, as disclosed in Patent Document 2 and shown in FIG. 1, when using a lead-free solder, when the interval between the first jet wave 8 and the second jet wave 9 is set narrow, these first When the first jet wave 8 and the second jet wave 9 flow down, a flow merge occurs between them, and the oxide film 2a easily rises on the jet waves 8 and 9 from this merged portion. It goes up.

Therefore, when the printed wiring board 30 is brought into contact with the jet wave of the molten solder 2 during flow soldering, the oxide film 2a also adheres, and if it adheres between adjacent soldered parts, a leakage current is generated. This causes a serious problem that the electronic function of the printed wiring board 30 cannot be expressed.
JP-A-9-47865 JP, 2004-71785, A This invention is a printed wiring board which is a work to be soldered by making it possible to eliminate the oxide film which is formed on the surface of the jet wave and tries to rise up the jet wave. This is to prevent the oxide film from adhering during the flow soldering and to cause a circuit bridge.

  According to the present invention, as described in the following (1) and (2), when the molten solder that has formed a jet wave returns to the solder bath, the oxide film on the surface does not rise up the surface of the jet wave, and the flow velocity distribution It is characterized by the formation of rows. In addition, it is characterized by a row shape that does not rise.

(1) That is, a member for guiding the flow of the lead-free solder spouted to the blowout port for sprinkling lead-free solder mainly composed of tin, which is relative to the flow portion where the lead-free solder has a high flow speed. In order to form a distribution row in which the slow flow portions are alternately arranged, the flow soldering device is configured such that a guide plate having a corrugated end portion in the flow-down direction is provided.

  As a result, a force that flows and pushes down the oxide that spreads in the form of a film formed on the surface of the jet wave flowing down on the guide plate, that is, the oxide film, is applied non-uniformly, and the jet wave is going to rise up. The oxide film to be pressed is pushed down so as to be cut off by the portion of the jet wave having a high flow velocity, and does not rise. That is, the oxide formed on the surface of the jet wave at the portion where the jet wave flows cannot maintain the film shape, and cannot rise up on the jet wave. As a result, the oxide film does not adhere to the printed wiring board in contact with the jet wave.

(2) Further, the guide portion where the lead-free solder mainly composed of tin jetted from the blower flows down is provided with a row of protrusions that divides the flow into a plurality of rows in the flow direction. Flow soldering device.

  As a result, the shape of the jet wave that is divided and flows down changes from a planar shape to a large number of rows and at the same time the flow velocity increases, and the oxide formed on the surface of the jet wave cannot maintain the film shape. You will not be able to climb up. As a result, the oxide film does not adhere to the printed wiring board in contact with the jet wave.

  As described above, according to the flow soldering apparatus of the present invention, the oxide film does not rise in the region of the jet wave contact with the printed wiring board, and the printed wiring board as the work to be soldered is brought into contact with the jet wave. However, the oxide does not adhere to the soldered portion and a bridge is not generated.

  As a result, a serious defect that inhibits the function of the electronic circuit formed on the printed wiring board by flow soldering does not occur.

  Hereinafter, embodiments of the present invention will be described.

Embodiment 1
The flow soldering apparatus according to the embodiment of the present invention is configured in the same manner as in FIG. 1 described in the background art above, in a solder bath, a pump, a blower body, a heater, a temperature control device, and the like (not shown). And as shown in FIG. 1, the jet wave of molten solder is formed from the upper part of the blower body to the guide plate.

  FIG. 2 shows the configuration of the guide plate 70 provided on the side of the first and second blowing ports 5 and 6 which are the blowing ports of the first and second blowing body 10 and 11 shown in FIG. It is a perspective view explaining an example. A corrugated end 71 having a corrugated end in the flow direction C of the curved surface where the molten solder 2 flows is formed. In addition, this guide plate 70 is being fixed to each blower body 10 and 11 of FIG. 1 so that height adjustment is possible to the arrow B direction by passing a screw through the screw insertion hole 72 which is a long hole.

  Thus, by providing the corrugated end 71 at the end of the guide plate 70 in the flow direction, the fluid resistance to the molten solder 2 flowing down the guide plate 70 is reduced, and the viscosity is higher than that of the conventional tin-37 lead solder. It is possible to increase the flow rate of lead-free solder, which is said to be high. Moreover, the flow velocity is relatively higher in the valleys of the waveform end 71 than in the peaks. That is, it is possible to form a distribution row in which the flow portions having a high flow velocity and the flow portions having a relatively low flow velocity are alternately arranged in the flow portions of the jet waves 8 and 9.

  As a result, the force to flow down the oxide, that is, the oxide film formed on the surface of the jet wave flowing down on the guide plate 70, is distributed in a comb-like shape and applied unevenly. The oxide film which is going to rise up the jet wave is pushed down so as to be cut off by the jet wave part having a high flow velocity, and does not rise up.

  That is, the oxide formed on the surface of the jet waves 8 and 9 cannot maintain the film shape at the portion where the jet waves 8 and 9 flow down, and rises on the jet waves 8 and 9. Can not be. Therefore, the oxide film does not adhere to the printed wiring board 30 that contacts the jet waves 8 and 9 when performing flow soldering.

  In the example of FIG. 2, an example in which the sinusoidal waveform end portion 71 is formed at the end portion of the guide plate 70 is shown, but it may be formed in a triangular waveform or the like. Further, such a guide plate is such that the first and second jet waves 8 and 9 are merged between the first blower body 10 and the second blower body 11 shown in FIG. When used on a site, an extremely large effect is obtained.

[Embodiment 2]
Next, a blower body having a configuration different from the blower body illustrated in FIG. 1 will be described.

  FIG. 3 is a perspective view illustrating an example of a blower body in which a large number of through holes are arranged in a row to form a blower opening. In FIG. 3, reference numeral 100 denotes a blower body, and the blower body 100 is formed with a cylindrical curved upper portion as shown in the figure, and a large number of through holes 101 are arranged in a row on the curved upper portion. The blower body 100 is connected to the pump shown in FIG. 1 and jets molten solder from the through-hole 101 so that a jet wave in which a large number of wave fronts are formed in a row can be obtained. It has been done. And the blower opening 102 comprised by the row | line | column of the through-hole 101 is provided above the cylindrical curved surface part, and the said jet wave flows down the cylindrical side curved surface, ie, the guide part 103, and a jet wave is made to flow down. It is formed and returned to the solder bath 1.

  In the example of FIG. 3, a row of pins 104 is provided in the guide portion 103 that is a cylindrical curved surface so as to be parallel to the row of through holes 101, and the molten solder jetted from the blowing port 102 is on the column side. When flowing down the partial curved surface, that is, the guide portion 103, the flow is divided into a plurality of rows in the flow direction C. The pitch of the pins 104 may be adjusted to the pitch of the through holes in the row of the through holes 101, but it is not always necessary.

  By configuring in this way, the molten solder jetted from the blow holes, that is, the rows of the through holes 101 is divided by the pins 104 when flowing down, and the flow velocity is increased at the same time as the shape of the jet wave is changed from the planar shape to the multiple rows. . As a result, the oxide formed on the surface of the jet wave cannot maintain the film shape, and the jet wave constituted by the divided down stream cannot rise up. Therefore, the oxide film does not adhere to the printed wiring board that comes into contact with the jet wave when performing flow soldering.

  3 shows an example of a pin having a cylindrical cross section, it is better to provide a pin having a streamline cross section in the flow direction C. In addition, plate-like members that are the destinations of streamlined pins may be provided in rows.

  Of course, you may provide the guide plate which has a waveform end part in the edge part of the flow direction C shown in FIG. 2 in the side part of the cylindrical part of FIG. In addition, a guide plate having a straight end portion having no corrugated end portion in FIG. 2 may be used, and the pins 104 illustrated in FIG. 3 may be provided on the curved surface.

  The present invention is applied to a device for soldering and mounting an electronic circuit device that is a daily necessities and an infrastructure, that is, a flow soldering device that is a production means. And it becomes possible to form an electronic circuit that does not impede function during soldering mounting.

It is sectional drawing which shows the structure of this kind of flow soldering apparatus. It is a perspective view of the guide plate which shows Embodiment 1 of this invention. It is a structure perspective view of the blower body which shows Embodiment 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Solder tank 2 Molten solder 3 1st pump 4 2nd pump 5 1st blowing port 6 2nd blowing port 7 Guide plate 8 1st jet wave 9 2nd jet wave 10 1st blowing body DESCRIPTION OF SYMBOLS 11 2nd blower body 12 Tray part 13 Screw 20 Conveyor 30 Printed wiring board 70 Guide board 71 Corrugated edge part 72 Screw insertion hole 100 Blow hole body 101 Through-hole 102 Blow hole 103 Guide part 104 Pin

Claims (2)

  A member that guides the flow of the lead-free solder spouted to a nozzle through which the lead-free solder containing tin as a main component is jetted, wherein a flow portion where the lead-free solder flows is fast and a portion where the flow is relatively slow A flow soldering apparatus comprising a guide plate having a tip end portion having a wave shape with respect to the flow-down direction in order to form alternately arranged distribution rows.   It has a cylindrical curved surface, and a number of through holes are arranged in a row at the top to form a blower to form a blower body. Lead-free solder mainly composed of tin jetted from the blower flows down. A flow soldering apparatus, wherein the columnar curved guide portion is provided with a row of protrusions for dividing the flow down into a plurality of rows in the flow direction.

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