JP6182926B2 - Soldering method - Google Patents

Description

The present invention relates to a soldering where the mounting components by soldering to the printed circuit board.

  A printed circuit board on which a component having a large number of IO (input / output) points or a component requiring a large current is increasing in number of layers in order to operate these components, and the plate thickness tends to increase. In addition, regarding mounting of components, through-hole mounting technology (IMT) technology inserts electronic component leads into holes called through-holes opened exclusively for IMT components from the top surface of a printed circuit board and solders them. . At this time, the inserted lead is taken out from the lower surface of the printed circuit board, and the lead surface and the printed circuit board are heated by passing the lower surface of the printed circuit board in contact with the solder flow in the flow tank, and the lead is soldered. The through hole is filled with solder.

  A technique is disclosed in which a slit hole is formed along a through hole to improve solder rising into the through hole of the printed circuit board (see, for example, Patent Document 1 below). In addition, a technique for positioning and mounting a PGA type component on a printed circuit board by forming a recess in a solder bump on the printed circuit board and inserting a lead of an electronic component into the recessed part and reflowing is disclosed (for example, (See Patent Document 2 below.) Also, a technique that prevents the formation of solder bridges between leads by raising and lowering wet pins between leads during soldering in a jet soldering apparatus is disclosed (for example, see Patent Document 3 below).

JP 2010-003984 A JP-A-1-321686 JP 2006-302922 A

  However, as the thickness of the printed board increases, it becomes difficult to ensure the amount of solder filled in the through holes. When solder cannot be filled in the through hole, there is a problem that electrical contact between the lead of the mounted component and the printed circuit board (through hole) cannot be performed sufficiently.

  In the case of soldering by a solder jet or the like, as the board thickness of the printed circuit board increases, it takes a long time to move up from the solder bath in the solder bath to the through hole. For this reason, it is necessary to raise the temperature of the printed circuit board and components above the melting point temperature of the solder, and the time for immersing the printed circuit board in the solder bath becomes longer, so the electrodes on the soldering surface break or the mounted components are damaged. May occur.

  In the case of soldering with solder pellets or solder paste, the component is inserted into the lead of the component and soldered to the printed circuit board by a reflow furnace. However, when the length of the through hole of the printed circuit board is long with respect to the pitch of the component leads, a necessary amount of solder pellets cannot be provided, and a sufficient amount of solder cannot be filled in the through hole.

  In one aspect, an object of the present invention is to efficiently fill solder into a through hole regardless of the thickness of a printed board.

In one proposal, the soldering method includes a first step of Ru by immersing a printed board in a solder bath, in the through hole of the printed circuit board, through inserting the lead of the component to be soldered, the leads to the solder bath a second step of Ru into contact, a third step of pulling the lead has a range tip of the lead is less than PC board thickness at the said through hole, in a state fitted with the components on the printed circuit board And a fourth step of removing the printed circuit board from the solder bath.

  According to one embodiment, solder can be efficiently filled into the through hole regardless of the thickness of the printed board.

FIG. 1-1 is a cross-sectional view illustrating a soldering procedure according to the embodiment (No. 1). 1-2 is sectional drawing which shows the procedure of soldering of embodiment (the 2). 1-3 is sectional drawing which shows the procedure of the soldering of embodiment (the 3). FIGS. 1-4 is sectional drawing which shows the procedure of the soldering of embodiment (the 4). FIG. 2 is a chart showing a temperature transition in the through hole during the soldering process. FIG. 3 is a perspective view showing an overall configuration of a soldering apparatus having a lead lifting function. FIG. 4 is an enlarged perspective view of FIG. FIG. 5 is a front view showing a lifting jig having a lead pulling function. FIG. 6 is a front view showing a part push-in state of a lifting jig having a lead lifting function. FIG. 7 is an enlarged view of FIG. FIG. 8 is a front view showing a part pulling state of the lifting jig having a lead pulling function. FIG. 9 is a diagram illustrating a configuration example for setting the pull-up amount. FIG. 10 is a diagram illustrating a modification example of a component lead.

  Hereinafter, preferred embodiments of the disclosed technology will be described in detail with reference to the accompanying drawings. FIGS. 1-1 to 1-4 are cross-sectional views illustrating a soldering procedure according to the embodiment. A printed board and an electronic component are shown, and through holes of the printed board and lead portions of the electronic component are shown.

  A through hole 101 is formed through the printed circuit board 100 from the front surface 100a to the back surface 100b. An electrode 102 is formed on the inner peripheral surface of the through hole 101 and led out to the printed circuit board 100 side.

  An electronic component (component) 120 is mounted on the through hole 101. A lead 121 is protruded from the lower surface of the electronic component 120. The length of the lead 121 is longer than the length of the through hole 101. As shown in FIG. 1-1, the lead 121 has a tip 121a that penetrates the printed circuit board 100 (through hole 101) in a state where the component 120 is mounted on the printed circuit board 100, and a predetermined amount L from the back surface 100b. And has a protruding length.

  First, as shown in FIG. 1-1, the back surface 100b of the printed circuit board 100 is immersed in a solder bath 130 of a solder bath. Then, the lead 121 of the component 120 is inserted into the through hole 101 of the printed board 100.

  Next, as shown in FIG. 1-2, the position of the printed circuit board 100 is fixed in a state where it is immersed in the solder bath 130 as in FIG. 1-1. Then, after elapse of a predetermined time after the state of FIG. 1A, the entire component 120 is pulled up in the height direction with respect to the printed circuit board 100 as shown in FIG. This raising amount is L1.

  The pulling amount L1 can be an arbitrary amount. At this time, the position of the tip 121a of the lead 121 may be equal to or less than the position reaching the front surface 100a of the printed circuit board 100 (in the through hole 101) (for example, between 0 to 100% of the substrate thickness from the back surface 100b of the printed circuit board 100, For example, even if it is 0%, the tip 121a of the lead 121 is pulled up to the position in the through hole 101, and the filling of the solder from the solder bath 130 into the through hole 101 is promoted. Become).

  As the lead 121 is pulled up, the solder in the solder bath 130 leaks to the lead 121 and leaks up in the through hole 101 due to the surface tension of the lead 121 (drawn into the through hole 101). Note that as the amount of the lead 121 pulled up increases, the filling of the solder into the through hole 101 is promoted, and the time (immersion time) for immersing the printed circuit board 100 in the solder bath 130 can be shortened.

  After this, as shown in FIG. 1C, the position of the printed circuit board 100 remains fixed, and the entire component 120 is pushed again toward the printed circuit board 100 (through hole 101), and the lead 121 is inserted into the through hole 101. To insert. The amount of insertion is lowered to the mounting position where the component 120 contacts the surface 100a of the printed circuit board 100.

  Thereafter, as shown in FIGS. 1 to 4, the entire printed circuit board 100 is pulled up from the solder bath 130. Thereby, soldering is completed. In this state, the through hole 101 of the printed circuit board 100 can be filled with solder.

  FIG. 2 is a chart showing a temperature transition in the through hole during the soldering process. FIG. 2A shows the temperature at each height position in the through hole 101 when the thickness of the printed circuit board 100 is 2.85 mm. 0% to 100% indicates the height from the back surface 100b of the printed circuit board 100, 0% is the temperature at the position of the back surface 100b of the printed circuit board 100 (the surface in contact with the solder bath 130), and 50% is the printed circuit board 100. The temperature at the intermediate position in the height direction (the direction of the through hole 101), 100%, is the temperature at the position of the surface 100 a of the printed circuit board 100.

  In FIG. 2A, the vertical axis represents the temperature in the through hole, and the horizontal axis represents the solder immersion time of the printed circuit board 100. 220 ° C. is the solder melting point temperature. (1) shown in this figure is a measurement start time (0 sec) when the printed circuit board 100 shown in FIG. 1-1 is immersed in the solder bath 130. Thereafter, as shown in FIG. 1-2 as (2) after 5 seconds, the entire part 120 was pulled up with a lifting amount L1.

  Here, by pulling up the component 120, only the height position of 0% (the back surface 100b of the printed circuit board 100) has a temperature equal to or higher than the melting point. The part 120 was gradually pulled up to 15 seconds shown in (3). During the period from (2) 5 seconds to (3) 15 seconds, after 10 seconds, the through hole 101 has a height position from 0% to 50% exceeding the melting point, and after 15 seconds, from 0% All the height positions up to 100% exceeded the melting point.

  (3) After 15 seconds, as shown in FIG. 1C, the component 120 is pushed again in the direction of the printed circuit board 100 (through hole 101), and the lead 121 is inserted into the through hole 101. As soon as the component 120 is mounted on the printed circuit board 100 as shown in FIG. 1-3, the printed circuit board 100 is pulled up from the solder bath 130.

  Thus, as shown in FIG. 2A, the temperature exceeds the solder melting point at all height positions in the through hole 101. (3) Fill the through hole 101 with solder in 15 seconds. It shows that you can. Thereby, the immersion time of the printed circuit board 100 with respect to the solder bath 130 can be shortened with the immersion time limit (15 seconds).

  The solder rising state in the through-hole 101 according to various plate thicknesses of the printed board 100 shown in FIG. 2A, (2) lead pull-up timing, and (3) push-in timing are within a control unit (not shown) of the soldering apparatus. It can be stored in advance in the memory. Accordingly, if the thickness of the printed circuit board 100 to be soldered is set, the lead is pulled up and pushed in at the timings (2) and (3), the corresponding characteristic line of FIG. This makes it possible to estimate the solder rise. For example, when the board thickness of the printed circuit board 100 is 2.14 mm, the solder melting point in the through-hole 101 can be satisfied after 10 seconds have elapsed, so that it is not necessary to wait for 15 seconds, and at this point of time exceeding 10 seconds. (3) The lead is pushed in, and the printed circuit board 100 can be removed from the solder bath 130 early.

  FIG. 2B shows the temperature change at the 75% position of the through hole. The horizontal axis is the immersion time. For comparison, the above-described embodiment of raising the lead 121 (the present plan) and the existing technology (conventional) in which the printed circuit board is simply immersed in a solder bath are shown.

  In both the embodiment (the present plan) and the conventional one, there is no difference in temperature for up to 5 seconds. However, in the embodiment (the present plan), the temperature is increased after 10 seconds by raising the temperature after 5 seconds. The temperature was 217 ° C., which was 19 ° C. higher than the conventional temperature (198 ° C.). And in embodiment (this plan), it becomes 226 degreeC and exceeds melting | fusing point at the time of 15 seconds when raising is completed. On the other hand, conventionally, it remains at 210 ° C. or below the melting point even at 15 seconds.

  That is, in the embodiment, the printed circuit board 100 can be taken out from the solder bath 130 after 15 seconds have passed since the immersion of the printed circuit board 100 was started. On the other hand, conventionally, it takes 25 seconds for the temperature in the through hole to exceed the melting point, and the printed circuit board 100 must be immersed in the solder bath 130 for 10 seconds longer than in the embodiment. Since the immersion limit time (15 seconds) is exceeded, problems such as electrode peeling occur.

(Equipment configuration for lifting component leads)
The above-described operation of pulling up the lead 121 of the component 120 with respect to the printed circuit board 100 is performed manually or by using a lifting device. Hereinafter, an apparatus configuration example will be described.

  FIG. 3 is a perspective view showing an overall configuration of a soldering apparatus having a lead lifting function. The soldering apparatus 300 has a solder bath 301 at the bottom of the printed circuit board 100. The solder bath 301 is filled with the solder bath 130 in contact with the back surface 100 b of the printed circuit board 100.

  A plurality of through holes 101 are opened up and down on the printed circuit board 100 placed horizontally (X direction). The component 120 has a plurality of leads 121 having a pitch that matches the opening pitch of the through holes 101. In the illustrated example, the component 120 is mounted so as to be orthogonal (standing) with respect to the horizontal surface of the printed circuit board 100. The lead 121 is erected toward the lower part (through hole 101) of the component 120.

  Such a component 120 is movable up and down in the height (Y) direction by the elevating mechanism 302. The lifting mechanism 302 includes a holding arm 303 that fixes and holds the component 120, a moving table 304 to which the holding arm 303 is attached, a pair of rails 305 that slidably support both ends of the moving table 304 in the height direction, and a moving table. A fixing screw 306a fixed to the center of 304 and a rotating shaft mechanism 306 including a rotating shaft 306b rotated by a motor (not shown) and screwed into the fixing screw 306a are included.

  FIG. 4 is an enlarged perspective view of FIG. The through hole 101 of the printed circuit board 100 and the lead 121 portion of the component 120 are enlarged. As shown in FIG. 4, the plurality of leads 121 protruding from the component 120 can be moved up and down along the height (Y) direction with respect to the through hole 101 of the printed circuit board 100 by the operation of the lifting mechanism 302.

  According to the above configuration, the moving table 304 is raised or lowered by switching the rotation direction of the motor under the control of a control unit (not shown). By using such an elevating mechanism 302, the lead of the component 120 can be pulled up (and pushed in) with respect to the through hole 101 of the printed circuit board 100, and the solder of the solder bath 130 is put into the through hole 101 as described above. Efficient filling can be promoted.

  FIG. 5 is a front view showing a lifting jig having a lead pulling function. The lifting jig 500 shown in FIG. 5 is operated manually. On the printed circuit board 100, lifting jigs 500 formed symmetrically at both ends of the component 120 are arranged. Although not shown, the printed circuit board 100 is immersed in the solder bath 130 of the solder bath 301 as in FIG.

  A protrusion 501 that is inserted into the opening 100 c of the printed circuit board 100 is formed to protrude from the bottom of the lifting jig 500. A locking holding portion 501 a is formed at the tip of the protrusion 501. For example, as shown in the drawing, the locking holding portion 501a is formed in a split pin shape in which the tip of the protrusion 501 is broken into two and the tip is inclined. The step 501b of the latch holding portion 501a expands and engages with the opening 100c of the printed circuit board 100 (two-dot chain line in the figure). Thereby, the lifting jig 500 can be fixed on the printed circuit board 100. After mounting (soldering) the component 120 on the printed circuit board 100, the lifting jig 500 can be removed from the printed circuit board 100 by pressing the step 501b inward and moving the protrusion 501 upward.

  The protrusion 501 is provided below the holding block 503. The holding block 503 supports a lever 505 that is rotatable about a shaft 504. The holding block 503 is provided with positioning pieces 503 a that are in contact with both ends of the component 120 and restrict the position of the component 120 when it is moved up and down (up and down).

  The lever 505 is provided with an operating piece 505a that is operated with a finger or the like at the upper part, and a protruding piece 505b that protrudes toward the component 120 is formed at the substantially central portion. The protruding piece 505b fits into the recessed groove 120d formed in the component 120 when the lever 505 rotates around the shaft 504. For this reason, a concave groove 120d is formed in advance on both sides of the component 120 in accordance with the fitting position of the protruding piece 505b. The concave groove 120d is formed in an oval shape in accordance with the rotation of the protruding piece 505b. At the lower end of the lever 505, a push-up piece 505c that protrudes toward the component 120 and contacts the lower end 120e of the component 120 is formed.

  A pulling member 510 made of an elastic body that pulls each other is provided at the lower ends of the pair of levers 505. In the illustrated example, one tension spring is provided between the pair of levers 505. However, a tension spring may be provided between each lever 505 and the holding block 503. By this pulling member 510, the pair of levers 505 are held in an open state around the shaft 504 as shown in FIG.

  FIG. 6 is a front view showing a part push-in state of a lifting jig having a lead lifting function. As shown in FIG. 5, after inserting the component 120 into the lifting jig 500, the operation piece 505 a of the pair of levers 505 is operated, and the pair of levers 505 is centered around the shaft 504 (A direction in the figure). Turn to.

  FIG. 7 is an enlarged view of FIG. As shown in FIG. 7, by rotating the lever 505 inward (A direction in the figure) about the shaft 504, the protruding piece 505b fits into the recessed groove 120d of the component 120, and the recessed groove 120d is moved downward. Push in. Thereby, the component 120 can be pushed in the direction of the printed circuit board 100 (Y direction). Accordingly, the above-described lead 121 provided on the component 120 can be pushed in the direction of the printed circuit board 100 (through hole 101) by the rotation of the lever 505. Reference numeral 505d denotes a lock protrusion, and the lock protrusion 505d is engaged with the holding block 503 in the state shown in FIG. 7 (inverted state of the lever 505) to hold the inverted state of the lever 505 (indented state of the component 120). be able to.

  On the other hand, for lifting the lead 121, the lever 505 may be rotated in the direction opposite to that in FIG. FIG. 8 is a front view showing a part pulling state of the lifting jig having a lead pulling function. As shown in FIG. 8, the operation piece 505 a of the pair of levers 505 is operated, and the pair of levers 505 is rotated outward (direction B in the figure) about the shaft 504. The push-up piece 505 c protruding from the lower end portion of the lever 505 pushes up the component 120 via the lower end 120 e of the component 120 and moves it in a direction away from the printed circuit board 100. Thereby, the above-mentioned lead 121 provided in the component 120 can be pulled up from the printed circuit board 100 (through hole 101).

  FIG. 9 is a diagram illustrating a configuration example for setting the pull-up amount. As shown in FIGS. 9A and 9C, the lead 121 of the component 120 has a predetermined pull-up amount L1 with respect to the printed circuit board 100 described above. This pull-up amount L1 can be changed according to the amount of rotation of the lever 505 (the amount of rotation in the direction B in the figure).

  As shown in FIG. 9B, the holding block 503 contacts the holding block 503 when the lever 505 rotates in the B direction, and the movement amount variable piece as a restricting member that restricts the amount of rotation (lifting amount) of the lever 505. 901 is provided. As shown in FIG. 9D, the movement amount variable piece 901 is provided in advance with a plurality of heights corresponding to the restriction amounts (movement amount variable pieces 901a to 901d).

  In the lever 505, the side piece 505 e contacts the holding block 503 when rotating in the B direction about the shaft 504. As shown in FIG. 9B, as the movement amount, that is, the lifting amount increases, the lifting amount of the push-up piece 505c at the lower end of the lever 505 increases, and the rotation amount of the lever 505 increases correspondingly. .

  For this reason, the moving amount variable piece 901 having a predetermined height that comes into contact with the lever 505 is attached to the holding block 503 portion with which the side piece 505e comes into contact. At this time, as the amount of rotation of the lever 505 increases, the amount of lifting increases. Therefore, as shown in FIG. 9D, the amount of movement variable frame 901a having a lower height as the amount of movement (lifting amount) increases. It is only necessary to select the moving amount variable frame 901d having a higher height as the moving amount (lifting amount) is smaller. The moving amount (pull-up amount) can be set differently according to the height of the moving amount variable piece 901.

  The lifting amount L1 of the lead 121 of the component 120 set by the movement amount variable piece 901 is set according to the thickness of the printed circuit board 100. For example, if the thickness of the printed circuit board 100 is 2 mm, a moving amount variable piece 901a having a moving amount of 2 mm is used. Not limited to this, as described above, the lifting amount L1 of the lead 121 of the component 120 may be set within the range of the thickness of the printed circuit board 100. For example, when the thickness of the printed circuit board 100 is 2 mm, a movement amount variable piece 901c having a movement amount of 1 mm may be used. In this case, by operating the lever 505, the lead 121 can be pulled up to 1 mm, which is half the thickness of the printed circuit board 100, and thereafter, the solder in the through hole 101 is naturally raised (up by capillary action). wait. Even in this case, as described above, the filling of the solder into the through hole 101 can be performed quickly and efficiently.

  According to the above configuration, when the lever 505 is operated, the lead 121 of the component 120 can be pulled up with a moving amount (pull-up amount L1) corresponding to the selected moving amount variable piece 901 without relying on intuition. It can be an accurate pulling amount.

  FIG. 10 is a diagram illustrating a modification example of a component lead. 10A to 10C show various shapes of the leads 121 of the component 120 for promoting the solder rising.

  FIG. 10A shows a case in which a split mold (in the illustrated example, two parts) 121b is formed in the length direction of the lead 121. FIG. By forming the split mold 121b in the lead 121, the lead 121 can be filled with solder, and the solder rising in the through hole 101 can be further promoted.

  FIG. 10B shows a case where a horizontal step 121 c is formed at the center of the lead 121. By forming the step 121 c on the lead 121, the step 121 c portion pulls up the solder, and the solder rise in the through hole 101 can be further promoted.

  FIG. 10C shows an example in which an inclined portion (in the illustrated example, a dogleg shape) 121 d is formed from the center portion to the lower end of the lead 121. By forming the inclined portion 121d on the lead 121, the inclined portion 121d portion pulls up the solder, and the solder rise in the through hole 101 can be further promoted.

  By making the leads 121 of the component 120 into the various shapes shown in FIG. 10, it is possible to promote the rising of the solder in the through hole 101.

  According to the embodiment described above, the component is moved up and down with respect to the printed circuit board, and the lead of the component is lifted up and pushed into the through hole of the printed circuit board. As a result, the solder that has leaked into the lead is pulled up into the through hole, and the solder can be quickly and efficiently filled into the through hole. In particular, even when the thickness of the printed board is thick, the solder having a temperature equal to or higher than the melting point can be filled in the through hole in a short time. Therefore, the immersion time of the printed board in the solder bath can be shortened, and problems such as electrode peeling can be prevented and efficient soldering can be performed.

  Further, when the terminal pitch is narrow and the thickness of the printed board is large, the conventional pellet solder cannot supply a sufficient amount of solder. However, in the above embodiment, the terminal pitch is narrow and the thickness of the printed board is small. Even when the thickness is thick, a sufficient amount of solder can be filled and supplied to the through hole.

  The following additional notes are disclosed with respect to the above-described embodiments.

(Appendix 1) a first step of immersing the printed circuit board in a solder bath;
A second step of inserting a lead of a component to be soldered into the through hole of the printed circuit board and bringing the lead into contact with the solder bath;
A third step of pulling up the lead within the through-hole with a predetermined pull-up amount;
A soldering method comprising:

(Appendix 2) The length of the lead is set to be longer than the thickness of the printed circuit board,
The soldering method according to claim 1, wherein, in the second step, a tip of the lead is immersed in the solder bath for a predetermined length.

(Supplementary note 3) The soldering method according to Supplementary note 1 or 2, wherein the lead lifting amount in the third step is such that the leading end of the lead has a range equal to or less than the thickness of the printed circuit board.

(Additional remark 4) After the said 3rd process, the said process WHEREIN: The 4th process which takes out the said printed circuit board from the said solder bath as a state which pushed the said lead into the said through hole and attached the said component to the said printed circuit board is included. The soldering method according to Supplementary Note 1 or 2,

(Appendix 5) a solder bath in which the printed circuit board is immersed in a solder bath;
An elevating mechanism for elevating the tip of a lead of a component to be soldered to the through hole of the printed circuit board between a position in contact with the solder bath and a predetermined position in the through hole;
A soldering apparatus comprising:

(Appendix 6) The lifting mechanism is
A moving table for holding the parts;
A rail that supports the movable table to be movable up and down, and a rotary shaft mechanism;
A motor coupled to the rotating shaft of the rotating shaft mechanism;
The soldering apparatus according to appendix 5, characterized by comprising:

(Appendix 7) The lifting mechanism is
Rotatable levers provided on both sides of the printed circuit board on which the components are mounted,
A protruding piece provided on the lever, engaged with a concave groove of the component at the time of rotation, and moving the component up and down relative to the printed circuit board based on a rotation operation of the lever;
The soldering apparatus according to appendix 5, characterized by comprising:

(Supplementary Note 8) A push-up piece is provided at the lower end of the lever, which is engaged with the lower end of the printed circuit board and lifts the component away from the printed circuit board based on the turning operation of the lever. The soldering apparatus according to appendix 7.

(Supplementary note 9) Soldering according to supplementary note 7 or 8, further comprising a regulating member that regulates a pivot amount of the lever and regulates a pull amount when the component is pulled away from the printed circuit board. apparatus.

(Supplementary note 10) The soldering apparatus according to supplementary note 9, wherein a plurality of the regulating members are prepared corresponding to a plurality of the lifting amounts, and those corresponding to a desired lifting amount are selectively used. .

100 Printed Circuit Board 100c Opening 101 Through Hole 120 Component (Electronic Component)
120d concave groove 121 lead 130 solder bath 300 soldering apparatus 301 solder tank 302 lifting mechanism 303 holding arm 304 moving table 305 rail 500 lifting jig 501a locking holding portion 503 holding block 504 shaft 505 lever 505b protruding piece 505c pushing piece 901 ( 901a to 901d) Moving amount variable frame

Claims (3)

A first step of immersing the printed board in a solder bath;
A second step of inserting a lead of a component to be soldered into the through hole of the printed circuit board and bringing the lead into contact with the solder bath;
A third step of pulling up the lead within the through hole so that the tip of the lead has a range equal to or less than a printed circuit board thickness ;
As a state where the component is attached to the printed board, a fourth step of taking out the printed board from the solder bath,
A soldering method comprising: The length of the lead is set longer than the thickness of the printed circuit board,
2. The soldering method according to claim 1, wherein, in the second step, the tip of the lead is immersed in the solder bath for a predetermined length. Wherein in the fourth step, pushing the lead into the through-hole, in a state fitted with the components on the printed circuit board, to claim 1 or 2, characterized in the score eject the said printed circuit board from the solder bath The soldering method as described.

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