JP7742625B2 - Soldering method - Google Patents

Description

The present invention relates to a soldering method, and more specifically to a method for inserting a pin terminal of an electronic component into a through-hole in a printed circuit board and soldering it to a land formed on the outer edge of the through-hole.

In recent years, most devices are equipped with printed circuit boards on which electronic components are mounted. During the manufacturing process of these printed circuit boards, soldering is performed to join various electronic components to the wiring patterns (lands) on the printed wiring board. In addition, various soldering devices have been proposed to mechanically perform the soldering process, and some are already in use.

For example, one type of soldering device supplies a solder piece (a piece of cut wire solder with a layer of flux inside the solder layer) into a solder hole that penetrates the axial direction of a roughly cylindrical iron tip, heats and melts the solder piece in an upright position within the solder hole, and then supplies the molten solder downward to perform the soldering.

Japanese Patent Application Publication No. 09-108826 JP 2011-056581 A JP 2009-195938 A

When using the proposed soldering device to insert a pin terminal of an electronic component into a through-hole in a printed circuit board and solder it to a land formed on the outer edge of the through-hole, it is necessary to move the soldering iron tip and the printed circuit board relative to each other to position the pin terminal within the solder hole. To increase the tolerance for controlling the relative movement, an enlarged section that enlarges the inner wall of the solder hole radially outward is sometimes provided at the lower end of the soldering iron tip.

As shown in Figure 9(a), when soldering a pin terminal P to a land Ld using a soldering iron tip with such an enlarged portion 510, the solder piece Wh supplied into the solder hole 51 first comes into contact with the tip of the pin terminal P. The solder piece Wh then receives heat from the soldering iron and begins to melt, and heat is transferred from the soldering iron to the pin terminal P via this molten solder piece Wh. When the temperature of the tip of the pin terminal P reaches a predetermined temperature or higher, the molten solder flows down along the pin terminal P, as shown in Figure 9(b). At this time, if the spatial volume of the enlarged portion (solder hole) 510 is large compared to the volume of the molten solder, the molten solder may not come into contact with the inner surface of the enlarged portion 510.

If the molten solder does not contact the inner peripheral surface of the enlarged portion 510, heat will not be transferred from the soldering iron to the pin terminal P or land Ld via the molten solder, resulting in a decrease in the amount of heat transferred from the soldering iron to the pin terminal P or land Ld. This decrease in heat transfer can lead to insufficient heating of the pin terminal P or land Ld, resulting in insufficient soldering. This insufficient heating is particularly noticeable when the thermal capacity of the terminal Ta to which the pin terminal P is connected is large, as shown in Figure 10(a), or when the area of the land Ld is large, as shown in Figure 10(b). While extending the soldering time is one possible solution to this problem, this creates a new problem: reduced efficiency of the soldering process.

The present invention was made in consideration of these conventional problems, and its purpose is to provide a method that enables good soldering without reducing the efficiency of the soldering work.

A soldering method according to one aspect of the present invention that achieves the above object is a soldering method in which a pin terminal protruding outward from a component body of an electronic component is inserted into a through hole formed in a printed circuit board using a heatable soldering iron tip that is approximately cylindrical and has a solder hole penetrating in the axial direction, and soldered to a land formed on the outer periphery of the through hole, the method comprising the steps of: bringing the soldering iron tip into contact with the printed circuit board so that a tip end of the pin terminal inserted into the through hole and protruding from the printed circuit board is positioned within the solder hole; supplying a solder piece into the solder hole; and soldering the supplied solder piece to the soldering iron tip. and a step of heating and melting the solder piece inserted into the solder hole to solder the pin terminal and the land, wherein the solder hole has an enlarged portion at its lower end that expands radially outward, the axial length of the enlarged portion from the lower end opening of the solder hole is longer than the length of the pin terminal protruding from the surface of the printed circuit board, and when the tip of the iron is in contact with the printed circuit board, an internal volume Vh of the solder hole from the tip of the pin terminal inserted into the solder hole to the lower end opening of the solder hole and a volume Vs of the solder piece satisfy the following formula (1):
Vs≧ 1.30×( Vh−Vp ₁ )・・・(1)
Vs: volume of solder piece Vh: internal volume of solder hole from the tip of pin terminal inserted into solder hole to the lower opening of the solder hole _Vp1 : volume of pin terminal located in solder hole

With this configuration, the solder hole is filled with molten solder up to the tip of the pin terminal or further, allowing heat to be efficiently transferred from the soldering iron to the pin terminal and land via the molten solder.

In the soldering method, it is preferable that the following formula (2) be further satisfied:
Vs≧ 1.30×( Vh-Vp ₁ ) +Vt-Vp ₂ ...(2)
Vt: Volume of the through-hole _Vp2 : Volume of the pin terminal located in the through-hole

As a result, even if molten solder flows into the through-hole, the solder hole will be filled with molten solder up to the tip of the pin terminal or even further, ensuring that heat is efficiently transferred from the soldering iron to the pin terminal and land via the molten solder.

In the soldering method, the solder hole may have an enlarged portion at its lower end that expands radially outward, and the axial length of the enlarged portion from the lower end opening of the solder hole may be longer than the length of the pin terminal that protrudes from the surface of the printed circuit board. Here, when viewed from below, the enlarged portion may expand radially outward from the entire outer periphery of the solder hole.

The soldering method of the present invention enables good soldering without reducing the efficiency of the soldering work.

1 is a perspective view of an example of a soldering apparatus AP according to an embodiment of the present invention. FIG. 2 is a perspective view showing the internal structure of the device main body A1. 3 is a schematic vertical cross-sectional view of the device main body A1 shown in FIG. 2. 3 is an exploded perspective view of a part of a drive mechanism provided in the apparatus main body A1 shown in FIG. 2. FIG. 1 is a partial vertical cross-sectional view of the iron tip 5a and the printed circuit board Bd. 10 is a diagram showing the operation process of soldering by the soldering device AP. FIG. 10 is a diagram showing the operation process of soldering by the soldering device AP. FIG. 10 is a diagram showing the state of soldering when using a soldering iron tip 5b. 1 is an example of a state diagram of conventional soldering. This is a state diagram when a terminal Ta with a large heat capacity and a land Ld with a large area are soldered.

The soldering method and soldering device used in the present invention will be described with reference to the accompanying drawings, but the present invention is not limited to these embodiments.

First embodiment (overall configuration of soldering device)
1 is a perspective view of a soldering apparatus AP soldering an electronic component Ep to a printed circuit board Bd. The printed circuit board Bd is fixed to a jig Gj and has four through holes Th formed therein, each with a land Ld formed around its periphery. Four pin terminals P extending from an electronic component Ep arranged on the back surface of the printed circuit board Bd are inserted upward into each of the four through holes Th, with the tips of the pin terminals P projecting from the top surface of the printed circuit board Bd.

Meanwhile, the soldering device AP comprises a manipulator ML as a moving means having a multi-joint arm Am, a device main body A1 attached to the tip of the manipulator ML, and a control device Cont that controls the operation of the manipulator ML and device main body A1. The manipulator ML is mounted on a base Bs, and the multi-joint arm Am is rotatable at each of its multiple joints. The control device Cont controls the rotational operation of the multi-joint arm Am of the manipulator ML to move the device main body A1 to the desired position in the X, Y, and Z directions. The control device Cont also controls the operation of the cutter unit 2, drive mechanism 3, solder feed mechanism 6, and heater unit (heating means) 4 of the device main body A1, which will be described later. In this embodiment, the cutter unit 2, drive mechanism 3, and solder feed mechanism 6 constitute the solder piece supply means.

When soldering is performed using the soldering device AP, the device body A1 is moved in the X and Y directions by the manipulator ML to position it relative to the land Ld of the printed circuit board Bd. Then, by moving the device body A1 in the Z direction, the tip of the iron tip 5a comes into contact with the land Ld. In the embodiment described below, this soldering device AP is used to position the pin terminal P protruding from the top surface of the printed circuit board Bd within the solder hole 51 (shown in Figure 3) of the iron tip 5a of the device body A1, and then melt the solder piece Wh supplied to the solder hole 51 of the iron tip 5a to solder the pin terminal P to the land Ld. Note that in this embodiment, the device body A1 is moved; however, the device body A1 may be fixed and the printed circuit board Bd may be moved, or both the device body A1 and the printed circuit board Bd may be moved.

(Device main body A1)
Fig. 2 shows a perspective view of the device main body A1, Fig. 3 shows a vertical cross-sectional view of the soldering device shown in Fig. 2, and Fig. 4 is an exploded perspective view of a part of the drive mechanism provided in the soldering device shown in Fig. 2. In Fig. 2, a part of the housing is cut away to show the inside of the device main body A1.

As shown in Figure 2, the device main body A1 has a device unit U, a support member SP that supports the device unit U so that it can move within a predetermined distance range in the Z direction, and a cover C (indicated by a wavy line in Figure 2) that covers the device unit U and the support member SP.

The support member SP comprises a plate-shaped base Mf having a rectangular YZ plane and a predetermined thickness in the X direction; a guide rail Mg having a predetermined width in the Y direction at the center of the Y direction on one side of the X direction of the base Mf, protruding in the X direction and continuing in the Z direction; and a block Mb attached to the guide rail Mg so as to be movable in the Z direction.

The upper end of the base Mf in the Z direction is attached to the tip of the articulated arm Am of the manipulator ML. The wall 11 of the equipment unit U is attached to the block Mb over almost the entire area in the Z direction. In other words, the equipment unit U is fixed to the block Mb and can move in the Z direction together with the block Mb. In addition, a movement restriction pin 91 is provided at the lower end of one side surface of the block Mb in the Y direction, protruding vertically outward from the side surface.

On the other hand, at the Y-direction end position of the lower Z-direction portion of one side surface in the X-direction of the base Mf, rectangular parallelepiped upper and lower stopper portions 93 and 94 are provided facing each other and spaced a predetermined distance apart in the Z-direction.

The movement restriction pin 91 provided on one side of the block Mb is located in the area between the upper stopper portion 93 and the lower stopper portion 94 of the base Mf. In the initial state, i.e., when the iron tip 5a is not in contact with the wiring board Bd, the weight of the device unit U and block Mb causes the movement restriction pin 91 to abut against the lower stopper portion 94. In other words, when the movement restriction pin 91 abuts against the lower stopper portion 94, downward movement of the device unit U in the Z direction is restricted. On the other hand, when the iron tip 5a abuts against the wiring board Bd and the device unit U moves upward in the Z direction, the movement restriction pin 91 abuts against the upper stopper portion 93, restricting upward movement of the device unit U in the Z direction.

(Device unit U)
The device unit U includes a support portion 1 , a cutter unit 2 , a drive mechanism 3 , a heater unit 4 , an iron tip 5 a , and a solder feed mechanism 6 .

The support portion 1 includes a flat, upright wall 11. For convenience, in the following description, as shown in Figure 2, the horizontal direction along the wall 11 is referred to as the X direction, the horizontal direction perpendicular to the wall 11 as the Y direction, and the vertical direction along the wall 11 as the Z direction. For example, as shown in Figure 2, the wall 11 has a ZX plane.

The support section 1 comprises a wall 11, a holding section 12, a sliding guide 13, and a heater unit fixing section 14. The wall 11 is a flat wall erected in the vertical direction. The wall 11 serves as a support member for the device main body A1. The holding section 12 is fixed at a position offset above the lower end of the wall 11 in the Z direction. The holding section 12 holds an air cylinder 31 (described below) of the drive mechanism 3. The heater unit fixing section 14 is a member that fixes the heater unit 4, and is provided at the end (lower end) of the wall 11 in the Z direction.

The sliding guide 13 is fixed near the lower end of the wall 11 in the Z direction. The sliding guide 13 is fixed to the wall 11 together with the lower cutter blade 22 of the cutter unit 2 (described later), and guides the upper cutter blade 21 of the cutter unit 2 (described later) so that it can slide in the X direction.

The sliding guides 13 are a pair of members facing each other in the Y direction. The sliding guides 13 have a pair of wall portions 131 and a retaining portion 132. The wall portions 131 are flat members extending in the X direction. One wall portion 131 is arranged in contact with the wall body 11, and the surface opposite the wall body 11 is in contact with the cutter lower end 22. The other wall portion 131 is in contact with the side of the cutter lower blade 22. In other words, the pair of wall portions 131 sandwich the cutter lower blade 22 from both sides in the Y direction. The pair of wall portions 131 and the cutter lower blade 22 are then fastened together to the wall body 11 with fasteners such as screws and fixed thereto.

A retaining portion 132 is provided on each of the pair of wall portions 131. The pair of wall portions 131 extend in the Z direction beyond the Z-direction upper surface of the lower cutter blade 22, and extend from the Z-direction upper end portions of the pair of wall portions 131 toward the other. In other words, the sliding guide 13 is provided with a pair of retaining portions 132. The Y-direction tips of the pair of retaining portions 132 do not contact each other; in other words, the sliding guide 13 has an opening at the top. At least a portion of the upper cutter blade 21 is positioned between the upper surface of the lower cutter blade 22 and the retaining portion 132. As a result, the upper cutter blade 21 is guided in the X direction and prevented from coming off in the Z direction.

The cutter unit 2 is a cutting tool that cuts the wire solder W fed by the solder feed mechanism 6 into solder pieces Wh of a predetermined length. The cutter unit 2 includes an upper cutter blade 21, a lower cutter blade 22, and a pusher pin 23.

As described above, the lower cutter blade 22 is fixed to the wall 11 together with the sliding guide 13. As shown in FIG. 3, the lower cutter blade 22 has a lower blade hole 221 and a gas inlet hole 222. The lower blade hole 221 is a through-hole that penetrates the lower cutter blade 22 in the Z direction, and receives the solder wire W that has penetrated the upper blade hole 211 (described later) of the upper cutter blade 21. The upper edge of the lower blade hole 221 is formed like a cutting blade. The upper blade hole 211 and the lower blade hole 221 are used to cut the solder wire W into solder pieces Wh of a predetermined length. The cut solder pieces Wh fall downward inside the lower blade hole 221 by their own weight or by being pushed by the pusher pin 23. The lower blade hole 221 is connected to the solder hole 51 (described later) of the iron tip 5a via the solder supply hole 422 (described later) of the heater unit 4. The solder piece Wh that falls inside the lower blade hole 221 reaches the solder supply hole 422 and then falls into the solder hole 51.

The gas inlet hole 222 is a hole that connects the outer surface of the cutter lower blade 22 with the lower blade hole 221. Gas supplied from a gas supply source (not shown) flows into the gas inlet hole 222. The gas then passes through the lower blade hole 221 and the solder supply hole 422 and reaches the solder hole 51. Note that this gas is used to suppress oxidation of the solder when it is heated and melted. In other words, it is a gas that suppresses contact between the molten solder and oxygen. Examples of gases that can be used include nitrogen gas, argon gas, helium gas, and carbon dioxide. In the soldering device AP of this embodiment, nitrogen gas is supplied.

As described above, the upper cutter blade 21 is disposed on the Z-direction upper surface of the lower cutter blade 22. The upper cutter blade 21 is guided by the sliding guide 13 so that its sliding direction is in the X direction when it slides, and is prevented from slipping out in the Z direction. In other words, the upper cutter blade 21 slides in the X direction on the Z-direction upper surface of the lower cutter blade 22. The upper cutter blade 21 is slid by the drive mechanism 3.

The upper cutter blade 21 has an upper blade hole 211 and a pin hole 212. The upper blade hole 211 is a through-hole that passes through the upper cutter blade 21 in the Z direction. The wire solder W fed from the solder feed mechanism 6 is inserted into the upper blade hole 211. The lower edge of the upper blade hole 211 is formed into a cutting blade shape. The pin hole 212 is a through-hole that passes through the upper cutter blade 21 in the Z direction. The rod portion 231 (described later) of the pusher pin 23 is slidably inserted into the pin hole 212.

The pusher pin 23 has a rod portion 231, a head portion 232, and a spring 233. The rod portion 231 is a cylindrical member that is slidably inserted into the pin hole 212. When the pusher pin 23 moves downward in the Z direction, the tip of the rod portion 23 protrudes from the pin hole 212. The head portion 232 is connected to the upper end of the rod portion 231 in the axial direction. The head portion 232 is disc-shaped and has an outer diameter that is larger than the inner diameter of the pin hole 212. The head portion 232 is not inserted into the pin hole 212. In other words, the head portion 232 acts as a stopper that limits the movement of the rod portion 231 into the pin hole 212.

The spring 233 is a compression coil spring that surrounds the radial outside of the rod portion 231. The lower end of the spring 233 in the Z direction contacts the upper surface of the cutter upper blade 21, and the upper end of the spring 233 in the Z direction contacts the lower surface of the head portion 232. In other words, the spring 233 receives a reaction force from the upper surface of the cutter upper blade 21, pushing the head portion 232 upward in the Z direction. As a result, the rod portion 231 connected to the head portion 232 is lifted upward in the Z direction, and the lower end of the rod portion 231 is maintained so that it does not protrude from the lower end of the pin hole 212. The lower end of the rod portion 231 in the Z direction is provided with a stopper (not shown) that prevents it from coming out of the pin hole 212.

The pusher pin 23 pushes downward the solder piece Wh that has been cut by the upper cutter blade 21 and the lower cutter blade 22 and remains in the lower blade hole 221. The pusher pin 23 is constantly pushed upward, i.e., toward the opposite side from the lower cutter blade 22, by the elastic force of the spring 233. In other words, when the head portion 232 is pushed, the rod portion 231 protrudes downward from the lower end of the pin hole 212 in the Z direction. The head portion 232 is then pushed by the cam member 33 of the drive mechanism 3, which will be described later.

In the upper cutter blade 21, the upper blade hole 211 and pin hole 212 are arranged side by side in the X direction. By sliding in the X direction, the upper cutter blade 21 moves to a position where the upper blade hole 211 and lower blade hole 221 overlap vertically, or to a position where the pin hole 212 and lower blade hole 221 overlap vertically. The upper cutter blade 21 may slide so that the upper blade hole 211 and lower blade hole 221 overlap when it slides to one sliding end, and the pin hole 212 and lower blade hole 221 overlap when it slides to the other sliding end.

When the upper blade hole 211 and the lower blade hole 221 are overlapping in the Z direction and wire solder W is fed from the solder feed mechanism 6, the wire solder W that passes through the upper blade hole 211 is inserted into the lower blade hole 221. As described above, the lower edge of the upper blade hole 211 is formed like a cutting edge, and the upper edge of the lower blade hole 221 is also formed like a cutting edge. The lower surface of the upper cutter blade 21 contacts the upper surface of the lower cutter blade 22. Therefore, when the upper cutter blade 21 slides in the X direction with the wire solder W inserted into the lower blade hole 221, the wire solder W is cut by the cutting edges of the upper blade hole 211 and the lower blade hole 221.

The upper cutter blade 21 is slid in the X direction by the cam member 33. Therefore, the upper cutter blade 21 and pusher pin 23 are synchronized with the cam member 33. The cam member 33 pushes the head portion 232 when the pin hole 212 overlaps with the lower blade hole 221 in the Z direction. Therefore, when the upper cutter blade 21 slides in the X direction, the tip of the rod portion 231 of the pusher pin 23 is housed in the pin hole 212. Therefore, when the upper cutter blade 21 slides in the X direction, contact between the tip of the rod portion 231 and the upper surface of the lower cutter blade 22 is prevented, and deformation or damage to the tip of the rod portion 231 and/or the lower cutter blade 22 is prevented.

As the upper cutter blade 21 slides in the X direction, the lower blade hole 211 and the pin hole 212 overlap in the Z direction. With the pin hole 212 overlapping the lower blade hole 211, the head portion 232 is pushed by the cam member 33. This causes the pusher pin 23 to move downward in the Z direction. When the pusher pin 23 protrudes downward in the Z direction from the pin hole 212, part of the pusher pin 23 is inserted into the lower blade hole 211. If a piece of solder (described below) remains at the entrance to the lower blade hole 211 after cutting the solder wire, the tip of the pusher pin 23 will push the piece of solder, causing it to fall.

As shown in Figures 2 and 3, the drive mechanism 3 has an air cylinder 31, a piston rod 32, a cam member 33, a slider portion 34, and a guide shaft 35. The air cylinder 31 is held in the holder 12. The air cylinder 31 is cylindrical with a bottom. A piston rod 32 is housed inside the air cylinder 31, and the piston rod 32 is slidably driven (extends and retracts) by air pressure supplied from the outside. The air cylinder 31 and the piston rod 32 form the actuator of the drive mechanism 3. The piston rod 32 is disposed inside the air cylinder 31, and a portion of the piston rod 32 always protrudes from one axial end of the air cylinder 31 (here, the lower end in the Z direction). The air cylinder 31 is held in the holder 12 so that the surface from which the piston rod 32 protrudes faces the cutter unit 2, i.e., faces downward in the Z direction.

The piston rod 32 passes through a through-hole (not shown) provided in the holding portion 12. The piston rod 32 is provided parallel to the guide shaft 35 and moves linearly back and forth along the guide shaft 35. The tip of the piston rod 32 is fixed to a cam member 33, and as the piston rod 32 expands and contracts, the cam member 33 slides in the Z direction. The sliding of the cam member 33 is guided by the guide shaft 35.

As shown in Figure 3, the lower end of the guide shaft 35 fits into a recessed hole provided in the lower cutter blade 22 and is fixed to the lower cutter blade 22 with a screw 351. The upper part of the guide shaft 35 passes through a hole provided in the holder 12, and its movement is restricted by a pin 352. In other words, the guide shaft 35 is fixed to the lower cutter blade 22 by the screw 351 and to the holder 12 by the pin 352.

In this embodiment, the guide shaft 35 is fixed by a screw 351 and a pin 352, but this is not limited to this and it may be fixed by a fixing method such as press fitting or welding. In addition, in this embodiment, the guide shaft 35 is a cylindrical member, but this is not limited to this and it may also be a polygonal or elliptical cross-section.

As shown in Figures 3 and 4, the cam member 33 is a rectangular member and includes a recess 330 formed by cutting out a portion of the long side in a rectangular shape, and a cylindrical support portion 331 connected to the cam member 33 and having a through-hole through which the guide shaft 35 passes. The slider portion 34 is slidably disposed in the recess 330 (in the X and Z directions). The support portion 331 extends parallel to the guide shaft 35 and is provided to suppress rattle of the cam member 33. In other words, if the cam member 33 has a certain thickness and is configured to be less likely to rattle, the cylindrical portion may be omitted and the support portion 331 may consist solely of a through-hole.

The cam member 33 comprises a cylindrical pin 332 located in the middle of the recess 330 and whose central axis is perpendicular to the guide shaft 35, a pin pressing portion 333 adjacent to the recess 330 that presses the pusher pin 23, and a bearing 334 located inside the support portion 331. The pin 332 is inserted into a cam groove 340 (described below) located in the slider portion 34. The bearing 334 is fitted onto the guide shaft 35 and is a member that allows the cam member 33 to slide smoothly and prevent rattling.

As shown in Figures 3 and 4, the slider portion 34 is a rectangular plate-like member that is formed integrally with the upper cutter blade 21. The slider portion 34 has a cam groove 340 that penetrates the plate in the thickness direction and extends in the longitudinal direction. The cam groove 340 has a first groove portion 341 on the upper side that extends parallel to the guide shaft 35, and a second groove portion 342 on the lower side that also extends parallel to the guide shaft 35. The first groove portion 341 and the second groove portion 342 are offset in the X direction, and the cam groove 340 has a connecting groove portion 343 that connects the first groove portion 341 and the second groove portion 342.

The pin 332 of the cam member 33 is inserted into the cam groove 340, and as the cam member 33 moves along the guide shaft 35, the pin 332 slides on the inner surface of the cam groove 340. When the pin 332 is positioned in the connecting groove portion 343 of the cam groove 340, it presses on the inner surface of the connecting groove portion 343. This causes the slider portion 34 and the upper cutter blade 21 formed integrally with the slider portion 34 to move (slide relative to the lower cutter blade 22) in the direction (X direction) that intersects the sliding direction (Z direction) of the cam member 33.

In this embodiment, a configuration is described in which the cam member 33 has a pin 332 and the slide portion 34 has a cam groove 340, but in reality, a configuration in which the cam member has a cam groove and the slide portion has a pin may also be used.

In this embodiment, air pressure is used as the actuator for the drive mechanism 3, but this is not limited to this and it may also be a system that uses a fluid other than air (for example, hydraulic oil) (hydraulics). Furthermore, this is not limited to using a fluid and it may also be a system that uses electricity, such as a motor or solenoid. In this embodiment, one actuator, cam, and cam groove are used to slide the upper cutter blade 21 and press down the pusher pin 23, but this is not limited to this. For example, multiple actuators (two) may be provided to slide the upper cutter blade 21 and press down the pusher pin 23.

As shown in Figures 2 and 3, the solder feed mechanism 6 supplies the solder wire W. The solder feed mechanism 6 includes a pair of feed rollers 61 and a guide tube 62. The pair of feed rollers 61 are rotatably attached to the support wall 11. The pair of feed rollers 61 feed the solder wire W downward by rotating while sandwiching the sides of the solder wire W between them. The pair of feed rollers 61 are biased toward each other, and this biasing force pinches the solder wire W between them. The length of the fed solder wire W is measured (determined) based on the rotation angle (number of rotations) of the feed rollers 61.

The guide tube 62 is an elastically deformable tube, and its upper end is located close to the portion of the feed roller 61 from which the solder wire W is fed. The lower end of the guide tube 62 is arranged to communicate with the upper blade hole 211 of the upper cutter blade 21. The lower end of the guide tube 62 moves in conjunction with the sliding of the upper cutter blade 21, and the guide tube 62 has a length and shape that prevents it from being excessively pulled or strained within the sliding range of the upper cutter blade 21.

The heater unit 4 is a heating device for heating and melting the solder pieces Wh, and as shown in FIG. 3, is fixed to the heater unit fixing portion 14 provided at the lower end of the wall body 22. The heater unit 4 includes a heater 41 and a heater block 42. The heater 41 generates heat when electricity is applied. In this example, the heater 41 has an electric heating wire wound around the outer periphery of the cylindrical heater block 42.

The heater block 42 has a cylindrical shape and is provided with a recess 421 with a circular cross section at its axial end for attaching the iron tip 5a, and a solder supply hole 422 that penetrates from the center of the bottom of the recess 421 to the opposite side. The heater block 42 is provided in contact with the cutter lower blade 22 so that the solder supply hole 422 and the lower blade hole 221 are in communication. By providing the heater block 42 in this manner, the solder piece Wh moves from the lower blade hole 221 to the solder supply hole 422.

(trowel tip)
The iron tip 5a is a cylindrical member with a solder hole 51 that penetrates the center in the axial direction and has a circular cross section. The iron tip 5a is inserted into a recess 421 in the heater block 42 and is prevented from coming out by a member (not shown). The solder hole 51 in the iron tip 5a is also connected to a solder supply hole 422 in the heater block 42, and solder pieces Wh are fed from the solder supply hole 422.

Figure 5 shows a partial vertical cross-sectional view of the lower portion of the iron tip 5a and the printed circuit board Bd. As mentioned above, the iron tip 5a has a cylindrical solder hole 51 with a radius r that penetrates the axial direction. The solder hole 51 has an enlarged portion 510 with a radius R that expands radially outward at its lower end, concentrically with the solder hole 51. The axial length M of the enlarged portion 510 from the lower opening of the solder hole 51 is set longer than the protruding length S of the pin terminal P from the printed circuit board Bd. The formation of the enlarged portion 510 on the iron tip 5a allows the pin terminal P to be positioned within the enlarged portion 510 of the iron tip 5a even if the axial center C2 of the pin terminal P and the axial center C1 of the iron tip 5a are not aligned. This increases the tolerance for controlling the relative movement of the iron tip 5a by the control means Cont. The diameter (2 × r) of the solder hole 51 is set larger than the outer diameter d of the solder piece Wh. The outer diameter d of the solder piece Wh is typically in the range of 0.6 mm to 1.2 mm. The iron tip 5a also has a release hole 53 above the enlarged portion 510 that connects the solder hole 51 to the outer periphery. The release hole 53 serves to allow nitrogen gas supplied from a gas supply unit (not shown) and vaporized flux to escape from the iron tip 5a when the lower end opening of the solder hole 51 is blocked by molten solder.

Heat is transferred from the heater 41 to the iron tip 5a, which melts the solder piece Wh. For this reason, the iron tip 5a is made of a material with high thermal conductivity, such as ceramics such as silicon carbide or aluminum nitride, or metals such as tungsten.

In the device main body A1, the iron tip 5a is cylindrical, but this is not limited to this and a cylindrical tip with a polygonal or elliptical cross section may also be used. It is also possible to prepare iron tips of different shapes to match the shape of the printed circuit board Bd or pin terminals P of the electronic component Ep to be soldered.

In the soldering method of the present invention, it is important that the internal volume Vh of the solder hole 51 from the upper end of the pin terminal P inserted into the solder hole 51 to the lower opening of the solder hole 51 and the volume Vs of the solder piece Wh supplied to the solder hole 51 satisfy the above formula (1). Since the volume Vs of the solder piece Wh can be considered to be approximately equal to the volume of the molten solder piece Wh, the above formula (1) specifies that when the soldering iron tip 5a is in contact with the printed circuit board Bd, the molten solder melted from the solder piece Wh has a volume equal to or greater than the spatial volume of the solder hole 51 obtained by subtracting the volume _Vp1 of the pin terminal P located in the solder hole 51 from the internal volume Vh of the solder hole 51 from the upper end of the pin terminal P inserted into the solder hole 51 to the lower opening of the solder hole 51.
In the case of solder pieces Wh containing flux FL, it is possible to increase the amount of solder supplied in consideration of the flux FL flowing out and reducing the volume of the solder pieces Wh. However, since the flux FL is usually contained inside the solder pieces Wh, when the solder pieces Wh begin to melt, the flux FL mixes with the solder pieces Wh integrally, and the change in volume of the solder pieces Wh due to the outflow of the flux FL is small.

By satisfying formula (1) above, the space within the solder hole 51 from the lower opening of the solder hole 51 to the tip of the pin terminal P or above is filled with molten solder, as shown in Figure 7(a) below. Because the thermal conductivity of molten solder is significantly higher than that of gas, heat is transferred more quickly from the iron tip 5a to the pin terminal P and land Ld via the molten solder than when the space within the solder hole 51 is not fully filled with molten solder, effectively preventing problems such as poor soldering.

Furthermore, while heat is being transferred from the soldering iron tip 5a to the pin terminal P or land Ld via the molten solder, the molten solder may flow down into the gap between the inner wall of the through hole Th and the pin terminal P. Even in such a case, it is preferable that the above formula (2) be satisfied so that the space within the solder hole 51 from the lower opening of the solder hole 51 to the tip of the pin terminal P is filled with molten solder. That is, it is preferable that the volume Vs of the molten solder is equal to or greater than the volume of the space within the solder hole 51, calculated by subtracting the volume Vp1 of the pin terminal P located within the solder hole ₅₁ from the internal volume Vh of the solder hole 51 from the upper end of the pin terminal P inserted into the solder hole 51 to the lower opening of the solder hole 51, plus the volume of the space within the through hole Th. Furthermore, if a back fillet is formed at the lower end of the through hole Th, the solder supply amount may be set taking into account the volume of the fillet. A more preferable value of Vs/(Vh- _Vp1 ) is 1.30 or greater.

(Operation of soldering device)
Next, the operation of the soldering apparatus AP will be described. Operational flow charts are shown in Figures 6 and 7. First, as shown in Figure 6(a), the control means Cont controls the rotation of the articulated arm Am of the manipulator ML to move the soldering tip 5a of the apparatus main body A1 to a position (separate position) where the axis C1 of the soldering tip 5a is aligned with and spaced upward from the axis C2 of the pin terminal P protruding from the printed circuit board Bd.

Next, as shown in Figure 6(b), the control means Cont controls the manipulator ML to move the iron tip 5a downward, bringing the lower end of the iron tip 5a into contact with the resist Re (or land Ld) of the printed circuit board Bd and positioning the pin terminal P of the electronic component Ep within the enlarged portion 510 of the solder hole 51 in the iron tip 5a. Then, a solder piece Wh is supplied into the solder hole 51 in the iron tip 5a. The lower end of the supplied solder piece Wh abuts against the tip of the pin terminal P and the upper end contacts the inner wall of the solder hole 51, causing the solder piece Wh to stand upright within the solder hole 51. Heat is transferred from the heater 41 (shown in Figure 3) to the iron tip 5a, and heat is transferred directly from the iron tip 5a to the solder piece Wh, heating it.

When the temperature of the solder piece Wh reaches the melting temperature of the flux FL (shown in Figure 5), the flux FL flows out of the solder piece Wh, removing the oxide film with low thermal conductivity on the surface of the solder piece Wh and promoting heat transfer from the iron tip 5a to the solder piece Wh. Then, as shown in Figure 6(c), when the temperature of the solder piece Wh reaches the melting temperature of the solder, the molten solder attempts to become spherical due to surface tension, but is restrained by the solder hole 51 and remains on the pin terminal P.

Then, when the pin terminal P is heated by the iron tip 5a via the molten solder and the temperature of the tip of the pin terminal P exceeds the melting temperature of the solder, the molten solder flows down the pin terminal P, filling the entire enlarged portion 510 of the solder hole 51, as shown in Figure 7(a), with some of the molten solder remaining in the upper solder hole 51 without being able to flow into the enlarged portion 510.

In this way, the entire pin terminal P in the solder hole 51 is immersed in molten solder, allowing heat to be quickly transferred from the iron tip 5a to the entire pin terminal P via the molten solder. When the entire pin terminal P and land Ld are heated to a temperature above the melting point of the solder, the molten solder flows down the pin terminal P into the through hole Th, as shown in Figure 7(b). Then, as shown in Figure 7(c), the molten solder wets and spreads over the land Ld, from which the oxide film has been removed by the flux FL. At the same time, the molten solder, whose surface tension has been reduced by the flux FL and heating, forms a clean fillet without becoming spherical.

The control means Cont then controls the manipulator ML to move the soldering iron tip 5a upward. This causes the molten solder to be cooled and solidified by the outside air, soldering the pin terminals P of the electronic component Ep to the lands Ld of the printed circuit board Bd. The soldering device AP repeats this series of operations to sequentially solder the pin terminals P of the electronic component Ep to the lands Ld of the printed circuit board Bd.

In this embodiment, the printed circuit board Bd is fixed and the iron tip 5a is moved, but the iron tip 5a may be fixed and the printed circuit board Bd may be moved. Alternatively, both the printed circuit board Bd and the iron tip 5a may be moved.

Second Embodiment
Another embodiment of the soldering tip that can be used in the soldering method according to the present invention is shown in Fig. 8. Fig. 8 is a partial vertical cross-sectional view of the soldering tip 5b and the printed circuit board Bd.

The iron tip 5b shown in Figure 8 is the same as the iron tip 5a of the first embodiment in that it has a cylindrical solder hole 51 with a radius r that penetrates the axial direction. However, it differs from the iron tip 5a in that the solder hole 51 does not have an enlarged portion 510 at its lower end. Even with this shape of iron tip 5b, the internal volume Vh of the solder hole 51 from the upper end of the pin terminal P inserted into the solder hole 51 to the lower opening of the solder hole 51, and the volume Vs of the solder piece Wh supplied to the solder hole 51, satisfy equation (1). As a result, as with the soldering device SP of the first embodiment, the entire pin terminal P in the solder hole 51 is submerged in the molten solder that flows down the pin terminal P, as shown in Figure 8(b). This allows heat to be quickly transferred from the iron tip 5b to the entire pin terminal P via the molten solder.

Experimental Examples 1 to 6
5, soldering was performed by changing the volume (length L) of the solder piece using the soldering iron tip having the following dimensions, and the soldering was evaluated according to the following criteria. The evaluation results are shown in Table 1.
Solder hole radius r: 0.585 mm
Radius of enlarged portion R: 0.730 mm
Height of enlarged part M: 2.0 mm
Outer diameter D of pin terminal: 0.64 mm x 0.64 mm
Pin terminal protrusion S: 1.55 mm
Outer diameter of solder piece d: 0.8 mm
Solder piece length L: 3 mm, 4 mm, 5 mm, 5.5 mm, 6 mm, 7 mm

(Evaluation criteria)
The tip of the iron was brought into contact with the printed circuit board, and two seconds later, a solder piece was supplied into the solder hole. Four seconds after the solder piece was supplied, the tip of the iron was removed from the printed circuit board, and the state of the soldering was visually observed and evaluated according to the following criteria.
"○": Solder has filled the entire through-hole. "△": Solder has filled about half of the through-hole. "×": Solder has not filled the through-hole.

In Experimental Examples 2 and 3, where soldering was performed under conditions that satisfied formula (1) defined in the present invention, i.e., Vs/(Vh- _Vp1 ) was 1.03 and 1.28, the solder filled approximately half of the through-hole, resulting in relatively good soldering. Furthermore, in Experimental Examples 4 to 6, where soldering was performed under conditions where Vs/(Vh- _Vp1 ) was 1.41 or higher, the solder filled the entire through-hole, resulting in even better soldering.
In contrast to this, in the soldering of Experimental Example 1 where Vs/(Vh-Vp ₁ ) was "0.77", the pin terminals and the like were not heated sufficiently and the molten solder did not flow into the through-holes at all.

Experimental Examples 7 to 12
5, soldering was performed by changing the volume (length L) of the solder piece using the soldering iron tip having the following dimensions, and the soldering was evaluated according to the above criteria. The evaluation results are shown in Table 2.
Solder hole radius r: 0.505 mm
Radius of enlarged portion R: 0.635 mm
Height of enlarged part M: 1.85 mm
Outer diameter D of pin terminal: 0.64 mm x 0.64 mm
Pin terminal protrusion S: 1.55 mm
Outer diameter of solder piece d: 0.8 mm
Solder piece length L: 2 mm, 2.7 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm

In Experimental Examples 8 and 9, where soldering was performed under conditions that satisfied formula (1) defined in the present invention, i.e., Vs/(Vh- _Vp1 ) was 1.02 and 1.14, the solder filled about half of the through-hole, resulting in relatively good soldering. In Experimental Examples 10 to 12, where soldering was performed under conditions where Vs/(Vh- _Vp1 ) was 1.32 or higher, the solder filled the entire through-hole, resulting in even better soldering.
In contrast to this, in the soldering of Experimental Example 7 where Vs/(Vh-Vp ₁ ) was "0.76", the pin terminals and the like were not heated sufficiently and the molten solder did not flow into the through-holes at all.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and additions, omissions, substitutions, and other modifications of the configuration are possible within the scope of the spirit of the present invention. The present invention is not limited by the above description, but is limited only by the appended claims.
In addition, within the scope of the spirit of the present invention, it is possible to replace the components in the above-described embodiments with well-known components as appropriate, and the above-described modified examples may be combined as appropriate.

The soldering method of the present invention enables good soldering without reducing the efficiency of the soldering work.

AP soldering device A1 device body 11 wall body 12 holding portion 13 sliding guide 14 heater unit fixing portion 15 actuator holding portion 16 spring holding portion 2 cutter unit 21 upper cutter blade 211 upper blade hole 212 pin hole 22 lower cutter blade 221 lower blade hole 23 pusher pin 231 rod portion 232 head portion 233 spring 3 driving mechanism 31 air cylinder 32 piston rod 33 cam member 330 recessed portion 331 support hole 332 pin 333 pin pushing portion 334 bearing 34 slider portion 340 cam groove 341 first groove portion 342 second groove portion 343 connection groove portion 35 guide shaft 4 heater unit 41 heater 42 heater block 421 recessed portion 422 solder supply holes 5a, 5b iron tip 51 solder hole 510 enlarged portion 6 Solder feed mechanism 61a, 61b, feed roller 62, guide tube Bd, printed circuit board C1, axial center of iron tip C2, axial center of pin terminal d, outer diameter L of solder piece, length D of solder piece, outer diameter r of pin terminal, radius R of solder hole, radius M of enlarged portion, depth S of enlarged portion, protrusion amount Ep of pin terminal from printed circuit board, electronic component FL, flux ML, manipulator Ld, land Re, resin P, pin terminal Th, through hole W, solder wire Wh, solder piece

Claims (2)

A soldering method using a heatable soldering iron tip having a generally cylindrical shape and a solder hole penetrating in the axial direction, in which a pin terminal protruding outward from a component body of an electronic component is inserted into a through hole formed in a printed circuit board and soldered to a land formed on the outer periphery of the through hole,
a step of contacting the tip of the soldering iron with the printed circuit board so that the tip of the pin terminal inserted into the through hole and protruding from the printed circuit board is positioned within the solder hole;
providing a solder piece into the solder hole;
a step of heating and melting the supplied solder piece in the solder hole to solder the pin terminal and the land;
and
the solder hole has an enlarged portion at its lower end that enlarges radially outward;
an axial length of the enlarged portion from a lower end opening of the solder hole is longer than a protruding length of the pin terminal from a surface of the printed circuit board;
A soldering method characterized by making the internal volume Vh of the solder hole from the tip of the pin terminal inserted into the solder hole to the lower end opening of the solder hole and the volume Vs of the solder piece satisfy the following formula (1) when the tip of the soldering iron is in contact with the printed circuit board.
Vs≧ 1.30×( Vh−Vp ₁ )・・・(1)
Vs: volume of solder piece Vh: internal volume of solder hole from the tip of pin terminal inserted into solder hole to the lower opening of the solder hole _Vp1 : volume of pin terminal located in solder hole The soldering method according to claim 1, further satisfying the following formula (2):
Vs≧ 1.30×( Vh-Vp ₁ ) +Vt-Vp ₂ ...(2)
Vt: Volume of the through-hole _Vp2 : Volume of the pin terminal located in the through-hole