JP2015119122A - Soldering method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a soldering method ensuring excellent solder wicking state, even when soldering a mounting component having a plurality of lead terminals to a part where the wiring pattern is dense.SOLUTION: A soldering method includes a component arrangement step of arranging a mounting component having a plurality lead terminals corresponding to a plurality of through holes and a dummy component having dummy terminals corresponding to dummy through holes on a printed board having the plurality of through holes and dummy through holes on the outside of through hole formation regions provided with the plurality of through holes, while sandwiching by heat conductors, and a flow solder step of soldering the printed board and mounting component and dummy component by flow soldering.

Description

  The present invention relates to a soldering method for performing flow soldering on a double-sided or multilayer printed circuit board.

  Conventionally, a printed circuit board is provided with a plurality of through-holes, and the lead terminals of the mounting components are inserted into the through-holes. After that, the lead terminals protrude from the solder pool that stores the heat-melted solder. A method is known in which a lead terminal is soldered to a printed board by a flow soldering process in which the back side of the board is brought into contact.

In this method, the molten solder rises from the back side of the printed circuit board to the front side by capillarity through the inside of the through hole, and soldering between the component surface of the printed circuit board and the land on the solder surface and the lead terminals of the component is performed. .
The state where the solder rises is called solder rise.

  In the printed circuit board, the substrate with copper foil on the surface is etched so as to form the necessary wiring, and the wiring pattern is formed, but if there is no need for wiring, the etching is not performed as it is. For example, the copper foil may be left and used for a portion where a ground terminal is provided.

A pattern portion where copper foil remains in such a wide range is called a solid pattern.
Copper foil has a high thermal conductivity, and if a solid pattern is formed, the solid pattern portion becomes a heat radiating part. Therefore, in the above-described flow soldering process, the printed circuit board is difficult to warm up. Solder may solidify by cooling in the middle of ascending.

  When this happens, the solder does not reach the surface of the printed circuit board sufficiently, and the electrical connection failure between the wiring pattern on the surface of the printed circuit board and the lead terminal occurs or the electrical connection has been established. However, since the solder is not sufficiently accumulated, the fixing strength is low, which causes a failure factor such that the mounted component comes off during use.

  Therefore, conventionally, a plurality of via holes penetrating the printed board apart from the through holes are provided in the vicinity of the through holes, and the heated and melted solder is also allowed to enter the via holes, and the heat of the invaded solder is introduced. A method for warming through holes and achieving good soldering is disclosed in Patent Document 1.

JP2003-69202A.

  Since there is a space for providing a via hole in a portion where the wiring density on the printed circuit board is low, for example, where a solid pattern is provided, a method as in Patent Document 1 can be applied.

  On the other hand, in the case of a printed circuit board on which a mounting component such as an electrical connector having a plurality of lead terminals or an intelligent power module (IPM) having a plurality of lead terminals is mounted, the wiring pattern corresponding to each of the plurality of lead terminals is dense. Therefore, it is difficult to freely form a through hole such as a via hole.

  An intelligent power module (IPM) is a module in which a drive circuit and a protection circuit for a power element are integrated on a small board, and is generally narrow and can be soldered to a large printed circuit board for mounting. It is a module with many pitch lead terminals.

  In addition, it is possible to form a wiring pattern on the assumption that a via hole is provided. In this case, however, the wiring pattern must be formed so as to avoid the via hole. There is a problem that it takes time and effort.

  Therefore, the present invention has been made in view of the above problems, and even when a mounting component having a plurality of lead terminals is flow-soldered in a place where the wiring patterns of the printed circuit board are densely packed, good soldering is achieved. It aims at providing the soldering method which can obtain a state.

The present invention has been proposed to achieve the above object, and is grasped by the following configuration.
According to the soldering method of the present invention, a plurality of through holes are formed on a printed circuit board having dummy through holes on the outer side of the through hole forming region where the plurality of through holes are provided. A component placement step of placing a mounting component having a plurality of corresponding lead terminals and a dummy component having a dummy terminal corresponding to the dummy through hole in a state of being sandwiched by a heat conductor; the printed circuit board; the mounting component; A flow soldering process in which the dummy component is soldered by flow soldering.

  According to the present invention, there is provided a soldering method capable of obtaining a good soldered state even when a mounting component having a plurality of lead terminals is flow soldered in a place where wiring patterns of a printed circuit board are dense. be able to.

It is a figure explaining the work procedure in the soldering method which is one Embodiment of this invention. It is a figure explaining each structure of the mounting component for implementing the soldering method of this invention, a printed circuit board, a dummy component, and a heat conductor, (a) is a side view which shows the state before soldering, (b) FIG. 4 is a side view showing a state after soldering. It is the EE sectional view taken on the line in (a) of FIG. It is a figure explaining the effect | action of soldering of the flow solder process B, (a) is a principal part expanded sectional view before soldering, (b) is the top view seen from the GG line direction of (a). (C) is an enlarged cross-sectional view of the main part after soldering. FIG. 4 is a diagram for explaining an example of another mounting structure different from the mounting structure of the heat conductor shown in FIG. 2 and FIG. 3, (a) is a front view thereof, and (b) is an H- It is the top view seen from the H line direction, (c) is the side view seen from the arrow I direction shown to (a). It is a figure explaining the modification of the attachment structure shown in FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as “embodiments”) will be described in detail with reference to the accompanying drawings.

  The soldering method according to the present invention is performed using a dummy component and a heat conductor when flow soldering a mounting component to a printed circuit board. The soldering procedure is as shown in FIG. Work is performed in the order of the placement process A and the flow solder process B.

  While referring to FIGS. 2 to 4, specific mounting components and structures of printed circuit boards, dummy components, heat conductors, etc., and a soldering method according to the present invention will be described. The shapes and structures of the mounting component 10 and the printed circuit board 20, the dummy component 30, and the heat conductor 40 shown in FIG. 3 are merely examples, and the present invention is not limited to the shapes and structures shown in this embodiment. Absent.

The mounting component 10 shown in FIG. 2 is an electrical connector for electrically connecting an external power supply device or electronic component and a printed wiring connected to the electronic component on the printed circuit board 20, for example.
The mounting component 10 shown in FIG. 2 is a module component (intelligent power module) in which electronic components are integrated on a small substrate, for example.
As shown in FIG. 2, the mounting component 10 is bent downward from the side surface of the component main body 11 (only the bottom surface is visible in this figure), and a plurality of conductive metal pieces (books) that extend straight downward. In the example, five lead terminals 12 are provided.

As shown in FIG. 4, the printed board 20 is a board in which a conductive wiring pattern 22 (hereinafter also simply referred to as a wiring pattern 22) is formed on the upper surface (front surface) of the printed board 20. Since the printed circuit board 20 is a double-sided or multilayer board, the wiring pattern exists not only on the top surface but also on the back surface.
For example, a generally used insulating substrate such as a ceramic substrate, a glass epoxy resin substrate, or a phenol resin substrate can be used for the printed circuit board 20.

  The wiring pattern 22 is provided with a protective film (resist) so as to draw a necessary wiring pattern on the copper foil provided on the surface of the printed circuit board 20, and the copper foil portion not provided with the resist is dry-etched or wet-etched. It can be formed by removing and then removing the resist.

  Further, as shown in FIG. 4A, the printed circuit board 20 has a plurality of through holes for inserting the lead terminals 12 of the mounting component 10 so as to penetrate from the upper surface 21A to the lower surface 21B of the insulating substrate 21. A hole 23 is formed corresponding to each of the lead terminals 12.

As shown in FIG. 2, on the both sides of an area in which a plurality of through holes 23 are provided (hereinafter also referred to as “through hole forming area S”), the outer print is sandwiched between the through hole forming areas S. A plurality of dummy through holes 24 (see FIG. 4) penetrating from the upper surface 21A to the lower surface 21B are formed at the position of the substrate 20.
In the present embodiment, the plurality of through holes 23 and dummy through holes 24 are formed in a line on a straight line.

  As shown in FIG. 2A, the dummy component 30 corresponds to the plurality of dummy through holes 24 formed on both outer sides of the through hole forming region S of the printed circuit board 20, one on each outer side. That is, a pair is provided.

Each dummy component 30 includes a plate-shaped main body 31 and dummy terminals 32 that penetrate the main body 31 and protrude vertically.
As will be described later, the dummy terminal 32 is preferably made of, for example, metal having good thermal conductivity.
On the other hand, as will be described later, the main body 31 is preferably made of a material having low thermal conductivity and difficult to transmit heat, for example, an insulating resin material.

As shown in FIG. 3, the heat conductor 40 includes heat conductors 40 a and 40 b attached to the lead terminal 12 and the dummy terminal 32 so that the side surfaces of the lead terminal 12 and the dummy terminal 32 are sandwiched from both sides.
A concave groove 42 corresponding to the lead terminal 12 and the dummy terminal 32 is provided on the sandwiching surfaces 41a and 41b of the heat conductors 40a and 40b.
Therefore, in a state where the lead terminal 12 and the dummy terminal 32 are sandwiched between the thermal conductors 40a and 40b, the outer peripheral surfaces of the lead terminal 12 and the dummy terminal 32 are encased in the thermal conductor 40, and the lead terminal 12 and The dummy terminal 32 and the heat conductor 40 are in contact with each other.

  The material of the heat conductor 40 is not particularly limited as long as it is a material having high heat conductivity, but copper, aluminum, and the like are preferable because they have high heat conductivity.

  Next, the soldering method of the present invention will be described while following the process procedure shown in FIG.

In the component placement step A, as shown in FIG. 2A, dummy through holes 24 are formed on the outer sides of a plurality of through holes 23 and a lead terminal hole forming region S where the through holes are formed. Printed circuit board 20, mounting component 10 having a plurality of lead terminals 12 corresponding to a plurality of through holes 23, dummy component 30 having a dummy terminal 32 corresponding to a dummy through hole 24, and heat conductors 40a and 40b. (Refer to FIG. 3) is a step of arranging in a state for performing the flow soldering step B.
Note that a solder resist is provided in a portion where it is difficult to attach solder on the lower surface (back surface) 21B of the printed circuit board 20 shown in FIG.

  Specifically, in the component placement step A, as shown in FIG. 2A, each lead terminal 12 of the mounting component 10 is inserted into the corresponding through hole 23 from the upper surface (front surface) 21A side of the printed circuit board 20, respectively. In addition, a necessary amount of gap is provided between the upper surface 21A of the printed circuit board 20 and the mounting component 10 (component main body 11) so that the upper surface (front surface) 21A of the printed circuit board 20 and the mounting component 10 are separated from each other. The mounting component 10 is disposed on the printed circuit board 20.

  Similarly, the dummy terminals 32 of the pair of dummy components 30 are inserted into the corresponding dummy through holes 24 of the printed circuit board 20 from the upper surface (front surface) 21A side of the printed circuit board 20, and the main body portion 31 of each dummy component 30 is connected to the printed circuit board. It arrange | positions in the state contact | abutted on the 21 A upper surface 21A.

As shown in FIG. 2A, the mounting component 10 arranged on the printed circuit board 20 in this way protrudes by a predetermined amount from the lower surface (back surface) 21B of the printed circuit board 20 straight downward. Are arranged.
Further, the lower end side of the dummy terminal 32 of each dummy component 30 is also arranged so as to protrude a predetermined amount from the lower surface (back surface) 21B of the printed circuit board 20 downward.

In the present embodiment, both the lead terminal 12 and the dummy terminal 32 protrude from the lower surface (back surface) 21B of the printed circuit board 20 by substantially the same length, but it does not necessarily have to protrude by the same length.
As described above, in the present embodiment, since the plurality of through holes 23 and the plurality of dummy through holes 24 are formed in a line on a straight line, each lead terminal 12 and each dummy terminal 32 is also formed. They are in a line on the same straight line.

Then, as shown in FIG. 2A, the heat conductor 40 is attached at a position between the printed board 20 and the mounting component 10 (component main body 11).
Specifically, as shown in FIG. 3, the side surfaces of the plurality of lead terminals 12 and the plurality of dummy terminals 32 are sandwiched between the heat conductors 40a and 40b from both sides, and both ends of the pair of heat conductors 40a and 40b. The part is sandwiched and fixed by a clip or the like (not shown) so that the heat conductors 40a and 40b are integrated with each other so that the heat conductor 40 is attached.

As described above, if the heat conductors 40a and 40b are integrated with a clip or the like, the heat conductors 40a and 40b can be easily removed by simply removing the clip after the soldering process. it can.
As shown in FIG. 3, in a state where the heat conductors 40 a and 40 b are commonly attached to the plurality of lead terminals 12 and the plurality of dummy terminals 32, the plurality of lead terminals 12 and the plurality of dummy terminals 32 are provided. Each outer peripheral surface is in contact with the inner surface of the concave groove 42.

The procedure of the component placement process A described above is merely an example, and may be performed by another procedure.
For example, before performing the operation of inserting each lead terminal 12 of the mounting component 10 and each dummy terminal 32 of the pair of dummy components 30 into the plurality of through holes 23 and the plurality of dummy through holes 24 of the printed circuit board 20, The lead terminal 12 and each dummy terminal 32 are fixed with the heat conductors 40a and 40b sandwiched between them, and thereafter, the lead terminals 12 are inserted into the plurality of through holes 23 and the plurality of dummy through holes 24 of the printed circuit board 20, respectively. 12 and each dummy terminal 32 may be inserted.

  Therefore, the component placement step A is a print having a plurality of through holes 23 and a dummy through hole 24 on the outer side of the through hole formation region S provided with the plurality of through holes 23 regardless of the procedure. A mounting component 10 having a plurality of lead terminals 12 corresponding to a plurality of through holes 23 and a dummy component 30 having a dummy terminal 32 corresponding to a dummy through hole 24 are sandwiched between the heat conductors 40a and 40b. It is the process of arranging in a state.

  The flow soldering process B is a molten solder (not shown) with the lower surface (back surface) 21B of the printed circuit board 20 on the lower side in the arrangement state of each component as shown in FIG. This is a step of immersing the lower surface (back surface) 21B in the solder pool in which is stored.

Then, the molten solder begins to rise upward through the gap between the lead terminal 12 and the through hole 23 by a capillary phenomenon.
At this time, the heat of the molten solder in the solder pool is transmitted to the thermal conductor 40 through each dummy terminal 32 and each lead terminal 12 having good thermal conductivity as described above.

And the temperature of the heat conductor 40 rises with the heat.
For this reason, not only the lower surface (back surface) 21B is heated by the heat from the solder pool, but also the upper surface (front surface) 21A side is heated by the heat of the heat conductor 40.

  Accordingly, it is possible to suppress the solder 50 from being cooled and solidified while the solder 50 is rising due to the capillary phenomenon, and to realize a good solder-up state. Therefore, a printed circuit board as shown in FIG. The solder 50 is neatly stacked on the upper surface (front surface) 21A side of 20 as well.

  In addition, the dummy terminal 32 of the dummy component 30 is formed of a metal having good thermal conductivity, and the heat of the molten solder is efficiently transferred to the thermal conductor 40, and the body portion 31 of the dummy component 30 has a thermal conductivity. Excessive heat dissipation in the middle of heat transfer can be suppressed by using a material that is low and difficult to transfer heat, such as an insulating resin material.

When the soldering in the flow soldering process B is completed, the printed circuit board 20 is taken out from the solder pool. Then, the heat conductor 40 is removed as the component removal process C.
Thereby, the soldering operation of the mounting component 10 is completed, and the printed circuit board 20 shown in FIGS. 2B and 4C is obtained.

  As described above, since the solder resist is provided in the portion where it is difficult to attach the solder 50 to the back surface of the printed circuit board 20, the solder 50 is formed in such a portion at the time of the flow solder process B. There is no.

  According to the configuration of the present embodiment as described above, it is possible to realize a state in which heating is performed not only from the back surface side of the printed board 20 but also from the upper surface side.

  Further, unlike the conventional method of providing via holes, it is not necessary to form holes where the wiring patterns around the lead terminals 12 are dense, and the wiring patterns outside the through-hole formation region S are not dense. Since it is only necessary to provide a through hole at the position, wiring is not complicated because the through hole for the dummy terminal (dummy through hole 24) is provided.

Furthermore, since the dummy through holes 24 can be provided where there are not many wiring patterns, the number of dummy through holes 24 can be increased as necessary.
Therefore, the amount of heat applied to the heat conductor 40 can be easily increased.

  In the present embodiment, when the plurality of lead terminals 12 and the plurality of dummy terminals 32 are sandwiched in common between the sandwiching surfaces 41a and 41b of the heat conductors 40a and 40b constituting the heat conductor 40, the lead terminals Since the concave groove 42 is formed so as to increase the contact area with the outer peripheral surface of 12 and the dummy terminal 32, it is possible to conduct heat to the heat conductor 40 satisfactorily.

However, it is not limited to this shape. For example, as shown in FIG. 5, the side surfaces of the lead terminal 12 and the dummy terminal 32 are made flat without forming the concave grooves 42 on the sandwiching surfaces 41a and 41b. It may be simply sandwiched from both sides.
In this way, the heating of the heat conductor 40 is somewhat disadvantageous, but it is not necessary to form the concave groove 42 in accordance with the position of the lead terminal 12 or the dummy terminal 32. 12 and the heat conductor 40 having high versatility can be used even when the arrangement intervals of the dummy terminals 32 are different.

Further, as a method for fixing the heat conductors 40a and 40b by sandwiching the plurality of lead terminals 12 and the dummy terminals 32 in common, as shown in FIG. 5, for example, a clip 61 generally known as “double clip” is used. Thus, the both ends of the heat conductor 40 may be sandwiched and fixed.
Such a clip 61 includes a clip main body 62 and a pair of opening / closing levers 63 for operating opening / closing of the clip main body 62.

In that case, a seating surface 43 (FIG. 5C) formed so as to be inclined downward from above according to the shape of the clamping surface of the clip main body 62 at a location outside the heat conductors 40a and 40b for stopping the clip 61. )) Is provided, the clip 61 can be attached in a more stable state.
In FIG. 5, the number of lead terminals 12 is five and the number of dummy terminals 32 is two.

For example, as shown in FIG. 6, the seat surface 43 extends from the top to the bottom in accordance with the sandwiching surface shape of the clip body 62, as shown in FIG. 6. You may provide in the cross-sectional shape which inclines toward.
If it does in this way, the heat conductors 40a and 40b can be stably clamped by the clip main body 62.

As mentioned above, although this invention has been demonstrated based on embodiment, this invention is not limited to the said embodiment.
For example, in the above embodiment, the case where the lead terminals 12 and the dummy terminals 32 are arranged in a line on the printed circuit board 20 has been described.
In general, it is considered that there are many arrangements of lead terminals, etc., but even if they are not arranged in a row, the same soldering process can be performed if the shape of the heat conductor is designed according to the arrangement state It is.
Further, it is obvious that the present invention can be suitably applied even when the printed circuit board 20 has a solid pattern.
Therefore, the present invention is not limited to the above-described embodiment, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.

A Component placement process B Flow soldering process S Through-hole formation region 10 Mounted component 11 Component body 12 Lead terminal 20 Printed circuit board 21 Insulating substrate 21A Upper surface (front surface)
21B Bottom (back)
22 Wiring pattern (conductive wiring pattern)
23 through hole 24 dummy through hole 30 dummy part 31 body part 32 dummy terminal 40 heat conductors 40a and 40b heat conductors 41a and 41b sandwiching surface 42 concave groove 43 seating surface 50 solder 61 clip 62 clip body 63 opening / closing lever

Claims (1)

A printed circuit board having a plurality of through holes and a dummy through hole on the outer side of the through hole forming region where the plurality of through holes are provided has a plurality of lead terminals corresponding to the plurality of through holes. A component placement step of placing a mounting component and a dummy component having a dummy terminal corresponding to the dummy through-hole in a state of being sandwiched between heat conductors;
A soldering method comprising: a flow soldering step of soldering the printed circuit board, the mounting component, and the dummy component by flow soldering.

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