JP2007027584A - Connection structure, circuit constituent and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a connection structure that can prevent a plated layer from flowing out when reflow treatment is applied, and a circuit constituent. <P>SOLUTION: Since an exposed part 28, from which a plated layer 29 is removed is formed around a joint 29, a failure such as unfavorable connection, etc. does not occur unless the plated layer 29 or cream solder S reaches outer regions of openings 26 and 27 passing over the outcrop 28 even if not only the cream solder S but a plating component forming the joint 29 have been melted during a reflow process. In this way, since the exposed part 28 acts as a buffer area to prevent the melted cream solder S from flowing out to the outer regions of the openings 26 and 27, infavorable connection and the like can be avoided. Further, by the method for forming the joint 29 and the exposed part 28 by forming a plated layer only at a necessary part on a bus bar substrate 22, the joint 29 and the exposed part 28 can be easily formed at a matching position in the openings 26 and 27. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a connection structure, a circuit structure, and a manufacturing method thereof.

  Conventionally, in order to distribute power from an in-vehicle power supply to various electrical components, electronic components such as switching elements are mounted on a circuit pattern formed on one surface of the circuit board, and on the other surface of the circuit board, An electric junction box is used in which a circuit structure in which a bus bar that is electrically connected to a switching element and that constitutes a power circuit is bonded via an insulating layer is housed in a waterproof case (see Patent Document 1). ).

The switching element is provided with a control terminal connected to a control circuit composed of a circuit pattern and a control element, and a power terminal connected to a power circuit. Of these, the power terminal is connected to the bus bar. That is, the circuit board is provided with an opening, and the bus bar is exposed at the bottom of the opening. The exposed surface is plated to ensure electrical continuity with the terminals. A power terminal is inserted into the opening and soldered to the bus bar. This soldering is generally performed by reflow soldering.
JP 2003-164039 A

  By the way, in recent years, Sn-Ag solder, which is lead-free solder that does not use lead, is frequently used from Sn—Pb eutectic solder in consideration of the environment. The melting point of this Sn—Ag solder is about 220 ° C., which is higher than the melting point of conventional Sn—Pb eutectic solder (180 ° C. to 190 ° C.). For this reason, when mounting electronic components using lead-free solder, the temperature of the reflow process must be 220 ° C. to 230 ° C., which is higher than when using conventional lead-containing solder. In order to improve the wettability of the solder, the bus bar is tin-plated, but since the melting point of this tin plating is 232 ° C., it may be melted during reflow.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a connection structure and a circuit structure that can avoid the flow of solder when a reflow process is performed.

  The connection structure according to the first aspect of the present invention for solving the above problem is a connection structure in which terminals of an electronic component are soldered to a planar terminal connection region, and the terminal connection region allows diffusion of the solder. A solder diffusion allowing portion is provided.

  According to a second aspect of the present invention, there is provided a circuit structure including a bus bar and an electronic component mounted on the bus bar by soldering, wherein the bus bar has a terminal connection region to which a terminal of the electronic component is connected. A solder diffusion allowing portion made of a plating layer formed on the surface is provided.

  According to a third aspect of the present invention, there is provided a circuit board having a conductive path formed on at least one surface side, an electronic component mounted on the one surface side of the circuit board, and a bus bar provided on the other surface side of the circuit board. The circuit board is provided with an opening that penetrates in the thickness direction in the circuit board, and the terminal of the electronic component is soldered to a terminal connection region facing the opening on the surface of the bus bar, The terminal connection region is provided with a solder diffusion allowing portion made of a plating layer formed on the surface of the bus bar.

  According to a fourth aspect of the present invention, there is provided a circuit board having a conductive path formed on at least one surface side, an electronic component mounted on the one surface side of the circuit board, and a bus bar provided on the other surface side of the circuit board. And a circuit structure in which an opening penetrating in the thickness direction is formed in the circuit board, and terminals of the electronic component are soldered to a terminal connection region facing the opening on the surface of the bus bar. In the bus bar forming step for forming the bus bar, and in the terminal connection region of the bus bar, a solder composed of a plating layer at a position on the inner side of the peripheral portion of the bus bar leaving an exposed region where the bus bar base material is exposed. A solder diffusion allowance portion forming step for forming a diffusion allowance portion, an adhesion step for adhering the bus bar to the circuit board, and solder adhered on the solder diffusion allowance portion. And a reflow step of soldering the terminals on the solder diffusion allowing portion by heating and melting the solder in a state where the terminals of the electronic component are placed on the solder. And

  According to the first to third aspects of the invention, since the solder stops at the solder diffusion permissible portion at the time of reflowing, connection failure and the like can be avoided.

  According to the invention of claim 4, the solder diffusion allowing portion is formed by forming the plating layer only in a necessary portion of the bus bar. According to such a method, the solder diffusion allowing portion can be easily formed in the terminal connection region.

Hereinafter, an embodiment embodying the present invention will be described in detail with reference to FIGS. The electrical junction box 1 of the present embodiment is one in which the circuit structure 20 is accommodated in the case 10.
The case 10 of the electrical junction box 1 includes a lower case 11 and an upper case 13 assembled from above the lower case 11 (see FIG. 1).

  The lower case 11 includes a frame body 12 formed of an insulating material such as a synthetic resin. The frame body 12 is formed in a frame shape substantially along the peripheral edge of the circuit structure body 20, and the circuit structure body 20 can be fitted almost tightly inside the frame body 12. Although not shown in detail in the frame body 12, a heat radiating plate for radiating heat generated from electronic components provided in the circuit structure 20 is attached.

  The upper case 13 is formed of a synthetic resin in the shape of a shallow dish whose bottom surface is opened as a whole, and is assembled to the lower case 11 while covering the upper side of the circuit structure 20. Openings are provided on both the front and rear surfaces of the upper case 13, and the PCB connector 14 and the fuse box 15 are mounted so as to close the openings.

  The PCB connector 14 assembled to the front end of the upper case 13 is formed in a horizontally long shape opened to the front surface by a synthetic resin. In the PCB connector 14, an external terminal 38 connected to the circuit structure 20 faces. The fuse box 15 assembled on the rear end side of the upper case 13 is made of synthetic resin, covers the entire rear surface side of the upper case 13 over its entire length, and its upper half is above the ceiling surface of the upper case 13. It is formed in a horizontally long shape that protrudes. In the fuse box 15, a bus bar terminal 22 </ b> A provided on a bus bar substrate 22 described later is accommodated. In the fuse box 15, an upper connector 16 is assembled from the front in a region protruding above the upper case 13, and a mating connector (not shown) is fitted from the front side. Yes.

  As shown in FIG. 2, the circuit structure 20 accommodated in the case 10 includes a control circuit board 21 and a bus bar board 22 arranged on the lower surface side of the control circuit board 21. As shown in FIG. 2, the control circuit board 21 has a rectangular plate shape as a whole and is formed in an outer shape with a corner on the left front end side dropped, and a conductor pattern (not shown) is formed on the upper surface side. Is formed.

  A bus bar substrate 22 is attached to the lower surface side of the control circuit board 21 via a thin adhesive sheet 23 having insulating properties. The bus bar substrate 22 is formed by punching a metal plate having excellent conductivity, and has an outer shape in which a plurality of bus bars 24 forming a conductive path serving as a power circuit are substantially aligned with the control circuit substrate 21 in parallel. There is no. A plurality of bus bar terminals 22A protrude from the rear edge of the bus bar substrate 22 side by side, and an external terminal 38 is connected to the front end portion by welding, for example.

  Electronic components (for example, a semiconductor switching element 31 and a mechanical relay switch 35) are mounted on the upper surface side of the circuit structure 20. Among the electronic components, the mechanical relay switch 35 includes a housing 36 and a plurality of terminals 37 connected to the housing 36 (see also FIGS. 4 and 5). These terminals include a power terminal 37 </ b> A that is connected to the bus bar substrate 22 and controls the power circuit, and a control terminal 37 </ b> B that is connected to the control circuit board 21 and controls the driving of the mechanical relay switch 35. Each terminal 37 protrudes from the bottom of the housing 36 and extends downward, and then is bent outward at a right angle, and its tip is arranged along the surface of the control circuit board 21 or the bus bar board 22.

  On the other hand, the semiconductor switching element 31 includes a housing 32 and a plurality of terminals 33 provided on the housing 32 (see also FIG. 4). Among the plurality of terminals 33, the drain terminal (power terminal) 33 </ b> A is provided on the entire lower surface side of the housing 32. The source terminal (power terminal) 33B and the gate terminal (control terminal) 33C are projected from the side surface of the housing 32 and bent downward in a crank shape, and their tips are the surfaces of the control circuit board 21 or the bus bar board 22. It is arranged along.

  The terminals 33 and 37 of these electronic components are connected to the land portion 25 provided on the conductor pattern of the control circuit board 21 or the bus bar board 22 by soldering as described below.

  In the control circuit board 21, the corresponding terminals 33A, 33B, and 37B can be inserted into positions corresponding to the power terminals 33A, 33B, and 37B connected to the bus bar board 22 among the terminals 33 and 37 of the electronic components. The openings 26 and 27 are formed so as to penetrate in the plate thickness direction, and the bus bar substrate 22 is exposed from the openings 26 and 27.

  Among these openings 26 and 27, the element opening 26 corresponding to the power terminals 33 </ b> A and 33 </ b> B of the semiconductor switching element 31 is a large rectangular shape that is slightly larger than the outer shape viewed from above the semiconductor switching element 31. The hole 26A is connected to a rectangular small hole 26B provided on one side of the hole 26A through which the source terminal 33B can be inserted. When the hole 26A is stacked with the bus bar substrate 22, the drain terminal 33A The bus bar 24 is connected to the bus bar 24 to which the source terminal 33B is connected. On the surface of each bus bar 24, the terminal connection region R facing the element opening 26 leaves a region from the peripheral edge of the element opening 26 to a slightly inner position, and the inner region A connecting portion 29 (corresponding to the solder diffusion allowing portion of the present invention) is formed by a plating layer whose outer shape is slightly smaller than the element opening 26. The drain terminal 33 </ b> A and the source terminal 33 </ b> B are connected to the connection portion 29 by solder S. An exposed portion of the bus bar substrate 22 formed in an annular shape around the connection portion 29 is an exposed portion 28 that restricts the solder S on the inside from melting and flowing out to the external region of the element opening 26. On the other hand, the gate terminal 33C is connected to the land portion 25 provided on the control circuit board 21 by soldering.

  On the other hand, the relay opening 27 for connecting the power terminal 37A of the mechanical relay switch 35 is formed in a rectangular shape at a position corresponding to each power terminal 37A in the installation area of each mechanical relay switch 35. Yes. Then, on the surface of each bus bar 24, the terminal connection region R that faces into the relay openings 27 is slightly more from the periphery of the relay openings 27 than the element openings 26. A region 29 up to the inner position is left as an exposed portion 28 where the bus bar 24 is exposed, and a connecting portion 29 made of a plating layer is formed in the inner region. A power terminal 37 </ b> A is connected to the connecting portion 29 by solder S.

  Next, the manufacturing procedure of the electrical junction box 1 will be described with reference to FIGS. FIGS. 5 and 6 show a case where the mechanical relay switch 35 is mounted as an example, but the same procedure can be performed for the semiconductor switching element 31. Therefore, both will be described below together. To do.

  First, the bus bar substrate 22 is formed by punching a metal plate by press working (FIG. 5A; bus bar substrate forming step). Although not shown in detail, at the time of punching, the bus bars 24 and the bus bars 24 and the outer frame surrounding the bus bars 24 are connected by connecting pieces so that the bus bars 24 constituting the bus bar substrate 22 are not separated. It is in a state.

  Next, a mask M is laminated on the bus bar substrate 22 (FIG. 5B), and a region other than the region to be the connection portion 29 is masked, and the connection portion 29 made of a plating layer containing tin by a well-known plating method. (FIG. 5C; connecting portion forming step). Thereafter, the mask is peeled off.

Next, the control circuit board 21 is attached to the surface side of the bus bar board 22 where the connection portion 29 is provided via the adhesive sheet 23 (FIG. 5D; bonding process). The adhesive sheet 23 is provided with a through hole 23 </ b> A penetrating in the thickness direction at a position aligned with the openings 26 and 27 of the control circuit board 21. A region inside the openings 26 and 27 and surrounding the connection portion 29 becomes an exposed portion 28 where the bus bar substrate 22 is exposed.
In addition to this bonding step, the bus bar terminal 22A may be bent within a range that does not interfere with the next component mounting step.

  Next, electronic components are mounted on the control circuit board 21. First, the cream solder S is applied to the land portion 25 of the control circuit board 21 and the connection portion 29 in the openings 26 and 27 by, for example, screen printing (FIG. 5E; solder attaching step). As this cream solder S, a lead-free type is used. The mechanical relay switch 35 is aligned so that the power terminal 37A is aligned with the connection portion 29 in the relay opening 27 and the control terminal 37B is aligned with the land portion 25 on the control circuit board 21. And placed on the control circuit board 21 (FIG. 5F). Similarly, the semiconductor switching element 31 includes a drain terminal 33A on the connection part 29 formed in the large hole part 26A in the element opening 26, and a source terminal 33B on the connection part 29 formed in the small hole part 26B. However, the gate terminal 33 </ b> C is aligned on the land portion 25 on the control circuit board 21 so as to be aligned and placed on the control circuit board 21. In this state, the circuit component 20 is placed in a reflow furnace (not shown), heated to the solder melting temperature, and then cooled to solder the terminals 33 and 37 (FIG. 6; reflow process).

  At this time, since the melting temperature of the solder and tin is very close, not only the cream solder S but also the plating component constituting the connection portion 29 is melted at the time of reflow, and the cream solder S flows out to the peripheral region and the connection is poor. It may cause etc. However, since the exposed portion 28 is provided around the connection portion 29, the plating layer or the cream solder S constituting the connection portion 29 does not reach the outer regions of the openings 26 and 27 beyond the exposed portion 28. As long as there is no failure such as poor connection. In this way, the exposed portion 28 becomes a buffer zone and restricts the cream solder S from flowing to the outer region of the openings 26 and 27.

  When the mounting of the electronic components is completed, the circuit structure 20 is completed by bending the bus bar terminals 22A and separating the bus bars 24 from each other and the bus bar 24 and the frame. Finally, the circuit structure 20 is accommodated in the case 10 and the PCB connector 14 and the fuse box 15 are assembled to complete the electrical junction box 1.

As described above, according to the present embodiment, even if the plating component constituting the connection portion 29 of the lower layer of the cream solder S is melted in the reflow process, the exposed portion 28 becomes a buffer zone and the cream solder S becomes the opening 26. , 27 can be prevented from flowing out to the outer region. Thereby, connection failure etc. can be avoided.
In addition, according to the method of forming the connection portion 29 and the exposed portion 28 by forming a plating layer only in a necessary portion of the bus bar substrate 22, the connection portion 29 and the exposed portion can be easily located at positions aligned in the openings 26 and 27. The portion 28 can be formed.

The technical scope of the present invention is not limited by the above-described embodiments, and, for example, those described below are also included in the technical scope of the present invention. In addition, the technical scope of the present invention extends to an equivalent range.
(1) According to each of the above embodiments, the electronic components are the semiconductor switching element 31 and the mechanical relay switch 35. However, even when other electronic components are mounted by soldering, the diffusion prevention unit of the present invention. Can be applied.
(2) In each of the above embodiments, the plating layer constituting the connection portion 29 is a plating layer containing tin, but there is no particular limitation on the components of the plating layer. Further, a plurality of layers containing different components may be stacked.

The perspective view of the electrical junction box of a 1st embodiment Perspective view of circuit structure Partial enlarged top view of the busbar substrate Partial enlarged top view of the circuit structure Partial enlarged sectional view showing the mounting process of the mechanical relay switch Partial enlarged sectional view showing a mechanical relay switch mounted on a circuit structure

Explanation of symbols

DESCRIPTION OF SYMBOLS 20 ... Circuit structure 21 ... Control circuit board 22 ... Bus-bar board | substrate 26, 27 ... Opening part 28 ... Exposed part 29 ... Connection part (solder diffusion allowance part)
31 ... Semiconductor switching element (electronic component)
33, 37 ... Terminal 35 ... Mechanical relay switch (electronic component)
R ... Terminal connection area S ... Cream solder (solder)

Claims (4)

In the connection structure where the terminals of the electronic component are soldered to the planar terminal connection area,
The terminal connection region is provided with a solder diffusion allowing portion for allowing diffusion of the solder.   In a circuit structure including a bus bar and an electronic component mounted on the bus bar by soldering, a terminal connection region to which the terminal of the electronic component is connected in the bus bar is formed on the surface of the bus bar. A circuit structure having a solder diffusion allowing portion made of a plating layer. A circuit board having a conductive path formed on at least one surface side, an electronic component mounted on the one surface side of the circuit board, and a bus bar provided on the other surface side of the circuit board,
The circuit board is formed with an opening penetrating in the thickness direction, and the terminal of the electronic component is soldered to a terminal connection region facing the opening on the surface of the bus bar,
The circuit structure according to claim 1, wherein a solder diffusion allowing portion made of a plating layer formed on the surface of the bus bar is provided in the terminal connection region. The circuit board includes a circuit board having a conductive path formed on at least one surface side, an electronic component mounted on the one surface side of the circuit board, and a bus bar provided on the other surface side of the circuit board. Is a method of manufacturing a circuit structure in which an opening penetrating in the thickness direction is formed and a terminal of the electronic component is soldered to a terminal connection region facing the opening on the surface of the bus bar,
A bus bar forming step for forming the bus bar;
In the terminal connection region of the bus bar, a solder diffusion allowance portion forming step of forming a solder diffusion allowance portion made of a plating layer at a position on the inner side of the peripheral portion, leaving an exposed region where the bus bar base material is exposed, and
Bonding step of bonding the bus bar to the circuit board;
A solder attachment step of attaching solder onto the solder diffusion permissible portion;
A reflow step of soldering the terminals on the solder diffusion allowing portion by heating and melting the solder in a state where the terminals of the electronic component are placed on the solder. Production method.

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