JP2004147416A - Circuit body forming method - Google Patents

Abstract

When mounting an electronic component such as a semiconductor switching element on a bus bar adhered to a printed circuit board, solder is prevented from spreading and accurately positioned on a regular mounting surface.
A bus bar is adhered to one surface of a printed circuit board, an electronic component is mounted on the bus bar exposed in a through hole provided in the printed circuit board, and a terminal exposed on the back surface of the main body of the electronic component is defined as the bus bar. A method of forming a circuit body in which terminals protruding to the side of the main body are connected to an electric circuit of the printed circuit board, wherein the bus bar to which terminals on the back surface of the main body of the electronic component are soldered is provided. A punched part consisting of a slit or a small hole is drilled at an outer position along the outer edge of the terminal, and the spread of the paste-like solder applied on the terminal mounting surface is blocked by the punched part, and surface tension is applied to the solder. Bulge is generated, and the bulge is pressed against the outer surface of the terminal to be mounted on the bus bar without shifting from the normal mounting position.
[Selection] Fig. 8

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of forming a circuit body, and more particularly, to a circuit body housed in an electric junction box mounted on an automobile, wherein a semiconductor switching element such as an FET is used instead of a relay, and the semiconductor switching method is used. A printed circuit board and a bus bar are used as electric circuit members connected to the elements, and in particular, the semiconductor switching element soldered to the bus bar can be mounted without displacement.
[0002]
[Prior art]
Recently, in order to meet the demands for downsizing the electrical junction box and increasing the speed of the switching function, a technology using a semiconductor switching element instead of a relay has been developed.
For example, Japanese Patent Application Laid-Open No. 10-35375 discloses a board including a bus bar on which a power supply circuit is formed, an FET as a semiconductor switching element incorporated in the power supply circuit, and a printed board for controlling the operation of the FET. The printed circuit board and the board on which the bus bar is arranged are spaced apart from each other in the upper and lower stages, and an FET is interposed therebetween. The drain terminal and the source terminal of the FET are connected to the bus bar, while the gate terminal is connected to the printed board. What is connected is proposed.
[0003]
[Patent Document 1]
JP-A-10-35375
[Problems to be solved by the invention]
In the electric junction box, at least two boards, that is, a board on which a bus bar is arranged and a printed board are required, and these boards must be separated from each other, and a space for interposing an FET therebetween must be secured. Therefore, although the use of FETs can reduce the size compared to the case of using a conventional relay, there is a problem that the height of the electric connection box becomes large in order to secure the above space.
Further, since the FET is arranged between the substrate on which the bus bar is arranged and the printed circuit board, the aging of the FET tends to be stuck between the two substrates, and it is necessary to take a complicated structure for heat radiation.
[0005]
When soldering the terminals of the above electronic components such as FETs and diodes to the printed circuit board to the lower bus bar, even if the electronic components such as FETs and diodes are accurately mounted in the correct positions, the electronic components are melted by solder. Position is likely to occur. In particular, when a plurality of FETs are arranged in an aligned state, there is a problem that even if the positional deviation dimension of each FET is minute, the FETs are not aligned and the positional accuracy is poor.
[0006]
The present invention has been made in view of the above problems, and in a circuit body for electrically connecting an electronic component to a printed circuit board and a bus bar, achieving a reduction in thickness and mounting terminals of the electronic component on the bus bar without displacement. Another object of the present invention is to make it possible to mount electronic components in an aligned state.
[0007]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a bus bar adhered to one surface of a printed circuit board, and mounting an electronic component on the bus bar exposed in a through hole provided in the printed circuit board. A method for forming a circuit body, wherein an exposed terminal is connected to the bus bar and a terminal projecting to the side of the main body is connected to an electric circuit of the printed circuit board,
The bus bar to which the terminal on the back surface of the main body of the electronic component is soldered is provided with a punched portion formed of a slit or a small hole at an outer position along the outer edge of the terminal. A forming method is provided.
[0008]
Paste solder is printed on the bus bar surface on which the above electronic components are mounted, and when the electronic components are mounted on the bus bar by an automatic mounting machine, the solder with good wettability is outward from the welding surface with the drain terminal. Therefore, the displacement of the electronic component is likely to occur due to the spread of the solder. Therefore, when the spread solder reaches the edge of the punched portion, the solder swells toward the main body of the electronic component by surface tension, thereby preventing the electronic component from shifting from the normal position. Can be implemented with high accuracy.
[0009]
The punched portion may be a slit extending linearly along the outer edge of the terminal exposed on the back surface of the electronic component, and the slit may be partial. Further, instead of the slit, one small hole may be provided along the outer edge of the drain terminal, or a plurality of small holes may be provided in parallel.
These punched portions may be formed with the required dimensions from the outline of the terminal, and the width of the slit-shaped punched portion and the diameter of the small hole are not limited, but from the viewpoint of securing the strength and the area for flowing the required current. It is preferable that the recess is not large.
[0010]
If the inner peripheral surface of the through hole is close to the outer surface of the electronic component, the punched portion is not necessarily formed between the inner peripheral surface of the through hole of the printed board and the facing surface of the electronic component. It is not necessary to provide them, but a punching section may be provided.
[0011]
The punching portion is formed at least at a position separated from a protruding side of a terminal protruding to the side of the main body of the electronic component.
The punching section is preferably provided along each side of the terminal exposed on the back surface of the main body of the electronic component. However, the terminal that projects to the side of the main body and is soldered on the copper foil of the printed circuit board is bent in a stepped manner and is fitted and positioned with the periphery of the through hole, so that the terminal protrudes to the side of the main body. It is not necessary to provide a punch on the side.
As described above, since the position where the terminal protrudes to the side of the main body does not easily cause a positional shift in the soldering position, the punched portion provided for preventing the positional deviation is provided at the position of the main body at a position away from the terminal protruding from the side of the main body. It may be formed along the outer edge of the terminal exposed on the back surface.
[0012]
The electronic component comprises a semiconductor switching element, and the drain terminal exposed on the back surface of the main body of the semiconductor switching element and the source terminal protruding on the side surface of the main body are soldered to the drain terminal and source terminal bus bars exposed inside the through hole, respectively. The drain terminal is connected along the inside of the punched portion, and a gate terminal, a logic input / output terminal, a power supply terminal, and the like protruding to the side of the main body of the semiconductor switching element are connected to a printed circuit of the printed circuit board. Are soldered to the respective terminal contact portions.
[0013]
Specifically, the method for forming a circuit body according to the present invention includes:
Forming a busbar component plate by punching out the busbar from one conductive plate in a connected shape;
A step of bonding the busbar component plate made of the single plate to one surface of a printed circuit board having the through holes through an adhesive;
A step of printing and applying paste solder on the bus bar and the printed board exposed inside the through hole,
The semiconductor switching elements, diodes and other electronic components are mounted on a printed circuit board by an automatic mounting machine, and the electronic components are mounted on a bus bar exposed inside a through hole, and are exposed on a back surface of the main body of the electronic component. Terminal (a drain terminal in the case of a semiconductor switching element) is connected to the bus bar for the drain terminal, some terminals (source terminals in the case of the semiconductor switching element) protruding to the side of the main body are connected to the bus bar for the source terminal, and Actual mounting process of soldering terminals (gate terminals and the like in semiconductor switching elements) to an electric circuit on a printed circuit board, respectively;
The method comprises the steps of cutting off the bus bar of the bus bar constituting plate and bending the tab of the external connection terminal formed on the bus bar along the outer edge of the printed circuit board.
[0014]
According to the above method, even when a large number of electronic components such as semiconductor switching elements and diodes need to be attached, the terminals of the electronic components can be soldered to the bus bar and the electric circuit of the printed board in one step. Therefore, the work efficiency is greatly improved as compared with the case where the terminals of the semiconductor switching elements are individually connected to the printed circuit board and the board on which the bus bars arranged separately from each other are proposed in Japanese Patent Application Laid-Open No. 10-35375. In addition, the electronic components such as the semiconductor switching elements can be arranged without disturbance.
[0015]
When the electronic component is a semiconductor switching element, the through hole formed in the printed circuit board and the main body of the semiconductor switching element are rectangular, and each of the main body of the semiconductor switching element mounted inside the through hole is formed. The sides are mounted at regular positions parallel to the sides of the through holes facing each other, and in a portion where a plurality of semiconductor switching elements are mounted in the one through hole, these semiconductor switching elements are aligned without displacement. You.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0017]
The method of forming a circuit body includes a step of punching a bus bar 1 shown in FIG. 1 from a single conductive metal plate in a state where the bus bar 1 is connected by an outer peripheral connection frame 10a and an inner portion 10b to form a bus bar structure 10, and a substantially rectangular shape. A step of forming the printed circuit board 2 having the through holes 20 punched out, a step of bonding the bus bar 1 and the printed circuit board 2 shown in FIG. 2 with an adhesive such as a polyamide resin, and a step of bonding the bus bar and the printed circuit board. A step of printing and applying a paste-like solder paste on the surface of the bus bar 1 exposed inside the through hole 20 and on a required portion on the printed circuit board 2, and the semiconductor switching element 3 and other electronic components shown in FIG. (Not shown), a step of folding the tab 11 of the bus bar 1 shown in FIG. 4, and a step of folding the bus bar 1 so as to meet the specifications of the electric circuit as shown in FIG. And a step to separate from the peripheral connecting frame 10a with cutting the coupling portion.
[0018]
As shown in FIG. 1, the bus bar 1 is formed by punching out a drain terminal bus bar 1A and a source terminal bus bar 1B in a required pattern in a region surrounded by a rectangular outer peripheral connection frame 10a. It is formed as a bus bar structure 10 mutually connected by a connection frame 10b.
[0019]
The drain terminal bus bar 1A and the adjacent source terminal bus bar 1B are exposed at the bottom surface of the through hole 20 in a state of being adhered to the printed circuit board 2, and the drain terminal bus bar 1A located inside the through hole 20 has solder. A slit-shaped punching portion 5 for preventing spread is provided.
[0020]
As shown in FIG. 6, the slit-shaped punched portion 5 is located along the outer edge of the drain terminal 31 exposed on the back surface (lower surface) of the main body 30 of the semiconductor switching element 3, specifically, The rectangular through hole 20 is provided at a position approximately 1 mm away from the outline 31 a in parallel with the linear peripheral edge of the rectangular through hole 20.
The punched portion 5 does not necessarily need to be provided at a position along the entire outer edge of the drain terminal 31, and may be provided at least in a direction in which the semiconductor switching element 3 may move due to the molten solder 40.
[0021]
In the present embodiment, as shown in FIG. 7A, in a portion where two semiconductor switching elements 3 (3-I, 3-II) are mounted in parallel in one through hole 20, these semiconductor switching elements 3 A punching portion 5 is provided between the outer side 30a of the main body 30 and the inner surface of the through hole 20 facing the same, and one punching portion 5 is provided between the semiconductor switching elements 3-I and 3-II. I have.
[0022]
As shown in FIG. 7B, the punching portion 5 is provided at a position where one semiconductor switching element 3 is mounted in one through hole 20 at a position facing the inner surface of the through hole 20.
[0023]
The busbar structure 10 is formed by punching a conductive material tin-plated into an alloy, and a pair of external circuit connection terminals are provided at a tip position of each busbar 1 on a pair of left and right sides surrounded by an outer peripheral connection frame 10a. Are provided in parallel.
Further, through holes 15 for connecting other electronic components and the bus bar 1 are punched at required positions of the bus bar 1 in advance.
[0024]
As shown in FIG. 6, the printed circuit board 2 is provided with an electric circuit made of a copper foil 22 on an upper surface of an insulating substrate 21, and this electric circuit controls a switching operation connected to a gate terminal 32 of the semiconductor switching element 3. It has a control circuit.
An insulating resin layer 23 is provided on the upper surface of the electric circuit layer made of the copper foil 22 except for a contact portion of the electric circuit.
Further, in this embodiment, the electric circuit is partially provided also on the lower surface side of the insulating substrate 21, connected to the electric circuit on the upper surface side, and the surface is covered with the insulating resin layer 24.
[0025]
The printed circuit board 2 is provided with a plurality of through holes 20 for mounting the semiconductor switching elements 3 in advance. These through holes 20 have a rectangular shape, and a recess 20 a for arranging the source terminal 32 extends in a part thereof.
[0026]
The method of assembling the bus bar 1, the printed board 2, and the semiconductor switching element 3 to form the circuit body 100 is as described above. After forming the bus bar 1 and the printed board 2 shown in FIG. Except for the area corresponding to 20, an insulating adhesive is applied to the lower surface of the printed circuit board, and the bus bar 1 is bonded and fixed. In this stacked state, the drain terminal bus bar 1A and the source terminal bus bar 1B are exposed in the through hole 20.
[0027]
Next, as shown in FIG. 8A, paste solder 40 is printed on the surface of the bus bar 1 exposed inside all the through holes 20. At the same time, the paste solder 40 is also printed on the contact portion of the copper foil on the printed circuit board 2 (not shown).
[0028]
After that, as shown in FIG. 8B, the semiconductor switching element 3 is mounted at a regular position of the through hole 20 by an automatic mounting machine. As shown in FIG. 9, the substantially rectangular drain terminal 31 exposed on the back surface of the main body 30 of the semiconductor switching element 3 is placed on the printed surface of the paste solder 40 of the drain terminal bus bar 1A, while being located on the side of the main body 30. , The source terminal 32 is provided on the printed surface of the paste solder 40 of the source terminal bus bar 1B, and the gate terminal 33 is provided on the solder paste of the terminal portion of the electric circuit (copper foil 22) of the printed circuit board 2. . The gate terminal 33 is bent stepwise more than the source terminal 32 by the thickness of the insulating substrate 21, and is accurately positioned on the upper surface of the terminal portion of the copper foil 22. Further, other electronic components (diodes and the like) mounted on the printed circuit board 2 are respectively installed at the contact portions of the copper foil on the printed circuit board (not shown). Next, the printed paste solder 40 is melted by reflow, the drain terminal 31 and the source terminal 32 of the semiconductor switching element are soldered to the bus bar 1, and the gate terminal 33 and the terminal of another electronic component are connected to the printed circuit board 2. It is soldered to the terminal of the copper foil 22.
[0029]
The bus bar 1 is made of the conductive material tin-plated as described above, and since tin plating has good wettability with molten solder, it is thin and easily spreads during reflow. Therefore, the solder spreads due to the melting of the paste solder at the time of reflow, and the drain terminal 31 of the semiconductor switching element provided on the upper surface of the paste solder is likely to be displaced. However, since the slit-shaped punched portion 5 is provided along the outer edge of the drain terminal 31, surface tension is generated in the molten solder as shown in FIGS. Without falling, the molten solder 40 is prevented from spreading. In addition, the swollen molten solder 40a comes into contact with the side surface of the drain terminal 31, and the drain terminal 31 prevents displacement due to the spread of the solder.
[0030]
At the position where the punched portion 5 is provided along the opposing outer edge of the drain terminal 31, the drain terminal 31 is pressed by the solder 40 swelled by surface tension from both sides, and is centered by the swelled solder 40 on both sides, so-called. Since a self-alignment effect is generated, positional deviation is regulated.
On the other hand, the side of the drain terminal 31 on the side from which the source terminal 32 and the gate terminal 33 protrude and the opposite side thereof have a misalignment because the contact of the gate terminal 33 is soldered to the electric circuit contact portion of the printed circuit board 2. Does not occur.
[0031]
As described above, the drain terminal 31 can be mounted at a proper position without causing a positional shift due to the spread of the molten solder 40. Therefore, each side of the rectangular semiconductor switching element 3 is positioned parallel to the opposite side of the rectangular through hole 20, and the plurality of semiconductor switching elements 3 are arranged in one through hole 20 in an aligned state. be able to.
[0032]
After the above-described mounting process of the semiconductor switching element 3 is completed, as described above, the tab 11 of the pass bar 1 protruding from the left and right edges of the printed circuit board 2 is bent upward so as to be connectable to an external circuit and a connector.
After the tab is bent, the outer connection frame 10a of the bus bar structure 10 is cut off, and the inner connection frame 10b connecting the bus bars is cut to divide the bus bar 1 into a shape that forms a required electric circuit. ing.
[0033]
According to the above steps, the bus bar 1 is directly fixed to the lower surface of the printed board 2, and the circuit body 100 including the semiconductor switching element 3 inserted into the through hole 20 of the printed board 2 and mounted on the bus bar 1 can be formed.
This circuit body 100 is thin because there is no space between the printed circuit board 2 and the bus bar 1 for interposing the semiconductor switching element, and the semiconductor switching element is mounted neatly without displacement, so that the positional accuracy is low. High quality and high quality.
[0034]
FIG. 10 shows a modification of the first embodiment, in which a slit-shaped punching portion 5 provided along the outer edge of the drain terminal 31 in a direction orthogonal to the direction in which the source terminal 32 and the gate terminal 33 protrude includes the source terminal 32 and the gate. The punching portion 5 is not provided at a portion close to the protruding side of the terminal 33, and the slit-like punching portion 5 is partially provided at the side away from the terminal 33.
[0035]
As described above, the position near the source terminal 32 and the gate terminal 33 is regulated by the soldering of the source terminal 32 and the gate terminal 33. Therefore, the punched portion 5 is provided at a remote position, and the position of the drain terminal 31 is adjusted. When the occurrence of the displacement is prevented, the drain terminal 31 can be positioned at the regular position.
[0036]
FIG. 11 shows a second embodiment of the present invention, in which a punched portion 5 'for interrupting solder spread provided on the bus bar 1 on which the drain terminal 31 is mounted is a small hole instead of a slit.
The punched portions 5 ′ formed of the small holes are provided one by one at the center of the four sides of the drain terminal 31 of the semiconductor switching element 3.
As described above, even if the punched portion 5 ′ made of a small hole is provided instead of the slit, when the molten solder 40 spreading when the drain terminal 31 is placed reaches the punched portion 5 ′, surface tension is generated. Since the bulge 40a is pressed against the outer surface of the drain terminal 31, it is possible to prevent the displacement of the drain terminal 31 from occurring.
The punched portion 5 'on the side of the source terminal 32 and the gate terminal 33 and the opposite side may be omitted.
[0037]
FIGS. 12A and 12B show a modification of the second embodiment. In FIG. 12A, two locations are provided along both outer edges of the drain terminal 31 in a direction orthogonal to the direction in which the source terminal 32 and the gate terminal 33 project. Provided. In (B), a punched portion 5 'consisting of two small holes is provided at a position away from the protruding side of the gate terminal.
[0038]
As described above, the size and shape of the punched portion provided to block the spread of the molten solder include the bus bar cross-sectional area, the amount of current required for the semiconductor switching element, the size of the semiconductor switching element, and the shape of the drain terminal. Is appropriately set in consideration of the above, but when a large current is required, it is preferable to make the punched portion a small hole.
[0039]
In the above-described embodiment, the punched portion is provided along the outer edge of the terminal exposed on the back surface of the main body of the semiconductor switching element. However, an electronic component such as a diode is similarly punched along the outer edge of the terminal exposed on the back surface of the main body. It is preferable to provide a recess to prevent displacement.
[0040]
【The invention's effect】
As apparent from the above description, according to the present invention, first, a bus bar is directly adhered to one surface of a printed circuit board, and electronic components such as semiconductor switching elements are inserted into through holes formed in the printed circuit board. The terminal exposed on the back surface of the electronic component is directly soldered to the bus bar, and the terminal protruding to the side of the main body is directly soldered to the electric circuit of the printed circuit board, so that the thickness of the circuit body can be reduced. The height can be reduced when the electrical junction box that houses the circuit body is placed flat.
In particular, when the bus bar is bonded to the printed board and the main body of the electronic component is inserted into a through hole formed in the printed board and the terminal exposed on the back surface of the main body is soldered to the bus bar, molten solder having good wettability is used. The spread of the terminals and the displacement of the terminals can be prevented by providing a punched part on the bus bar and utilizing the fact that surface tension is generated when the spread solder reaches the punched part, thereby preventing the occurrence of displacement of the electronic components. it can.
In this way, by merely providing a slit-shaped or small-hole punched portion in the bus bar, the electronic component can be mounted without shifting from the normal mounting position, and the positional accuracy can be improved. In particular, when a plurality of electronic components are arranged in parallel, they can be mounted in an aligned state, and the quality of the formed circuit body can be improved.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view of a bus bar and a printed circuit board, showing a forming process according to a first embodiment of the present invention.
FIG. 2 is a perspective view showing a state in which the bus bar and a printed board are bonded.
FIG. 3 is a perspective view showing a state where a semiconductor switching element is mounted on a laminate of the bus bar and a printed circuit board.
FIG. 4 is a perspective view showing a state where a tab of the bus bar is bent.
FIG. 5 is a perspective view of a completed circuit body from which the connection frame of the bus bar has been removed.
FIG. 6 is a sectional view before mounting a semiconductor switching element.
FIGS. 7A and 7B are plan views showing positions where punching portions for interrupting solder spread are arranged.
FIGS. 8A, 8B, and 8C are drawings showing steps for mounting a semiconductor switching element, and FIG. 8D is an enlarged view of a main part.
FIG. 9 is a perspective view of a portion where a semiconductor switching element is mounted.
FIG. 10 is a schematic diagram showing a modification of the first embodiment.
FIG. 11 is a main part plan view showing a punching unit according to a second embodiment.
FIGS. 12A and 12B are main part plan views showing a modification of the second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Pass bar 1A Drain terminal pass bar 1B Source terminal pass bar 2 Printed circuit board 3 Semiconductor switching element 5 Punching part 20 for cutting off solder spread 20 Through hole 21 Insulating substrate 22 Copper foils 23 and 24 used as an electric circuit Insulating resin layer 30 Semiconductor switching Element body 31 Drain terminal 32 Source terminal 33 Gate terminal 40 Solder 40a Swelled portion due to surface tension

Claims (5)

A bus bar is adhered to one surface of the printed circuit board, electronic components are mounted on the bus bar exposed in through holes provided in the printed circuit board, and terminals exposed on the back surface of the main body of the electronic component are connected to the bus bar and the main body is connected. A method of forming a circuit body in which a terminal protruding laterally is connected to an electric circuit of the printed circuit board, wherein the bus bar to which a terminal on the back surface of the main body of the electronic component is soldered is connected to an outer edge of the terminal. A method for forming a circuit body, characterized in that a punched portion formed of a slit or a small hole is formed at an outer position along the hole. 2. The circuit body according to claim 1, wherein the punching portion includes the slit extending linearly along an outer edge of the terminal or one or a plurality of the small holes arranged in parallel along the outer edge of the terminal. 3. Formation method. 3. The bus bar according to claim 1, wherein the bus bar between the inner peripheral surface of the through hole of the printed circuit board and a terminal exposed on the back surface of the main body of the electronic component does not have the punched portion. 4. A method for forming a circuit body. 4. The circuit body according to claim 1, wherein the punching portion is formed at least at a position away from a protruding side of a terminal protruding to a side of the main body of the electronic component. 5. Method. The electronic component comprises a semiconductor switching element, and the drain terminal exposed on the back surface of the main body of the semiconductor switching element and the source terminal protruding on the side surface of the main body are soldered to the drain terminal and source terminal bus bars exposed inside the through hole, respectively. The drain terminal is connected along the inside of the punched portion, and a gate terminal, a logic input / output terminal, a power supply terminal, and the like protruding to the side of the main body of the semiconductor switching element are connected to a printed circuit of the printed circuit board. The method for forming a circuit body according to any one of claims 1 to 3, wherein the circuit body is soldered to each of the terminal contact portions.

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