JPH10164730A - Branching connection box - Google Patents

Abstract

PROBLEM TO BE SOLVED: To support the supporting condition of a terminal stably and prevent cracking from occurring at the soldered part of a terminal soldered to a printed circuit board. SOLUTION: This connection box is provided with a collector block 7 whose terminal 4 is formed vertically, the bottom wall part 6 of a connection box case 3 which supports the base end part of the connector block 7, and a printed circuit board 5 which is fitted under the bottom wall part 6 and to which the base end part of the terminal 4 is soldered. The terminal 4 is supported against the bottom wall part 6 so as to be in a vertically fitted condition by forming a terminal supporting hole 9. The printed circuit board 5 is formed out of a raw material having expandability, and a clearance 11 is formed between the printed circuit board 5 and the bottom wall part 6, thus it is possible to absorb thermal stress working with a difference in thermal expansion coefficient between them.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a branch connection box used for branch connection to a wire harness or the like of an automobile.

[0002]

2. Description of the Related Art The branch junction box generally includes a printed circuit board formed by impregnating a paper with a phenol resin and hardening it into a thick plate, and a junction box case formed of a polypropylene resin or the like. The base end of the terminal is soldered to the substrate, and the terminal is pressed into a terminal support hole provided in the bottom wall of the connection box case so that the terminal is stably supported in an upright state. Is configured.

[0003] The junction box case has a coefficient of thermal expansion of about 5 to 10 times that of a printed circuit board, so that the printed circuit board hardly thermally deforms due to a temperature change. Large thermal deformation. Therefore, due to the difference in thermal expansion between the junction box case and the printed circuit board,
Large thermal stress acts between the bottom wall of the connection box case that supports the shaft of the terminal and the printed circuit board to which the base end of the terminal is soldered, and the terminal is inclined. Then, a large tensile stress or a large compressive stress caused by the thermal stress acts on the solder portion of the terminal soldered to the printed circuit board, and when this stress is repeatedly applied, a crack occurs in the solder portion to cause a conduction failure. There was a problem that caused.

In order to solve the above problem, conventionally, as shown in, for example, Japanese Patent Application Laid-Open No. 7-95716, a plurality of connector blocks having terminals erected are provided on a block support bottom wall of a resin case. In a branch connection box formed by protruding an edge on the base side of a terminal from a bottom wall and wiring these terminals by a printed circuit board disposed on the back side of the bottom wall, the printed circuit board is formed by a flexible material. By soldering the root edge of each terminal to the conductive pattern of the printed circuit board, the thermal stress at the time of thermal expansion and contraction is reduced by the bending of the printed circuit board, and cracks are generated in the solder portion. There is a known device that prevents such a problem.

[0005]

In the branch junction box described in the above publication, when the ambient temperature changes and the block supporting bottom wall of the resin case thermally expands and contracts, the printed circuit board is expanded and contracted in accordance with the thermal expansion and contraction. Therefore, the stress acting on the solder portion of the printed circuit board can be reduced to some extent, and the formation of cracks in the solder portion can be suppressed. However, when the ambient temperature significantly changes and the printed circuit board receives a large tensile stress or a compressive stress, the large stress cannot be absorbed by the expansion and contraction displacement of the printed circuit board, so that a crack is formed in the solder portion. There is a problem that it cannot be prevented.

For example, when the branch junction box is installed in an engine room of an automobile, when the engine is started in a cold region, the ambient temperature is reduced from about -35 ° C. to 130 ° C. Since the temperature may rise to about C, it is inevitable that a large stress is applied to the solder portion. Even in such a case, it is desired to prevent the formation of cracks in the solder portion. Was.

[0007] In view of such circumstances, the present invention provides a method for cracking a solder portion of a terminal soldered to a printed circuit board even when the ambient temperature changes significantly while stably supporting the supporting state of the terminal. To provide a branch junction box capable of preventing the formation of a branch junction box.

[0008]

The invention according to claim 1 is
A connector block on which terminals are erected, a bottom wall of a connection box case supporting a base end of the connector block, and a base end of the terminal mounted below the bottom wall and soldered. In a branch connection box including a printed board, a terminal support hole for supporting a terminal in an upright state is provided in the bottom wall portion, and the printed board is formed of an elastic material. A gap is provided between the wall and the wall for absorbing thermal stress acting in accordance with the difference between the two coefficients of thermal expansion.

According to the above configuration, when the ambient temperature changes within a predetermined range and the bottom wall of the junction box case thermally expands and contracts,
Following the expansion and contraction of the printed circuit board, the stress acting on the solder portion of the printed circuit board is reduced. Further, when a remarkable temperature change occurs in which the printed board cannot be expanded or contracted by following the thermal expansion and contraction of the bottom wall, the terminal may be deformed by bending between the printed board and the bottom wall. Thereby, the stress acting on the solder portion is absorbed.

According to a second aspect of the present invention, in the branch junction box according to the first aspect, when a thermal stress corresponding to a difference in thermal expansion coefficient between the printed circuit board and the bottom wall portion acts, the terminal is inclined. A terminal supporting hole for supporting the terminal in a state where the connection is prevented is formed in the bottom wall of the connection box case.

According to the above configuration, when a remarkable temperature change occurs in which the printed board cannot be expanded and contracted by following the thermal expansion and contraction of the bottom wall, the terminal is provided between the printed board and the bottom wall. By bending and deforming, the stress acting on the solder portion is absorbed, and the main body of the terminal is held in the terminal support hole in an upright state.

[0012]

1 and 2 show an embodiment of a branch junction box according to the present invention. This junction box is composed of a junction box case 3 composed of an upper case 1 and a lower case 2 formed of polypropylene resin or the like.
And a printed circuit board 5 to which the base end 4a of the terminal 4 is soldered.

The upper case 1 has a bottom wall 6 in the form of a thick flat plate, a plurality of connector blocks 7 protruding from the upper surface of the bottom wall 6, and positions corresponding to the installation sections of the connector blocks 7. And a ridge 8 projecting from the back surface of the bottom wall portion 6. Each of the connector blocks 7 is formed in a box shape having an open upper surface, and is configured such that a connector (not shown) on the wire harness side is fitted and a terminal is connected. A terminal support hole 9 for supporting the terminal 4 is formed in the bottom wall portion 6 of the upper case 1, and a shaft portion of the terminal 4 is press-fitted into the terminal support hole 9 so that a base end portion 4a of the terminal case 4 is connected to the bottom. It is configured to be supported in a state of protruding below the wall portion 6.

The printed board 5 is made of a flexible printed board (FPC) formed of a thin sheet-like material having elasticity, and is constituted by bonding two insulating sheets made of polyimide or polyester or the like. In addition, a conductor pattern (not shown) is formed on one of the insulating sheets.

The printed board 5 has an insertion hole 10 into which the base 4a of the terminal 4 is inserted.
Then, by inserting and soldering the base end 4a of the terminal 4 into the insertion hole 10 of the printed board 5, the terminal 4 is connected to a predetermined portion of the conductor pattern, The printed circuit board 5 is mounted on the lower surface of the upper case 1 in a state where a gap 11 for absorbing thermal stress acting in accordance with the difference in thermal expansion coefficient between the two is formed between the printed circuit board 5 and the bottom wall 6. It can be attached.

That is, a gap 11 corresponding to the length of the ridge 8 is formed between the printed circuit board 5 and the bottom wall 6 of the upper case 1 so that the bottom wall 6 will be described later. When a remarkable temperature change occurs in which the printed circuit board 5 cannot be expanded and contracted by following the thermal expansion and contraction of the portion 6,
The terminal 4 is allowed to bend and deform between the printed board 5 and the bottom wall 6. Therefore, the printed circuit board 5 to which the base end 4a of the terminal 4 is soldered, and the bottom wall 6 connected to the terminal 4 by press-fitting the shaft of the terminal 4 into the terminal support hole 9 are provided. The thermal stress acting between them is absorbed.

For example, when the junction box is installed in the engine room of an automobile, the engine is operated in a cold region, and the ambient temperature of the junction box is -35 °.
When the temperature rises from about C to about 130 ° C. and the bottom wall 6 of the junction box case 3 having a large thermal expansion coefficient undergoes a large thermal expansion,
A tensile stress that cannot follow this acts on the printed circuit board 5 having a small coefficient of thermal expansion, and the terminal 4 bends and deforms in the gap 11 as shown by a virtual line in FIG.
Therefore, as in the case where the printed circuit board 5 is brought into close contact with the lower surface of the bottom wall portion 6, excessive tensile stress such that a crack is formed in the solder portion 12 of the terminal 4 soldered to the printed circuit board 5 is generated. This prevents the solder portion 12 from acting.

As described above, the terminal support hole 9 for supporting the terminal 4 in the upright state is formed in the bottom wall portion 6 of the connection box case 3 and the printed board 5 is formed of an elastic material. While the terminal 4 is supported by the terminal support holes 9 of the bottom wall 6 and the bottom wall 6 thermally expands and contracts due to the ambient temperature acting within a predetermined range, the printed circuit board is caused to follow the expansion and contraction. By expanding and contracting 5, it is possible to reliably prevent excessive thermal stress from acting on the solder portion 12.

A gap 11 is provided between the printed circuit board 5 and the bottom wall 6 for absorbing a thermal stress acting in accordance with a difference in thermal expansion coefficient between the two. If there is a remarkable temperature change in which the printed circuit board 5 cannot be expanded and contracted by following the thermal expansion and contraction of the terminal 6, the terminal 4 is deformed by bending the terminal 4 between the printed circuit board 5 and the bottom wall 6. Accordingly, between the printed circuit board 5 to which the base end 4a of the terminal 4 is soldered corresponding to the difference in the coefficient of thermal expansion, and the bottom wall 6 supporting the terminal 4 in the terminal support hole 9. The acting thermal stress can be absorbed.

Therefore, the terminal 4 and the printed circuit board 5
Material and thickness of the bottom wall 6 and the junction box case 3
In consideration of the overall shape of the connector and the installation position of the connector block 7, etc., the size of the space 11 is set so that excessive stress does not act on the solder portion 12. It is possible to effectively prevent cracks from being formed due to the application of a large stress, and to improve the reliability of the conduction state of the circuit.

In the above embodiment, the thickness of the bottom wall 6 and the diameter of the terminal support hole 9 are set to appropriate values, so that the difference in the thermal expansion coefficient between the printed circuit board 5 and the bottom wall 6 is improved. Even when a large thermal stress corresponding to
Since the body of the terminal 4, that is, the portion above the shaft portion of the terminal 4 supported by the terminal support hole 9 is configured to be prevented from being inclined, the upper portion of the terminal 4 is set in the upright state. And can be easily connected to the terminal on the wire harness side. Therefore, it is possible to effectively prevent a situation in which the upper portion of the terminal 4 is bent and deformed due to excessive resistance acting when the terminal 4 is connected.

In the above embodiment, the connection box case 3
The bottom wall 6 and the connector block 7 are integrally formed. However, the bottom wall 6 and the connector block 7 are formed separately, and the connector block 7 is attached to the upper surface of the bottom wall 6. It may be configured to be attached by means such as screwing to the device.

[0023]

As described above, according to the first aspect of the present invention, there is provided a connector block in which terminals are erected, a bottom wall portion of a connection box case for supporting a base end of the connector block, and a connection member. In a branch connection box having a printed circuit board attached to the lower surface of the box case and soldered to the base end of the terminal, a terminal support hole for supporting the terminal in an upright state is provided on the bottom wall, The printed circuit board is formed of a material having elasticity, and a gap is provided between the printed circuit board and the bottom wall for absorbing thermal stress acting in accordance with a difference in thermal expansion coefficient between the two. ,
While the terminal is supported by the terminal support hole of the bottom wall, when a remarkable temperature change occurs, the terminal is bent and deformed between the printed board and the bottom wall to reduce the thermal stress. Inhibits the tensile stress based on the soldering of the terminals soldered to the printed circuit board, effectively prevents cracks from being formed in the soldering, and improves the reliability of circuit conduction. Can be improved.

Further, according to the present invention, when the thermal stress corresponding to the difference in the thermal expansion coefficient between the printed circuit board and the bottom wall portion is applied, the terminal is prevented from being tilted. Since the terminal supporting hole for supporting is formed in the bottom wall of the connection box case, the upper part of the terminal can be easily connected to the terminal on the wire harness side by maintaining the upper part in an upright state. There is an advantage that it is possible to effectively prevent a situation in which the upper portion of the terminal is bent and deformed due to the action of an excessive resistance.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a branch junction box according to the present invention.

FIG. 2 is a perspective view of the state of attachment of the printed circuit board viewed from the back side.

FIG. 3 is a sectional view taken along line AA of FIG.

[Explanation of symbols]

 3 Connection Box Case 4 Terminal 5 Printed Circuit Board 6 Bottom Wall 7 Connector Block 9 Terminal Support Hole 11 Gap 12 Solder

Claims (2)

[Claims] A connector block in which terminals are erected,
In a branch junction box including a bottom wall of a connection box case supporting a base end of the connector block, and a printed circuit board attached below the bottom wall and soldered to a base end of the terminal. A terminal support hole for supporting the terminal in an upright state in the bottom wall portion, and forming the printed circuit board from a stretchable material; A branch junction box having a gap for absorbing thermal stress acting in accordance with a difference in expansion coefficient. 2. A terminal box for supporting a terminal in a state where the terminal is prevented from being inclined when a thermal stress corresponding to a difference in thermal expansion coefficient between the printed circuit board and the bottom wall is applied. 2. The junction box according to claim 1, wherein the junction box is formed on a bottom wall of the case.