JP4882933B2 - Electronic parts busbar joint structure - Google Patents

Description

  The present invention relates to an electronic component bus bar bonding structure, and more particularly to an electronic component bus bar bonding structure in which terminals of an electronic circuit component are soldered to a bus bar.

  In an electronic circuit component such as an IC, a package structure such as SIP, DIP, and ZIP in which a large number of lead terminals protrude from the side surface in a row is common. Hereinafter, an electronic circuit component having such a package structure is also referred to as an electronic circuit component with leads. A chip-shaped electronic circuit component having terminals exposed at both ends of the bottom surface of the package is also known.

In mounting these electronic circuit components, it is common to solder the lead terminals of the electronic circuit components with leads and the terminals of the chip-like electronic circuit components to the conductor pattern of the printed circuit board. However, these terminals are soldered to the bus bar. It is also known to attach. Hereinafter, a structure in which an electronic circuit component is soldered to a bus bar is referred to as an electronic component bus bar bonding structure. This type of electronic component bus bar joint structure is described in Patent Document 1 below.
JP 2002-93995 A

(Object of invention)
However, the above-described conventional electronic component bus bar joint structure has a problem that its long-term reliability decreases due to thermal stress applied to the solder joint between the terminal of the electronic circuit component and the bus bar. The present invention has been made in view of the above problems, and an object of the present invention is to provide an electronic component bus bar joining structure that is excellent in manufacturability and excellent in the thermal cycle life of a solder joint.

(Summary of the Invention)
Each invention made in order to solve the above-mentioned problems is an electronic device comprising a plurality of bus bars and electronic circuit components extending on a substrate via an insulating sheet, and terminals of the electronic circuit components are joined to the bus bars by soldering. Applied to parts busbar joint structure.

A feature of the first invention is that a bus bar that is arranged on one side of the electronic circuit component and whose tip is joined to a terminal of the electronic circuit component is fixed to the substrate, and is arranged on the other side of the electronic circuit component and the tip is electronic. The bus bar joined to the terminal of the circuit component is fastened to the board through a long hole formed in the longitudinal direction of the bus bar so as to be displaceable in the longitudinal direction of the bus bar by a screw.

  That is, according to the present invention, the front end portion is soldered to the terminal of the electronic circuit component, and the bus bar extending to at least one side of the both side surfaces of the electronic circuit component is fastened to the substrate so as to be relatively displaceable. In this way, thermal stress per unit area or stress applied to the solder joint between the lead terminal of the electronic circuit component and the bus bar is reduced, and as a result, the long-term reliability of the solder joint is greatly increased. I found that it can be improved.

  More specific description will be given below.

  The bus bar soldered to the terminal of the electronic circuit component is usually extended long in a direction away from the electronic circuit component. The predetermined fixing area of the bus bar is preferably mechanically fixed to a metal substrate (may be a case) with screws or the like. The fixing of the bus bar to the board is provided at a considerable distance from the terminal bonding area of the bus bar that is bonded to the terminal of the electronic circuit component. Note that the terminal joint region of the bus bar is usually the tip of the bus bar. The portion of the bus bar between the fixed region and the terminal joint region expands and contracts in the longitudinal direction of the bus bar due to temperature change. However, since the board to which the bus bar is fixed and the bus bar are usually made of different materials, the solder joint that joins the bus bar and the terminal of the electronic circuit component due to the difference in coefficient of linear expansion between the bus bar and the board. However, there is a problem that the thermal stress is mainly applied in the longitudinal direction of the bus bar, and the durability is lowered. Copper is usually used for the bus bar from the viewpoint of reducing electrical resistance, and aluminum (which may be a resin) is usually used for the substrate from another economical viewpoint.

  In the present invention, the bus bar on one side of the electronic circuit component has a long hole that is long in the longitudinal direction of the bus bar, and is fastened to the substrate by a screw that passes through the long hole. As a result, even if the bus bar expands or contracts in the longitudinal direction due to the difference in linear expansion coefficient between the substrate and the bus bar, the fixed area of the bus bar can be displaced relative to the substrate in the longitudinal direction of the bus bar accordingly. As a result, the expansion and contraction of the bus bar does not give a thermal stress to the solder joint, and the thermal cycle life (also referred to as a cooling cycle life) of the solder joint can be greatly improved.

  When the bus bar is made of copper and the board is made of aluminum, the relative expansion and contraction phenomenon in the longitudinal direction of the bus bar with respect to the board due to the difference in the coefficient of linear expansion between the board and the bus bar. The linear expansion coefficient of ordinary copper bus bars and lead terminals Is smaller than that of a resin or aluminum substrate.

  When the bus bar is fixed to the board at room temperature so that relative displacement is not possible, and the terminals of the electronic circuit components are soldered to the bus bar, the aluminum (or resin) board expands more in the longitudinal direction of the bus bar than the bus bar when the temperature rises. . It is assumed that the bus bar is fixed to the substrate in a fixing region that is further away in the longitudinal direction of the bus bar than the solder joint with the electronic circuit component. As a result, at the solder joint between the electronic circuit component and the bus bar, the bus bar is pulled toward the fixed region, and shear stress is generated at the solder joint. This condition disappears when the temperature drops. When this cooling / heating cycle is repeated over a long period of time, the solder joint is damaged by the repeatedly applied shear stress.

  In the present invention, since the bus bar can be displaced relative to the substrate in the longitudinal direction of the bus bar, the stress does not occur, and as a result, the thermal cycle life of the solder joint is greatly improved. In addition, the repetition of the temperature change is generated by heat generated by the electronic circuit component or the bus bar or by the environmental temperature of the electronic circuit component. The environmental temperature of the electronic circuit component becomes particularly significant when the electronic circuit component is disposed in the engine room or mounted on a large heat generating component such as a motor.

  In addition, the long hole can be formed at the same time as the punching and press forming of the bus bar from the copper plate, as well as the conventional circular hole, and it does not interfere with the solder joint. Productivity is not reduced.

  In a preferred embodiment, the bus bar that is arranged on one side of the electronic circuit component and whose tip is joined to the terminal of the electronic circuit component is fixed to the substrate so as not to be relatively displaceable by a screw, and the other side of the electronic circuit component The bus bar that is disposed in the front end and is joined to the terminal of the electronic circuit component is fastened to the substrate so as to be displaceable in the longitudinal direction of the bus bar by passing through a long hole formed long in the longitudinal direction of the bus bar. . That is, in this aspect, of the pair of bus bars arranged on both sides of the electronic circuit component, the bus bar on one side is fixed to the fixing region with a screw, and the bus bar on the other side can be relatively displaced with respect to the substrate by the long hole. The structure to hold is adopted. In this way, the pair of bus bars that are integrally joined by soldering to the electronic circuit component as a whole can be expanded and contracted with respect to the board as a fulcrum by temperature change, Due to the difference in linear expansion coefficient between the electronic circuit component integral and the substrate, no stress is applied to the integral. Therefore, the thermal cycle life can be greatly improved as compared with the conventional structure in which all the bus bars are fixed to the substrate. In addition, since some bus bars can be fixed to the substrate with screws as in the past, it is possible to suppress a decrease in the mechanical stability of the bus bars.

  In a preferred embodiment, the plurality of bus bars arranged on one side of the electronic circuit component and having the tip portions joined to the terminals of the electronic circuit component are fixed relative to the substrate by screws so that the other of the electronic circuit components is not displaced. A plurality of bus bars that are arranged on the side and whose tips are joined to the terminals of the electronic circuit component pass through a long hole formed in the longitudinal direction of the bus bar, and are fastened to the board so that they can be displaced in the longitudinal direction of the bus bar by screws. Has been. That is, in this aspect, a configuration is adopted in which all the bus bars on one side of the electronic circuit component are fixed to the fixing region with screws, and all the bus bars on the other side are held so as to be relatively displaceable with respect to the substrate by the long holes. Yes. In this way, the electronic circuit components can be translated in the longitudinal direction of the bus bar due to the expansion and contraction of each bus bar, so that the torsional stress is prevented from occurring in the solder joint and the thermal cycle life is improved. Can do. In addition, since all the bus bars on one side of the electronic circuit component can be fixed to the substrate with screws as usual, it is possible to suppress a decrease in the mechanical stability of the bus bar.

In a preferred embodiment, the electronic circuit component has a DIP structure having at least a pair of lead terminals protruding from both side surfaces and individually soldered to the bus bars on both sides. In this way, in addition to the difference in linear expansion coefficient between the bus bar and the substrate, the difference in linear expansion coefficient between the lead terminal of the electronic circuit component and the substrate can also be absorbed.

In a preferred embodiment, the electronic circuit component is composed of a chip-shaped component in which terminals of the electronic circuit component are exposed at both ends of the bottom surface and are joined to the upper surface of the bus bar by solder. In this aspect, the same effect as described above can be obtained.

  According to a second aspect of the present invention, the screw is electrically insulated from the bus bar by the hooked insulating sleeve and is screwed into the female screw hole of the board so that the bus bar can be relatively displaced through the free hole of the bus bar. The dimensional difference between the inner diameter and the outer diameter of the screw is set to be larger than the sum of the maximum amount of expansion and contraction in the longitudinal direction of the bus bar and the tube thickness of the flanged insulating sleeve due to temperature changes in a predetermined use environment.

  That is, according to the present invention, the dimensional difference between the inner diameter of the free hole of the bus bar and the outer diameter of the screw is the sum of the maximum amount of expansion and contraction in the longitudinal direction of the bus bar due to the temperature change in a predetermined use environment and the tube thickness of the insulating sleeve with hook Therefore, stress is applied to the solder joint between the bus bar and the terminal of the electronic circuit component due to the relative expansion and contraction in the longitudinal direction of the bus bar with respect to the board caused by the difference in linear expansion coefficient between the bus bar and the board. Almost never occurs. For this reason, compared with the prior art in which each bus bar is completely fixed to the substrate, the thermal cycle life of the solder joint can be greatly extended.

  A preferred embodiment of an electronic component bus bar joining structure of the present invention will be described with reference to the drawings. It should be noted that the present invention should not be construed as being limited to the following embodiments, and it is natural that the technical idea of the present invention may be realized by a combination of other known techniques.

(Embodiment 1)
The electronic component bus bar joining structure of this embodiment will be described with reference to FIGS. FIG. 1 is a schematic longitudinal sectional view cut in the longitudinal direction of the bus bar, and FIG. 2 is a schematic plan view of FIG.

(overall structure)
In FIG. 1, reference numeral 1 denotes a resin mold IC having a DIP structure which constitutes an electronic circuit component referred to in the present invention, 2 is a substrate made of a thick metal plate, and 3A and 3B are bus bars connected to each lead terminal 4 of the resin mold IC. . In this embodiment, the bus bars 3A, 3B and the lead terminals 4 are made of copper, and the substrate 2 is made of an aluminum alloy. The lead terminal 4 protrudes horizontally from both side surfaces of the resin mold IC 1 and then extends obliquely downward. Thereafter, the tip of the lead terminal 4 extends further horizontally and is individually soldered to the bus bars 3A and 3B on both sides of the resin mold IC1. A resin film 5 for electrical insulation is provided on the surface of the substrate 2. 6 is solder which joins the front-end | tip part of the lead terminal 4, and the front-end | tip part of bus-bar 3A, 3B. The bus bar 3A is fixed to the substrate 2 completely with screws 7A sandwiching the resin film 5 or in the longitudinal direction of the bus bars 3A, 3B. The bus bar 3B is held on the substrate 2 so as to be relatively displaceable in the longitudinal direction with respect to the substrate 2 with the resin film 5 sandwiched between the screws 7B. The resin mold IC1 is bonded to a bus bar 3C disposed on the substrate 2 with the resin film 5 interposed therebetween via a solder layer.

(Fixing the bus bar 3A)
8A is a resin flanged insulating sleeve fitted to a screw 7A for fastening the bus bar 3A. In order to simplify the illustration, the flanged insulating sleeve 8A is painted black in FIG.

  The bus bar 3 </ b> A and the resin film 5 have through-holes having a circular cross section that communicate with each other, and a female screw hole 21 is formed in the substrate 2 so as to communicate with these through-holes. The bus bar 3A is fixed to the substrate 2 by passing through these through holes and screwing the screws 7A into the female screw holes 21. A sleeve 8A with a flange made of resin fitted to the screw 7A electrically insulates the screw 7A from the bus bar 3A.

(Fixing the bus bar 3B)
Reference numeral 8B denotes a resin flanged insulating sleeve fitted to a screw 7B for fastening the bus bar 3B. In order to simplify the illustration, the flanged insulating sleeve 8B is painted black in FIG.

  A long hole 9 is formed in the bus bar 3B, and this long hole 9 communicates with a through hole provided in the resin film 5 and a female screw hole 22 provided in the substrate 2. The bus bar 3 </ b> B is supported by the substrate 2 by passing screws 7 </ b> B into the female screw holes 22 through the long holes 9 and the through holes of the resin film 5. A sleeve 8B with a flange made of resin fitted to the screw 7B electrically insulates the screw 7B from the bus bar 3B. The long hole 9 is formed long in the longitudinal direction of the bus bar 3B as shown in FIG. 2, and the screw 7B is screwed in such a range that the bus bar 3B can be displaced relative to the substrate 2 in the longitudinal direction. Has been done.

  2 illustrates the resin mold IC 1 having 2 × 6 lead terminals 4. However, the number of the lead terminals 4 is not limited to this, and may be a ceramic package IC or the like. . Further, as a material of the substrate 2, the bus bars 3 </ b> A and 3 </ b> B, and the lead terminals 4, it is naturally not limited to the above.

(Function)
The stress state at the time of temperature change of this electronic component bus bar joining structure will be described below. However, it is assumed that the bus bars 3A and 3B are made of copper and the substrate 2 is aluminum.

  When the temperature becomes high, the substrate 2 extends in the longitudinal direction of the bus bars 3A and 3B rather than the bus bars 3A and 3B. As a result, the screw 7B and the flanged insulating sleeve 8B fastened to the substrate 2 move away from the screw 7A in the longitudinal direction of the bus bars 3A and 3B. However, since the long diameter of the long hole 9 is equal to or greater than the maximum displacement amount of the screw 7B with respect to the substrate 2 when the assumed maximum temperature change, the relative displacement of the screw 7B is pulled by the bus bars 3A and 3B in the longitudinal direction. No stress or compressive stress is applied. Therefore, no shear stress is generated in the solder 6 that joins the lead terminal 4 of the electronic circuit component 1 and the bus bars 3A, 3B. The thermal cycle life of the solder 6 is greatly improved.

  FIG. 2 is a schematic plan view, and illustrations of the insulating sleeves 8A and 8B with hooks are omitted.

(Modification)
In the above embodiment, the cylindrical portion of the flanged insulating sleeve 8B has a cylindrical shape, but may instead be a long hole fitted into the long hole 9 of the bus bar 3B. In this case, the screw 7B is displaced in the longitudinal direction of the bus bars 3A and 3B with respect to the flanged insulating sleeve 8B due to a temperature change, but the same effect as described above can be obtained.

(Modification)
In the above embodiment, the screws 7A and 7B are made of metal, but the screws 7A and 7B may be made of an electrically insulating resin. In this case, the flanged insulating sleeves 8A and 8B can be omitted.

(Modification)
A modification is shown in FIG. In this embodiment, the resin mold IC1 which is an electronic circuit component with leads shown in FIG. 1 is changed to a chip-shaped component 1A. On the bottom surface of the chip-like component 1A, terminals are exposed at both ends in the left-right direction in FIG. 3, and the pair of terminals are individually joined to the bus bars 3A and 3B directly below by solder 6A. . Even in this case, the same effects as those of the first embodiment can be obtained. Also in this embodiment, it is natural that the screws 7A and 7B can be resin screws.

(Embodiment 2)
The electronic component bus bar joining structure of this embodiment will be described with reference to FIGS. 4 is a schematic longitudinal sectional view cut in the longitudinal direction of the bus bar, and FIG. 5 is a schematic plan view of FIG. However, in FIG. 5, as with FIG. 2, the illustration of the hooked insulating sleeve is omitted.

  This embodiment is characterized in that, instead of providing the long hole 9 in the bus bar 3B in the first embodiment shown in FIG. 1, a through hole 31 having a circular cross section is provided in the bus bar 3B in the same manner as the bus bar 3A. Therefore, the through hole 31 of the bus bar 3B communicates with the through hole provided in the resin film 5 and the female screw hole 22 provided in the substrate 2. The bus bar 3 </ b> B is supported by the substrate 2 by passing through the through hole 31 and the through hole of the resin film 5 and screwing the screw 7 </ b> B into the female screw hole 21. Further, the bus bar 3 </ b> A is supported by the substrate 2 by passing through the through hole 31 and the through hole of the resin film 5 and screwing the screw 7 </ b> A into the female screw hole 21. That is, the bus bar 3B is fastened to the substrate 2 in the same manner as the bus bar 3A.

  However, in this embodiment, the through holes 31 of the bus bars 3A and 3B are free holes. The dimensional difference between the inner diameter of the through hole (free hole) 31 provided in the bus bar 3A and the sum of the outer diameter of the screw 7A and the tube thickness of the flanged insulating sleeve 8A is the substrate of the bus bar 3A due to the assumed maximum temperature change. 2 is set larger than the maximum amount of relative expansion / contraction in the longitudinal direction (at the position of the solder 6). Similarly, the dimensional difference between the inner diameter of the through hole (free hole) 31 provided in the bus bar 3B and the sum of the outer diameter of the screw 7B and the cylinder thickness of the flanged insulating sleeve 8B is the bus bar due to the assumed maximum temperature change. It is set to be larger than the maximum relative expansion / contraction amount (at the position of the solder 6) in the longitudinal direction with respect to the substrate 2 of 3B.

  Furthermore, the screwing amounts of the screws 7A and 7B are set in a range in which the bus bars 3A and 3B can be relatively displaced (stretched) in the longitudinal direction of the bus bars 3A and 3B with respect to the screws 7A and 7B.

  In this way, as in the first embodiment, the stress of the solder 6 due to the difference in linear expansion coefficient between the bus bars 3A and 3B and the substrate 2 can be reduced, and the thermal cycle life can be greatly extended.

  Of course, it is not essential to make the inner diameter of the through hole 31 of the bus bar 3A coincide with the inner diameter of the through hole 31 of the bus bar 3B.

(Modification)
Resin screws may be employed as the screws 7A and 7B. In this case, the cylinder thickness of the flanged insulating sleeves 8A and 7B can be set to zero.

1 is a schematic longitudinal sectional view showing an electronic component bus bar joining structure according to Embodiment 1. FIG. FIG. 2 is a schematic plan view of the electronic component bus bar joining structure of FIG. 1. It is a model longitudinal cross-sectional view of the electronic component bus-bar joining structure which shows the deformation | transformation aspect of Embodiment 1. It is a model longitudinal cross-sectional view which shows the electronic component bus-bar joining structure of Embodiment 2. FIG. FIG. 5 is a schematic plan view of the electronic component bus bar joining structure of FIG. 4.

Explanation of symbols

1A Chip-shaped parts 1 Resin mold IC (electronic circuit parts)
2 Substrate 3A Bus bar 3B Bus bar 3C Bus bar 4 Lead terminal (terminal)
5 Resin film 6 Solder 7A screw 7B screw 8A Insulated sleeve with flange 8B Insulated sleeve with flange 9 Long hole 21 Female screw hole 22 Female screw hole 31 Through hole

Claims (6)

A plurality of bus bars and electronic circuit components extending through an insulating sheet on a substrate;
In the electronic component bus bar joining structure in which the terminals of the electronic circuit components are joined to the bus bar by soldering,
The bus bar, which is disposed on one side of the electronic circuit component and whose tip is joined to a terminal of the electronic circuit component, is fixed to the substrate,
The bus bar, which is arranged on the other side of the electronic circuit component and whose tip is joined to the terminal of the electronic circuit component, passes through a long hole formed long in the longitudinal direction of the bus bar and is screwed into the length of the bus bar. An electronic component bus bar joining structure, wherein the electronic component bus bar joining structure is fastened to the substrate so as to be displaceable in a direction. In the electronic component busbar joining structure according to claim 1,
The bus bar, which is arranged on one side of the electronic circuit component and whose tip is joined to a terminal of the electronic circuit component, is fixed to the substrate so as not to be relatively displaced by a screw,
The bus bar, which is arranged on the other side of the electronic circuit component and whose tip is joined to the terminal of the electronic circuit component, passes through a long hole formed long in the longitudinal direction of the bus bar and is screwed into the length of the bus bar. An electronic component bus bar joining structure, wherein the electronic component bus bar joining structure is fastened to the substrate so as to be displaceable in a direction. In the electronic component busbar joining structure according to claim 1,
The plurality of bus bars arranged on one side of the electronic circuit component and having the tip part joined to the terminal of the electronic circuit component are fixed to the substrate so as not to be relatively displaced by screws,
The plurality of bus bars arranged on the other side of the electronic circuit component and having tips connected to the terminals of the electronic circuit component pass through long holes formed in the longitudinal direction of the bus bar and are screwed into the bus bar. An electronic component busbar joining structure characterized in that the electronic component busbar joining structure is fastened to the substrate so as to be displaceable in the longitudinal direction. In the electronic component busbar joining structure according to claim 1,
The electronic circuit component has a DIP structure having at least a pair of lead terminals protruding from both side surfaces and individually soldered to the bus bars on both sides. In the electronic component busbar joining structure according to claim 1,
The electronic circuit component is an electronic component bus bar joining structure comprising chip-like components that are exposed to terminals of the electronic circuit component at both ends of the bottom surface and joined to the upper surface of the bus bar by solder. A plurality of bus bars and electronic circuit components extending through an insulating sheet on a substrate;
In the electronic component bus bar joining structure in which the terminals of the electronic circuit components are joined to the bus bar by soldering,
Screw, the bus bar is screwed into the female screw hole of the displaceable relative to the substrate through the遊孔of the bus bar by flanged insulating sleeves being electrically insulated from said bus bar,
The dimensional difference between the inner diameter of the free hole and the outer diameter of the screw is set to be larger than the sum of the maximum expansion / contraction amount in the longitudinal direction of the bus bar and the tube thickness of the flanged insulating sleeve due to temperature change in a predetermined use environment. An electronic component bus bar joining structure characterized by being made.