JP2003008164A - Electrical part mounting structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure a junction reliability of soldered electrical parts. SOLUTION: The opening width of a resin opening 15A of a circuit board 10 in its mounting surface side is set to be large than the width of a root 14a of an electrical part 13, an a lower side 14c of the root 14a is brought into contact with an upper surface of a bus bar 11. Under this condition, soldering is carried out from the resin opening 15B on the rear side of the mounting surface. Even when a high temperature of melted solder is transmitted to the circuit board 10, the electrical part 13 does not contact the resin 12 of the circuit board 10, thus generating no stress such as to forcibly separate the soldered junction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric component mounting structure, and more particularly, to improving reliability of bonding when soldering an electric component such as a relay to a circuit board in which a bus bar is resin-molded.

[0002]

2. Description of the Related Art Conventionally, an electric connection box such as a junction box is mounted on a vehicle body of an automobile, and the electric connection box includes an internal circuit constituting a required circuit. The internal circuit is often formed by stacking bus bars, single core wires, etc. with an insulating plate interposed, but a circuit board in which the bus bar is resin-molded may be used together. When the circuit board is also used in this way, electric parts such as a relay and a diode attached to the electric connection box may be directly mounted on the circuit board by soldering or the like.

FIG. 8 shows a conventional structure for mounting electric parts on a circuit board. A bus bar 2 made of a strip-shaped conductive material and arranged around a required internal circuit is molded with a resin 3 around the bus bar 2. The circuit board 1 is covered and the electric component 4 such as a relay is mounted on a required portion of the upper surface 1a which is a mounting surface of the circuit board 1.

As shown in FIG. 9A, the mounting locations of the electric components 4 are provided on the upper and lower surfaces 1a and 1b of the circuit board 1,
A terminal hole 2a is formed in a portion where the bus bar 2 is exposed in the resin openings 6A and 6B which are not covered with the resin 3, and the root portion 5 of the lead terminal 5 protruding from the bottom surface 4a of the electric component 4 is formed.
A tip portion 5b narrower than a is inserted into the terminal hole 2a.
At this time, the lower side 5c with the step of the root portion 5a is the circuit board 1
The electric component 4 is brought into a stable state by being brought into contact with the upper surface 1a which is a mounting surface of the electric component 4. The opening width of the resin opening 6A on the upper surface 1a is made narrower than the width of the lower side 5c of the root 5a and the opening width of the resin opening 6B on the lower surface 1b because the root 5a is thus brought into contact. ing.

In the above state, as shown in FIG. 9 (B), the melted solder H is immersed in the flow on the lower surface 1b of the circuit board 1, and the tip portions 5b of the lead terminals 5 and the bus bars 2 are joined by soldering. ing. In addition, when the electric component is for large current, etc., as shown in FIG.
Two b'are provided, and two terminal holes 2a 'are also formed in the bus bar 2'in the resin openings 6A' and 6B 'so that the lower side 5c' of the root 5a 'is brought into contact with the upper surface 1a'. Sometimes soldered.

In addition to the electric component mounting structure as described above, as disclosed in Japanese Patent Application Laid-Open No. 5-13892 of FIG. The bottom surface 8a of the electric component 8 is brought into contact with the electric component 8 to stabilize the mounting state of the electric component 8.
The bottom surface 8a 'of the electric component 8'directly to the substrate 7'
There is also disclosed a structure which abuts on the upper surface 7b 'of the.

[0007]

The solder H for joining the tip 5b of the lead terminal 5 and the bus bar 2 is about 180.degree. C. with leaded solder to bring it into a molten state, and 275.degree. C. with lead-free solder depending on the constituent material. The temperature is as high as 290 ° C. Such a high temperature is transmitted to the resin 3 forming the circuit board 1 in addition to the lead terminals 5 and the bus bar 2 to be soldered. The lead terminals 5, the bus bar 2, and the resin 3 undergo thermal expansion when subjected to high-temperature heat transfer. However, since the materials are different from each other, the thermal expansion coefficients are also different, and even if they receive the same high-temperature transfer, they are thermally expanded. Since the amount to be applied is different, there is a problem that stress is generated in the direction of separating the soldered parts.

For example, when the heat transfer of the molten solder is received in FIG. 8, when the expansion of the resin 3 in the thickness direction is larger than the expansion of the tip portion 5b of the lead terminal 5 in the vertical direction, the resin 3 is Lower side 5c of the root portion 5a of the lead terminal 5
Since they are in contact with each other, stress is generated in the direction of lifting the electric component 4. This stress acts as a force in the direction where the tip 5b of the lead terminal 5 and the bus bar 2 are joined by soldering in the direction of pulling the tip 5b out of the terminal hole 2a. There is also a possibility that electrical continuity cannot be secured, and there is a problem that the joint reliability of soldering is significantly reduced.

Furthermore, even if you are lucky enough to solder
Since the accuracy with respect to the thickness of the resin 3 covering the bus bar 2 is low, there is a problem that the accuracy of the mounting height of the electric component 4 on the circuit board 1 cannot be ensured as specified.

In addition, these problems do not occur only in the electric component mounting structure of FIG. 8, but in any of the electric component mounting structures of FIG. 10 and FIGS. 11A and 11B, the resin contacts the resin. Since the electric components are positioned by the above, the thermal expansion of the resin at the time of soldering causes a stress to separate the joint portions, and the jointability due to the soldering is deteriorated.

The present invention has been made in view of the above problems, and it is an object of the present invention to maintain the joining reliability for soldering without generating a stress that separates the joining portion even when the heat of fusion at the time of soldering is received. I am trying.

[0012]

Means for Solving the Problems In order to solve the above problems, the present invention provides a bus bar by providing a resin opening portion on a mounting surface of a portion where a bus bar is covered with a resin mold for mounting an electric component and a back surface thereof. In addition to exposing the terminal, an electric component is inserted into the terminal hole formed in this exposed portion, and the tip end of which the step is made narrower than the root of the lead terminal protruding from the bottom surface of the electric component is inserted and soldered to the bus bar. In the mounting structure, in the circuit board, the opening width of the resin opening portion on the mounting surface side is set to be larger than the width of the lower side of the lead terminal at which the root portion is stepped, and the lower side of the root portion contacts the upper surface of the bus bar. (EN) Provided is an electrical component mounting structure in which soldering is performed from a resin opening on the back surface side of a mounting surface in this state.

As described above, when the resin opening portion on the mounting surface side of the electric component of the circuit board is set to have an opening width within which the root portion of the lead terminal can be accommodated, the bus bar with the stepped bottom side is exposed. The electrical components can be brought into direct contact with each other to stabilize the electrical components. In addition, even if the heat of fusion is transferred by being immersed in the flow of molten solder during soldering, the lead terminals of electrical components are not in contact with the resin, so stress that separates the joint due to the difference in the coefficient of thermal expansion from the resin Can be prevented. As a result, it is possible to reliably maintain the joint at the joint and to secure reliability by soldering.

Since it is generally difficult to increase the thickness accuracy of the resin portion which covers the bus bar on the circuit board, the root portion of the lead terminal is brought into contact with the resin portion which is the outer surface of the circuit board as in the prior art. Compared with the case where it is carried out, the mounting height accuracy of the electric component can be improved by directly bringing the root portion into contact with the bus bar having a constant thickness. Further, since the mounting height of the electric component itself can be reduced by the thickness of the resin as compared with the conventional case, the height of the circuit board on which the electric component is mounted can be made compact and the accommodation property in the electric junction box can be improved. Further, the above-mentioned soldering can be applied by a method of using a soldering iron, vapor phase soldering, etc., in addition to immersing in the flow of molten solder.

The lead terminal has a plurality of tip portions, and the same number of terminal holes as the tip portions are formed in the bus bar exposed at the resin opening to insert the tip portions of the lead terminal. ing. Even for electrical components with multiple tips that are compatible with large currents, etc., the resin opening on the mounting surface side should be larger than the width of the bottom side of the root of the lead terminal, and the number of tips corresponds to the number of tips. By providing the holes in the bus bar, the plurality of tip portions of the lead terminals and the bus bar can be surely connected to each other by soldering without being stressed at the joints, similarly to the above.

An opening hole is formed in the center of the root portion of the lead terminal. When the opening hole is formed in this way, the wide root part is also composed of narrow parts on both sides and the upper and lower sides of the opening hole, there is no wide part in the lead terminal, and the heat distribution is different in each part of the lead terminal. Can be made almost uniform. When the heat distribution becomes uniform, the conditions at the time of soldering and at the time of solidification of the molten solder become uniform, and the solder itself has a good warp and the degree of bonding can be improved.
In addition, in order to make the width of each part of the lead terminal uniform, in addition to forming the opening hole as described above, the root part of the lead terminal is located near the lower side of the step where it contacts the upper surface of the bus bar. The shape above the range may be narrower than the width of the lower side.

Further, according to the present invention, a hole is provided at the tip of the lead terminal to allow the molten solder to enter at the time of soldering to increase the contact point with the solder. When a hole is provided in the tip part to be inserted into the terminal hole of the bus bar in this way, the molten solder also enters this hole part, and the contact area with the solder increases, and the tip part and the terminal hole of the bus bar by soldering It is possible to increase the bonding strength of the, and further improve the connectivity.

In the soldering, the back surface of the mounting surface of the circuit board is immersed in the flow of the molten solder, the molten solder is caused to flow into the resin opening portion on the back surface side, and the tip portion and the bus bar are joined. The substrate is such that the peripheral edge of the resin opening on the back surface is tapered in such a manner that the opening size is reduced from the rear surface to the internal bus bar side, and the peripheral edge of the resin opening on the upstream side of the flow of the molten solder is The angle of inclination is made larger than the peripheral edge on the downstream side so that the flow of the molten solder is guided into the resin opening.

When the resin opening portion on the back surface side of the circuit board is formed as described above, the molten solder smoothly flows into the resin opening portion when immersed in the flow of the molten solder, so that the tip portion of the lead terminal and the bus bar are securely connected. Can be joined. Furthermore, if the angle of inclination of the peripheral edge of the resin opening is larger on the upstream side than on the downstream side, there is a difference between the speed at which the molten solder flows into the resin opening and the speed at which the molten solder flows out, blocking the situation where the solder bridges the resin opening. It is possible to achieve proper soldering. In addition,
The various electric component mounting structures described above can be applied alone or in appropriate combination.

[0020]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an electric component mounting structure according to a first embodiment of the present invention, in which a bus bar 11 made of a conductive material forming a required circuit is molded with a resin 12 and covered with a circuit board 10 to mount an electric component 13 thereon. Installed. In the electric component 13, the lead terminal 14 is projected from the bottom surface 13a, and a tip end portion 14b, which is narrowed by forming a step from the lower side 14c of the root portion 14a, is joined to the bus bar 11 by soldering.

As shown in FIG. 2 (A), the mounting portion of the electric component 13 includes the upper and lower surfaces 10a of the bus bar 11,
10b is provided with resin openings 15A and 15B that open the resin 12 covering the bus bar 11 so that a part of the bus bar 11 is exposed so as to come into contact with the lead terminals 14.
The opening width L1 of the resin opening 15A of the upper surface 10a on the mounting surface side of No. 3 is set to be wider than that of the conventional resin opening 6A of FIG. Specifically, the opening width L1 is the width dimension L of the wide root portion 14a of the lead terminal 14 of the electric component 13.
The width is made wider than 2, so that the root portion 14a is set inside the resin opening portion 15A. The bus bar 11 exposed in the resin opening 15A has a terminal hole 11a for connection, and the hole width of the terminal hole 11a is set wider than that of the tip portion 14b of the lead terminal 14.

To attach the electric component 13 to the circuit board 10, the tip portion 14b of the lead terminal 14 is inserted into the terminal hole 11a through the resin opening 15A on the mounting surface side. By this insertion, as shown in FIG. 2B, the root portion 14 a of the lead terminal 14 is set within the resin opening 15 A, and the root portion 14 a
The lower side 14a of a directly contacts the upper surface 11b of the bus bar 11, and the electric component 13 is mounted on the circuit board 10 in a stable state.

The lower surface 10b of the circuit board 10 with the electric components 13 mounted thereon is dipped in the flow of the molten solder H for soldering. The melted solder H wraps around the tip portion 14b of the lead terminal 14 in the resin opening 15B of the lower surface 10b, joins the bus bar 11 and the tip portion 14b as shown in FIG. 1, and also in the terminal hole 11a. It penetrates and joins the periphery of the tip portion 14b and the terminal hole 11a.

At the same time as the soldering, the high temperature solder H comes into contact with the circuit board 10 so that high heat is transferred to the bus bar 1
1, the resin 12, and the lead terminal 14 are thermally expanded. However, in the mounting structure of the first embodiment, since the electric component 13 and the lead terminal 14 are not in contact with the resin 12 that covers the bus bar 11, even if the resin 12 thermally expands, there is no effect on the joint portion by soldering. Not affecting. Further, the bus bar 11 and the lead terminal 14 also thermally expand, but their amounts are smaller than that of the resin 12, and since both of them are metal members, they thermally expand to the same extent as the soldering location, so that the soldering location is separated. No stress is generated, the bonded state is stably maintained, and the reliability of soldering is secured.

Further, in the above mounting structure, since the lead terminals 14 are brought into direct contact with the bus bar 11 having a certain thickness accuracy, the accuracy of the mounting height of the electric component 13 is also improved, and the root portion 14a is further improved. Since it is accommodated in the resin opening 15A, the mounting height of the electric component 13 is reduced by the thickness of the resin 12 above the bus bar 11.

FIG. 3 shows an electrical component mounting structure of a modified example of the first embodiment. Since the electrical component 13 'is for a large current, the lead terminals 14' have tip portions 14b-1 ', 14b.
-2 'is provided in two places. Correspondingly, the bus bar 11 'in the resin opening 15A' on the mounting surface side having a size capable of accommodating the root portion 14a 'also has terminal holes 11a-1', 1 '.
Two 1a-2 'are provided. Other configurations are similar to those of the first embodiment.

The electrical component 13 'is attached by the lead terminal 1
Insert the two tip portions 14b-1 ', 14b-2' of 4'into the terminal holes 11a-1 ', 11a-2' of the bus bar 11 ', and the lower side 14c' of the root portion 14a 'is the upper surface of the bus bar 11'. It is in contact with. In this state, the lower surface side of the circuit board 10 'is dipped in the molten solder, and the two tip portions 14b-1' and 14b-2 'are placed in the resin opening 15B'.
It is joined to 1 '. Also during this soldering, stable solderability is ensured without being affected by thermal expansion, especially the thermal expansion of the resin 12 '.

FIG. 4A shows a circuit board 10 "applied to an electric component mounting structure of another modification of the first embodiment.
In the circuit board 10 ″, the peripheral edge 15B-a ″ of the resin opening 15B ″ of the lower surface 10b ″ which is the back surface of the mounting surface is not vertical, and the opening width from the lower surface 10b ″ to the internal bus bar 11 ″ side is reduced. It is formed by inclining in a taper shape. Further, when the solder is soaked in the flow of the molten solder for soldering, the peripheral edge 15B− on the upstream side of the solder flow
The inclination angle X of a1 ″ is set to the peripheral edge 15B on the downstream side of the flow.
It is set to be larger than the inclination angle Y of -a2 ". Other configurations are the same as those in the first embodiment.

As shown in FIG. 4B, the lead terminal 1
Soldering the 4 "tip 14b" and the bus bar 11 "is
Edge 15B-a "of resin opening 15B" of lower surface 10b "
Because of the inclination, the melted solder H smoothly flows into the resin opening 15B ″ to solder the periphery of the tip end 14b ″ and the inside of the terminal hole 11a ″. Of the flow is the upstream peripheral edge 15B-a
1 "and the peripheral edge 15B-a2" on the downstream side have different inclination angles, the resistance of the flowing solder H is also different, and there is a difference in the flow velocity when flowing into the resin opening 15B "and when flowing out. As a result, the excess solder H is removed from the resin opening 1
Proper soldering is performed by cutting off the state of staying within 5B ″ and bridging the opposite edges.

FIGS. 5A and 5B show an electric component mounting structure of a second embodiment of the present invention, in which an opening hole 24d is formed in a wide root portion 24a of the lead terminal 24 protruding from the electric component 23.
Open. By opening the opening hole 24d in this manner, the width of the portion of the root portion 24a remaining on the top, bottom, left, and right of the opening hole 24d is approximately the same as the width of the narrow tip portion 24b protruding from the lower side 24c of the root portion 24a. As a result, the widths of the respective parts of the lead terminal 24 are substantially the same.
On the other hand, the circuit board 20 has the same configuration as that of the first embodiment.

When the lead terminal 24 and the bus bar 21 are soldered by immersing the lower surface of the circuit board 20 in the flow of molten solder, the lead terminal 24 has substantially the same width in each portion.
The heat of the melted solder H is evenly transferred, the solder H has good warp, and the soldering condition is also appropriate. Note that, as in the first embodiment, the soldering location is not adversely affected by the stress due to thermal expansion. Also,
The electric component mounting structure of the second embodiment is also applicable to the two modified examples of the first embodiment.

FIG. 6 shows an electric component mounting structure of a modified example of the second embodiment, in which a lead terminal 24 'protruding from an electric component 23' has a base 24 having a narrow tip 24b '.
The immediate range of the lower side 24c 'with the step of a'is set to be wide like the above, but an upper part of the immediate range is a narrow range 24e' substantially equal to the tip portion 24b '.
With such a shape, the widths of the respective parts of the lead terminal 24 'become substantially equal, the warp at the time of soldering is good, and the joining by soldering is also good.

FIGS. 7A and 7B show an electric component mounting structure according to the third embodiment of the present invention, in which a narrow width protruding from the lower side 34c of the root portion 34a of the lead terminal 34 protruding from the electric component 33 is provided. A hole 34f is formed in the tip portion 34b of the. On the other hand, the circuit board 30 has the same configuration as that of the first embodiment. The lead terminal 34 and the bus bar 31 of the circuit board 30 are soldered by immersing them in the flow of the molten solder, and the molten solder H flows around the tip end portion 34b and inside the terminal hole 31a of the bus bar 31. It also flows into the hole 34f of the tip portion 34b. Therefore, in addition to the periphery of the tip portion 34b, the inside of the hole portion 34f is also soldered, so that the joint strength is further improved and a reliable joint is realized. The electrical component mounting structure of the third embodiment is the same as that of the first embodiment in that it is not adversely affected by thermal expansion, and the modified example of the first embodiment and the second embodiment and its modified example. Is also applicable.

[0034]

As is apparent from the above description, when the electric component mounting structure of the present invention is used, even if the high heat of the molten solder is transmitted, a stress for separating the joint is generated at the joint portion by the soldering. Since it does not occur, the required bondability can be secured and the reliability of soldering can be maintained. Further, the present invention is
It can also be applied to electrical components for large currents, and can secure the joint reliability as in the case of ordinary electrical components. Furthermore, by sloping the peripheral edge of the resin opening on the side where it is immersed in the molten solder in a tapered manner, the flow of solder can be optimized and good soldering can be realized.

In addition, by making the shape of the root of the lead terminal to have a uniform width dimension, the heat transfer rate to the lead terminal becomes uniform, and the solder paste becomes good, and a proper joining state is obtained. Can be secured. Further, when the hole portion is provided at the tip portion, the melted solder also enters the hole portion, and a more firmly joined state can be secured. Further, it is also possible to apply the various mounting structures described above in an appropriate combination, and in addition to realizing the optimum soldering in consideration of the usage status of the electric component and the circuit board, etc. The mounting height accuracy can also be improved.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an electric component mounting structure according to a first embodiment of the present invention.

2A is a schematic cross-sectional view when a lead terminal is inserted into a circuit board, and FIG. 2B is a schematic cross-sectional view when soldering.

FIG. 3 is a schematic cross-sectional view of an electric component mounting structure of a modified example of the first embodiment.

FIG. 4 is an electric component mounting structure of another modification of the first embodiment, (A) is a sectional view of a circuit board, and (B) is a schematic sectional view at the time of soldering.

FIG. 5 is an electric component mounting structure according to a second embodiment of the present invention, in which (A) is a schematic cross-sectional view when the lead terminal is inserted into the circuit board, and (B) is a schematic view of a state in which soldering is completed. FIG.

FIG. 6 is a schematic cross-sectional view of an electric component mounting structure of a modified example of the second embodiment.

FIG. 7 is an electric component mounting structure according to a third embodiment of the present invention, (A) is a schematic cross-sectional view when a lead terminal is inserted into a circuit board, and (B) is a schematic view of a state in which soldering is completed. FIG.

FIG. 8 is a schematic sectional view of a conventional electrical component mounting structure.

9A is a schematic perspective view of a conventional electrical component mounted on a circuit board, and FIG. 9B is a schematic cross-sectional view of a conventional soldering process.

FIG. 10 is a schematic cross-sectional view of a conventional mounting structure for an electric component for large current.

11A and 11B are schematic cross-sectional views of another conventional electrical component mounting structure.

[Explanation of symbols]

10 circuit board 11 bus bars 12 resin 13 electrical parts 14 Lead terminal 14a root part 14b tip 14c Lower side 15A, 15B resin opening H solder

Continued front page    F-term (reference) 5E319 AA02 AA07 AB01 AC02 AC11                       CC23 GG03 GG20                 5E336 AA01 BB01 CC03 EE02 GG06

Claims (6)

[Claims] 1. A resin opening is provided on a mounting surface and a back surface of a circuit board where a bus bar is covered with a resin mold to mount an electric component, to expose the bus bar, and to a terminal hole formed at the exposed position. In an electrical component mounting structure in which a stepped and narrowed tip end portion of the lead terminal protruding from the bottom surface of the electrical component is inserted and soldered to a bus bar, the circuit board is a resin on the mounting surface side. Set the opening width of the opening larger than the width of the bottom side with the step of the root of the lead terminal, and solder from the resin opening on the back side of the mounting surface with the bottom side of the root in contact with the top surface of the bus bar. An electrical component mounting structure configured to be attached. 2. The lead terminal has a plurality of tip portions, and the same number of terminal holes as the tip portions are formed in a bus bar at a portion exposed by the resin opening to connect the tip portions of the lead terminal. The electrical component mounting structure according to claim 1, which is inserted. 3. The electrical component mounting structure according to claim 1, wherein an opening hole is formed in the center of the root portion of the lead terminal. 4. The root portion of the lead terminal is located above a range immediately adjacent to a lower side provided with a step for abutting the upper surface of the bus bar,
The electrical component mounting structure according to any one of claims 1 to 3, wherein the width is set to be narrower than the width of the lower side. 5. The lead terminal according to claim 1, wherein a hole portion is provided at a tip end portion of the lead terminal to allow molten solder to enter at the time of soldering to increase contact points with the solder. The electrical component mounting structure described in. 6. The soldering is performed by immersing a back surface of a mounting surface of the circuit board in a flow of the molten solder and allowing the molten solder to flow into a resin opening portion on the back surface side to join a front end portion and a bus bar. In the circuit board, the peripheral edge of the resin opening on the back surface is tapered in such a manner that the opening size is reduced from the back surface to the inner bus bar side, and the resin opening on the upstream side of the flow of the molten solder is formed. The electrical component mounting structure according to any one of claims 1 to 5, wherein the peripheral edge has a larger inclination angle than the peripheral edge on the downstream side to guide the flow of the molten solder into the resin opening.