JP2018137295A - Electronic unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem in which, while in potting in which a circuit board is housed in a case and resin is injected in that state, it is conceivable to form a space on a bottom surface of the case when the resin is not to be injected to a part of a lower surface of the circuit board, although, it is desired to seal the space with a small amount of resin in advance so that the injected resin does not enter the space, it is impossible to supply the resin because the space is covered with the circuit board.SOLUTION: At the periphery of a space, a seating surface abutting against a lower surface of a circuit board is formed. A groove is formed on the outside of the seating surface and along the seating surface. A resin reservoir formed at a position not covered by the circuit board in a state where the circuit board is accommodated in the case is caused to communicate with the seating surface via the groove, so that the resin injected into a resin reservoir passes through the groove and is supplied to the seating surface.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an electronic unit in which resin is poured into a case in a state where the circuit board is housed in the case, and the circuit board is sealed with the resin.

  A plurality of electronic components are mounted on the circuit board, and some of the electronic components must be isolated from moisture in the air. In addition, when an insect or the like enters the surface of the circuit board, a short circuit failure may occur. In order to eliminate such problems, a circuit board is conventionally stored in a case that opens upward, filled with resin in that state, embedded in the resin, and then cured. The potting which isolates from the outside is performed (for example, refer patent document 1).

  In the above-mentioned conventional one, a partition plate is provided in the case, the space in the case is partitioned into two spaces by this partition plate, and only one of the spaces is filled with resin.

Japanese Patent Laid-Open No. 11-31764 (FIGS. 1 and 2)

  In the above conventional one, in the space on the resin filling side, the resin is filled up and down across the circuit board, and the circuit board is sealed so as to be in contact with the resin over the entire upper surface and lower surface.

  When the outside air temperature changes periodically after the resin is cured, the filled and cured resin repeats expansion and contraction, and stress is repeatedly applied to the circuit board. In particular, when a terminal board or the like is soldered to a circuit board, there is a risk that the solder will break due to repeated application of stress and cause a failure. For this reason, it is desirable to fill the resin in a portion where the stress is not desired to be applied so that the resin does not contact the circuit board.

  In view of the above problems, an object of the present invention is to provide an electronic unit capable of forming a space not filled with resin below a circuit board.

  In order to solve the above-described problems, an electronic unit according to the present invention includes a part of the lower surface of a circuit board in a state where the circuit board is accommodated in a case that opens upward so as to be substantially parallel to the bottom surface of the case. In an electronic unit in which a space surrounding the circuit board is formed on the bottom surface of the case and the circuit board is sealed with resin, a seating surface that contacts the lower surface of the circuit board is formed at the periphery of the space, and the outside of the seating surface. And a groove formed along the outside of the seat surface and communicating with the seat surface and the resin reservoir.

  If a small amount of resin is supplied between the seating surface and the lower surface of the circuit board, and the resin is cured in advance, then a large amount of resin is poured into the case, and the resin is sealed with the previously cured resin. Therefore, the resin does not flow into the space surrounded by the seating surface. However, in a state where the circuit board is housed in the case, the seating surface is covered with the circuit board and hidden from above, so that the resin cannot be supplied directly. Therefore, the resin is poured into the resin reservoir, and the resin is supplied from the resin reservoir to the seat surface through a groove communicating the resin reservoir and the seat surface.

  However, since the resin is supplied from the resin reservoir to the seat surface while flowing in the groove, the resin may not be uniformly supplied from the groove to the seat surface. Therefore, a wall portion is formed at the boundary between the groove and the seat surface. At the same time, by providing gate portions that serve as resin passages at a plurality of locations on the wall, and by limiting the locations where the resin is supplied to the seat surface, the amount of resin supplied to the seat surface is controlled. It is desirable to make it.

  If the opening widths of the plurality of gate portions are made uniform, it may be difficult to adjust the amount of resin supplied from the groove to the seating surface. Therefore, it can be considered that the amount of resin passing through the gate portion is made different from the amount of resin passing through the other gate portion by making the opening width of the gate portion different from the opening width of other gate portions.

  Alternatively, the length of the wall portion is configured to be different from the length of the other wall portions, the time until the resin reaches each gate portion is adjusted, and the amount of resin supplied to the seating surface is partially It may be possible to make adjustments.

  Further, the depth of a part of the groove is configured to be different from the depth of the other part, and the amount of resin supplied to the seating surface is adjusted by adjusting the time until the resin reaches each gate part. May be partially adjustable.

  As is apparent from the above description, in the present invention, when the resin is supplied to the seating surface, the resin is supplied to the seating surface through the groove, so that the seating surface is directly covered with the circuit board. Even if the structure cannot supply the resin, the resin can be reliably supplied to the seating surface.

The figure explaining the accommodation state of the circuit board in a case Enlarged view showing the shape of the bottom of the case Plan view showing the relationship between resin reservoir and groove IV-IV cross section Diagram explaining the flow of resin from the groove to the seating surface Enlarged view showing the area around the column

  Referring to FIG. 1, 1 is an example of a case according to the present invention, which is made of resin and is injection-molded. In the present embodiment, two types of circuit boards 2 and 3 are accommodated in the case 1. The circuit board 2 is a power supply board and does not necessarily need to be potted in the present embodiment. On the other hand, the circuit board 3 is a control board and is preferably potted. Both circuit boards 2 and 3 are electrically connected via pin terminals 21. Then, after both circuit boards 2 and 3 are stored in the case 1, the partition plate 4 is set in the case 1 to isolate the space in which the circuit board 2 is stored from the space in which the circuit board 3 is stored. Then, the resin is poured into the space on the side where the circuit board 3 is stored.

  Notches 41 are provided at both ends of the partition plate 4, and the bottom side 42 is configured to abut on the upper surface of the circuit board 2. The notch 41 is mounted so as to fit in the guide 11 formed on the inner surface of the case 1.

  The pin terminal 21 is soldered on the lower surface of the circuit board 2. However, if stress due to expansion and contraction of the resin after filling acts on the soldered portion, solder cracking may occur. Therefore, the space 5 is formed so that the resin is not filled in the portion where the pin terminal 21 is soldered.

  With reference to FIGS. 2 to 5, a seat surface 53 with which the lower surface of the circuit board 2 abuts is formed at the periphery of the space 5. Then, a groove 52 was formed along the circuit board 3 side of the seat surface 53. The groove 52 communicates the resin reservoir 51 and the seat surface 53 formed at two locations. Both of the resin reservoirs 51 are formed at positions that are not covered by the circuit board 52 in a state where the circuit board 2 is installed, and even if the circuit board 2 is installed in the case 1, the resin is stored in the resin reservoir 51. Can be injected. If the resin reservoir 51 is not covered with the circuit board 2, the resin can be directly injected into the resin reservoir 51. However, when the resin reservoir 51 is hidden by the circuit substrate 2, the resin passage that guides the resin to the resin reservoir 51. May be provided separately so that the resin reservoir 51 functions as a buffer.

  Therefore, before the circuit board 3 is sealed with resin, the resin is injected into the resin reservoir 51, and the resin is supplied to the seat surface 53 through the groove 52, and between the seat surface 53 and the lower surface of the circuit board 2. The resin was allowed to turn. Then, once the resin is cured in a state where the resin is supplied between the seating surface 53 and the lower surface of the circuit board 2, a large amount of resin is injected to seal the circuit board 3 thereafter. The resin does not enter the space 5.

  By the way, when the resin injected into the resin reservoir 51 flows into the groove 52, if the resin is supplied to the seat surface 53 from a position near the resin reservoir 51, the resin is not sufficiently supplied to a position away from the resin reservoir 51. Occurs. Therefore, a plurality of wall portions 54 are formed on the seat surface 53, and a gate portion 55 is formed between the wall portions 54 so that the resin is supplied to the seat surface 53 through the gate portion 55.

  Details of the wall portion 54 and the gate portion 55 will be described with reference to FIG. In FIG. 5, CL is the center line of case 1. Three gate portions 55 are formed between the resin reservoir 51 on one side and the central gate portion 55 on the center line CL. By narrowing the length of the wall portion 54 for forming each gate portion 55 to D1, D2, and D3 from the resin reservoir 51 toward the center line CL, the gate portion 55 closer to the center line CL is made more. Resin was supplied. However, instead of sequentially reducing the lengths D1, D2, and D3 of the wall portions, the lengths of the specific wall portions may be different from the lengths of the other wall portions.

  Further, by gradually increasing the open width of each gate portion 55 in the same manner toward the center line CL as S1, S2, and S3, more resin is supplied to the seating surface 53 from the gate portion 55 on the side close to the center line CL. I did it. However, instead of sequentially narrowing S1, S2, and S3, a specific opening width may be made different from other opening widths.

  Further, by gradually decreasing the depth of the groove 52 sequentially toward the center line CL, when the resin flows toward the center line CL, the liquid level of the resin is lifted at the bottom surface of the groove 52, and the center line The liquid level increased as it approached CL, and more resin was supplied to the seating surface 53 from the gate portion 55 on the side close to the center line CL. However, only a part of the groove 52 may be shallowed without continuously changing the depth of the groove 52.

  On the other hand, resin cannot be supplied from the groove 52 to the seat surface 53 located on the opposite side of the circuit board 3 with the space 5 interposed therebetween. Therefore, a support 56 for supporting the lower surface of the circuit board 3 is formed on the seat surface 53, and as shown in FIG. 6, the through hole 22 through which the support 56 passes is formed in the circuit board 2 and is connected to the through hole 22. A resin supply unit 23 is formed, and a small amount of resin is supplied from the resin supply unit 23 so that the resin can be supplied between the seat surface 53 around the support column 56 and the surface of the circuit board 2.

  In addition, this invention is not limited to an above-described form, You may add a various change in the range which does not deviate from the summary of this invention.

1 Case 2 Circuit board (no potting)
21 Pin terminal 3 Circuit board (potting)
4 Partition plate 5 Space 51 Resin pool 52 Groove 53 Seat surface 55 Gate part 56 Post

Claims (5)

  In a state where the circuit board is accommodated in a case that opens upward and is substantially parallel to the bottom surface of the case, a space that surrounds a part of the lower surface of the circuit board is formed on the bottom surface of the case. In the electronic unit in which the substrate is sealed with resin, a seating surface that contacts the lower surface of the circuit board is formed at the periphery of the space, and a resin reservoir formed outside the seating surface and along the outside of the seating surface. An electronic unit comprising a groove formed and communicating with a seating surface and a resin reservoir.   2. The electronic unit according to claim 1, wherein a wall portion is provided at a boundary between the groove and the seating surface, and a gate portion serving as a resin passage is provided at a plurality of locations on the wall portion.   The electronic unit according to claim 2, wherein an opening width of the gate portion is different from an opening width of another gate portion.   4. The electronic unit according to claim 2, wherein the length of the wall portion is different from the length of the other wall portion.   5. The electronic unit according to claim 1, wherein a depth of a part of the groove is different from a depth of another part.

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