JP6086816B2 - Electronic equipment - Google Patents

Description

  The present invention relates to an electronic device in which a circuit board disposed in a casing is potted with a space remaining below the circuit board.

  In order to isolate the circuit board from the outside air, potting is performed in which the circuit board is disposed in the casing, the resin is poured in that state to cure the resin, and the circuit board is covered with the resin. However, if the resin is simply poured into the casing, the resin is filled above and below the circuit board, so a large amount of resin must be filled into the casing. As a result, the cost of the resin increases, and the electronic device after filling becomes heavy.

  Therefore, a horizontal hook-shaped holding part that protrudes inward from the peripheral wall of the casing is provided over the entire circumference, and the resin is poured into the upper surface of the circuit board in a state where the circuit board is placed on the hook-like holding part and potting is performed. Have been proposed (see, for example, Patent Document 1).

  In such a configuration, the resin poured into the upper surface of the circuit board spreads in the outer edge direction along the upper surface of the circuit board, but the peripheral edge of the lower surface of the circuit board and the upper surface of the holding portion are in contact with each other. Therefore, the resin flow is stopped at the contact portion, and the resin does not flow below the circuit board. In this state, that is, in a state where the resin is filled only above the upper surface of the circuit board, the resin is cured to leave a space not filled with the resin below the circuit board.

JP-A-8-162742 (FIG. 1)

  In the above-described conventional electronic device, the circuit board is simply placed on the horizontal holding part, so that a gap may be formed between the lower surface of the circuit board and the holding part due to warping or distortion of the circuit board. . It is the contact part between the lower surface of the circuit board and the holding part that prevents the resin from entering the space formed below the circuit board. Even if it exists, resin will flow into the space through the gap.

  Since such a gap changes depending on the state of warping or distortion of the circuit board, it is difficult to manage the leakage amount for each individual, and therefore, there is a problem that the injection amount of the resin cannot be defined to a constant value. .

  Therefore, in view of the above-described problems, the present invention provides that when the circuit board is placed on the holding portion and the resin is injected, the resin flows into the space between the lower surface of the circuit board and the holding portion. It is an object to provide an electronic device that can be prevented.

  In order to solve the above problems, an electronic device according to the present invention is in contact with an entire upper surface of a lower surface of a circuit board inside a casing opened upward, and holds the circuit board at a predetermined distance from the bottom of the casing. Forming a horizontal holding portion, and pouring resin onto the upper surface of the circuit board with the holding portion holding the circuit board, leaving a space not filled with resin between the circuit board and the bottom of the casing. In the potted electronic device, an annular groove is formed on the horizontal upper surface of the holding part, and the groove is closed with the circuit board in a state where the circuit board is placed on the holding part. Resin that has turned around the outer peripheral edge to the lower surface side of the circuit board is captured by the groove.

  The resin that has turned around the floor periphery of the circuit board and has entered the lower surface side of the circuit board tends to flow inward through a gap between the lower surface of the circuit board and the upper surface of the holding portion due to surface tension. However, since the groove is provided in the middle, the resin stops flowing due to surface tension when entering the groove. If the groove fills with resin, the resin will flow inward again, but since the resin is hardened at that time, the resistance when passing through the gap has increased, and in the space formed below the circuit board The amount of resin flowing in is greatly reduced.

  In addition, since the flow of the resin is prevented by partially expanding the gap between the resin passages by the groove portions as in the labyrinth seal, the sealing performance can be improved by providing the groove portions in multiple stages. Therefore, it is desirable that the groove portion is composed of a plurality of serrated grooves that are continuous in the inner and outer directions.

  As is apparent from the above description, the present invention prevents the resin from flowing into the space formed below the circuit board by providing a groove in the holding portion, so that the resin filling amount is made constant. Can do.

The figure which shows the structure of one embodiment of this invention The figure which shows the state which sets the circuit board to the casing III-III sectional view showing the state when resin is injected Sectional drawing which shows the other form of a groove part

  Referring to FIG. 1, reference numeral 1 denotes an electronic device according to the present invention. In the electronic device 1, an uncured resin P such as urethane resin is poured into the casing 2 from above the circuit board 3 with the circuit board 3 disposed in the casing 2, and the electronic device 1 mounted on the upper surface of the circuit board 3. The component is heated with the resin P covered, and the resin P is cured.

  With reference to FIG. 2, a horizontal stepped holding portion 21 is formed in the casing 2 over the entire circumference, and the circuit board 3 is placed on the holding portion 21. When the circuit board 3 is placed on the holding unit 21, the entire circumference of the lower surface of the circuit board 3 is in contact with the upper surface of the holding unit 21. In the present embodiment, the annular groove 4 is formed on the upper surface of the holding portion 21 over the entire circumference.

  Referring to FIG. 3, there may be a gap between the outer peripheral portion of the lower surface of circuit board 3 and the upper surface of holding portion 21 due to warping or distortion of circuit board 3. In this state, when an uncured resin P is poured, the resin spreading outward along the upper surface of the circuit board 3 flows around the outer peripheral edge of the circuit board 3 and flows below the circuit board 3, and passes through the gap. Flow further inward.

  However, since the groove 4 is provided on the upper surface of the holding portion 21, the resin P that has advanced inward in the gap is captured in the groove 4. Even if the resin P further flows through the gap, the resin P is continuously captured in the groove 4. If the groove 4 is filled with the resin P, the resin P may flow further inward from the groove 4, but at that time, the curing of the resin P has started, the viscosity increases, and the resistance when flowing through the gap increases. Therefore, the resin P hardly flows inward from the groove 4. In addition, since the resin P contracts as the resin P hardens, the resin P in the groove 4 contracts, so that the circuit board 3 is attracted to the holding portion 21, and the gap narrows and further the resin P flows. It becomes difficult.

  The flow of the resin P along the gap is greatly affected by the surface tension of the resin P. However, the flow of the resin P into the groove 4 cancels the influence of the surface tension once. Therefore, it is possible to prevent the inward flow of the resin P by providing the groove portions 4 in a multiple rather than in a single layer.

  Therefore, as shown in FIG. 4, the groove portions 5 are not single but multiple. In the present embodiment, a six-fold structure and a sawtooth shape are formed so that many grooves can be formed in a narrow range.

  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.

DESCRIPTION OF SYMBOLS 1 Electronic device 2 Casing 21 Holding part 3 Circuit board 4 Groove part 5 Groove part

Claims (2)

  A horizontal holding part that holds the circuit board at a predetermined distance from the bottom part of the casing is formed inside the casing that opens upward and contacts the entire circumference of the lower surface of the circuit board, and the circuit board is formed in the holding part. In an electronic device that is potted to leave a space not filled with resin between the circuit board and the bottom of the casing by pouring resin onto the upper surface of the circuit board while holding the An annular groove was formed in the circuit board, the circuit board was placed on the holding part, the groove was closed with the circuit board, and when the resin was filled, the circuit board turned around the outer periphery of the circuit board and turned around to the lower surface side of the circuit board. An electronic device characterized in that resin is captured by the groove. The electronic device according to claim 1, wherein the groove portion includes a plurality of serrated grooves that are continuous in the inner and outer directions.

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