JPH079426Y2 - Electronics - Google Patents

Description

[Detailed Description of the Device] [Outline] In an electronic device in which a substrate is floated in the center of a bottomed case and sealed with a moisture-proof material, sinking or cracking occurs when the moisture-proof material shrinks by taking measures to absorb stress. Try not to.

[Industrial application field]

The present invention relates to an electronic device in which both surfaces of a substrate are sealed with a moistureproof material.

[Conventional technology]

There is an electronic device having a structure as shown in FIG. 5 as an electronic device that supports a substrate on which components are mounted while floating in the center of a bottomed case. (A) is an example in which the double-sided mounting substrate 21 is supported by the step 12 at the center of the bottomed case 11, and 22 is an electronic component. (B)
In this example, the main board 21 'is arranged at the bottom of the case 11, and the sub board 21 is supported in the air by the leg portions 23 standing upright from the main board 21'.

In order to make the inside of the case 11 have a moisture-proof structure, there is a method of filling and sealing with a resin. FIG. 7 is an explanatory diagram thereof. When the substrate 21 is supported at the center of the case 11 and the moisture-proof potting material (resin) 31 is injected as shown in (a),
When the resin 31 is in a liquid state, it thermally expands as shown in (b), and eventually hardens into a gel state as shown in (c). Then, if the resin 31 is left to stand at room temperature, the resin 31 begins to shrink, so that stress in the direction of the arrow is generated as shown in FIG. Further, if it is left at room temperature or low temperature, cracks (cavities) 33 may occur as shown in (e), and if moisture enters here, it may cause a trouble such as a short circuit. This crack 33 is the result of yielding to the internal stress during contraction, which results in the sink mark 32.
May disappear.

FIG. 6 is an enlarged view showing the sink marks 32, the cracks 33, the bubbles 34, etc., which are caused by the contraction of the moisture-proof material.

[Problems to be solved by the device]

The cracks 33 described above do not occur in the single-sided moisture-proof structure as shown in FIG. 8 or the double-sided moisture-proof structure using the bottomless case 11 'as shown in FIG.

However, the structure shown in FIG. 8 cannot be applied to the electronic device shown in FIG. 5, and the structure shown in FIG. 9 has a drawback that a step of bonding the substrate 21 to the step portion 12 is required.

The present invention is intended to prevent the occurrence of cracking of the moisture-proof material, which causes a short circuit, by incorporating a means for absorbing the stress when the moisture-proof material contracts.

[Means for Solving the Problems]

The present invention relates to an electronic device in which a board on which parts are mounted is floated in the center of a bottomed case and is supported, and a moisture-proof material is filled in the case to seal the periphery of the board. Between, while installing a hollow balloon whose inside is separated from the moisture-proof material, the inside of the balloon is in communication with the outside air, or a breathing hole is formed on the bottom surface of the case,
Further, a thin film is stretched so that a part above the bottom surface becomes a hollow pressure adjusting chamber.

[Action]

When the moisture-proof material filled in the case shrinks, the balloon installed in the bottomed case or the pressure regulation chamber isolated by the thin film deforms itself to absorb the shrinkage stress of the moisture-proof material. Therefore, even though it is a bottomed case, it is possible to prevent the moisture-proof material from cracking, bubbles, and the like, as in the bottomless case of FIG.

〔Example〕

FIG. 1 is a sectional view of a first embodiment of the present invention according to claim 1. In this example, a balloon 41 made of resin or metal is housed in the hollow of the bottomed case 11, and its opening is connected to a space above the case (or below as shown by a broken line) by a pipe 42. Therefore, since the balloon 41 can freely expand or contract, the stress when the moisture-proof material 31 filled in the case expands or contracts can be absorbed.

FIG. 2 is a sectional view of a second embodiment of the present invention according to claim 1. In this example, the balloon 41 shown in FIG. 1 is installed at the bottom of the case, and the pipe 42 is pulled out upward through the inside of the case wall.

FIG. 3 is a cross section of a third embodiment of the present invention according to claim 2. In this example, the bottomed case 11 is divided into an upper part 11A and a lower part 11B,
A moisture-proof chamber 45 for accommodating a pressure-reducing chamber 44 with a thin film 43 made of aluminum or the like, which is easily broken, interposed between them, and a substrate 21 on the upper part.
Is formed. Reference numeral 46 is a breathing hole for communicating the pressure adjusting chamber 44 with the outside air.

FIG. 4 is an explanatory view of the manufacturing process of FIG. At the time of injecting the moisture-proof material of (a), the moisture-proof material 31 is injected with the thin film 43 adhered to the case upper portion 11A. After that, when the moisture-proof material 31 is cured as shown in (b), the thin film 43 is broken to form the damaged portions 46 at a plurality of places. This is for facilitating the thin film 43 to follow the displacement of the moisture-proof material 31 when the moisture-proof material 31 contracts after the case lower part 11B is bonded as shown in FIG.

[Effect of device]

As described above, according to the present invention according to claims 1 and 2,
Since the stress of the moistureproof material filled in the bottomed case can be absorbed, it is possible to prevent harmful cracks and bubbles from being generated in the moistureproof material after shrinkage. In addition, since the outer wall of the balloon and the thin film that separate the air layer from the moisture-proof material are present in the balloon and the pressure adjustment chamber, even if the balloon and the pressure adjustment chamber are deformed due to the absorption of contraction stress of the moisture-proof material, the internal air Does not come into contact with the substrate, and a completely sealed and moisture-proof structure can be formed.

[Brief description of drawings]

 1 to 3 are cross-sectional views of each embodiment of the present invention, FIG. 4 is an explanatory view of the manufacturing process of the embodiment of FIG. 3, and FIG. 5 is a configuration diagram of an electronic device having a hollow support substrate, FIG. 6 is an enlarged view of cracks of the moisture-proof material, FIG. 7 is an explanatory view of cracking of the moisture-proof material, FIG. 8 is a sectional view of a single-sided moisture-proof structure, and FIG. 9 is a sectional view of a double-sided moisture-proof structure of a bottomless case. is there.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuji Uno 1-2-2 Goshodori, Hyogo-ku, Hyogo-ku, Hyogo Prefecture Fujitsu Ten Limited (56) Reference JP-A-58-215095 (JP, A) Special Opening Sho 57-143897 (JP, A) Actual Opening Sho 59-182983 (JP, U)

Claims (2)

[Scope of utility model registration request] 1. A substrate (21) on which components are mounted is floated and supported in the center of a bottomed case (11), and a moistureproof material (31) is filled in the case (11) to cover the substrate (21). In an electronic device for sealing the surroundings, a hollow balloon (41) whose inside is separated from the moisture-proof material is installed between the substrate (21) and the bottom surface of the case (11), and Electronic equipment characterized in that the inside communicates with the outside air. 2. A substrate (21) on which components are mounted is floated and supported in the center of a bottomed case (11), and a moistureproof material (31) is filled in the case (11) to cover the substrate (21). In an electronic device for sealing the surroundings, a breathing hole (46) is formed on the bottom surface of the case (11), and a thin film is formed so that a part above the bottom surface becomes a hollow pressure adjusting chamber (44). 43) An electronic device characterized by being provided with an extension.