JP2001015949A - Hermetically sealed electronic circuit case and enclosure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reliability of a hermetically sealed electronic circuit case in such an environment that the temperature in the environment frequently rises to high values, by installing a sealant storing section to a vent hole which communicates the inside and outside of the case with each other, and using a thermosetting resin which becomes an air-permeable liquid in the initial stage of heating and cures thereafter as a sealant. SOLUTION: An electronic circuit 6 housed in a hermetically sealed electronic circuit case is sealed with a silicon gel 7 which secures insulation and relieves vibrations after the circuit 6 is fixed to the main case 1 of the case with an adhesive 8. In addition, a cover 2 is fixed to the case 1 for closing the opening of the case 1 which is provided for housing the circuit 6 in the case 1 with a thermosetting adhesive, such as the epoxy adhesive, etc. After the opening is closed with the cover 2, a vent hole 10 which is provided for preventing the internal pressure of the case 1 from rising when the adhesive cures is sealed with an adhesive 5. The amount of the adhesive 5 is increased immediately before the inside air of the case 1 is discharged by installing an adhesive storing section to the vent hole 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic circuit case having a waterproof (gas-proof) structure even in an environment in which the temperature, pressure, and atmospheric conditions change over a wide range, such as when mounted and used in an engine room of an automobile. About.

[0002]

2. Description of the Related Art A case structure in which an electronic circuit is sealed is known, for example, as described in Japanese Utility Model Application Laid-Open No. 63-57782. However, conventionally, when the electronic circuit is hermetically sealed, no special countermeasures have been taken against an increase in internal pressure due to thermal expansion of a filler such as air or silicon gel in the case under a high temperature environment.

[0003]

In the conventional sealing structure, the case itself is damaged by the gas remaining inside the case sealed at high temperature or the expansion of the filler such as silicon gel, or the inside of the silicone gel or the like is damaged. Insulation material or gel-like vibration damping material to be sealed squirts out of a minute gap, or a large negative pressure is generated inside the case when the temperature drops to low temperature due to air leak etc. generated at high temperature. Water or corrosive gas may flow into the case through a small gap, which may cause a failure of the electronic circuit, which may cause a situation that may not be completely sealed.

The present invention addresses the above-mentioned problems by reducing the increase in the internal pressure of the case at high temperatures. In particular, the purpose is to provide a highly reliable electronic circuit in an environment where the amount of change to a high temperature and the frequency of change to a high temperature are high, rather than the amount and frequency of a change to a low temperature relative to normal temperature, such as in the engine room of an automobile. I do. Further, it is possible to suppress an increase in component cost and weight due to an increase in strength of the case structural member and a reduction in minute gaps.

[0005]

The above problem can be solved by setting the internal pressure of the case housing the electronic circuit to a negative pressure at normal temperature and normal pressure. For example, an electronic circuit arranged in an engine room of an automobile is placed in an environment having a temperature change of about −40 ° C. to + 150 ° C. Therefore, simply, by making the internal pressure of the case normal pressure at about 50 ° C. to 60 ° C., the pressure difference from the surroundings becomes the same at high and low temperatures, that is, the maximum pressure difference is reduced. can do.

As described above, the means for reducing the pressure inside the case is based on the heating temperature at the time of bonding the opening for surrounding the electronic circuit and the interior of the electronic circuit and the cover member for closing the opening. A gas such as air remaining inside is expanded and gradually sealed in the expanded state, thereby generating a negative pressure inside the case. For example, there is a method of sealing the case while keeping the inside of the case under negative pressure.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described.

FIG. 1 shows an example of a sealed electronic circuit case structure according to the present invention.

[0009] The electronic circuit 6 to be installed is a main case 1
Is fixed to the main case 1 with an adhesive 8.

After being fixed to the main case 1, it is sealed with a silicone gel 7 for insulation retention and vibration reduction.

Further, the cover 2 is fixed to a portion which is open for mounting the electronic circuit 6 with a thermosetting adhesive such as an epoxy adhesive.

After closing the opening with the cover 2, the cover 2
Is sealed with an adhesive 5 in order to avoid an increase in internal pressure when the adhesive is cured.

At the time of sealing with the adhesive 5, the pressure of the air remaining inside the case is controlled so that the pressure around the electronic circuit case is negative when the surroundings of the electronic circuit case are in a scientific standard state. Thus, a state in which the internal pressure does not increase even in a high temperature of the sealed circuit case after sealing can be realized.

Here, a mechanism for controlling the internal pressure of the sealed electronic circuit case to a negative pressure in a scientific standard condition will be described.

The fixing of the electronic circuit 6, the sealing of the silicon gel 7, and the adhesion of the cover 2 are as described above.

Vent 1 for removing internal pressure when attaching the cover
When closing 0 with the adhesive 5, it is heated to about the actual use temperature of the electronic circuit.

The air remaining inside the electronic circuit case is heated and expanded.

FIG. 2 is a simplified view showing a situation when the vent 10 is sealed.

In this state, before the adhesive 5 that seals the ventilation port 10 is completely cured, air corresponding to the increase in internal pressure is applied to the ventilation port 10.
And is discharged out of the electronic circuit case.

Immediately before the internal air is discharged, the adhesive 5 for sealing the ventilation hole is pushed out to increase the amount of the adhesive in the adhesive reservoir 3.

When the internal pressure of the electronic circuit case and the atmospheric pressure of the outside air are in an equilibrium state, the state of the adhesive 5 is naturally restored to the same level inside and outside the electronic circuit case.

That is, the state is as shown in FIG.

While maintaining this state, the adhesive 5 that blocks the air vent is completely cured.

Since the inside of the electronic circuit case is in equilibrium with the outside air pressure at a high temperature, when the temperature of the electronic circuit case decreases, the volume of the expanded residual air decreases, and the inside of the electronic circuit case decreases. The pressure will be lower than around the electronic circuit case. That is, it is possible to seal the electronic circuit case at a normal temperature by setting the internal pressure of the electronic circuit case to a negative pressure.

Here, another embodiment of the present invention will be described.

The above-described embodiment provides a means for heating the air remaining in the electronic circuit case and then closing the air vent with an adhesive to generate a negative pressure inside the electronic circuit case. The means for sealing the vent is not limited to the adhesive.

FIG. 3 shows another embodiment of the present invention.
The ventilation opening is formed as shown in FIG. 3, the electronic circuit is heated to about the actual use temperature, and the air is ventilated while the remaining air inside the electronic circuit case is inflated by using a thermocompression bonding machine 14 or the like. It is a structure that blocks the mouth.

FIG. 4 shows an example of the shape after the vent is closed by heat compression molding.

As described above, the air remaining inside the electronic circuit case is expanded by heating, and by closing the ventilation hole in this state, the surroundings of the electronic circuit case become scientifically standard when the electronic circuit case becomes a standard state. The inside is maintained at a negative pressure.

In the above-described embodiment, the internal pressure of the electronic circuit case at room temperature is controlled to a negative pressure by heating, expanding and sealing the residual air. The same effect can be obtained by sealing afterwards.

This will be described with reference to FIG.

A vent is provided at an arbitrary position in the electronic circuit case, and air remaining in the electronic circuit case is exhausted from the vent.

After the internal pressure of the electronic circuit case reaches an arbitrary pressure, the vent pipe protruding to the outside is cut by a thermoforming machine or the like.

The end face of the cut is naturally sucked inward by the internal negative pressure and seals the ventilation tube.

FIG. 6 shows an example in which sealing is performed in this embodiment.

In the embodiment shown in FIGS. 5 and 6, since a small air leak potentially existing in the base material of the electronic circuit case can be sensed, a sealed circuit case can be configured more effectively.

[0037]

The sealed circuit case according to the present invention can provide a sealed circuit case that can maintain a sealed state of an electronic circuit used in an environment having severe temperature conditions without damaging the circuit case at a high temperature.

[Brief description of the drawings]

FIG. 1 shows an example of a sealing structure using an adhesive.

FIG. 2 shows a sealing mechanism using an adhesive.

FIG. 3 shows an example of a sealing structure using thermocompression bonding.

FIG. 4 shows an example of a sealing structure using thermocompression bonding.

FIG. 5 is an example of a sealed structure in which negative pressure is generated inside an electronic circuit by performing forced exhaust.

FIG. 6 shows an example of a sealed structure in which negative pressure is generated inside an electronic circuit by performing forced exhaust.

[Description of Signs] 1 ... Main case, 2 ... Circuit case cover, 3 ... Adhesive reservoir, 4 ... Cover adhesive, 5 ... Seal adhesive, 6 ... Electronic circuit, 7 ... Silicon gel, 8 ... Substrate adhesive, 9 ... electronic parts, 10 ... vent, 11 ... vent pipe, 12 ... heat forming machine,
13: exhaust pipe, 14: thermocompression bonding machine, 15: vent hole after thermoforming.

Continued on the front page (72) Inventor Shinya Igarashi 2477 Takaba, Hitachinaka-shi, Ibaraki F-term in Hitachi Car Engineering Co., Ltd. (Reference) 3E084 AA05 AA14 AB10 BA01 CA03 DA03 FA09 GA08 HA03 HB08 HC03 HD03 KA01 4E360 AB12 AB31 BC20 EA03 EA18 ED07 EE09 GA06 GA23 GA29 GA60 GB99

Claims (9)

[Claims] 1. A housing comprising: an electronic circuit; a case hermetically surrounding the electronic circuit; and a vent that passes through the inside and the outside of the case. Wherein the sealing material is a liquid through which air passes at the beginning of heating, and is a thermosetting resin that cures later. 2. A sealed electronic circuit case comprising an electronic circuit and a case in which the electronic circuit is housed, and in a normal temperature and normal pressure environment, the inside of the case is kept at a negative pressure. 3. The sealed electronic device according to claim 2, wherein the inside of the case has a positive pressure with respect to the surroundings at a maximum temperature or a minimum pressure in an environment in which the electronic circuit case is installed. Circuit case. 4. An electronic circuit and a case for protecting the interior of the electronic circuit, wherein a production process for sealing the case is performed in a high temperature state, and the inside of the case becomes a negative pressure at normal temperature. Sealed electronic circuit case. 5. A cover member for closing the open surface (opening) after the electronic circuit is inserted and fixed through an open surface (opening) provided in a case member for protecting the interior of the electronic circuit. A hermetically sealed electronic circuit case which is joined with a conductive resin adhesive or the like to cover the entire periphery of the electronic circuit, wherein the internal pressure of the circuit case is made lower than that of the outside of the circuit case. 6. The sealed electronic circuit case structure according to claim 5, wherein when the cover is joined to an open surface (opening) for mounting the electronic circuit therein, a heat hardening furnace. A sealed electronic circuit case, wherein the inside is made to have a negative pressure, or only the inside of the case is made to have a negative pressure as compared with the outside of the circuit case to be sealed at the same time as joining. 7. A cover member for closing the open surface (opening) after the electronic circuit is inserted and fixed from an open surface (opening) provided in a case member for protecting the interior of the electronic circuit. In an electronic circuit case having a structure in which the electronic circuit case is joined with a conductive resin adhesive or the like and covers the entire electronic circuit, a ventilation hole is provided in a case member including the cover, and after the cover member is joined, the internal pressure of the circuit case is reduced. A hermetically sealed electronic circuit case for closing the ventilation hole so that the air pressure becomes negative under an environment of normal temperature and normal pressure. 8. The method according to claim 7, wherein the ventilation hole has a seal,
Performed while the case member is in a high temperature state, or
By performing while applying a negative pressure inside the case,
A sealed electronic circuit case, wherein the internal pressure of the circuit case becomes negative under an environment of normal temperature and normal pressure. 9. The method according to claim 7, wherein the step of sealing the ventilation holes with a thermosetting resin adhesive or the like and heating the case member to cure the adhesive has a low viscosity. Occasionally, the air inside the case is heated and expanded to leak from the ventilation hole, and then the curing of the adhesive proceeds, the ventilation hole is sealed, and the internal pressure of the circuit case is in an environment of normal temperature and normal pressure. Sealed electronic circuit case with negative pressure.