JP2020113605A - Electronic component potting method and electronic device using the same - Google Patents

Abstract

To provide an electronic component potting method and an electronic device using the same, which requires high reliability and high accuracy.SOLUTION: An electronic device includes a circuit board 1, an electronic component 3 mounted on the circuit board 1, a metal housing 2 in which the circuit board 1 and the electronic component 3 are housed, and a potting material 7 that is filled and cured in the housing 2 so as to cover and protect the circuit board 1 and the electronic component 3, and the potting material 7 is made of an elastic adhesive, and a PET film 8 is attached to the surface of the potting material 7.SELECTED DRAWING: Figure 10

Description

The present invention relates to a method for potting an electronic component in which a resin is poured into a housing in which a circuit board is housed and the circuit board is sealed with the resin, and an electronic device using the same.

Conventionally, regarding the flexibility and automation of processing machines as a means of production equipment that responds to market trends such as diversification of products and shortening of product life, maintenance and monitoring of processing quality is maintained regardless of small, medium, or mass production. For example, in-line measurement is required. In-line measurement requires highly reliable, highly accurate and efficient measurement under the environment at the processing site.

Further, there is known a highly precise contact-type small digital length measuring device which is good at measuring multiple points adjacent to each other with a slim and compact gauge and is capable of accurately measuring various shapes. The small digital length measuring instrument has a small optical scale built in within a diameter of about 10 mm as a sensor part, and is a pencil type high precision digital length measuring device that enables multi-point adjacent measurement, or a machine control gauge measuring head for in-line use. Is used as.

The small digital length measuring sensor unit is an apparatus that has electronic parts, a printed circuit board, etc. and is used in an environment where the temperature changes greatly or where coolant or oil of machine tools is scattered. Therefore, not only high accuracy but also small size, space saving, waterproofing, and high environment resistance such as resistance to general coolants and oils due to on-site outer diameter measurement, step measurement, thickness measurement, multi-point measurement, etc. There is a strong demand for durability for repeated measurements and long life without maintenance.

In order to make the sensor part small, space-saving, waterproof, and highly environmentally resistant to oil, it is necessary to store the digital scale in a metal housing to increase the airtightness inside the housing. There is. In electronic devices that require waterproofness and oil resistance, such as small digital length measuring devices, a metal housing is used to prevent liquid from entering the inside of the device, especially important parts such as the sensor part, and the joint part Sealing materials such as O-rings and packing are used. However, in the method of screwing the metal lid to the body to cover the printed circuit board, the size of the lid increases by at least several mm, which is an obstacle to miniaturization.

Therefore, when arranging electronic components such as semiconductor bare chips and capacitors on the circuit board, the circuit board is stored in a plastic or metal case, and the gap between the circuit board and the case is filled with potting material and sealed. Therefore, electronic components are covered and protected.

For example, in Patent Document 1, a casing-like case made of a metal such as aluminum or stainless steel, or a plastic such as polybutylene terephthalate (PBT), polycarbonate (PC), or polyethylene terephthalate (PET) is used. It describes that a potting material is filled and cured in a gap with the circuit board, and a lid made of the same material as the case is attached to an opening of the case.

Further, in Patent Document 2, there is a case where a power supply unit or the like that does not need to be potted is included depending on the circuit configuration on the circuit board. Therefore, a part of the circuit board in the casing is potted by using a partition member. Is described.

JP-A-6-85116 JP, 2017-45955, A

As described in Patent Document 1, in a case where the circuit board is simply housed in a metal case or the like and the circuit board is potted with a resin, since the resin and the metal have a difference in linear expansion coefficient, the hardness after curing is When the resin is expensive, the potting material may peel off due to a temperature change, a gap may be formed, and waterproofness may be impaired. Further, if the housing is made of plastic, it is difficult to use it for a circuit board that requires an electromagnetic shield or a magnetic shield depending on the circuit board.

In particular, in a small digital length measuring instrument or the like, the digital scale is forced to be housed in a metal casing for higher accuracy. Further, instead of the resin having a high hardness after curing, potting a resin having a high elasticity to a portion exposed to the outside is disadvantageous in terms of strength. Furthermore, since the resin with high elasticity is inferior in coolant resistance to the resin with high hardness, it was difficult to use it for those requiring high environmental reliability such as in-line measurement. ..

Further, in the case where there is a movable part in the housing like a digital scale of a small digital length measuring device, it is necessary to provide a space in a part of the housing as described in Patent Document 2, It was difficult to use the partition member in order to improve the sealing property.

The object of the present invention is to solve the above-mentioned problems of the conventional technology, and is sufficient for an electronic device that is required to have high reliability and high accuracy in a harsh environment such as a processing site, which is used for in-line measurement. Another object of the present invention is to provide a potting method for electronic parts that can be used in practice and an electronic device using the same.

The present invention to achieve the above object is a potting method for an electronic component in which a potting material is poured from an opening into a metal housing in which a circuit board is housed and sealed, and the potting material is an elastic adhesive. The casing is placed on a jig, the uncured potting material is poured into the casing through the opening, and a PET film is attached to the surface of the potting material to cure the potting material.

Further, in the above, it is preferable that the jig is made of polyacetal and the potting material is made of an epoxy/modified silicone resin-based elastic adhesive.

Further, when pouring the uncured potting material, it is desirable that a vinyl chloride resin masking tape provided with a hole matched to the size of the opening is bonded to the surface slope of the jig.

Further, when the PET film is attached to the surface of the potting material, the PET film is preliminarily attached to a polypropylene sheet larger than the opening, and the PET film is aligned with the opening, It is desirable to press it from above the poured potting material.

Further, when the potting material is cured, it is desirable that a predetermined time elapses with a weight placed on the polypropylene sheet and the PET film that are in a stuck state.

Further, the present invention provides a circuit board, an electronic component mounted on the circuit board, a metal housing that houses the circuit board and the electronic component, and covers and protects the circuit board and the electronic component. In the electronic device having the potting material filled and cured in the housing as described above, the potting material is made of an elastic adhesive, and the PET film is attached to the surface of the potting material.

Further, in the above, it is desirable that the potting material is an epoxy/modified silicone resin-based elastic adhesive.

Furthermore, in the above, it is desirable that the thickness be 0.08 to 0.12 mm.

Further, the inside of the casing has a space partitioned by a partition plate, and the portion facing the outside is filled and cured with the potting material.

Further, it is desirable that a lever, a fulcrum, and a digital scale are housed as movable parts in the space.

According to the present invention, the potting material is an elastic adhesive, the metal casing is installed in the jig, the uncured potting material is poured into the casing, and the PET film is attached to the surface of the potting material. Since the potting material is hardened, it absorbs and disperses the mechanical stress applied to the joint with the metal casing and the thermal stress due to temperature changes, improving durability, and also has excellent coolant resistance and oil resistance, as well as air bubbles, etc. It is possible to eliminate defects in appearance.

Therefore, a potting method for an electronic component and a method for potting the electronic component, which can be practically used even for an electronic device that is required to have high reliability and high accuracy in a harsh environment such as a processing site, which is used for in-line measurement. The electronic device used can be obtained.

1 is a plan view of an electronic device according to an embodiment of the present invention. Sectional drawing of the electronic device which concerns on one Embodiment of this invention (state before potting) Sectional drawing which shows the state which installed the housing of the electronic device shown in FIG. 2 in the jig. Sectional drawing which shows the state which stuck the masking tape on the surface of the jig in FIG. FIG. 4 is a cross-sectional view showing a state in which an uncured potting material is poured inside the housing in FIG. Sectional drawing which shows the preparatory work which sticks a PET film Sectional drawing which shows the state which stuck the PET film Sectional drawing which shows the state when hardening potting material Sectional drawing which shows the state after hardening of the potting material Sectional view showing the state where potting is completed Sectional drawing of the electronic device which concerns on other embodiment (state in which potting is completed).

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a plan view of an electronic device according to an exemplary embodiment of the present invention. FIG. 2 is a sectional view showing a state before potting. The circuit board 1 is housed in a metal case 2. A wiring pattern for forming a predetermined circuit is formed on the circuit board 1, and semiconductors such as mini-molded on the wiring pattern, chip components such as a chip resistor and a chip capacitor, and electronic components such as a thick film resistor film. The component 3 is mounted.

The size of the housing of the measuring head of the small digital length measuring device is as small as 30×9 mm. The cable extending from the circuit board 1 is extended to the outside through the side surface or the bottom surface of the housing 2 using a sealing material such as an O-ring or packing.

FIG. 3 is a sectional view showing a state in which the housing 2 is installed on the jig 4, and FIG. 4 is a sectional view showing a state in which the masking tape 5 is attached to the surface of the jig 4. At the start of potting, the housing 2 is installed on a jig 4 surrounding the periphery. The jig 4 has a slanted surface such that its central portion has the same height as the housing 2 and its outer peripheral portion is lower than that. In FIG. 3, the upper center part of the housing 2 is an opening, and a masking tape 5 having a hole matched to the size of the opening is attached to the surface slope of the jig 4 as shown in FIG.

FIG. 5 is a cross-sectional view showing a state where the uncured potting material 7 is poured into the housing 2. After the masking tape 5 is attached to the surface of the jig 4 as shown in FIG. 4, an elastic adhesive which is the potting material 7 is poured into the housing 2 through the opening as shown in FIG. By pouring an uncured resin, the circuit board 1 on which the electronic parts 3 such as the semiconductor mini chip-molded with the potting material 7, the chip parts such as the chip resistor and the chip capacitor, the thick film resistor film, etc. are mounted, and others. The potting is performed to cover the parts of and to block the outside air.

The potting material 7 has excellent impact resistance and moisture resistance, and is a semiconductor chip-molded on the wiring pattern formed on the circuit board 1, chip components such as chip resistors and chip capacitors, thick film resistor film, etc. It is necessary to satisfactorily protect the electronic component 3 and to have excellent adhesion to the circuit board 1 and the housing 2. Furthermore, it is important that the workability of filling and curing is excellent. Further, the potting material 7 is not a generally used resin having a high hardness after curing, but an elastic adhesive having a high elasticity in order to make it resistant to temperature changes.

Therefore, as the potting material 7, a two-component epoxy/modified silicone resin-based elastic adhesive containing silicon is used. Therefore, the potting material 7 is assumed to have good adhesiveness also to plastic materials, especially PET (polyethylene terephthalate) resin. It is also suitable for bonding stainless steel and aluminum. Further, it has high reliability, and curing starts 40 minutes after mixing in an environment of 23°C. However, the potting material 7 cannot adhere to polyethylene, polypropylene, fluororesin, polyacetal, or the like.

The potting material 7 composed of an epoxy/modified silicone resin-based elastic adhesive is an adhesive that does not easily peel off, and the cured adhesive layer becomes a tough and flexible rubber-like elastic body having a flexible property. .. Therefore, it is possible to absorb and disperse the mechanical stress and the thermal stress applied to the joint portion with the metal housing 2, improve the durability, and realize higher quality bonding.

Since the potting material 7 is hardened as a rubber-like elastic body, (1) it absorbs external vibrations, shocks and other stresses, and stresses are less likely to concentrate at the bonding interface, and (2) there is a difference in the coefficient of linear expansion. It has the advantage of adapting to the adhesion of large dissimilar materials and (3) exhibiting a high peel adhesion strength. Therefore, unlike conventional methods, the properties of a hard and brittle epoxy adhesive and the low adhesive strength of an elastomer adhesive have a negative effect under severe environmental conditions and do not cause peeling.

Further, since the potting material 7 is set as a rubber-like elastic body, it has an effect of dispersing and absorbing internal stress. In addition, it is resistant to heat cycles, absorbs thermal strains such as expansion and contraction, and provides stable adhesiveness in a wide range of environments.

The masking tape 5 is used to prevent the adhesive from adhering to an unintended part. The jig 4 is used to increase the area where the masking tape 5 is attached and to prevent the tape from slipping. The masking tape 5 is made of vinyl chloride resin and has a thickness of 0.1 mm. The vinyl chloride resin is preliminarily perforated in the same shape as the opening of the housing 2. The jig 4 is made of polyacetal so that even if the potting material 7 is attached, it can be easily peeled off.

6 and 7 are cross-sectional views showing the treatment of the opening, FIG. 6 is a preparatory work for sticking the PET film 8 (polyethylene terephthalate: polymer film), and FIG. 7 is a cross-section showing the state where the PET film 8 is stuck. It is a figure. The PET film 8 is attached to the surface of the potting material 7, which is an elastic adhesive, and the exposed portion and opening of the potting material 7 are minimized to enhance the strength and the coolant resistance. The PET film 8 has high coolant resistance and can also hide defects in appearance such as bubbles.

The PET film 8 is a tough plastic and has excellent gas barrier properties, chemical resistance, acid resistance, alkali resistance, and oil resistance. Therefore, the weaknesses of using the potting material 7 as an elastic adhesive are: It is possible to compensate for the fact that the coolant resistance is inferior to that of a resin having high hardness.

The PET film 8 has a thickness of 0.08 to 0.12 mm (desirably 0.1 mm), and has the same shape as the opening of the housing 2 and is cut to a size of about 0.2 mm, strictly speaking. There is. In addition, one drop of alcohol is previously placed between the polypropylene sheet (PP sheet) 9 and the PET film 8 to be stuck. Then, the PET film 8 adhered to the polypropylene sheet (PP sheet) 9 is aligned with the opening and pressed against the poured potting material 7.

If only the PET film 8 is used, the protruding potting material 7 will also adhere to the surface of the PET film 8 as the adhesive 20 that protrudes. Therefore, to prevent this, a polypropylene sheet 9 sufficiently larger than the opening is used. As a result, the protruding adhesive 20 is accumulated between the masking tape 5 and the polypropylene sheet 9 and does not reach an extra portion.

Since the polypropylene sheet 9 is non-adhesive to the potting material 7, which is an elastic adhesive of epoxy/modified silicone resin, it can be easily peeled off after the potting material 7 is cured. Further, since the polypropylene sheet 9 is transparent, it can be pressed while visually confirming that the position of the PET film 8 is at the center of the opening.

FIG. 8 is a cross-sectional view showing a state when the potting material 7 is cured, and the weight 21 is put on the polypropylene sheet 9 and the PET film 8 which are in the stuck state. In this state, the potting material 7 is cured when a predetermined time elapses. The PET film 8 is flattened and adhered by the weight 21. Here, since the potting material 7 is an epoxy/modified silicone resin-based elastic adhesive that also has good adhesiveness to PET resin, peeling of the PET film 8 is also prevented.

FIG. 9 is a cross-sectional view showing a state after the potting material 7 is cured, and the polypropylene sheet 9 and the masking tape 5 are peeled off. Since the potting material 7 does not have adhesiveness with the polypropylene sheet 9, only the PET film 8 can be clean and free from gaps and peeling.

FIG. 10 is a cross-sectional view showing a state in which potting is completed, which is an electronic device in which the housing 2 is removed from the jig 4, and the circuit board 1 and the electronic component 3 are covered and protected by resin. The circuit board 1 is not simply housed in the metal casing 2 and potted, and there is no gap even when the temperature changes and the waterproof property is excellent. Further, since the potting material 7 is not directly exposed to the outside, the PET film 8 is also tough in combination with the toughness, and particularly excellent in coolant resistance and oil resistance. Furthermore, there is no appearance defect such as bubbles.

FIG. 11 is a sectional view of an electronic device according to another embodiment. FIG. 6 is a cross-sectional view showing a state where potting of an electronic device which has a movable portion inside and which requires a space is completed. For example, in the case of a small digital length measuring device, a lever 25, a fulcrum 23, and a digital scale 22 are housed inside the housing 2 with respect to the stylus portion 24. Then, the stylus portion 24 and the lever 25 rotate about the fulcrum 23, and the movement is enlarged and detected by the digital scale 22. The digital scale 22 is connected to the circuit board 1 to quantify the displacement of the stylus portion 24. It is necessary to fill the potting material 7 on the circuit board 1 side to enhance the environment resistance.

The inside of the housing 2 is divided by a partition plate 12, or the substrate 1 itself is used as a partition plate, and the potting material 7 is filled only in the portion facing the outside, that is, the circuit board 1 side, while leaving the space 11 inside. In addition, the digital scale must be housed in the metal housing 2 for higher accuracy.

In this case, if the potting material 7 having a low viscosity before curing is used, the potting material 7 leaks from the partition plate 12 to the space 11, which may hinder the movement of the lever 25, the fulcrum 23, and the digital scale 22 which are movable parts. There is. Further, if the potting material 7 is filled only in a necessary portion or a portion facing the outside while leaving the space 11 inside, the potting material 7 may be hardened in an uneven state due to leakage or the like. Moreover, since a gap is formed, the appearance is impaired and the waterproof property is impaired.

Therefore, as already described with reference to FIGS. 1 to 10, as the potting material 7, a two-component epoxy/modified silicone resin-based elastic adhesive containing silicon is used, and the PET film 8 is formed on the surface of the potting material 7. Paste and press with the weight 21.

Normally, in order to fill the potting material 7 only in a necessary portion and a portion facing the outside while keeping the space 11 inside, a potting material having a high viscosity before curing is used so as not to leak into the internal space. There is a need. However, if the viscosity before curing is high, the surface will not become flat after filling, and the surface will be cured with unevenness, and bubbles will easily enter. However, with the method described above, the surface including the surface can be neatly shaped. Further, it can be comparable to an electronic device that has no space 11 inside and is completely potted.

1... Circuit board 2... Housing 3... Electronic component 4... Jig 5... Masking tape 7... Potting material 8... PET film 9... Polypropylene sheet (PP sheet)
11... Space 12... Partition plate 20... Overhanging adhesive 21... Weight 22... Digital scale 23... Support point 24... Stylus part 25... Lever

Claims (10)

A potting method for an electronic component, in which a potting material is poured from an opening into a metal housing in which a circuit board is housed and sealed,
An elastic adhesive is used as the potting material, the housing is set on a jig, the uncured potting material is poured into the housing from the opening, and a PET film is attached to the surface of the potting material. A potting method for an electronic component, which comprises curing the potting material. 2. The potting method for an electronic component according to claim 1, wherein the jig is polyacetal, and the potting material is an epoxy/modified silicone resin-based elastic adhesive. When pouring the uncured potting material, a masking tape of vinyl chloride resin provided with a hole matched to the size of the opening is adhered to the surface slope of the jig. 3. The potting method for an electronic component according to 1 or 2. When the PET film was attached to the surface of the potting material, the PET film was previously attached to a polypropylene sheet larger than the opening, and the PET film was aligned with the opening and poured. The potting method for the electronic component according to claim 1, wherein the potting material is pressed from above. The potting of an electronic component according to claim 4, wherein, when the potting material is cured, a predetermined time is allowed to pass while a weight is placed on the polypropylene sheet and the PET film which are in a stuck state. Method. A circuit board, an electronic component mounted on the circuit board, a metal housing in which the circuit board and the electronic component are housed, and the inside of the housing so as to cover and protect the circuit board and the electronic component. In an electronic device having a potting material filled and cured in
An electronic device, wherein the potting material is made of an elastic adhesive, and a PET film is attached to the surface of the potting material. The electronic device according to claim 6, wherein the potting material is an epoxy/modified silicone resin-based elastic adhesive. The electronic device according to claim 6, wherein the PET film has a thickness of 0.08 to 0.12 mm. The interior of the housing has a space partitioned by a partition plate, and the portion facing the exterior is filled and cured with the potting material, according to any one of claims 6 to 8. Electronic device. The electronic device according to claim 9, wherein a lever, a fulcrum, and a digital scale are housed as movable parts in the space.

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