JP7211822B2 - Electronic component potting method and electronic device using the same - Google Patents

Description

The present invention relates to an electronic component potting method for pouring resin into a housing containing a circuit board and sealing the circuit board with the resin, and an electronic device using the same.

Conventionally, as a means of production equipment to respond to market trends such as diversification of products and shortening of product life, the flexibility and automation of processing machines have been used to maintain and monitor processing quality, regardless of whether it is small, medium, or mass production. Inline measurement is required. In-line measurement requires highly reliable, highly accurate, and highly efficient measurement under the environment of the machining site.

Also known is a high-precision contact-type compact digital length measuring instrument that is slim and compact, excels at measuring multiple points adjacent to each other, and can accurately measure various shapes. The compact digital length measuring instrument is a pencil-type high-precision digital length measuring instrument with a built-in small optical scale with a diameter of about 10 mm as a sensor part, enabling adjacent multi-point measurement, or a machine control gauge measuring head for in-line use. is used as

The compact digital length measuring instrument sensor unit has electronic components and printed circuit boards, and is a device used in an environment where there are large temperature changes or where the coolant or oil of a machine tool scatters. Therefore, for on-site outer diameter measurement, step measurement, thickness measurement, multi-point measurement, etc., it is not only highly accurate, but also compact, space-saving, waterproof, and has high environmental resistance such as resistance to general coolants and oils. , durability for repeated measurements, maintenance-free and long life, etc. are strongly desired.

A compact digital length measuring instrument needs to house the digital scale in a metal case and improve the airtightness inside the case in order to make the sensor part small and space-saving, waterproof, and have high environmental resistance such as resistance to oil. There is Electronic devices that require waterproofness and oil resistance, such as compact digital length measuring instruments, use metal housings to prevent liquids from entering the interior of the device, especially important parts such as the sensor section. , sealing materials such as O-rings and packing are used. However, in the method of screwing a metal lid to the body to cover the printed circuit board, the size of the lid increases by at least several millimeters, which is an obstacle to miniaturization.

Therefore, when electronic components such as semiconductor bare chips and capacitors are placed on a circuit board, the circuit board is housed in a plastic or metal case, and the gap between the circuit board and the case is filled with potting material for sealing. In recent years, electronic components have been covered and protected.

For example, in Patent Document 1, a housing-like case made of metal such as aluminum and stainless steel, or plastic such as polybutylene terephthalate (PBT), polycarbonate (PC), polyethylene terephthalate (PET), etc., and the inside of the case and It is described that a gap between the circuit board and the circuit board is filled with a potting material and hardened, and that a cover made of the same material as the case is attached to the opening of the case.

In addition, in Patent Document 2, there are cases where a power supply section or the like that does not require potting is included depending on the circuit configuration on the circuit board, so a part of the circuit board in the casing is potted using a partition member. is stated.

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

As described in Patent Document 1, the circuit board is simply housed in a metal case or the like, and the circuit board is potted with resin. With high resin, the potting material may peel off due to temperature changes, creating gaps and impairing waterproofness. In addition, if the housing is made of plastic, it is difficult to adopt it for a circuit board that requires electromagnetic shielding or magnetic shielding.

In particular, in the case of a small digital length measuring instrument, etc., the digital scale must be housed in a metal housing in order to achieve high precision. Moreover, potting a highly elastic resin instead of a resin having a high hardness after curing at a location exposed to the outside is disadvantageous in terms of strength. In addition, highly elastic resins are less resistant to coolant than hard resins, making it difficult to use for in-line measurements that require high environmental reliability. .

In addition, in the case where there is a movable part in the housing such as a digital scale of a small digital length measuring instrument, 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 performance.

The object of the present invention is to solve the above-mentioned problems of the prior art, and to be sufficient for electronic devices that require high reliability and high accuracy in severe environments such as machining sites, such as those used for in-line measurement. To provide an electronic component potting method and an electronic device using the method.

The present invention for achieving the above object is a potting method for electronic components, in which a potting material is poured from an opening into a metal housing in which a circuit board is accommodated and sealed, wherein the potting material is an elastic adhesive, The housing is placed on a jig, the uncured potting material is poured into the housing through the opening, a PET film is adhered to the surface of the potting material, and the potting material is cured.

In the above, it is desirable that the jig is made of polyacetal and the potting material is made of epoxy/modified silicone resin-based elastic adhesive.

Furthermore, when pouring the uncured potting material, it is desirable to adhere a vinyl chloride resin masking tape having a hole matching the size of the opening to the inclined surface of the jig.

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

Furthermore, when curing the potting material, it is desirable to allow a predetermined time to pass in a state in which a weight is placed on the polypropylene sheet and the PET film that are stuck together.

Further, the present invention provides a circuit board, an electronic component mounted on the circuit board, a metal case housing the circuit board and the electronic component, and a circuit board and the electronic component that cover and protect the circuit board and the electronic component. and a potting material that is filled and cured in the housing so that the potting material is composed of an elastic adhesive, and a PET film is attached to the surface of the potting material.

Furthermore, in the above-described method, it is preferable that the potting material is an epoxy/modified silicone resin-based elastic adhesive.

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

Further, the inside of the housing has a space separated by a partition plate, and the portion facing the outside is filled and hardened with the potting material.

Furthermore, it is desirable that the space accommodates a lever, a fulcrum, and a digital scale as movable parts.

According to the present invention, the potting material is an elastic adhesive, a metal housing is placed on a jig, an uncured potting material is poured into the housing, a 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 case and the thermal stress due to temperature changes, improving durability, as well as being excellent in coolant and oil resistance, preventing air bubbles, etc. defects in appearance can also be eliminated.

Therefore, a potting method for electronic components that is sufficiently practical even for electronic devices that require high reliability and high accuracy in severe environments such as processing sites that are used for in-line measurement, and the same. An electronic device can be obtained.

1 is a plan view of an electronic device according to an embodiment of the present invention; FIG. Sectional view of an electronic device according to an embodiment of the present invention (state before potting) FIG. 3 is a cross-sectional view showing a state in which the housing of the electronic device shown in FIG. 2 is installed on a jig; Sectional view showing a state in which the masking tape is attached to 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 into the inside of the housing. Sectional view showing preparatory work for pasting PET film Cross-sectional view showing a state where a PET film is pasted Cross-sectional view showing the state when curing the potting material Cross-sectional view showing the state after curing of the potting material Cross-sectional view showing the completed potting Cross-sectional view of an electronic device according to another embodiment (state in which potting is completed)

BEST MODE FOR CARRYING OUT THE INVENTION 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 one embodiment of the present invention. FIG. 2 is a sectional view showing a state before potting. A circuit board 1 is housed in a metal housing 2 . A wiring pattern forming a predetermined circuit is formed on the circuit board 1, and electronic devices such as semiconductors mini-molded on the wiring pattern, chip parts such as chip resistors and chip capacitors, and thick film resistor films. Part 3 is installed.

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

3 is a cross-sectional view showing a state where the housing 2 is installed on the jig 4, and FIG. 4 is a cross-sectional view showing a state where the masking tape 5 is attached to the surface of the jig 4. As shown in FIG. At the start of potting, the housing 2 is placed on a surrounding jig 4 . The jig 4 has the same height as the housing 2 at the central portion, and has an inclined surface lower than the height of the housing 2 at the outer peripheral portion. In FIG. 3, the central upper part of the housing 2 is an opening, and a masking tape 5 provided with a hole matching the size of the opening is adhered to the surface slope of the jig 4 as shown in FIG.

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

As the potting material 7, a semiconductor mini-molded on the wiring pattern formed on the circuit board 1, a chip component such as a chip resistor, a chip capacitor, a thick film resistor film, etc., which has excellent impact resistance and moisture resistance. It is necessary that the electronic component 3 is well protected and that the adhesiveness to the circuit board 1 and the housing 2 is excellent. Furthermore, it is important that the workability of filling and curing is excellent. Also, the potting material 7 is not a commonly used resin having a high hardness after curing, but an elastic adhesive having high elasticity in order to be resistant to temperature changes.

Therefore, as the potting material 7, a two-liquid epoxy/modified silicone resin-based elastic adhesive containing silicone is used. Therefore, the potting material 7 has good adhesion to plastic materials, particularly PET (polyethylene terephthalate) resin. It is also suitable for bonding stainless steel and aluminum. Moreover, it is highly reliable and starts to cure after 40 minutes of 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 made of epoxy/modified silicone resin-based elastic adhesive is adhesive that does not come off easily, and the hardened adhesive layer becomes a very stable rubber-like elastic body with tough and flexible properties. . Therefore, it is possible to absorb and disperse the mechanical stress and thermal stress applied to the joint with the metal housing 2, improve the durability, and achieve higher quality adhesion.

Since the potting material 7 is made to harden as a rubber-like elastic body, (1) stresses such as external vibrations and impacts are absorbed, and stresses are less likely to be concentrated on the adhesive interface, and (2) differences in linear expansion coefficients are minimized. It has the advantage of being adaptable to adhesion of large dissimilar materials, and (3) exhibiting high peel adhesion strength. Therefore, the hard and brittle properties of epoxy-based adhesives and the low adhesive strength of elastomer-based adhesives do not adversely affect under severe environmental conditions and cause peeling, as in the past.

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

Masking tape 5 is used to prevent the adhesive from adhering to unintended parts. The jig 4 is used to increase the area to which the masking tape 5 is affixed so as to prevent the tape from slipping. The masking tape 5 is made of vinyl chloride resin and has a thickness of 0.1 mm. A hole having the same shape as the opening of the housing 2 is formed in the vinyl chloride resin in advance. The jig 4 is made of polyacetal so that even if the potting material 7 adheres, it can be easily removed.

6 and 7 are cross-sectional views showing the processing of the opening, FIG. 6 is a preparatory work for attaching a PET film 8 (polyethylene terephthalate: polymer film), and FIG. It is a diagram. A PET film 8 is attached to the surface of the potting material 7, which is an elastic adhesive, and the exposed portions and openings of the potting material 7 are minimized to increase strength and coolant resistance. The PET film 8 has high coolant resistance and can hide appearance defects such as air bubbles.

In addition, the PET film 8 is a tough plastic, and has excellent gas barrier properties, chemical resistance, acid resistance, alkali resistance, and oil resistance. It is possible to compensate for the fact that the coolant resistance is inferior to that of a resin having a high hardness.

The PET film 8 has a thickness of 0.08 to 0.12 mm (preferably 0.1 mm), and is cut to have the same shape and approximately the same size as the opening of the housing 2, strictly speaking, as small as 0.2 mm. there is Also, one drop of alcohol is dripped between the polypropylene sheet (PP sheet) 9 and the PET film 8 in advance so that they are attached to each other. Then, the PET film 8 adhered to the polypropylene sheet (PP sheet) 9 is aligned with the opening and pressed from above the poured potting material 7 .

If only the PET film 8 is used, the protruding potting material 7 adheres to the surface of the PET film 8 as the protruding adhesive 20. To prevent this, a polypropylene sheet 9 sufficiently larger than the opening is used. As a result, the squeezed-out adhesive 20 stays between the masking tape 5 and the polypropylene sheet 9, and does not reach unnecessary places.

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

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

FIG. 9 is a cross-sectional view showing the 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 adhesion to the polypropylene sheet 9, only the PET film 8 can be kept clean without gaps or peeling.

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

FIG. 11 is a cross-sectional view of an electronic device according to another embodiment. FIG. 4 is a cross-sectional view showing a state in which potting of an electronic device that has a movable part inside and requires space is completed. For example, in the case of a compact digital length measuring instrument, a lever 25 , a fulcrum 23 , and a digital scale 22 are accommodated inside the housing 2 with respect to the stylus portion 24 . Then, the stylus portion 24 and the lever 25 are rotated about the fulcrum 23, and the movement is magnified and detected by the digital scale 22. FIG. A digital scale 22 is connected to the circuit board 1 to digitize the displacement of the stylus portion 24 . The circuit board 1 side needs to be filled with a potting material 7 to improve environmental resistance.

The inside of the housing 2 is partitioned by a partition plate 12, or the board 1 itself is used as a partition plate, and only the part facing the outside, the circuit board 1 side, is filled with the potting material 7 while keeping the space 11 inside. In addition, the digital scale must be housed in the metal housing 2 for high precision.

In this case, if the potting material 7 with low viscosity before hardening is used, the potting material 7 may leak from the partition plate 12 into 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 Also, 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 harden in an uneven state due to leakage or the like. Moreover, since a gap is formed, the appearance is spoiled and the waterproof property is spoiled.

Therefore, as already explained with reference to FIGS. 1 to 10, the potting material 7 uses a two-liquid epoxy/modified silicone resin-based elastic adhesive containing silicon, and the surface of the potting material 7 is coated with a PET film 8. and pressed by the weight 21.

Normally, in order to fill only the necessary portion, the portion facing the outside, with the potting material 7 while leaving the space 11 inside, a potting material having a high viscosity before curing is used to the extent that it does not leak into the internal space. There is a need. However, if the viscosity before hardening is high, the surface will not be flat after filling, and the hardening will remain uneven, and air bubbles will easily enter. However, according to the method described above, it is possible to obtain a finely shaped state including the surface. In addition, it can be compared with a potted electronic device having no space 11 inside.

DESCRIPTION OF SYMBOLS 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 Protruding adhesive 21 Weight 22 Digital scale 23 Fulcrum 24 Stylus 25 Lever

Claims (10)

A potting method for electronic components in which a potting material is poured from an opening into a metal housing containing a circuit board and sealed,
The potting material is an elastic adhesive, the housing is installed on a jig, the uncured potting material is poured into the housing through the opening, and a PET film is attached to the surface of the potting material, A method of potting an electronic component, comprising curing the potting material. 2. The method of potting electronic components according to claim 1, wherein the jig is made of polyacetal, and the potting material is made of epoxy/modified silicone resin based elastic adhesive. 2. A masking tape made of vinyl chloride resin having a hole corresponding to the size of the opening is attached to the jig surface when the uncured potting material is poured into the jig. 3. The method for potting 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. 4. The method of potting an electronic component according to claim 1, wherein the potting material is pressed from above. 5. The potting of electronic components according to claim 4, wherein when the potting material is cured, a weight is placed on the polypropylene sheet and the PET film that are in a state of sticking together, and the potting material is allowed to pass for a predetermined period of time. Method. A circuit board, an electronic component mounted on the circuit board, a metal housing containing the circuit board and the electronic component, and an interior of the housing that covers and protects the circuit board and the electronic component. and a potting material that is filled and cured in an electronic device,
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. 7. The electronic device according to claim 6, wherein the potting material is an elastic adhesive of epoxy/modified silicone resin. 8. The electronic device according to claim 6, wherein the PET film has a thickness of 0.08 to 0.12 mm. 9. The potting material according to any one of claims 6 to 8, wherein the inside of the housing has a space separated by a partition plate, and the portion facing the outside is filled and hardened with the potting material. electronic device. 10. The electronic device according to claim 9, wherein a lever, a fulcrum, and a digital scale are accommodated as movable parts in the space.

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