JPH0653681A - Coating method for resin of board mounted with electronic component and coating product - Google Patents

Abstract

PURPOSE:To eliminate generation of a part in which coating is insufficient by incorporating a board in a case and then pouring resin material in the case. CONSTITUTION:A printed board 2 mounted with an electronic component is mounted in a case 3. In this case, an electric connection of the board 2 to the case 2 is conducted by screw clamping as a noise remedy, and a mounting operation for bringing a component to be required for heat dissipating into close contact with an inner surface 3a of the case 3 is executed. Then, a resin material 4 having low hardness and high thixotropy is poured in the case 3. Thus, a part above an upper part of the component 1 and a surface of the board 2 are covered with a predetermined layer thickness. That is, the component 1 of the components 1 on the board 2 which is merely mounted on the board 2 is covered entirely with a resin layer 4a, and the component to be mounted in a close contact state with the surface 3a of the case 3 for heat dissipating is covered on the surface of the component except the contact surface with the case 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin coating method used as a waterproof, moisture proof, and vibration proof measure for a substrate on which an electronic component is mounted, and the weight of the coating product is reduced and the substrate is easily attached and wired. It is intended to provide a novel resin coating method for a substrate on which an electronic component is mounted and a coating product capable of achieving both of the above.

[0002]

2. Description of the Related Art It is necessary to take waterproof / moisture proof measures and anti-vibration measures for electronic parts used in a situation where the environment changes remarkably, such as electric components for automobiles. For example, as shown in FIG. A method is known in which a printed circuit board b on which a, a, ... Are mounted is housed in a case c, and then a resin material d is injected into the case c and hardened.

However, this method does not cause any problem as long as the size of the substrate and the volume of the case are small, but the increase in the size of the substrate and the volume of the case inevitably increases the amount of the resin material d used, resulting in an increase in weight. There is a disadvantage that the resin itself is cracked due to expansion or contraction of the resin material d due to a change in ambient temperature, or a large stress is applied to the electronic component (in order to reduce this, the viscosity should be as low as possible). It is necessary to use low hardness resin material.)

Therefore, as shown in FIG. 11, after the printed material b on which the electronic components a, a, ... Are mounted is coated with the resin material e, it is mounted in the case c by screwing or the like. There is a way.

As a result, the amount of the resin material e to be used only needs to cover the periphery of the electronic component mounted board.

[0006]

However, the above method has the following problems in mounting the electronic component-mounted board on the case.

(1) In order to mount the resin-coated substrate in the case, it is necessary to provide a mounting portion for the case on the substrate. However, since resin coating cannot be applied to this portion, water or the like enters. There is a risk.

That is, when the mounting hole is formed in the substrate, it becomes impossible to mount the substrate because the hole diameter of the mounting hole becomes small due to the resin, or when the mounting hole is formed near the mounting hole due to contact with the screw at the time of mounting. There is a high possibility that a break or the like will occur in the formed resin layer.

(2) As a countermeasure against noise, a separate means for electrically connecting the substrate and the case is required.

As a means for making an electrical connection between the board and the case, it is common to carry out the conductive pattern on the board to the periphery of the mounting hole of the board and fix the board with screws. Target. However, in the resin-coated substrate, the matters described in (1) above and the presence of the resin between the screw and the conductor pattern hinder the electrical connection between the two.

Therefore, it is necessary to individually adopt, for example, a method of using a terminal member connected to the ground pattern on the substrate to make contact with the case outside the resin material e.

(3) Although some electronic components such as power control semiconductor elements require heat radiation processing, a method is used in which a part of the case is used as a heat dissipation plate so that the electronic components are closely attached to the case. Therefore, another method for heat dissipation must be adopted.

[0013]

In order to solve the above-mentioned problems, the present invention stores a substrate on which electronic components are mounted in a case, and then a resin material having a low hardness and a high thixotropy is contained in the case. The surface of the electronic component and / or the substrate is coated with a predetermined layer thickness by injecting into.

[0014]

According to the present invention, the board on which the components are mounted is mounted in the case, and then the resin material is injected to cover the surface of the electronic component or the board with the resin having a predetermined layer thickness necessary for waterproofing and moistureproofing. Therefore, there is no inconvenience that the resin is insufficiently covered when the substrate is attached to the case, and the electrical connection between the pattern on the substrate and the case is not obstructed as a measure against noise.

It is not necessary to fill the resin material in the case in which the board on which the components are mounted is mounted, and a resin material having low hardness and high thixotropy is used to secure a necessary and sufficient resin layer thickness. The material can be reduced.

Further, since the electronic component can be closely attached to the case so that the case can be used as a heat radiating plate and then the resin layer having a predetermined thickness can be formed, it is necessary to use a special method for the heat radiating treatment. Absent.

[0017]

EXAMPLES A resin coating method and a coating product for a substrate on which an electronic component is mounted according to the present invention will be described below with reference to the illustrated examples.

1 to 5 show the procedure of the coating process according to the first embodiment of the present invention, in which the amount of the resin material used is reduced by coating the electronic component with a necessary layer thickness. In addition, it is not necessary to make full use of a special method for attaching the electronic component-mounted board to the case.

FIG. 1 shows a printed circuit board 2 on which electronic components 1, 1, ... Are mounted, and a rectangular parallelepiped metal case 3 having an opening at one end surface.

First, as shown in FIG. 2, the printed circuit board 2 on which electronic components are mounted is mounted in the case 3.

At this time, the method of mounting is screwing and / or
Alternatively, fitting between members may be appropriately used.

To prevent noise, the board and the case 3 are electrically connected as usual by screws or the like, or parts for which heat dissipation is required due to large heat generation are closely attached to the inner surface 3a of the case 3. Perform the installation work.

Next, as shown in FIG. 3, the resin material 4 is injected into the case 3.

As the resin material 4, for example, silicone can be used as an inorganic material having a high insulating property, but at that time, low hardness and high thixotropy are required.

In the present invention, as shown in FIG. 10, the resin material is not injected until the case 3 is full to harden the electronic components 1, 1, ... The purpose is to cover the upper part of the electronic components 1, 1, ... And the surface of the substrate with a predetermined layer thickness as shown in Fig. 4, and fill the range above this with a resin material. There is no.

That is, in order to cover the surfaces of the electronic parts and the substrate with a necessary and sufficient layer thickness for waterproofing, moistureproofing, etc.,
A certain range is required for hardness and thixotropy.

For example, in silicone, 0.5 mm
In order to secure a certain layer thickness, it is necessary to satisfy the following conditions.

(1) Hardness (Shore A5-30).

(2) Thixo ratio (1.5 to 4.0).

(3) Viscosity (3000-15000 cp)
s).

Regarding the hardness of the resin, in the resin used for molding electronic parts and the like, A30 or less is "low", A30 to A60 is "medium", and A60 is A60.
The above is defined as "high", and the thixo ratio is 1.
The range of 0 to 1.5 is defined as "low", the range of 1.5 to 2.0 is defined as "medium", and the range of 2.0 or more is defined as "high". Regarding the viscosity, 5,000 cps or less is defined as "low", the range from 5,000 cps to 20,000 cps is defined as "medium", and 20,000 cps or more is defined as "high".

By the above procedure, as shown in FIG.
The printed circuit board 2 is hardened in the case 3 while being embedded in the resin layer 4a, and the surfaces of the electronic component and the substrate are covered with a predetermined layer thickness.

FIG. 5 shows the electronic components 1, 1, ... Covered with the resin material 4. Of the electronic components 1, 1 ,. As for the mounted component, the entire component is covered with the resin layer 4a, and a part (see 1'in the figure) attached in a state where a part of the component is closely attached to the inner side surface 3a of the case 3 for heat dissipation, The surface of the parts other than the contact surface with the case 3 is the resin layer 4a.
Will be covered by.

Regarding the electrical connection between the printed circuit board 2 and the case 3, as shown in FIG. 5A, the ground pattern 2a of the printed circuit board 2 is formed so as to be continuous up to the periphery of the mounting hole. Then, after inserting the screw f into this mounting hole, the screw f may be screwed into the screw hole of the boss g provided upright on the bottom surface of the case 3 (note that the vicinity of the screw head is partially cut in the figure). (Not shown), or using a lead wire 1 as shown in FIG. 5 (b).

6 to 9 show the procedure of the coating process according to the second embodiment of the present invention.

The second embodiment differs from the first embodiment described above in that in the first embodiment, one type of resin material 4 is used to coat an electronic component mounted substrate. However, in the second embodiment, the coating of the electronic component mounted substrate is performed in two steps using two types of resin materials having different hardness and thixotropy.

Therefore, with respect to the constituent parts shown in the second embodiment, the parts having the same functions as those of the constituent parts shown in the first embodiment are designated by the same reference numerals as those used in the first embodiment. Therefore, the description thereof will be omitted.

First, as shown in FIG.
The printed circuit board 2 on which 1 ... Is mounted is mounted in the case 3.

At this time, the mounting of the printed circuit board 2 to the case 3 and the electrical connection between the circuit board and the case 3 as a measure against noise are carried out as usual, and the components requiring heat radiation are attached to the inner surface of the case 3. A mounting operation is performed so as to be in close contact with 3a.

Next, as shown in FIG. 7, the first resin material 5 is injected into the case 3.

The first resin material 5 is mainly used for burying the printed board 2.

For example, silicone can be used, but the first resin material 5 has a lower viscosity and a lower hardness than the resin material used in the first embodiment.

This is because by using a material having a lower hardness as the resin material of the lower layer located near the bottom of the case 3, the occurrence of the stress due to the volume change caused by the influence of the ambient temperature can be reduced as much as possible. Is.

At this time, the following are guidelines for the viscosity and hardness.

(1) Hardness (Shore A10 or less).

(2) Viscosity (5000 cps or less).

Next, as shown in FIG. 8, the second resin material 6 is poured on the first resin material 5.

The second resin material 6 is used for the electronic parts 1, 1, ...
..Used to cover a portion near the upper part of .. with a predetermined layer thickness, for example, silicone can be used, in which case the hardness is low (however, the hardness is higher than that of the first resin material) And high thixotropy is required.

That is, a predetermined range of hardness and thixotropy is required to cover the electronic components 1, 1, ... With a layer thickness necessary for waterproofing, moisture proofing, etc., and the conditions are the same as in the first embodiment. This is as shown in the conditions (1) to (3) relating to the resin material described in (4).

By the above procedure, as shown in FIG. 9, the printed circuit board 2 is hardened in the case 3 while being embedded in the first resin layer 5a, and the electronic components 1, 1 ,.
Is covered with the second resin layer 6a with a predetermined layer thickness.

Therefore, by forming a resin material having a low viscosity and a low hardness in the lower layer of the case 3, it is possible to reduce the stress due to the temperature change, so that the resin or the solder is cracked or the electronic parts 1, 1 It is possible to prevent an unreasonable force from being applied to.

Although two resin layers are formed in this example, several kinds of resin materials having different viscosities, hardnesses and thixotropies are used as necessary to form the resin layers in multiple layers. It may be done.

[0053]

As is apparent from the above description, according to the present invention, the surface of an electronic component or a board is waterproofed and dampproofed by injecting a resin material after mounting a board on which components have been mounted in a case. Since it is covered with resin with a predetermined layer thickness necessary for such as, it is not necessary to sharpen the nerve about the entry of water etc. from the part where the resin cannot be applied when attaching to the case to the substrate, Further, as a measure against noise, it does not interfere with the method of electrically connecting the pattern on the board and the case with screws for mounting the board.

For this reason, it is not necessary to fill the resin material in the case in which the component-mounted board is mounted, and a resin material having low hardness and high thixotropy is used to secure a necessary and sufficient resin layer thickness. It is possible to reduce the amount of materials used, and when using the case as a heat dissipation plate, it is possible to form a resin layer of a predetermined thickness after the electronic parts are attached in close contact with the case. No need to adopt a method.

The above-mentioned embodiment is only one embodiment of the present invention, and the technical scope of the present invention should not be construed narrowly by only this embodiment. For example, in the above-mentioned embodiment, components are already mounted. Although the substrate is attached to the bottom surface of the case, all the embodiments such as attachment to the inner surface of the case without departing from the spirit of the present invention are included in the technical scope of the present invention.

[Brief description of drawings]

FIG. 1 is a diagram showing a coating processing procedure according to a first embodiment of the present invention, showing a printed circuit board on which components are mounted and a case.

FIG. 2 is a diagram showing a coating processing procedure according to the first embodiment of the present invention, showing a state in which a printed circuit board on which components have been mounted is attached to a case.

FIG. 3 is a diagram showing a processing procedure of coating according to the first embodiment of the present invention, showing injection of a resin material into a case.

FIG. 4 is a diagram showing a coating processing procedure according to the first embodiment of the present invention, showing a coating state of a component-mounted printed circuit board with a resin layer.

FIG. 5 is a perspective view of an essential part showing a covered state of the component-mounted printed circuit board by the coating process according to the first embodiment of the present invention.

FIG. 6 is a diagram showing a coating processing procedure according to the second embodiment of the present invention, showing a state in which a printed circuit board on which components have been mounted is attached to a case.

FIG. 7 is a diagram showing a processing procedure of coating according to the second embodiment of the present invention, showing injection of a first resin material into a case.

FIG. 8 is a diagram showing a processing procedure of coating according to the second embodiment of the present invention, showing injection of a second resin material into a case.

FIG. 9 is a diagram showing a coating processing procedure according to the second embodiment of the present invention, showing a coating state of a component-mounted printed circuit board with a resin layer.

FIG. 10 is a diagram showing a conventional example.

FIG. 11 is a diagram showing a conventional example different from FIG.

[Explanation of reference numerals] 1 electronic component 2 substrate 3 case 4 resin material 5 first resin material 6 second resin material

Claims (4)

[Claims] 1. A substrate on which an electronic component is mounted is housed in a case, and a resin material having low hardness and high thixotropy is injected into the case so that the surface of the electronic component and / or the substrate has a predetermined layer thickness. A method for coating a resin on a board on which an electronic component is mounted, characterized in that the resin is coated with the resin. 2. The electronic component and / or the substrate of the substrate is housed in a case after the electronic component is mounted, and a plurality of kinds of resin materials having different viscosities, hardness, and thixotropy are sequentially injected into the case. A resin coating method for a substrate on which an electronic component is mounted, characterized in that the surface is coated with a predetermined layer thickness. 3. The resin coating method for a substrate on which an electronic component is mounted according to claim 2, wherein the substrate on which the electronic component is mounted is housed in a case, and then the first resin having low or medium viscosity and low hardness is first formed. After injecting the material into the case, by injecting the second resin material having a higher hardness and higher thixotropy than the first resin material into the case, the surface of the electronic component and / or the substrate is predetermined. A resin coating method for a substrate on which an electronic component is mounted, characterized in that the resin is coated with a layer thickness of. 4. The electronic component-mounted board is housed in a case, and is coated with a predetermined layer thickness in the case by the resin coating method for the electronic component-mounted board according to claim 1, 2, or 3. A coated product having a cured electronic component and / or substrate.