JP2000059011A - Electronic circuit substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid erroneous operations, even when substrate are bedewed or wetted with salt water. SOLUTION: A frame 14 is formed of non-fluid silicone resin, so as encircle an electronic component and then the inside of the frame 14 is coated with highly fluid silicone resin 15. The frame 14 encircling the whole electronic component is formed generally on the periphery of a printed substrate. The level of the frame 14 even if the level is lower than the sealing thickness, will not overflow with the silicone resin by the surface tension thereof, may be set to less than 0.5 mm with respect to e.g., a sealing thickness of 1 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic circuit board having improved humidity resistance and water resistance in a circuit board or a hybrid IC manufactured by soldering.

[0002]

2. Description of the Related Art A conventional electronic circuit board is shown in FIGS.
This will be described with reference to FIG. 9 and 10 show a state after soldering and before resin sealing. The electronic circuit board 1 manufactured by soldering mounts the electronic components 2 and 3 for surface mounting on the cream solder formed on the printed circuit board 5 and then continuously transports the board to remove the cream on the board. A reflow soldering method in which solder is heated and melted to perform solder joining, or a lead component 4
Is generally inserted into a hole of a substrate, and soldering is performed by applying molten solder from the opposite side of the substrate to perform soldering. There are several other soldering methods, but even with electronic circuit boards using any of these methods, the solder joints are exposed to the outside while they are electrical joints for electronic circuits. I have. On the other hand, the use environment of electronic circuit boards is various, and they are often used not only indoors but also outdoors, and are affected by salt water in hot and humid conditions, dusty environments, and along the coast. In such a harsh environment, the life of the electronic circuit board is generally shortened, and the possibility of causing a malfunction is increased. Conventionally, two methods have been mainly used to extend the life of the electronic circuit board and reduce operation failures.

[0003] One is a method of applying a thin resin coating 11 on the surface of an electronic circuit board as shown in FIG. 11 (prior art 1), and mainly uses urethane or acrylic resin. Since the resin alone does not have fluidity, it is used after being dissolved in a solvent. As the solvent, toluene and alcohols are used. The thickness of the coating is about 10 to 30 μm.

In another method, as shown in FIG. 12, an entire electronic circuit board is placed in a case 13 and a resin 1 is placed therein.
In this method, the entire substrate is covered with a resin (prior art 2), and a urethane resin or a silicone resin is mainly used as a resin material. The coating thickness is determined by the depth of the case, but generally has a thickness of 5 to 10 mm on one side, and a thickness of 10 to 20 mm as a whole.

[0005]

However, in the above prior art 1, since the coating film thickness is thin, malfunction occurs when dew condensation or salt water is applied. Also, when a large battery or odd-shaped component is mounted on a circuit board on which chip components are mounted due to its thin film thickness, even if resin is applied from above the odd-shaped component, the chip components below the odd-shaped component are coated. Not done. In addition, lead components with long leads are 10
Coating cannot be performed with a film thickness of about 30 μm. For the above reasons, the prior art 1 is insufficient as a sealing method used in a severe environment.

Further, in the prior art 2, all the problems as in the prior art 1 can be solved because the whole substrate is covered with resin. However, the cost of the electronic circuit board becomes extremely high because a special case is required, a two-liquid mixing device including a main agent and a curing agent is required, and the amount of the resin material used is large. In addition, there is another problem that the use of the special case makes the electronic circuit board large and hinders reduction in size and weight of the electronic device to be incorporated. If there is no case, it is preferable to use a low-viscosity material in consideration of fluidity in order to perform resin sealing on the entire board, but if you want to seal components at the end of the circuit board, The viscous material drips under the substrate, and it is extremely difficult to stably perform the production so as not to hang.

On the other hand, a high-viscosity material is suitable for sealing only a part of a specific part, but requires a complicated manual operation for sealing the entire circuit board due to low fluidity. I do. Even in the case of automation, it is not generally performed because complicated operations must be repeated using a robot. Further, it is difficult to form a uniform film thickness due to low fluidity.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, it is an object of the present invention to provide an electronic circuit board which does not malfunction even in a harsh environment of dew or salt water and does not deteriorate its life. All or some of the electronic components are formed so as to be surrounded by a frame over the periphery where the electronic components are present, and the inner portion surrounded by the frame is sealed with resin.

According to the present invention, it is possible to provide an electronic circuit board excellent in humidity resistance characteristics by eliminating the above-mentioned disadvantages.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of an electronic circuit board which forms an electronic circuit by performing an electrical connection by soldering an electronic component on the circuit board; A frame having a height of about 0.5 to 2 mm and a width of about 0.5 to 2 mm from the surface is formed so as to surround all or some of the electronic components over the periphery where the electronic components are present, and is surrounded by this frame. The sealed inner part is sealed with a resin. According to the present invention, the humidity resistance can be further improved.

The invention according to claim 2 further uses a non-flowable silicone resin (resin A) as a material for forming the frame.

According to a third aspect of the present invention, a silicone resin (resin B) having a viscosity of 5P (poise) to 50P is used as a material for sealing the inside surrounded by the frame.

The invention according to claim 4 has a diameter of 0.5 to 0.5 which is not buried even after soldering on a circuit board in a portion surrounded by a frame.
When there is a hole of about 2 mm, the viscosity is 100P to 50P.
Fill the hole using a silicone resin (resin C) in the range of 0P, and then put the silicone resin (resin B) inside the frame.
It is made to be sealed with.

According to a fifth aspect of the present invention, when another component is mounted on a portion that needs to be coated in the portion surrounded by the frame, the component mounted on the component is placed on top of the component mounted thereon. Both parts are sealed by applying a resin and pouring it into a part below the upper part that requires application.

According to a sixth aspect of the present invention, the thickness of the resin applied to the portion surrounded by the frame is higher than the height of the frame.

According to a seventh aspect of the present invention, when the height of the lead or the electrode is about 0.5 to 2 mm, a resin is applied from above the part so that the lead or the electrode portion is set to 0.1 mm.
The sealing is performed for about 5 to 2 mm.

In the invention according to claim 8, when there is a part having a height of about 0.5 to 2 mm and need not be coated with resin in a part where the frame needs to be formed, this part serves as a role of the frame. A frame is formed from the end of the component, and a resin puddle having a width of about 2 to 5 mm and a height of about 2 to 5 mm is formed at the start portion.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a sectional view of a sealed electronic circuit board according to the present invention. FIG. 2 is a plan view of a sealed electronic circuit board according to the present invention. The frame 14 is formed using a non-fluid silicone resin so as to surround the electronic component, and a high-fluid silicone resin 15 is applied inside the frame 14. The frame 14 is generally formed on the periphery of the printed circuit board to surround all the electronic components. However, the frame 14 may not be limited to the above due to restrictions on component arrangement and circuit design. If there is a component that does not need to be applied, only that component may be placed outside the frame.

Further, when the component arrangement is divided and concentrated at a plurality of places, there may be a case where a plurality of parts are surrounded by a frame. The height of the frame should be equal to or higher than the required sealing thickness. Even if the height of the frame is lower than the sealing thickness, the height of the frame may be 0.5 mm or more with respect to the sealing thickness of 1 mm because the surface does not overflow with the surface tension of the silicone resin. In general, since the height of the surface mounting chip component is 1 mm or less, the standard sealing thickness is 1 mm.
mm or more. However, as described in the prior art, all of the multi-pin surface mount components 2 such as QFP and the lead components 4 such as electrolytic capacitors cannot be sealed with a sealing thickness of 1 mm. A method of sealing all components including these components will be described in detail later.

(Embodiment 2) Next, FIG. 3 shows a manufacturing process of the present electronic circuit board. If the circuit board has a hole with a diameter of 0.5 mm or more, it is necessary to fill the hole because the liquid dripping occurs when the low-viscosity resin 15 is applied. Next, a frame is formed. The frame is formed by moving the robot equipped with the dispenser while discharging the resin at a constant speed. The nozzle diameter attached to the dispenser is 1-3 mm.

Next, low-viscosity silicone resin 15 is applied over the entire surface of the frame. The application method is to move the robot equipped with the dispenser while discharging the resin. The nozzle diameter attached to the dispenser is 2-5 mm, 2 × 1
In some cases, a flat nozzle of about 0 mm may be used. Curing is performed in this state. The curing is performed at room temperature for about 5 hours. Approximately 10 hours are required for complete curing, but reversal is possible in 5 hours. After the inversion, a frame is formed on the opposite surface, and the entire surface is coated.
The application method is the same as for the surface. In this state, the composition is cured at room temperature for about 5 hours to complete.

(Embodiment 3) FIG. 4 is a cross-sectional view of an electronic circuit board in a case where filling is performed. As a material used for filling the holes, a silicone resin having a viscosity of 100 poise to 500 poise is used. If the viscosity is less than 100 poise, dripping will occur even if the holes are filled. When the viscosity is 500 poise or more, the fluidity becomes low and it becomes difficult to fill the hole in a short time.

(Embodiment 4) FIG. 5 shows sealing in a state where a large-sized deformed component such as a battery is mounted on a chip component requiring sealing. By applying a resin from above the deformed part, the electrodes of the deformed part can be sealed, and at the same time, the resin that flows can be applied to the chip part below.

(Embodiment 5) FIG. 6 shows a state 16 in which the sealing thickness is higher than the height of the frame 14. In order to increase the height of the frame, it is necessary to increase the nozzle diameter. For example, when a height of 2 mm is required, the nozzle diameter needs to be 3 mm, but the distance between the component and the end of the board may be 2 mm or less. On the other hand, when there is a tall part, the sealing thickness needs to be higher than the height of the part. Material of frame 14 and low-viscosity material 16
Even if the low-viscosity material 16 is sealed higher than the height of the frame due to the surface tension of the material, it does not flow out.

Embodiment 6 FIG. 7 shows a state 1 in which a long lead component such as an electrolytic capacitor is sealed.
7 is shown. In the case of long lead components, the lead length that needs to be sealed may be 3 to 4 mm. It is difficult to make the overall sealing thickness 3 mm or more because of the height of the frame, so the resin is partially applied on the lead component, and the lead is transferred by the resin that has flowed down the lead component. Take the sealing method.

(Embodiment 7) FIG. 8 shows a method of forming a frame when there is a large-sized deformed part which does not need to be sealed with resin like a terminal block. When the distance between the odd-shaped component and the electronic component is 2 mm or less, there may be no place to form a frame. In this case, the formation of the frame is started from the end of the deformed part by regarding the deformed part as a frame. In this case, it is difficult to make the distance between the frame and the odd-shaped part zero, and there is a problem that the low-viscosity resin flows out. To solve this, a resin pool is formed at the beginning and end of the frame formation to prevent the liquid from flowing out. In the method of forming the resin pool, the nozzle is stopped for a certain time at the beginning and end of the frame formation, and the resin is continuously applied during this time. The diameter of the resin pool must be 2 mm or more and the height must be 2 mm or more.

Table 1 shows the humidity resistance and the product cost of the present invention. In the present invention, both the condensation test and the salt water test have passed, but in the prior art 1, both have failed.
Both pass in the prior art 2, but the product cost of the present invention is significantly lower.

[0029]

[Table 1]

[0030]

As is clear from the above description, the following effects can be obtained by the electronic circuit board of the present invention.

For example, it is possible to uniformly form a resin sealing film having a thickness of 0.5 mm or more over the entire surface of the electronic circuit board. It becomes possible to seal even surface mount components.

Further, since a non-flowable silicone resin is used as a material for forming the frame, the height of the frame can be easily secured, and the width for securing the height does not need to be wide.

When a silicone resin having a viscosity of 5P (poise) to 50P is used as a material for sealing the inside surrounded by the frame, it is possible to prevent liquid dripping from a through hole having a diameter of 0.4 mm or more. .

If there is a hole having a diameter of 0.5 mm or more that cannot be filled even after soldering on the circuit board in the portion surrounded by the frame, fill the hole with a silicone resin having a viscosity of 100P to 500P. Since the inside of the frame is sealed with the silicone resin, dripping can be prevented.

Even if there is a component above the place to be sealed, both can be sealed.

Further, a sealing film thickness larger than the height of the frame can be formed. In addition, by sealing the lead component from above, it is possible to seal a lead component longer than the height of the frame.

In the case where a large-sized deformed part is present, even if there is no place for forming the frame, the part can be sealed by using the part as a part of the frame.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an electronic circuit board according to a first embodiment of the present invention.

FIG. 2 is a plan view of the substrate.

FIG. 3 is a process diagram of an electronic circuit board sealing method according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view illustrating a case where an electronic circuit board according to a third embodiment of the present invention is filled with holes.

FIG. 5 is a cross-sectional view of an electronic circuit board according to a fourth embodiment of the present invention, in which the electronic circuit board is sealed with a large-sized irregular component such as a battery.

FIG. 6 is a cross-sectional view when the sealing thickness is larger than the height of the frame of the electronic circuit board in Embodiment 5 of the present invention.

FIG. 7 is a cross-sectional view of an electronic circuit board according to a sixth embodiment of the present invention when it is sealed with a lead component.

FIG. 8 is a cross-sectional view of a case where an odd-shaped part of an electronic circuit board is used as a frame in a seventh embodiment of the present invention.

FIG. 9 is a sectional view of a conventional electronic circuit board before sealing.

FIG. 10 is a plan view of the substrate.

FIG. 11 is a cross-sectional view showing the same substrate sealed.

FIG. 12 is a sectional view of the same substrate sealed by another means.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electronic circuit board 2 Multi-pin surface mounting parts, such as QFP and SOP 3 Chip parts 4 Lead parts, such as an electrolytic capacitor 5 Printed circuit board 14 Frame 15 Sealing part of the part enclosed by the frame 16 Sealing higher than the height of the frame Part 17 Sealing part for long lead parts 18 Sealing part for large irregular parts such as batteries 19 Parts that do not need to be sealed 20 Resin pool

Continuation of the front page (72) Inventor Hirozumi Nakamura 1006 Kazuma Kadoma, Kazuma, Osaka Matsushita Electric Industrial Co., Ltd. F term (reference) 5E314 AA40 BB06 BB07 CC01 DD01 FF01 FF21 GG01

Claims (8)

[Claims] 1. An electronic circuit board for soldering electronic components on a circuit board and electrically connecting them to form an electronic circuit, wherein a frame is formed on the circuit board so as to surround the electronic component. An electronic circuit board that seals the inner part surrounded by a frame with resin. 2. The electronic circuit board according to claim 1, wherein the material of the frame is a non-fluid silicone resin. 3. The electronic circuit board according to claim 1, wherein the material for sealing the inside surrounded by the frame is a silicone resin having a viscosity of 5P (poise) to 50P. 4. When there is a hole having a diameter of 0.5 mm or more which cannot be filled after soldering, the hole inside the frame is filled with a silicone resin having a viscosity of 100P to 500P and then a viscosity of 5P to 50P. The electronic circuit board according to claim 1, wherein said electronic circuit board is sealed with said silicone resin. 5. The electronic circuit board according to claim 1, wherein when another component is mounted on the component requiring sealing, the resin is sealed from above the component mounted thereon. 6. The electronic circuit board according to claim 1, wherein the thickness of the resin sealed in the portion surrounded by the frame is higher than the height of the frame. 7. The electronic circuit board according to claim 1, wherein when the height of the lead or the electrode is higher than the height of the frame, the resin is sealed from above the component. 8. When there is a component that does not need to be sealed with resin in a portion where the frame is required to be formed, the component is used as a role of the frame, and the formation of the frame is started from the end of the component. Item 2. The electronic circuit board according to Item 1.