JPH0746756B2 - Electric circuit device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to an electric circuit device in which a printed wiring board having a metal base is mounted in a metal chassis, and in particular, an electric circuit with improved heat dissipation. Regarding circuit devices.

(Prior Art) For an electric circuit device having a printed wiring board, a method of accommodating a printed wiring board on which electric components are mounted in a case or a chassis has been used. However, downsizing of the device
When the density of heat generation increases with the increase in density, reliability decreases due to the problem of heat dissipation.

Therefore, recently, as a printed wiring board, a metal core board based on a metal having excellent heat dissipation has been developed. However, even in the metal core printed wiring board, as long as the board is provided in the chassis, the heat generated from the electric components is evenly distributed throughout the board, and the temperature rise in the chassis cannot be avoided. There is also a method of installing a fan for air cooling in the chassis to force the heat to escape to the outside, but this increases the size of the device and increases power consumption.

On the other hand, a method of contacting the metal base of the metal core printed wiring board with the chassis is also conceivable, but if the end surface of the metal base is contacted with the inner surface of the chassis, the contact area will not be sufficient and the heat from the board to the chassis will The conductivity is poor and the improvement of the heat dissipation effect can hardly be expected. Further, in the method of bringing the surface of the metal base into contact with the inner surface of the chassis, when a plurality of boards are stacked in the same chassis at a predetermined interval, only the board at the end can be brought into contact with the inner surface of the chassis. A large number of boards cannot be mounted in the same chassis, which reduces the space factor in the chassis.

(Problems to be Solved by the Invention) As described above, in the conventional device in which the printed wiring board having the metal base is mounted in the chassis, the board is surrounded by the chassis although the board itself has good heat dissipation. Therefore, there is a problem that it is difficult to enhance the heat dissipation by a simple means that does not rely on forced air cooling or the like. Further, when the metal substrate is brought into contact with the inner surface of the metal chassis to increase the heat dissipation effect, there is a problem that a large number of substrates cannot be mounted in the same chassis due to a reduction in space factor.

INDUSTRIAL APPLICABILITY The present invention can bring the metal base of the printed wiring board into close contact with the inner surface of the metal chassis with a wide contact area without impairing the space factor, and can achieve a high heat dissipation effect without using forced air cooling, which is small and reliable. An object is to provide a high electric circuit device.

[Structure of the Invention] (Means for Solving the Problems) An electric circuit device according to the present invention includes a printed wiring board having a metal base and mounted with electric parts, and a metal chassis for housing the printed wiring board. In the electric circuit device including, a circular printed wiring board is used as the printed wiring board, a cylindrical metal chassis is used as the metal chassis, and a peripheral portion of the circular printed wiring board has a predetermined angle with respect to a mounting surface of an electric component. It is characterized in that the outer peripheral surface of the metal base in this peripheral portion is brought into close contact with the inner peripheral surface of the cylindrical metal chassis.

(Operation) Since the outer peripheral surface of the peripheral portion, which has an angle with respect to the component mounting surface, is brought into close contact with the inner peripheral surface of the metal chassis of the metal substrate of the printed wiring board by drawing or bending, The contact area is sufficiently secured, and the adhesion between them is high. Therefore, the heat generated from the components is transmitted from the peripheral portion of the metal base body to the metal chassis and is radiated to the outside air from the metal chassis.

In this case, since the contact surface of the metal base with the inner peripheral surface of the metal chassis is only the peripheral portion having an angle, it is possible to mount a large number of wiring boards in one metal chassis under the same conditions. A high heat dissipation effect is exhibited regardless of the mounting position of. Further, in the present invention, since the circular printed wiring board is used as the printed wiring board and the cylindrical metal chassis is used as the metal chassis, heat can be effectively released. In other words, in the case of a circular printed wiring board, heat uniformly moves from the center to the outside, so that there are parts (for example, four corners in the case of a square printed wiring board) where the heat resistance increases locally. Therefore, there is no fear that the heat radiation effect is reduced due to the non-uniformity of the heat radiation property.

On the other hand, for example, in the case of a square printed wiring board, the corners of the four corners are thinner than the other sides, that is, the heat does not move uniformly, so the thermal resistance increases,
The heat dissipation effect decreases.

Furthermore, in the case of a circular printed wiring board, the distance between the component and the circumference of the cylindrical metal chassis, which is the heat dissipation portion, is closer than in the case of printed wiring boards of other shapes, so the thermal resistance becomes smaller. Therefore, the heat can effectively escape.

Further, since the circular printed wiring board and the cylindrical metal chassis are in uniform contact with each other at any part, there is no part where the adhesion is deteriorated. If there is a portion where the adhesiveness is partially reduced, the heat dissipation effect is greatly reduced even if the adhesiveness of other portions is good. Therefore, it is not possible to secure uniform adhesiveness as in the present invention. It's important.

(Embodiment) FIG. 1 is a sectional view of an electric circuit device according to an embodiment of the present invention. In the figure, the metal chassis 1 has a cylindrical shape with one end open and the other end closed, and is made of a metal material such as aluminum, stainless steel, or iron, preferably a metal material having good thermal conductivity such as aluminum. . A printed wiring board 2 is mounted inside the metal chassis 1.

The printed wiring board 2 has an insulating layer 4 and a wiring layer 5 sequentially formed on a metal base 3 having a good thermal conductivity, such as an aluminum plate, on which an electric component 6, such as an IC chip or a chip resistor chip capacitor, is formed. This chip component is mounted with solder 7 or the like. Alumina, glass, a resin layer or the like can be used for the insulating layer 4. Further, as the wiring layer 5, for example, one formed by a screen printing method using a conductor paste, or one obtained by patterning by etching a substrate to which a copper foil is bonded via an insulating resin can be used.

Here, the peripheral portion 3a of the metal base 3 is bent upward at a substantially right angle by, for example, drawing, and the outer peripheral surface of the peripheral portion 3a is in close contact with the inner peripheral surface of the metal chassis 1. The drawing method is a method of pressing by using concave and convex dies, and since the dimensional accuracy after processing is high, the outer peripheral surface of the peripheral portion 3a of the metal base 3 can be easily formed on the inner peripheral surface of the metal chassis 1. Can be closely attached to the surface. When the metal base 3 is drawn, the insulating layer 4 is preferably a resin layer so as to prevent damage such as cracks due to impact during drawing. Further, like the metal substrate 3, it is desirable that the metal chassis 1 is formed into the cylindrical shape by drawing. By this, the outer peripheral surface of the peripheral portion 3a of the metal substrate 3,
It is possible to further improve the adhesion with the inner peripheral surface of the metal chassis 1.

In FIG. 1, the peripheral portion 3a of the metal base 3 is bent upward, that is, the mounting surface of the component 6 is inward, but it may be bent downward. is there.

Next, the manufacturing process of the electric circuit device of FIG. 1 will be described with reference to FIGS. In each figure, (a) is a sectional view and (b) is a plan view.

First, the insulating layer 4 and the wiring layer 5 are formed on the disk-shaped metal substrate 3.
Are sequentially formed by a screen printing method or the like to produce a printed wiring board 2 (FIG. 2). Next, the peripheral portion 3a is bent upward at a right angle so that the peripheral portion 3a of the metal substrate 3 has a cylindrical shape by drawing (FIG. 3). The conditions for the drawing process are appropriately selected according to the material and thickness of the base body 3 and the material and type of the insulating layer 4 and the wiring layer 5, for example, the base body 3
An aluminum plate having a thickness of 0.5 mm is used as the insulating layer 4, and an insulating resin having a thermosetting type 1,2 polybutadiene resin as a main component applied to a thickness of 100 μm is used as the insulating layer 4. Further, a resin copper paste is used as the wiring layer 5. When using, the clearance between the concave mold and the convex mold used for drawing is 0.02 mm, and the pressure is preferably about 500 to 1000 kg.

Next, as shown in FIG. 4, the electric component 6 is mounted by the solder 7. The shape of the component 6 is not particularly limited, but a planar mounting component in which heat is easily transferred to the base 3 is preferable. As a mounting method, cream solder is applied to a predetermined position to which the solder 7 is attached by a dispenser or the like, then the component 6 is mounted and soldering is performed by a reflow method. At this time, the component 6 may be temporarily fixed with an adhesive so that the position of the component 6 does not change due to the surface tension of the solder 7. When the pattern surface is convex, cream solder can be applied by screen printing. In that case, a reflow method using an infrared heater or a reflow method using a paper phase is suitable.

Next, the printed wiring board 2 on which the electric component 6 is mounted in this way
Is inserted into the metal chassis 1 as shown in FIG. 5, and the outer peripheral surface of the peripheral portion 3a of the metal base 3 is brought into close contact with the inner peripheral surface of the metal chassis 1. In this case, it is desirable to apply an adhesive having good thermal conductivity to both peripheral surfaces in advance.

The electric circuit device thus obtained was connected to a power source in the state shown in FIG. 4, and the temperature on the substrate 2 was measured locally by a color thermometer (thermotracer manufactured by NEC Saneisha Co., Ltd.) under operating conditions. No exotherm was seen and was in the range of about 60-65 ° C. Further, as shown in FIG. 5, when the substrate 2 was assembled in the metal chassis 1, the temperature was similarly measured from the upper opening of the chassis 1 by the color thermometer, and as a result, the component 6 was obtained.
The temperature was about 50 ° C. even in the vicinity of, and the temperature rise could be suppressed by about 10 ° C. compared to the state where the substrate 2 was not incorporated in the chassis 1.

Next, more specific experimental examples of the present invention will be described.

Experimental example 1 0.5 mm thick hard aluminum (JIS A
-2017) plate, the surface was brush-polished, and after degreasing and cleaning, an insulating layer was printed using an insulating resin paste having the following composition.

Insulating resin paste composition Thermosetting 1,2 polybutadiene resin 100 parts by weight Hydrogenated polybutadiene resin 10 parts by weight Alumina powder 20 parts by weight Titanium oxide powder 10 parts by weight Colloidal silica 1 part by weight Next, in air at 180 ° C for 20 minutes After being dried for 10 minutes at 350 ° C in a nitrogen atmosphere, a copper paste composed of 6 parts by weight of phenoxy resin, 90 parts by weight of copper powder, 10 parts by weight of silver powder and 18 parts by weight of butyl carbitol acetate was used. Then, a wiring layer was formed by a screen printing method and cured in a nitrogen atmosphere.

Next, the surface other than the component mounting area was coated with a solder resist CCR506G manufactured by Asahi Chemical Laboratory and dried in air at 120 ° C. for 20 minutes.

Next, an electroless nickel plating solution (Niclad 741) manufactured by Okuno Seiyaku Co., Ltd. was maintained at 65 ° C. and a plating step was performed for 5 to 10 minutes to form a plated film of 2 to 5 μm. This board is punched into a circle with a diameter of 60 mm by a press, and the inner diameter is 45 mm.
Cylindrical drawing was performed to obtain φ.

Next, cream solder was applied to the electrode portion of the wiring layer with a dispenser to assemble the parts, and then reflowed for 2 minutes on a 240 ° C. hot press to mount the parts.

Two kinds of substrates thus obtained were prepared and inserted into a cylindrical aluminum chassis having an inner diameter of 46 mmφ at a predetermined interval. At this time, the outer peripheral surface of the peripheral portion of the aluminum base,
A good thermal conductive silicon compound was previously applied to the contact surface of the aluminum chassis with the aluminum substrate. A flexible wiring board having a thickness of 200 μm was used to connect these two types of substrates.

With the device thus obtained, the temperature on the substrate surface was measured with a color thermometer while the power was turned on and in operation. It was

On the other hand, for comparison, when the temperature on the board surface was measured without inserting the board into the chassis, the temperature rise reached 80 ° C with respect to the ambient temperature.

Experimental Example 2 A printed wiring board was prepared in the same manner as in Example 1 using an aluminum plate of 100 × 50 × 1.0 mm as a metal substrate, and then cream solder was applied to a predetermined portion of the wiring layer by screen printing. The components were mounted on this, and reflowed for 1 minute on a 240 ° C. hot press to mount.

Then, the end face was bent 90 ° at a position of 10 mm from both ends of the substrate and inserted into a box-shaped aluminum chassis for assembly.

For the device obtained in this way, when the power was turned on and the temperature on the board surface and the temperature on the outer surface of the chassis were measured in the operating state, the temperatures on the board surface, parts, and the outer surface of the chassis were almost the same, and the local While avoiding an excessive temperature rise,
It was confirmed that a high heat dissipation effect could be obtained.

EFFECTS OF THE INVENTION According to the present invention, the peripheral portion of the metal base of the printed wiring board is angled with respect to the component mounting surface, and then the outer peripheral surface is brought into close contact with the inner peripheral surface of the metal chassis. The heat from the components can be effectively dissipated to the external atmosphere through the metal base and the metal chassis without using a large-sized forced air cooling unit that consumes power.

In addition, according to the present invention, a plurality of substrates are placed in the same chassis, unlike the case where the surface of the metal base that remains flat is brought into contact with the metal chassis regardless of the large contact area between the metal base and the metal chassis. They can be arranged in a stack, the space factor in the chassis is not impaired, and the heat dissipation of all the boards can be enhanced regardless of the stacking position.

[Brief description of drawings]

FIG. 1 is a sectional view of an electric circuit device according to an embodiment of the present invention, and FIGS. 2 to 5 are views for explaining a manufacturing process of the device. 1 ... Metal chassis, 2 ... Printed wiring board, 3 ... Metal base, 3a ... Peripheral part, 4 ... Insulating layer, 5 ... Wiring layer, 6
…… Electrical parts, 7 …… Solder.

Claims (6)

[Claims] 1. An electric circuit device comprising a printed wiring board having a metal base, on which electrical components are mounted, and a metal chassis for housing the printed wiring board, wherein the printed wiring board is a circular printed wiring board. The metal chassis is a cylindrical metal chassis, and the peripheral portion of the circular printed wiring board is formed into a shape having a predetermined angle with respect to the mounting surface of the electric component, and the outer peripheral surface of the metal substrate in the peripheral portion is formed. An electric circuit device, wherein the electric circuit device is in close contact with the inner peripheral surface of the cylindrical metal chassis. 2. The electric circuit device according to claim 1, wherein a peripheral portion of the circular printed wiring board is substantially perpendicular to a mounting surface of an electric component. 3. The electric circuit device according to claim 1 or 2, wherein the circular printed wiring board is drawn. 4. The electric circuit device according to claim 1 or 2, wherein the cylindrical metal chassis is drawn. 5. The circular printed circuit board according to claim 1, wherein an insulating layer and a wiring layer are formed on the metal substrate by screen printing. The electric circuit device described. 6. The electric circuit device according to claim 1, wherein a plurality of the circular printed wiring boards are laminated in the same cylindrical metal chassis at predetermined intervals.