JPH08228056A - Metal base circuit board - Google Patents

Abstract

PURPOSE: To reduce contact electric resistance by increasing the area of a contact portion of a crushed protruding member with an upper side of a ground circuit to be greater than the area of a contact portion of a lateral side of the ground circuit with the protrusion. CONSTITUTION: A metal plate 1 is electrically connected with a ground circuit 4 in two ways. On one hand, a part of the ground circuit 4 is pushed out together with a protrusion 5 in forming the protrusion 5, and the other part remains to form a lateral side. The lateral side of the ground circuit 4 contacts the protrusion 5 to form an electric circuit. On the other hand, a part of the metal plate 1 constituting the protrusion 5 is deformed by crushing the protrusion 5 so that the deformed part contacts the surface of the ground circuit 4. The area of the lateral side of the ground circuit 4 is limited by the thickness of the conductor and the size of the protrusion 5. Therefore, by increasing the area of the protrusion 5 crushed for positively using the upper side of the ground circuit, contact electric resistance can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor-mounted circuit board used in electric equipment, communication equipment, automobiles and the like.

[0002]

2. Description of the Related Art A metal-based circuit board is used in a field requiring high-density mounting because it is excellent in heat dissipation. Especially, a metal plate using aluminum or aluminum alloy. Has been used a lot.

It is known that, in a metal base circuit board, an induction current due to a high frequency is generated in the metal plate to deteriorate the electrical characteristics of the circuit board. In order to prevent this phenomenon, conventionally, an earth circuit and a metal plate have been electrically connected.

As a method for electrically connecting the metal plate and the earth circuit, an insulating layer existing on the surface of the metal plate is removed by cutting with a tool such as an end mill or a drill to form an earth connection point. Form and then ultrasonic wire
It is known to perform bonding or to apply a conductive paste.

Alternatively, the metal plate on the back surface of the ground circuit is pushed out from the back surface to the side surface of the protruding portion, or the pushed protruding portion is slightly crushed from the surface to the side surface of the protruding portion, and the earth circuit made of copper foil. And were electrically connected by using the above wire bonding method or a conductive paste (Japanese Utility Model Laid-Open No. 11010495).

However, the cutting method using a tool has a slow cutting speed because aluminum or an alloy containing aluminum as a main component has a property of being difficult to cut,
In addition, since the cutting process is performed for each location, the production efficiency is extremely low.

On the other hand, the method disclosed in Japanese Utility Model Laid-Open No. 11010495 has an advantage of high production efficiency, but when the obtained metal base circuit board is actually used, the crushed portion and the ground circuit are brought into contact with each other. There is a drawback that the electric resistance increases with the lapse of time. This drawback becomes remarkable especially when exposed to high temperature steam, under a heat shock environment, or when subjected to a temperature history by a solder bath.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and the rear portion of the metal plate of the earth circuit is extruded from the rear surface. In a metal-based circuit board in which a metal plate and a metal plate are electrically connected, the contact electric resistance is small, and the contact electric resistance does not increase even in actual use for a long period of time, and the electric reliability is high. It is to provide a metal-based circuit board.

[0009]

According to the present invention, there is provided a ground circuit made of metal foil on at least one main surface of a metal plate with an insulating layer interposed therebetween, and a part of the metal plate under the ground circuit is grounded. On the metal base circuit board in which the ground circuit and the metal plate are electrically connected by pressing the projection from the ground circuit side and then crushing it after forming the projection from the The metal base circuit board is characterized in that the area of the portion in contact with the circuit upper surface is larger than the area of the side surface of the ground circuit and the portion in contact with the protrusion, and more specifically, the protrusion is crushed. The diameter of the portion is 1.05 with respect to the diameter of the portion inside the metal substrate of the protrusion.
It is a metal-based circuit board characterized by being more than twice and less than 1.5 times.

Further, the present invention is a metal base circuit board, wherein the metal plate is aluminum or an alloy containing aluminum as a main component and having an elongation at break of 5% or more in a tensile strength test, A metal base circuit board having a surface roughness of 0.5 μm or more and 2.5 μm or less (Rz) on at least the surface of the contact portion of the metal foil with the crushed protrusion, or the metal foil is crushed at least. The metal-based circuit board is characterized in that it is a composite foil in which Ni is laminated on Cu or a composite foil in which Al is laminated on Cu at the contact portion with the protruding portion.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic view showing an example of a metal-based circuit board of the present invention. (A)-(d) shows sequentially the process of processing in many pieces arrangement | positioning, (a) is a top view before processing, (b) is a sectional view before processing, (c) is (c). When the protrusion is pushed out from the back side of the ground circuit, (d)
Further, shows a situation in which the protrusion is pressed and crushed from the front side. Further, (e) is an enlarged view of a circuit piece sectioned by a dotted line in (a) plan view, (f) is an enlarged sectional view of one circuit piece, and (g) is The crushed protrusion is further enlarged and illustrated.

As illustrated in FIG. 1 (g), the electrical connection between the metal plate 1 and the earth circuit 4 is made via two paths. One of the paths is a side surface portion of the ground circuit 4. That is, when the protrusion 5 is formed, a part of the ground circuit 4 is extruded together with the protrusion 5, and the other part is left as it is to form the side surface. The side surface of the ground circuit 4 immediately contacts the protrusion 5 made of the same material as the metal plate to form an electrical path. The other one of the paths is a portion in which a portion of the metal plate 1 forming the protrusion 5 is deformed by pressing and crushing the protrusion 5 and comes into contact with the surface of the ground circuit 4.

Since the area of the side surface portion of the earth circuit 5 is substantially determined by the thickness of the conductor forming the earth circuit 4 and the size of the protrusion 5, the inventor has a limit in securing a sufficiently large area. On the other hand, when the upper surface of the earth circuit is positively used for the electrical connection part, it is possible to secure a remarkably large contact area, and it is easy to achieve stable electrical connection with low electrical resistance. As a result, the present invention has been achieved.

In the present invention, it is essential that the area of the contact between the crushed protrusion 5 and the upper surface of the earth circuit 4 is larger than the area of the contact between the side surface of the earth circuit 4 and the protrusion 5. . If the area of the contact portion between the projection 5 and the upper surface of the ground circuit 4 is small, the electrical resistance between the metal plate 1 and the ground circuit 4 may be reduced, but the overall electrical resistance is sufficiently reduced. I can't get it to happen. In order to sufficiently reduce the electric resistance of the whole and to secure a stable electric connection state, the area of the contact portion between the crushed protrusion 5 and the upper surface of the earth circuit 4 is the side surface of the earth circuit 4 and the protrusion. It must be larger than the area of the part in contact with the part 5.

The diameter of the crushed portion of the protrusion 5 must be 1.05 times or more, and preferably 1.10 times or more, the diameter of the portion of the protrusion 5 inside the metal plate 1. .

The shape of the protruding portion 5 is determined by the shape of the die for pushing it out, but in general, it is often a cylindrical shape having a diameter of about 2 mm. The general thickness of the earth circuit 4 which is to be electrically connected to the protrusion is about 35 μm. Therefore, the contact area between the protrusion 5 and the side surface of the ground circuit 4 is about 2 × π × 35 × 10 ⁻³ (= 0.22) mm ² . On the other hand, the diameter of the protrusion 5 before being crushed matches the portion of the protrusion 5 inside the metal plate 1, and the size thereof is about 2 × 2 × π / 4 (= 3.14) mm ² .

When the diameter of the crushed portion of the protrusion 5 is less than 1.05 times the diameter of the portion of the protrusion 5 inside the metal plate 1, the crushed protrusion 5 and the upper surface of the ground circuit 4 are in contact with each other. The area of the portion cannot necessarily be larger than the area of the portion in contact with the side surface portion of the earth circuit 4. Therefore, the diameter of the crushed portion of the protrusion 5 needs to be 1.05 times or more the diameter of the portion of the protrusion 5 inside the metal plate 1.
If it is 1.10 times or more, a sufficiently stable electrical contact state can be obtained, which is preferable.

On the other hand, when the diameter of the crushed portion of the protrusion 5 exceeds 1.5 times the diameter of the portion of the protrusion 5 inside the metal plate 1, the metal is This is not practical because problems such as deformation of the plate 1 and damage to other circuits around the earth circuit 4 occur.
Further, it is desirable to adjust the height of the protrusions after crushing so that it is generally about 0.8 to 1.2 mm so as not to hinder the assembly work at the mounting stage.

The shape of the projecting portion 5 is determined by the cross-sectional shape of the punch of the press die, and may be circular, square, rectangular or any other polygonal shape, and can be arbitrarily selected, and the projecting portion 5 is formed. Any position may be used as long as it can be connected to the ground circuit 4, and it is preferable that a part of the ground circuit 4 is extruded to form the ground connection projection 5. Connectivity is obtained.

The metal plate 1 is made of aluminum or an alloy containing aluminum as a main component. Although various kinds of aluminum and alloys containing aluminum as a main component are available depending on their chemical composition and heat treatment conditions, the present invention has an elongation at break of 5% or more when a tensile test (JIS H4000) is carried out. Those having excellent plastic deformability are preferable.
When aluminum or an alloy containing aluminum as a main component, which has an elongation at break of less than 5% when a tensile test is performed, part of the protrusion 5 is not easily deformed when the protrusion 5 is crushed. As a result, the diameter of the crushed portion of the protrusion 5 cannot be 1.1 times or more that of the portion of the protrusion 5 in the metal substrate, or even if it can be achieved, the wear of the mold is reduced. Because there are problems such as severe. The thickness of the metal plate 1 can be normally 1.0 mm to 5.0 mm.

It is important that the surface roughness of the earth circuit 4 has an appropriate range of roughness because it makes electrical contact with the protrusion 5, and as a result of the study by the present inventors, it is 0.5 in Rz (JIS B0601). μ
It is preferably at least m and not more than 2.5 μm. If it is less than 0.5 μm or more than 2.5 μm, the electrical contact condition is not good, and as a result, the initial purpose cannot be achieved.

For the ground circuit 4, a metal foil such as a copper foil, an aluminum foil, or a nickel foil may be used alone or bonded, and further, a surface of which is plated with gold or the like may be used. Of these, the case where the surface is copper, aluminum, or nickel is preferable in terms of easiness of bonding with aluminum or an alloy containing aluminum as a main component that constitutes the protrusion 5.

The conductive metal foil to be the conductive circuit 3 may be a copper foil, an aluminum foil, a nickel foil or the like, which may be used alone or in combination, or may have a nickel-plated or gold-plated surface.

As the insulating layer 2, any material having an insulating property can be used. For example, an epoxy resin, a phenol resin, an unsaturated polyester resin, a polyimide resin or the like impregnated in a glass cloth, an inorganic filler. There are those filled with −, those formed only with a resin layer, those adhered in a film shape, and the like.

[0026]

EXAMPLES The present invention will be described in more detail with reference to Examples. (Example 1) Aluminum plate having a thickness of 1.5 mm (JIS H400
0, A1050P-H24; elongation at break during tensile test 20%) is prepared, and an aluminum oxide-containing epoxy resin with a thickness of 80 μm is used as an insulating layer, and a copper foil with a thickness of 35 μm is adhered to it and then conductive by etching. A circuit and a ground circuit were formed.
The roughness of the Cu surface forming this earth circuit is Rz
Was 2.3 μm. Then, a height of 0.75 mm was extruded from the back surface of the aluminum plate at the portion where the earth circuit was provided by a press die having a diameter of 2.0 mm to form a protrusion for ground connection. Then, the protrusion for connecting the earth was crushed from the surface by a press die to a diameter of 3.0 mm, and the earth circuit and the aluminum plate were electrically connected.

With respect to the metal base circuit board thus obtained, after the contact resistance between the ground circuit and the metal board was exposed to a high temperature environment or a heat shock was applied by the following method. After further heating in a solder bath, evaluation was performed. The results were good, as shown in Table 1, with no increase in resistance value even under high temperature environment, after heat shock, and further after heating the solder bath.

<Method of measuring contact resistance> As shown in the schematic connection diagram of FIG. 2, 3 from the edge of the protrusion for ground connection.
A resistance measuring device (A & D) between the ground circuit and the back metal plate (aluminum or aluminum alloy) at a distance of mm.
, AD-58111 DIGITAL LOW OH
MMETER) range of 200 mΩ and 2 Ω.

Example 2 The diameter after crushing is 2.4 mm.
A metal base circuit board was obtained by the same operation as in Example 1 except that the metal base circuit board was crushed. For this metal base circuit board, the contact resistance between the ground circuit and the metal plate was evaluated as in Example 1. The results were good, as shown in Table 1, with no increase in resistance value even under high temperature environment, after heat shock, and after heating the solder bath.

(Example 3) An aluminum alloy plate having a thickness of 1.5 mm (JIS H4000, A5052P-H34; elongation at break at a tensile test of 13%) was prepared, and an epoxy resin containing aluminum oxide having a thickness of 80 μm was prepared. Using as an insulating layer, a copper foil of 35 μm was adhered and etched to form a conductive circuit and a ground circuit. Then, from the back surface of the aluminum plate where the earth circuit is located, use a press die with a diameter of 2.0 mm to achieve a height of 0.7.
Only 5 mm was extruded to form a protrusion for connecting the ground. Then, the protrusion for earth connection was crushed from the surface by a press die to a diameter of 2.2 mm and crushed to electrically connect the earth circuit and the aluminum plate. The metal-based circuit board thus obtained was evaluated in the same manner as in Example 1. As a result, as shown in Table 1, the solder bath heating was performed both in a high temperature environment and after heat shock. There was no increase in the resistance value after that, which was good.

Example 4 A metal base circuit board was obtained by the operation of Example 3 except that a 10 μm thick Al laminated copper foil (total thickness of 35 μm) was used in place of the copper foil. . Immediately before the step of extruding the protruding portion, the surface roughness of aluminum on the surface of the ground circuit is Rz, 0.6 μ.
It was m. This metal base circuit board was evaluated in the same manner as in Example 1. As a result, as shown in Table 1, the resistance value did not rise even under a high temperature environment, after a heat shock, or after heating the solder bath. None was good.

(Embodiment 5) A metal base circuit board obtained in the same manner as in Embodiment 1 except that the diameter after the projections are pressed and crushed is 2.1 mm. The same evaluation as in Example 1 was made. As a result, as shown in Table 1, there was no increase in the resistance value even in a high temperature environment, after heat shock, and after heating the solder bath, which was good.

Comparative Example 1 A metal base circuit board obtained in the same manner as in Example 1 except that the diameter of the protrusion after crushing was 2.06 mm. The same evaluation as in Example 1 was made. As a result, as shown in Table 1, the resistance value after the heat shock in the high temperature environment and further after the solder bath heating was significantly increased.

[0034]

[Table 1]

[0035]

The metal base circuit board of the present invention realizes a highly reliable ground connection which has a low contact resistance and a small change with time, so that the contact resistance rises with time and the electronic circuit operates normally. The defect that it does not work is solved, and stable electronic circuit functions can be obtained even at high temperatures.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a metal-based circuit board of the present invention. (A)-(d) shows sequentially the process of the process by many arrangement | positioning which becomes this invention, (a) is a top view before process, (b) is sectional drawing before process, (c). ) Shows a situation in which the protrusion is pushed out from the back side of the ground circuit, and (d) shows a situation in which the protrusion is further pressed and crushed from the front side.
Further, (e) is an enlarged view of a circuit piece sectioned by a dotted line in the (a) plan view, and (f) is a sectional view in which the circuit piece is divided and enlarged.
(G) is the figure which expanded and illustrated the part of the protrusion which was crushed.

FIG. 2 is a schematic connection diagram for measuring a contact resistance between an earth circuit and a metal substrate.

[Explanation of symbols]

 1: Metal plate 2: Insulating layer 3: Conductive circuit 4: Earth circuit 5: Projection for earth connection 7: Resistance measuring device 8: Measurement probe

Claims (5)

[Claims] 1. A grounding circuit made of metal foil is provided on at least one main surface of a metal plate via an insulating layer, and a part of the metal plate under the grounding circuit is extruded from the side with respect to the grounding circuit to form a protrusion. Then, in the metal base circuit board in which the ground circuit and the metal plate are electrically connected by crushing the protrusion from the ground circuit side, the area of the portion where the crushed protrusion and the upper surface of the ground circuit contact each other. Is larger than the area of the portion where the side surface of the ground circuit and the protrusion contact each other. 2. The metal base according to claim 1, wherein the diameter of the portion where the protrusion is crushed is 1.05 times or more and 1.5 times or less the diameter of the portion of the protrusion that is inside the metal plate. Circuit board. 3. The metal-based circuit board according to claim 1, wherein the metal plate is aluminum or an alloy containing aluminum as a main component, which has an elongation at break of 5% or more in a tensile strength test. 4. The roughness of the surface of the surface of the ground circuit, which is the contact portion with at least the crushed protrusion, is 0.
The metal base circuit board according to claim 1, wherein the metal base circuit board has a thickness of 5 μm or more and 2.5 μm or less (Rz). 5. The ground circuit is made of a composite foil in which Ni is laminated on Cu or a composite foil in which Al is laminated on Cu, at least at a portion contacting the crushed protrusion. The metal-based circuit board described.