JP2515138B2 - Electronic circuit mounting case and manufacturing method thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an aluminum case for mounting an electronic circuit and a method for manufacturing the same, and more particularly to disposing a ground electrode in the case.

[Prior art]

Electronic circuits such as hybrid thick film integrated circuits used in vehicles, aircraft, communication devices, etc. are mounted in aluminum cases. That is, as shown in FIGS. 6 to 8, a substrate 41 provided with a hybrid integrated circuit 42 is provided with an adhesive on a conventional aluminum (Al) case (hereinafter referred to as Al case) 1.
The aluminum pad (aluminum pad) 9 for the ground electrode uses the solder 63, and the substrate 45 on which the power transistor 47 and the heat sink 46 are provided via the heat conductive adhesive 62. It is joined to the Al case 1 (Figs. 6 and 7). Then, an Al wire 5 as a ground conductor is joined 51 between the hybrid integrated circuit 42 and the aluminum pad 9 by ultrasonic bonding (eighth embodiment).
Figure).

What should be noted here is that the Ni plating layer 2 is applied to the entire surface of the conventional Al case described above.
The aluminum pad 9 and the like are connected to the Al case 1 through the plated layer 2.
Is to be joined to. The Ni plating layer 2 is indispensable for providing the aluminum pad 9 as a ground electrode on the Al case 1.

That is, first, the Al case 1 is usually manufactured by die casting an Al alloy such as Al-Si-Cu for the purpose of moldability, weight reduction, heat dissipation and the like. Therefore, in order to ground one end of the Al wire 5 to the Al case 1, even if an attempt is made to directly join by ultrasonic bonding or the like, sufficient joining cannot be obtained. This is mainly because the Al wire 5 is pure Al.

Therefore, it is conceivable to join the pure aluminum Al pad 9 to the Al die cast Al case 1 in advance, and most of the Al cases currently use this aluminum pad 9. However, soldering between the aluminum pad 9 and the Al case 1 is not sufficient, and the aluminum pad 9 may not play a sufficient role as a ground electrode.

As is well known, the operation of hybrid integrated circuits is stabilized,
Grounding in a hybrid integrated circuit has an important meaning to prevent radio interference such as noise. Particularly in hybrid integrated circuits used in automobiles, aircrafts, etc., ground faults are an important matter that must be absolutely avoided. Also,
Electronic circuits must withstand a wide range of temperature conditions from -40 to 150 ° C, and no joint failure is allowed.

Therefore, in order to completely bond the ground electrode to the Al case 1, the Ni plating layer 2 is conventionally provided on the surface of the Al case 1 to achieve complete bonding between the Al case 1 and the aluminum pad 9. That is, the Ni plating layer 2 has a function of remarkably improving the wettability of the solder, so that the aluminum pad 9 can be completely removed.
It can be soldered to the Al case 1.

As described above, in the conventional electronic circuit mounting case, the Ni plating layer 2 is provided on the surface of the Al case 1 and the aluminum pad 9 as the ground electrode is soldered thereon, and the aluminum pad 9 serves as the ground conductor. The Al wire 5 was connected.

[Problems to be solved]

However, in the conventional electronic circuit mounting case, a Ni plating layer has to be applied to the surface thereof, and the plating process is complicated. Further, the aluminum pad 9 as the ground electrode is arranged at a position determined by the layout of the hybrid integrated circuit 42, the power transistor 47, etc. arranged in the Al case 1. In other words, the disposition position of the aluminum pad 9 is determined by what kind of electronic circuit such as the hybrid integrated circuit 42 the Al case 1 is used for, and the position of the aluminum pad 9 is different if the electronic circuit is different.

Therefore, when designing the Al case 1 used for a certain hybrid integrated circuit 42, as shown in FIG.
2, convex joint 1 for joining the power transistor 47
5,17 and the convex joint 16 for joining the aluminum pad 9 in advance
It needs to be installed in the Al case 1. The height of the convex joint 16 must be set to a predetermined height so that the Al wire 5 can be easily connected between the hybrid integrated circuit 42 and the aluminum pad 9.

Also, in mounting and assembling the hybrid integrated circuit 42 and the like, in order to ensure the required quality, great quality control is required so as not to impair the functions of the Ni plating layer and the aluminum pad.

As described above, in the conventional Al case 1 for electronic circuit mounting, by using the aluminum pad 9, various steps such as formation of the Ni plating layer 2 and formation of the ridge joint 16 are performed.
It required design and quality control.

The present invention has been achieved as a result of various studies on conventional Ni plating layers and aluminum pads in view of the problems of the related art. It is possible to perform welding with a simple structure without using such Ni plating layers and aluminum pads. It is intended to provide an electronic circuit mounting Al case provided with a ground electrode, which is free from defects and is easy to manufacture, and a manufacturing method thereof.

[Means for solving problems]

The present invention relates to an aluminum case for mounting an electronic circuit, which is provided with a ground electrode for joining a ground conductor, wherein the ground electrode is a build-up portion of an aluminum material which is easily welded to the ground conductor made of Al wire on the aluminum case. The aluminum case for mounting an electronic circuit is characterized in that the built-up portion is formed by the above, and the built-up portion is formed with a surface shape to which a ground conductor made of Al wire can be welded.

In the present invention, the built-up portion forming the ground electrode is provided at a desired position in the Al case manufactured by die casting or the like.

That is, this build-up portion is provided on a convex joint portion (FIG. 1) previously provided on the Al case, or on an arbitrary flat surface portion, a concave portion or the like on the Al case. The build-up portion is made of a ground electrode material such as pure Al rod on the surface of the Al case, TIG (tungsten inert gas) arc welding, MIG (metal inert gas).
It is formed by fusion bonding using arc welding or the like (see FIG. 3). As a result, the joint surface between the Al case and the overlaid portion is melted and mutually completely joined.

Further, the material for the grounding electrode of the above-mentioned built-up portion is usually pure Al, which is the same material as the grounding conductor made of the Al wire, or an Al alloy containing a small amount of Si, and can be easily welded to the grounding conductor. Use different materials.

In addition, the surface of the built-up portion is formed into a flat surface shape or the like on which the ground conductor can be welded. Further, such a surface shape is formed mainly by cutting the upper surface portion with a milling cutter or the like after forming the overlay portion. However, it is preferable that the height of the built-up portion be substantially the same as that of the hybrid integrated circuit so that the ground conductor can be easily welded to the hybrid integrated circuit.

Next, as a method of manufacturing the above electronic circuit mounting case, a built-up portion made of an aluminum material that is easily welded to a ground conductor is formed on an electronic circuit mounting aluminum case, and then the surface of the built-up portion is formed. There is a method for manufacturing an electronic circuit mounting case, characterized in that the ground conductor made of Al wire is processed into a surface shape that can be welded.

Further, it is preferable that the above-mentioned built-up portion is formed by melting an aluminum material in an inert atmosphere such as argon gas as shown in the embodiment.

[Action and effect]

The grounding electrode of the Al case for mounting an electronic circuit of the present invention is
An overlay is made of Al material on the Al case.
A ground conductor made of wire is formed into a surface shape that can be welded. Therefore, unlike the conventional case, it is not necessary to use an aluminum pad as a ground electrode and a Ni plating layer for soldering on the Al case is not required. Further, since the weld overlay and the Al case are melt-bonded to each other, the ground electrode and the Al case are completely bonded.

Further, conventionally, a pure aluminum aluminum pad is used as a ground electrode, and the aluminum pad is a small piece having a diameter of about 3 mm, and when soldering this, precise operation is required. However, in the present invention, since the aluminum pad is not used but the built-up portion is used, the shape of the ground electrode is extremely easy.

Further, conventionally, it was necessary to form a convex bonding portion at a predetermined position for bonding an aluminum pad. However, in the present invention, it is not necessary to preliminarily provide a convex joint portion because the overlay is directly built up on the Al case. Further, conventionally, it was necessary to previously provide the height of the convex joint portion above the Al case in consideration of the thickness of the aluminum pad. However, the present invention provides the desired height of the ground electrode when forming the overlay portion. It should be served.

Further, according to the present invention, it is possible to form the built-up portion of an arbitrary material each time according to the material of the ground conductor made of Al wire. Further, conventionally, quality control was required to prevent damage to the Ni plating layer and aluminum pad when mounting and assembling the hybrid integrated circuit, but in the present invention, such quality control is also unnecessary.

Further, according to the manufacturing method of the present invention, the excellent electronic circuit mounting case as described above can be easily manufactured.

As described above, according to the present invention, an Al case for mounting an electronic circuit, which has a ground electrode and is easy to manufacture without using a Ni plating layer and an aluminum pad, does not cause welding defects, and a method of manufacturing the same. A method can be provided.

〔Example〕

Regarding the Al case for mounting an electronic circuit according to the present invention,
This will be described with reference to FIGS.

As shown in FIG. 1, the Al case 1 of this example is formed by fusion-bonding a built-up portion 3 as a ground electrode. Al case 1 above
Is an Al die-cast using JIS ADC12 material. The formation of the build-up portion 3 on the Al case 1 is performed as shown in FIG.
A pure Al rod 85 was formed by TIG welding on the ridge joint 18 of the Al case 1.
Was performed by fusion welding using a torch 81 and a tungsten electrode 82. Reference numeral 86 is an Ar (argon) gas that forms an inert atmosphere.

The pure Al rod 85 has a diameter of 1.6 mm and its material is Al99.
% Of JIS A1100 material, which is an Al material that can be easily welded to the ground conductor. The conditions for TIG welding are AC voltage 150 V, Ar
The volume was 10 l / min for 3 seconds. As a result, a build-up portion 30 of pure Al having a diameter of about 4 mm and a height of about 3 mm was formed on the convex joint portion 18. Then, the upper surface of the build-up forming portion 30 has a diameter of 10 mm.
It was cut with a milling cutter to make a flat surface 31 so that the ground conductor made of Al wire could be easily welded. This gives a height of 2.7 mm and a diameter of 4 mm above the convex joint 18 of the Al case 1.
The built-up portion 3 as a ground electrode having a size of mm was formed.

The space between the weld overlay 3 and the ridge joint 18 is the JIS of the Al case 1.
The ADC12 material and the JIS A1100 material of the overlay portion 3 were fused to each other to form a fusion joint 32. The state of the metal structure of this joint is shown in the micrograph of FIG. 5 (magnification 400 times). From the same photograph, it can be seen that there is no crack or blow hole between the Al case 1 and the overlay portion 3 and a sufficient fusion-bonded state is shown.

Next, for the joint strength test, as shown in FIG.
An Al wire 5 serving as a ground conductor was joined 51 on the above-mentioned overlay portion 3 by ultrasonic bonding, and the joining strength between the overlay portion 3 and the Al case 1 was measured. As the Al wire 5, a pure Al wire having a diameter of 300 μm, which is thicker than usual, is used.
Two-step bonding was performed at a pressure of 350 g / cm ² , a power of 8 W × 3 seconds and a power of 8 W × 3.5 seconds. Welding strength test was performed using welded Al
The wire 5 was pulled vertically and the load at break was measured. As a result, the strength average of 50 test pieces was 515 g, the standard deviation was 92 g, and all fractures occurred in the Al wire 5.

Also, regarding the Al case 1 provided with the above-mentioned built-up portion 3,
As shown in the figure, similar to the above-mentioned conventional technology (FIGS. 6 and 7),
The hybrid integrated circuit 42 and the like were mounted by bonding, and the Al wire 5 was bonded to the overlay portion 3. As a result, we were able to obtain an excellent hybrid integrated circuit device that was free from radio interference such as noise.

As described above, according to this example, the Ni plating layer, the aluminum pad, and the ground electrode having a sufficient joint state with a simple structure that does not require a soldering process between the both are provided.
An electronic circuit mounting case can be obtained.

[Brief description of drawings]

1 to 5 show an Al case according to an embodiment, and FIG. 1 is a sectional view showing a joined state of the Al case and the overlay portion,
Fig. 3 is a cross-sectional view of an Al case for mounting a hybrid integrated circuit, Figs. 3 and 4 are explanatory views of the build-up portion formation, and Fig. 5 is an optical micrograph (magnification 400 times) of the metallographic structure of the fused joint. 6 to 8 show a conventional Al case, FIG. 6 is a plan view of a hybrid integrated circuit mounted state, FIG. 7 is a cross-sectional view thereof, and FIG. 8 is a cross-section of a joint between the Al case and an aluminum pad. It is a figure. 1 …… Al case, 2 …… Ni plating layer, 3 …… Overlay part, 32 ……
Fusion joint, 42 …… Hybrid integrated circuit, 5 …… Al wire, 81…
… Torch, 85 …… Pure Al rod, 9 …… Aluminum pad,

Claims (4)

(57) [Claims] 1. An aluminum case for mounting an electronic circuit, which is provided with a ground electrode for joining a ground conductor, wherein the ground electrode is an overlay of an aluminum material which is easily welded to the ground conductor made of an Al wire on the aluminum case. An aluminum case for mounting an electronic circuit, characterized in that the built-up portion is formed into a surface shape capable of welding the ground conductor made of Al wire. 2. The aluminum case for mounting an electronic circuit according to claim 1, wherein the aluminum material of the built-up portion is pure aluminum. 3. On an aluminum case for mounting an electronic circuit
An electronic circuit mounting, characterized in that a build-up portion made of an aluminum material that is easily welded to a ground conductor made of Al wire is formed, and then the surface of the build-up portion is processed into a surface shape capable of welding the ground conductor. Case manufacturing method. 4. The method for manufacturing an electronic circuit mounting case according to claim 3, wherein the build-up portion is formed by melting an aluminum material in an inert atmosphere.