JPH10335769A - Hybrid integrated circuit substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hybrid integrated circuit having high reliability which is applicable to high power applications. SOLUTION: In a hybrid integrated circuit, an aluminum circuit 3 having an Alumite layer 4 at least on a side of an insulation layer 2 is mounted on an aluminum plate 1 via the isolation layer 2. Additionally, copper, further nickel and/or nickel-gold layer 6 is provided on the aluminum circuit 3, so that a hybrid integrated circuit substrate is excellent in solder characteristics and wire-bonding characteristics using a gold wire.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hybrid integrated circuit, and more particularly to a high heat dissipation electronic component or a hybrid integrated circuit in which a high heat generation electronic component and a control circuit electronic component are mounted. The present invention relates to a substrate for a hybrid integrated circuit capable of obtaining a hybrid integrated circuit having excellent thermal shock resistance and hence excellent reliability.

[0002]

2. Description of the Related Art Conventionally, as a circuit board on which a high heat-generating electronic component is mounted, a metal plate having good heat conductivity, for example, a metal plate such as aluminum or copper is used as a base material, and several tens of A metal-based circuit board is used in which an insulating layer made of a resin containing an inorganic filler having a thickness of about μm is provided, and a conductive foil on which a circuit is formed is further laminated on the insulating layer.

[0003] The above-mentioned metal-based circuit board has high thermal conductivity and can be mounted and used for electronic components generating a large amount of heat. Therefore, the metal-based circuit board is preferably used for high power applications. By using thick copper foil as a circuit conductor, a substrate for a hybrid integrated circuit which can cope with an application of a larger current, which could not be applied conventionally, has been developed.

However, in the above-mentioned substrate for a large current metal-based hybrid integrated circuit using a thick copper foil as a circuit conductor, the base metal is aluminum and the circuit conductor is copper. There is a problem that the warpage of the substrate is large due to the difference in expansion coefficient, and the dielectric breakdown voltage value of the substrate is reduced due to residual stress generated due to the difference in thermal expansion coefficient and the like.

Furthermore, when electronic components such as semiconductor elements and ceramic chip resistors are mounted, since the Young's modulus of copper is small, stress concentrates on the solder joining the electronic components and the copper circuit, and thermal shock causes There has been a problem that electrical reliability is lacking, such as breakage from solder or its vicinity.

On the other hand, a circuit board using an aluminum / copper clad foil has conventionally existed (Japanese Patent Publication No. 1-151).
No. 53), but the maximum thickness of aluminum is 100
μm and those thicker than that were not produced because the aluminum / copper clad foil could not be produced in a roll form.

Although attempts have been made to produce a circuit board by laminating an aluminum foil of 200 μm or more, a practical circuit board has not been obtained because of the low adhesive strength between the aluminum foil and the insulating layer. . Furthermore, in a circuit board using an aluminum foil, wire bonding using an aluminum wire is possible when wire bonding an aluminum circuit and an electronic component, but wire bonding using an electrically reliable gold wire is possible. In this case, there is a problem that an alloy of gold and aluminum is formed and a reliable electrical connection cannot be achieved.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to generate warpage due to a difference in thermal expansion between an aluminum metal plate and a circuit conductor, and to provide a dielectric breakdown voltage. To solve the problem of solder rupture due to thermal shock and the decrease in electrical reliability due to thermal shock, and to provide a substrate for hybrid integrated circuits with high heat dissipation and high electrical reliability, In particular, it is an object of the present invention to provide a hybrid integrated circuit which can be used for a large current application. Still another object of the present invention is to achieve the above object more effectively by achieving wire bonding having excellent electrical connection reliability using a highly reliable gold wire.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a substrate for a hybrid integrated circuit having an aluminum circuit formed on at least one principal surface of an aluminum plate via an insulating layer, wherein at least the insulating layer of the aluminum circuit is provided. A hybrid integrated circuit substrate having an alumite layer on the side in contact with the substrate, and preferably the hybrid integrated circuit substrate, wherein the thickness of the aluminum circuit is 200 μm or more and 1000 μm or less.

The present invention also provides the hybrid integrated circuit substrate as described above, wherein the alumite layer has a needle-like crystal structure, and the thickness of the alumite layer is 0.1 μm or more and 10 μm or less. is there.

Further, the present invention provides that the copper layer is formed on at least a part of the aluminum circuit, and that a nickel layer and / or a nickel layer is further formed on the copper layer.
The substrate for a hybrid integrated circuit described above, wherein a gold layer is formed.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing an example of the hybrid integrated circuit substrate of the present invention. The substrate for a hybrid integrated circuit of the present invention,
An aluminum circuit 3 is formed on an aluminum plate 1 with an insulating layer 2 interposed therebetween. The aluminum circuit 3 has an alumite layer 4 on at least a surface in contact with the insulating layer 2.

In the present invention, it is essential that the alumite layer 4 exists on the surface of the aluminum circuit 3 on the side in contact with the insulating layer 2. Normally, the surface of the aluminum foil used as a circuit conductor is clean and smooth, but on the contrary, the adhesiveness or the adhesiveness to the resin constituting the insulating layer 2 does not increase. The present inventor has shown that when the surface of a circuit conductor aluminum foil having a clean and smooth surface is oxidized to form an alumite layer, the adhesion and adhesion between the aluminum circuit 3 and the insulating layer 2 are significantly improved. Have been found experimentally, and have led to the present invention. The above effect is expected between the aluminum plate 1 and the insulating layer 2, but according to the results of the study by the present inventor, only a slight effect was recognized due to the thick aluminum plate 1. Is not as noticeable as the relationship between the aluminum circuit 3 and the insulating layer 2.

The aluminum foil for the aluminum circuit 3 having the alumite layer 4 on at least one surface can be easily obtained by using a commonly available aluminum foil for a conductor circuit and oxidizing the surface. As a method for oxidizing the surface, known methods such as a method of heating in an oxygen-containing atmosphere and a method of anodic oxidation can be applied. Among these, the method of applying an alternating current in an alkaline electrolyte and performing anodic oxidation is preferable because an alumite layer having a needle-like structure described later can be obtained.

In the present invention, the alumite layer 4 preferably has a needle-like crystal structure. Unless it has a needle-like structure, it may not be possible to obtain sufficient adhesive strength,
This is because the adhesion of the foil after the moisture resistance test and the heat resistance test is poor, and delamination may occur between the aluminum circuit and the insulating layer. Here, the needle-like structure means that when the alumite layer is broken and its cross section is observed using an operating electron microscope, elongated columnar crystal grains grow in the direction of the surface from the aluminum layer while being in close contact with each other. A structure in which the surface of the alumite layer formed by crystal grains shows sharp irregularities.
Regarding the condition of the unevenness, it is preferable that the height from the peak to the valley of the unevenness is about 0.01 to 5 μm in order to achieve the object of the present invention.

The thickness of the alumite layer 4 is 0.1 μm.
The thickness is preferably 10 μm or less. If the thickness is less than 0.1 μm, the reason is unknown, but sufficient adhesion may not be obtained. If the thickness is more than 10 μm, the alumite layer itself causes cohesive failure, and the adhesion reliability of the aluminum circuit is reduced. This is because the property may be reduced.

In the present invention, the thickness of the aluminum circuit 3 formed on the aluminum plate 1 is at least 200 μm.
000 μm or less is preferable. Although there is no problem if the thickness of the aluminum circuit 3 is smaller than 200 μm, there is no advantage in manufacturing. That is, from the viewpoint of electric resistance, 2
An aluminum foil of 00 μm or less is equivalent to a copper foil of 105 μm or less in thickness, but if the thickness is about this, the amount of warpage due to the rigidity of the aluminum plate is 100 μm or less,
This is because it is at a level that does not cause a problem in electrical and mounting. On the other hand, the thickness of the aluminum circuit 3 is 1000 μm
In the case where the ratio exceeds the above, difficulty arises in forming an aluminum circuit. That is, when an aluminum foil is provided on an aluminum plate via an insulating layer, and then the aluminum foil is processed by an etching method to produce a circuit, it is necessary to increase the circuit interval due to the influence of the etching factor. In addition, the mounting density of the circuit board is reduced, and the use of the circuit board is limited. For the above reasons, the thickness of the aluminum circuit 3 is preferably 200 μm or more and 1000 μm or less.

In the present invention, the copper layer 5 can be formed on at least a part of the aluminum circuit 3, so that the electronic component can be soldered on the aluminum circuit. As a method of forming the copper layer 5 on at least a part of the aluminum circuit 3, a conventionally known method can be used. For example, a desired portion of the aluminum circuit can be easily obtained by applying copper plating. it can. When the alumite layer 4 is formed on the surface of the aluminum circuit 3, the alumite layer 4 can be easily peeled off by, for example, etching with an alkaline aqueous solution. Further, rust prevention treatment such as imidazole treatment may be performed on the copper layer 5.

Further, according to the present invention, by forming a nickel layer and / or a nickel-gold layer 6 on the copper layer 5, it becomes possible to wire-bond the aluminum circuit 3 using a gold wire. In other words, when trying to wire-bond a gold wire directly to the aluminum circuit 3,
Gold diffuses into aluminum and forms an alloy layer, which lowers the electrical reliability of the wire-bonded part. Conventionally, it is possible to extremely increase the electrical reliability when making an electrical connection with the substrate wiring, and furthermore, it is possible to perform wire bonding using an aluminum wire in a portion where the aluminum circuit 3 is exposed. The characteristics from are also maintained. The nickel layer can be obtained by a conventionally known plating method, and the nickel-gold layer can be easily obtained by plating gold after providing the nickel layer, but is limited to this method. Not something.

The insulating layer 2 is made of a cured resin filled with an inorganic filler. As the resin, any resin may be used as long as it has an electric insulating property by firmly bonding the aluminum plate 1 and the aluminum circuit 3 after curing.
Epoxy resins, phenolic resins, butyral, and the like are preferable, and epoxy resins are particularly preferable because of their high bondability between metals and high electrical insulation. As the inorganic filler to be filled in the resin, those which are electrically insulative, have high thermal conductivity, and are capable of being highly filled in the resin are preferable, and examples thereof include aluminum oxide, silicon oxide, magnesium oxide, aluminum nitride, silicon nitride, and nitride. Boron or the like is used alone or in combination. Among them, aluminum oxide and silicon oxide are preferably selected because they are inexpensive and easily available, and boron nitride is preferably selected because a circuit substrate having a low dielectric constant can be obtained. Also, as an inorganic filler,
Glass fiber, glass cloth, inorganic fiber and the like may be mixed.

The thickness of the insulating layer 2 is 50 μm or more and 200
μm or less is preferred. If the thickness of the insulating layer 2 is less than 50 μm, insulation reliability may be reduced, and
When the value exceeds the above, the insulation reliability is secured, but the thermal conductivity is reduced, and it may not be possible to mount an element having a high calorific value.

The aluminum plate 1 used for the substrate for a hybrid integrated circuit of the present invention is not particularly limited, but aluminum and its alloys are used. Also,
When aluminum and its alloy are present on the insulating layer side,
Since the effects of the present invention are expected, a clad plate in which aluminum and its alloy are laminated on at least one surface can also be used. The thickness of the aluminum plate 1 is not particularly limited, but is generally 0.5 mm or more and 5.0 m or more.
m or less are used.

Further, although not shown in the drawings, electronic components such as semiconductor elements and ceramic chip resistors are connected and mounted on the substrate of the present invention by soldering, gold and / or aluminum wires, etc. An integrated circuit can be obtained. Note that another circuit board such as a resin board may be partially mounted for control or the like.

Hereinafter, the present invention will be described in more detail with reference to examples.

[0025]

【Example】

[Example 1] A protective film was attached to one side of an aluminum foil having a thickness of 0.5 mm, and AC was 4 to 30 A in an alkaline solution.
Anodizing was performed at a current density of / dm ² to remove the protective film, thereby producing an aluminum foil having an alumite layer on one surface. At this time, the alumite layer is 0.2μ
m.

Next, aluminum oxide (manufactured by Showa Denko KK; SRW) was placed on a 3.0 mm-thick aluminum plate.
Bisphenol A type epoxy resin containing 5% by volume (made by Yuka Shell Co .; EP828) is 80 μm in thickness of the insulating layer.
Then, the aluminum foil was placed so that the alumite layer was in contact with the insulating layer, and pressed under heating to produce a metal base substrate.

Further, a copper layer having a thickness of 10 μm is formed on the entire surface of the aluminum foil of the metal base substrate by plating, and a desired position is masked by using a screen printing method, and then the copper layer and the aluminum foil are respectively etched. Thus, a circuit was formed to produce a metal-based circuit board. A nickel layer and a gold layer were formed at desired positions on the copper layer on the aluminum circuit by plating. The thicknesses of the nickel layer and the gold layer are 5 μm and 0.03 μm, respectively.
And

Further, a semiconductor element, a ceramic chip resistor and the like were mounted on the circuit pattern of the metal-based circuit board by soldering to form a hybrid integrated circuit. At this time, for electrical connection between the semiconductor element and the aluminum circuit, a gold wire of φ25 μm is used when the pad material of the aluminum circuit is nickel or nickel-gold, and φ25 μm is used when the pad material of the aluminum circuit is aluminum.
The wire bonding was performed using an aluminum wire of m.

With respect to the metal-based circuit board and the hybrid integrated circuit obtained by the above operation, for the metal-based circuit board, the adhesive strength between the aluminum foil and the insulating layer and the peeled portion were measured by the following method. , A heat cycle test under the following conditions was performed to examine the electrical reliability of the gold wire. Table 1 shows the results.

<Measurement Method of Foil Bonding Strength> The untreated one and the one after the moisture resistance test and the heat resistance test shown below are described in 5.7 of JIS C6841 Test method of copper-clad laminate for printed wiring boards. The test was performed according to the test method for peel strength. Moreover, the peeled part after peeling was observed using SEM. The moisture resistance test was performed under the condition of leaving the circuit board at 85 ° C. and 85% RH for 1000 hours, and the heat resistance test was performed under the condition of leaving the circuit board at 150 ° C. for 1000 hours.

<Method of Measuring Reliability of Devices and Other Elements by Heat Cycle Test>
A heat cycle test was performed with the temperature conditions of 0 minute, 150 ° C., and 30 minutes as one cycle. After 1000 cycles, the electrical connection state of the semiconductor element, the ceramic chip resistor, and the like was checked by a continuity check using a tester and an appearance inspection.

[0032]

[Table 1]

Examples 2 to 7, Comparative Example 1 The thickness, crystal structure, and surface treatment of nickel plating and / or nickel gold plating of the alumite layer are shown in Table 1 by adjusting the anodic oxidation conditions of the aluminum foil. Except for the conditions,
Various metal-based circuit boards and hybrid integrated circuits obtained through the same operations as in Example 1 were evaluated in the same manner as in Example 1 to obtain Examples 2 to 7. In addition, a metal-based circuit board using no aluminum oxide treatment, that is, using an aluminum foil as it was, and a hybrid integrated circuit using the same were manufactured, and the same evaluation as in Example 1 was performed to obtain a comparative example. Table 1 also shows these results.

[0034]

According to the hybrid integrated circuit substrate of the present invention, the aluminum circuit is firmly adhered to the aluminum plate by providing an alumite layer on the side of the aluminum circuit in contact with the insulating layer. It does not cause problems such as warpage due to the difference in the coefficient of thermal expansion, lowering of dielectric breakdown voltage, breakage of solder due to thermal shock, and lowering of electrical reliability due to it. It is a substrate.
In addition, the substrate for a hybrid integrated circuit of the present invention is capable of easily mounting electronic components such as semiconductor elements by providing a copper layer having excellent solder adhesion on an aluminum surface, and further providing a nickel and / or nickel-gold layer. Therefore, the electronic component and the aluminum circuit can be wire-bonded using a gold wire with high electrical reliability, so that a hybrid integrated circuit with high electrical reliability can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a substrate for a hybrid integrated circuit of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Aluminum plate 2 Insulating layer 3 Aluminum circuit 4 Alumite layer 5 Copper layer 6 Nickel and / or nickel-gold layer

Claims (6)

[Claims] 1. A hybrid integrated circuit substrate having an aluminum circuit formed on at least one main surface of an aluminum plate via an insulating layer, wherein an alumite layer is formed on at least a surface of the aluminum circuit in contact with the insulating layer. A substrate for a hybrid integrated circuit, comprising: 2. The substrate for a hybrid integrated circuit according to claim 1, wherein the thickness of the aluminum circuit is 200 μm or more and 1000 μm or less. 3. The substrate for a hybrid integrated circuit according to claim 1, wherein the alumite layer has a needle-like crystal structure. 4. An alumite layer having a thickness of 0.1 μm or more and 10 μm or more.
3. The device according to claim 1, wherein
Or a substrate for a hybrid integrated circuit according to claim 3. 5. The substrate for a hybrid integrated circuit according to claim 1, wherein a copper layer is formed on at least a part of the aluminum circuit. 6. The substrate for a hybrid integrated circuit according to claim 5, wherein a nickel layer and / or a nickel-gold layer is further formed on the copper layer.