JPH06232521A - Wiring board - Google Patents

Abstract

PURPOSE:To prevent migration of various types of ions and to provide a wiring board, having high insulating property, on which dielectric breakdown is hardly generated. CONSTITUTION:A conductive circuit part 3 is provided on a conductive board 1 through the intermediary of an insulating layer 2, and a unidirectional polarity voltage is applied between the conductive circuit part 3 and the conductive board 1 of the temperature of 60 deg.C or higher on the title wiring substrate. The conductive circuit part 3 is provided with the first metal layer containing 50% or more of one of aluminum, titanium, iron nickel, tin and silver, or an alloy containing one or more kinds of the above-mentioned metals, and the second metal layer, and the first metal layer is provided adjacent to the side of the insulating layer 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board used for electronic parts used in electric equipment, communication equipment, automobiles and the like.

[0002]

2. Description of the Related Art Conventionally, one of wiring boards is a wiring board in which a patterned metal foil is provided on a metal base plate via an insulating layer. In addition, as a metal foil for sticking a substrate, for example, a copper foil or a copper surface containing zinc as a main component (90% by weight) is used.
As described above, a copper foil plated with an alloy as described above can be used (Japanese Patent Publication No. 59-12039).

[0003]

A wiring board using the above metal base board is usually used at high temperature with a power semiconductor element mounted, and a copper foil circuit to which components are soldered is usually a positive electrode. Used. However, when a direct current voltage or an alternating half-wave of a negative electrode is applied to the metal base plate side and the copper foil side is a positive electrode at a high temperature of 60 ° C. or higher, such a wiring board ionizes copper or zinc and causes migration, resulting in a short time. There was a problem that caused dielectric breakdown.

An object of the present invention is to prevent migration due to metal ions and improve withstand voltage characteristics when a unidirectional voltage is applied at high temperature.

[0005]

The object of the present invention is to provide a conductive circuit portion on a conductive substrate with an insulating layer interposed between the conductive circuit portion and the conductive substrate at a substrate temperature of 60 ° C. or higher. A wiring board to which a voltage having a unidirectional polarity is applied between the conductive circuit portion, aluminum, titanium,
A first metal layer having any one of iron, nickel, tin, lead, and silver or an alloy containing 50% or more of one or more of these metals; and a second metal layer made of copper. The metal layer is achieved by the wiring board of the present invention, which is a wiring board provided in contact with the insulating layer side.

The wiring board of the present invention has the following constitution. First, as the conductive substrate, the plate thickness is 0.3 to 5.0 m.
A metal or metal alloy plate of aluminum, copper, stainless steel, iron or the like having a thickness of about m is used. As the insulating layer provided on the conductive substrate, glass epoxy resin of about 30 to 500 μm, epoxy resin filled with inorganic filler, or the like is used.

The conductive circuit portion includes a first metal layer and a second metal layer, and the first metal layer provided in contact with the insulating layer side is aluminum having a thickness of about 1 μm to 1 mm,
Titanium, iron, nickel, tin, lead, silver, or an alloy containing 50% or more of one or more of these metals is used. In the case of an alloy, it is preferable to contain 90% or more of one or more of these metals. An alloy containing one or more of these metals in an amount less than 50% is not preferable because migration of metal ions occurs and dielectric breakdown easily occurs. Copper having a thickness of about 5 μm to 1.0 mm is used for the second metal layer.

The conductive circuit portion is not limited to the metal foil in which the first metal layer and the second metal layer are joined, and the third and fourth arbitrary metal foils (layers) are joined between the metal joining foils. It may be provided (that is, the first metal layer and the second metal layer may not be provided in contact with each other). Further, a metal may be optionally bonded onto the surface of the metal bonding foil bonded to the insulating layer.

As a method of producing the dissimilarly bonded metal foil of the first and second metal layers, a rolling method, an electroplating method, a hot dipping method, or the like can be used.

For the patterning of the dissimilar metal bonding foil, ferric chloride, ammonium chloride, sulfuric acid / hydrogen peroxide solution is used to etch both metals at the same time with one etching solution or two or more times by changing the etching solution. Form a circuit.

Semiconductor elements such as transistors, diodes, triacs and thyristors are mounted on the wiring board on which the circuit is formed. If necessary, passive elements such as resistors and capacitors, and external lead terminals are attached and packaged.

The electronic component thus completed has a positive voltage on the pattern side and a negative electrode on the base metal plate side between the circuit pattern and the metal base plate, and at least a DC voltage and / or an AC half-wave has a constant voltage of 12V to 10,000V. Is applied, and at least a part of the metal base substrate is 60
In an environment with a temperature of ℃ or more, we were able to suppress dielectric breakdown and dramatically extend the service life compared to conventional wiring boards.

[0013]

The inventors of the present invention suppress migration and prevent dielectric breakdown by forming a part of the conductive circuit portion with aluminum, titanium, iron, nickel, tin, lead, silver or alloys thereof as described above. I found that I could suppress it. Although the cause is not necessarily clear, it is considered that aluminum, titanium, iron, nickel, tin, lead, and silver form a passivation, and this passivation prevents migration.

The above-mentioned metallic materials have a standard oxidation-reduction potential at PH 6.8 to 7.2 according to the PH-potential diagram (for example, "Handbook of Metal Surface Technology" published by Nikkan Kogyo Shimbun Co., Ltd., First Edition, 1984, 5th edition, page 8). It is a metal that forms a passivity at +0.5 V or higher.

That is, metals such as chromium, copper, magnesium, and zinc, which easily corrode near neutrality around PH 6.8 to 7.2 and generate ions, as shown in the PH / potential diagram of the above-mentioned material, migrate. It is easy to cause, but aluminum, titanium, iron, nickel, tin according to the present invention,
Since lead and silver form a passivation and constitute a metal oxide, migration is unlikely to occur, and it is assumed that long-term withstand voltage reliability at high temperatures is high.

In the examples described later, the passivation treatment is not performed before bonding to the insulating layer, but from the above viewpoint, it is effective to perform the passivation treatment in advance and then to bond to the insulating layer. Assumed to be the target.

The applicant of the present invention uses a bonding foil of aluminum and copper as a metal foil for a wiring board, and affixes the aluminum foil side in contact with an insulating layer to form a copper foil portion surface that requires soldering. At the same time, a wiring board in which the copper foil portion unnecessary for ultrasonic wire bonding is removed by etching to expose the aluminum portion surface has been proposed (JP-A-59-59).
No. 33894). Here, the structure in which the bonding foil of aluminum and copper is used and the aluminum foil side is in contact with the insulating layer to be bonded is similar to the structure of the present invention, but the bonding foil in the above publication uses aluminum and copper as wirings, respectively. However, unlike the present invention, a metal layer such as aluminum is not provided between the copper foil and the insulating layer in order to prevent migration from the copper foil. Further, according to the present invention, copper or zinc is ionized under a severe condition that a DC voltage or an AC half wave is applied at a relatively high substrate temperature of 60 ° C. or more, with a positive electrode on the copper foil side and a negative electrode on the metal base plate side. The invention is different from the invention disclosed in the above-mentioned publication in that the object is to solve the problem of causing migration and causing dielectric breakdown in a short time.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a wiring board according to the present invention, to which a copper bonding foil whose insulating layer side is a dissimilar metal surface is bonded, will be described with reference to the drawings.

FIG. 1 is a sectional view of a wiring board according to an embodiment of the present invention, and FIG. 2 is a sectional view of a wiring board on which a semiconductor element is further mounted and which is used as an electronic circuit board.
In each of the embodiments described below, the basic structure of the wiring board does not change, and therefore the description will be given with reference to FIGS. [Embodiment 1] As shown in FIG.
A 0 mm thick aluminum plate was used, on which 5 μm of iron was deposited through an insulating layer 2 of 150 μm epoxy resin.
Dissimilar metal bonding foil 3 bonded to a 5 μm copper foil by rolling
(4 is a copper foil) was laminated with iron on the insulating layer side. Next, copper was etched with a sulfuric acid / hydrogen peroxide water-based etching solution to form a circuit, and then iron was etched with ferric chloride to form a circuit. Semiconductor element 6
As a plastic package 7 with 6 bipolar transistors and external lead terminals 8 mounted via solder 5.
After being bonded together, they were sealed with silicone gel and resin 9 (FIG. 2).

125 pieces of 10 products thus completed
Hold in the ℃ high temperature tank, after the substrate temperature becomes 125 ℃,
AC half-wave, 1,000 V peak (peak value) was applied with the pattern side as the positive electrode and the metal base plate side as the negative electrode. As a result, the average life of the dielectric breakdown (hereinafter referred to as average life) was 200 hours. Example 2 An aluminum plate having a thickness of 1.0 mm was used as the metal base plate 1, and 5 μm of nickel was mixed with 10 μm through an insulating layer 2 of an epoxy resin filled with an inorganic filler of 80 μm.
A dissimilar metal bonding foil 3 (4 is a copper foil) electroplated on a copper foil of 5 μm was attached with the nickel side being the insulating layer side. Next, copper and nickel were simultaneously formed with an etching solution of ferric chloride. Four diodes as semiconductor elements 6 and external lead terminals 8 were mounted on this via solder 5 and a plastic package 7 was attached, and then sealed with resin 9 (FIG. 2).

[0021] The 10 products thus completed are
Hold in the ℃ high temperature tank, after the substrate temperature becomes 125 ℃,
A DC voltage of 400 V was applied with the positive electrode on the pattern side and the negative electrode on the metal base plate side. As a result, the average life expectancy is 1,50
It was 0 hours. Example 3 An aluminum plate having a thickness of 1.5 mm was used as the metal base plate 1, and 5 μm of tin was deposited on it through an insulating layer 2 of a glass epoxy prepreg adhesive of 80 μm.
A dissimilar metal bonding foil 3 (4 is a copper foil) obtained by hot-dip-plating a copper foil having a thickness of μm was attached with tin as the insulating layer side. Next, copper and tin were simultaneously formed with an etching solution of ferric chloride to form a circuit. Four diodes as semiconductor elements 6 and external lead terminals 8 were mounted on this via solder 5, a plastic package 7 was bonded, and then sealed with resin 9.

125 pieces of 10 products thus completed
Hold in the ℃ high temperature tank, after the substrate temperature becomes 125 ℃,
A DC voltage of 400 V was applied with the positive electrode on the pattern side and the negative electrode on the metal base plate side. As a result, the average life expectancy is 100
It was 0 hours. Example 4 An aluminum plate having a thickness of 2.0 mm was used as the metal base plate 1, and aluminum having a thickness of 20 μm was bonded to a copper foil having a thickness of 100 μm through the insulating layer 2 of an epoxy resin filled with an inorganic filler having a thickness of 150 μm. The dissimilar metal bonding foil 3 (4 is a copper foil) was laminated with aluminum as the insulating layer side. This was etched with caustic soda solution for aluminum and hydrogen peroxide / sulfuric acid mixture solution for Cu to form a circuit. After this, the following Example 1
A bipolar transistor was mounted in the same manner as in.

125 pieces of 10 products thus completed
Hold in the ℃ high temperature tank, after the substrate temperature becomes 125 ℃,
AC half-wave, 1,000 V peak (peak value) was applied with the pattern side as the positive electrode and the metal base plate side as the negative electrode. As a result, the average life was 250 hours. [Embodiment 5] Ten finished products having the same structure as in Embodiment 1 were held in a high temperature bath at 70 ° C, and after the substrate temperature reached 70 ° C, an AC half-wave, 1,000 V peak (peak value) Was applied with the positive electrode on the pattern side and the negative electrode on the metal base plate side.
As a result, the average life was 2500 hours. Comparative Example 1 A sample in which only the 35 μm copper foil was bonded to the insulating layer in Example 1 was prepared and a life test was conducted.
As a result, the average life was 2 hours. [Comparative Example 2] In Example 2, a 35 µm copper foil was plated with 3 µm of chromium, and a sample in which chromium was laminated on the insulating layer side was prepared to perform a life test. As a result, the average life was 1.7 hours. [Comparative Example 3] In Example 3, a 35 µm copper foil was plated with 5 µm of zinc, and a sample was prepared by pasting with zinc being the insulating layer side, and a life test was conducted. As a result, the average life was 1.7 hours. [Comparative Example 4] Instead of the Al / Cu bonding foil in Example 4, a rolled copper foil having a thickness of 100 µm was adhered to the insulating layer to form a circuit, and ten products were similarly prepared and a life test was conducted. As a result, the average life was 2 hours. [Comparative Example 5] Ten finished products having the same structure as Comparative Example 1 were held in a high temperature bath at 70 ° C, and after the substrate temperature reached 70 ° C, an AC half-wave, 1,000 V peak (peak value) Was applied with the positive electrode on the pattern side and the negative electrode on the metal base plate side.
As a result, the average life was 114 hours. [Comparative Example 6] Ten products completed with the same structure as in Example 1 were held at room temperature of 25 ° C and it was confirmed that the substrate temperature was 25 ° C. High value) was applied with the pattern side as the positive electrode and the metal base plate side as the negative electrode. As a result, the average life was 3500 hours. [Comparative Example 7] Instead of the product of Example 1, a product having the same configuration as that of Example 1 was produced by using a circuit board in which only the 35 µm copper foil was bonded instead of the dissimilar metal bonding foil 3. A life test was performed on 10 of these products under the same conditions as in Comparative Example 5 except that the substrate temperature was 25 ° C. As a result, life expectancy is 33
It was 90 hours.

Examples 1 to 4 and Comparative Examples 1 to 4 described above
The results of No. 6 are shown in Table 1. In Table 1, Vp indicates the peak value of AC half-wave, and the endurance time ratio indicates Example / Comparative Example or Comparative Example / Comparative Example.

[0025]

[Table 1]

[0026]

As described in detail above, according to the present invention, the conductive circuit portion is made of aluminum, titanium, iron,
A first metal layer having an alloy containing 50% or more of any one of nickel, tin, lead, and silver, or one or more of these metals; and a second metal layer made of copper, the first metal By providing the layer in contact with the insulating layer side, the temperature is at least 60 ° C. locally on the wiring board and the pattern side is the positive electrode and the base metal plate side is the negative electrode in one direction such as DC voltage or AC half wave. Even if the voltage of the polarity of is applied for a long time, migration of various ions does not occur,
It was possible to provide a wiring board having high insulation properties in which dielectric breakdown is unlikely to occur.

[Brief description of drawings]

FIG. 1 is a perspective view of a metal base plate of the present invention with an insulating layer interposed therebetween.
FIG. 6 is a cross-sectional view of a wiring board in which a bonding foil of a copper foil and a dissimilar metal foil is bonded together with the dissimilar metal foil side as an insulating layer.

FIG. 2 is a cross-sectional view of a wiring board used as an electronic circuit board on which semiconductor elements are further mounted on the wiring board used in FIG.

[Explanation of symbols]

 1 Metal Base Plate 2 Insulating Layer 3 Dissimilar Metal Bonding Foil 4 Copper Foil 5 Solder 6 Semiconductor Element 7 Resin Package 8 External Lead Terminal 9 Resin

Claims (1)

[Claims] 1. A conductive circuit portion is provided on a conductive substrate via an insulating layer, the substrate temperature is 60 ° C. or higher, and a voltage having a unidirectional polarity is applied between the conductive circuit portion and the conductive substrate. A wiring board to be applied, wherein the conductive circuit section has a first alloy containing 50% or more of aluminum, titanium, iron, nickel, tin, lead, silver, or one or more of these metals. A metal layer,
A second metal layer made of copper, the first metal layer being provided in contact with the insulating layer side.