JP3419620B2 - Method for manufacturing ceramic circuit board having metal circuit - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a ceramic circuit board having a metal circuit.

[0002]

2. Description of the Related Art In recent years, with the high performance of industrial equipment such as robots and motors, the transition of high power and high efficiency inverters and other high power modules has progressed, and the heat generated from semiconductor elements has also continued to increase. ing. In order to efficiently dissipate this heat, various methods have been conventionally used for high power module substrates. Especially recently, since ceramic substrates with good heat conduction have become available,
A structure in which a metal plate such as a copper plate is joined to a substrate, a circuit is formed, and then a semiconductor element is mounted as it is or after being subjected to a treatment such as plating is being adopted.

Such a module was originally used for a simple machine tool, but has been used for a welding machine, a drive part of an electric train, and an electric vehicle in the past few years. There has been a demand for an increase in circuit copper thickness in order to increase the density, improvement in durability against thermal shock, and further miniaturization. At present, the only ceramic substrate that can meet this requirement is an aluminum nitride substrate.

There are various methods for joining a metal and a ceramic, but for joining a copper plate and an aluminum nitride substrate,
An active metal brazing method in which a brazing material containing an active metal is interposed between the two and heat-treated to form a joined body (see, for example, JP-A-60-1
77634) or a DBC method (for example, Japanese Patent Laid-Open No. 56-163093) in which an aluminum nitride substrate whose surface is oxidized and a copper plate are heated and bonded at a temperature lower than the melting point of copper and higher than the eutectic temperature of Cu-O. is there.

The active metal brazing method has the following advantages over the DBC method. (1) Since the processing temperature for obtaining the bonded body is low, the residual stress caused by the difference in thermal expansion between the aluminum nitride substrate and the copper plate is small. (2) Since the brazing material is a ductile metal, it is highly durable against heat shock and heat cycles.

[0006]

However, in the active metal brazing method, since the temperature is raised to near the melting point of the brazing material and the joining is performed, stress remains in the joined body, and durability against recent heat shock and heat cycles is present. It was not possible to meet the requirements of the above, and further improvement was awaited.

In view of the above, an object of the present invention is to provide a method for manufacturing a ceramics circuit board having a metal circuit with further improved durability against heat shock and heat cycle.

[0008]

That is, the present invention is summarized as follows. (Claim 1) A bonded body of a ceramic substrate and a metal plate, a bonded body in which a metal of the bonded body is etched to form a metal circuit, and / or a bonded body of a ceramic substrate and a metal circuit pattern are -20 ° C. A method for manufacturing a ceramics circuit board having a metal circuit, comprising the step of contacting the following atmosphere with a waviness correction step. (Claim 2) The ceramic substrate has a thickness of 0.3 to 0.8 m.
2. The method for manufacturing a ceramics circuit board having a metal circuit according to claim 1, wherein the ceramic circuit board has a thickness of 0.3 mm or more, and is an aluminum nitride substrate, a silicon nitride substrate, or an alumina substrate having a thickness of 0.3 mm. (Claim 3) The metal circuit according to claim 2, wherein the ceramics substrate is an aluminum nitride substrate, which is oxidized in the atmosphere to form an oxidized surface containing alumina on the surface. A method for manufacturing a ceramics circuit board having the following. (Claim 4) The method for producing a ceramics circuit board having a metal circuit according to claim 2, wherein the joined body is joined by an active metal brazing method. (Claim 5) The method for producing a ceramics circuit board having a metal circuit according to claim 3, wherein the bonded body is bonded by an active metal brazing method. (Claim 6) The joined body is vacuum-packed and the temperature is set to -20.
The method for producing a ceramics circuit board having a metal circuit according to claim 1, 2, 3, 4, or 5, wherein the method is brought into contact with methanol / dry ice at -80 ° C.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below.

The present invention utilizes the principle that the residual stress caused by the difference in thermal expansion has a hysteresis with respect to temperature in a bonded body of ceramics, a metal plate and a metal circuit. That is, FIG. 1 shows the temperature on the horizontal axis and the stress applied to the ceramic substrate on the metal circuit surface on the vertical axis. As shown in FIG. 1, the stress at the time when the joining of the metal plate and the ceramic is completed. Assuming that the residual stress is a, if it is frozen to -20 ° C or lower, the copper plate is plastically deformed and the stress moves to the position of b, and when it is returned to room temperature, it moves to the position of c and the residual stress a. Will decrease to the residual stress c. As a result, the strength of the circuit board and the durability against heat shock and heat cycle are improved.

According to the present invention, a metal plate is bonded to a ceramic substrate and the metal of the bonded body is etched to form a metal circuit, or a metal circuit pattern is previously processed from the metal plate and bonded to the ceramic substrate. A ceramic circuit board having a metal circuit is manufactured by forming a metal circuit with a metal circuit, and the undulation correction process of the present invention involves etching the metal of the bonded body at the stage when the metal plate and the ceramic substrate are bonded. This is performed at the stage where the metal circuit is formed by forming the metal circuit pattern and / or at the stage where the ceramic substrate and the metal circuit pattern are joined. Desirably, it is performed at a stage close to the final product.

The processing temperature in the undulation correcting process is -2.
It is necessary to be 0 ° C. or lower, preferably −40 to −80 ° C., and the effect of reducing residual stress is small at a temperature higher than −20 ° C. If the treatment temperature is lower than −80 ° C., the thermal stress at the time of cooling is too large and the bonded body may be damaged.

As a method of treating at -20 ° C. or lower, a method of introducing into a refrigerating apparatus using a refrigerant such as fluorine, a liquefied gas such as liquid nitrogen or liquid hydrogen, or a methanol / dry ice bath is adopted. .

Examples of the ceramic substrate used in the present invention include alumina, silicon nitride, aluminum nitride and the like. If the thickness is too thick, the thermal resistance becomes large, and if it is too thin, the durability is lost. .3 to 0.8
It is preferably about mm.

The surface texture of the ceramic substrate is important, and minute defects and dents have a great influence on the contact area with the metal plate, so that it is desirable that the surface is smooth, and it is subjected to treatments such as honing and machining. It is desirable that it is. In the present invention, an aluminum nitride substrate having a high thermal conductivity is desirable, and particularly in the atmosphere, the temperature is 1100 ° C.
An aluminum nitride substrate on which an oxidized surface containing alumina is formed by performing an oxidation treatment to some extent is desirable.

Copper, aluminum, tungsten, molybdenum and the like are used as the material of the metal circuit, but copper is generally used. The thickness of the metal circuit is preferably thicker than 0.3 mm because the current density tends to increase in recent years. In the present invention, the circuit board may have a structure in which a metal circuit is formed on the front surface of the ceramic substrate and a metal radiator plate is formed on the back surface thereof. As the material of the metal heat dissipation plate, the above-mentioned materials are used, and the thickness thereof is preferably 0.2 mm or less.

On one surface of the ceramic substrate, a metal circuit,
As a method of forming a metal heat sink on the other surface, a method of etching a bonded body of a ceramic substrate and a metal plate, a metal circuit punched from the metal plate and / or a pattern of the metal heat sink is bonded to the ceramic substrate. Can be performed by a method or the like, and as a method for joining the metal plate or the metal circuit pattern and the ceramics substrate in these cases,
An active metal brazing method, a DBC method, a Mo-Mn method, a copper sulfide method, a copper metallizing method or the like is adopted.

The metal component of the brazing filler metal in the active metal brazing method contains silver and / or copper as a main component, and the active metal as a sub component for ensuring wettability with the ceramic substrate during melting. This active metal component reacts with the ceramic substrate to generate oxides and nitrides, and these products strengthen the bond between the brazing material and the ceramic substrate.
Specific examples of the active metal include titanium, zirconium,
Hafnium, niobium, tantalum, vanadium and their compounds. An example of these ratios is 1 to 7 parts by weight of active metal per 100 parts by weight of the total amount of 69 to 95 parts by weight of silver and 5 to 31 parts by weight of copper. Bonding temperature is 820-86
0 ° C is preferred.

[0019]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples.

Example 1 96 parts by weight of aluminum nitride powder, 4 parts by weight of yttria powder and 2 parts by weight of oleic acid were premixed in a vibration mill, and then 8 parts by weight of ethyl cellulose, 3 parts by weight of glycerin trioleate and 12 parts by weight of water. Were mixed and mixed with a mixer. This mixture is molded at a molding speed of 1.0 m / min and a molding pressure of 55.
Extrusion molding at ~ 70kg / cm ² and 1 in far infrared
After drying at 20 ° C. for 5 minutes, degreasing was performed in air at 480 ° C. for 10 hours, and then firing was performed at a temperature of 1950 ° C. for 30 minutes. The surface of the obtained sintered body was subjected to honing treatment to obtain an aluminum nitride substrate.

90 parts by weight of silver powder, 10 parts by weight of copper powder, 3 parts by weight of zirconium powder, 3 parts by weight of titanium powder, 15 parts by weight of terpineol and 5 parts by weight of a toluene solution of polyisobutylmethacrylate are added in a solid content and kneaded well. Then, the brazing paste was adjusted. This brazing filler metal paste was applied to the aluminum nitride substrate (60 mm × 3
A 6 mm × 0.65 mm) circuit surface (front surface) was applied by screen printing to form an L-shaped pattern with a pattern ratio of 0.20, and the entire surface of the heat dissipation surface (back surface) was applied. The coating amount (after drying) at that time was 9 mg / cm ² .

Next, on the surface, 60 mm × 36 mm × 0.
A copper plate with a thickness of 3 mm and a back surface of 60 mm x 3
After placing a copper plate having a thickness of 6 mm × 0.15 mm in contact with the copper plate, the temperature is set to 8 at a vacuum degree of 1 × 10 ^-5 Torr or less.
After heating at 40 ° C. for 30 minutes, it was cooled at a temperature decreasing rate of 2 ° C./minute to manufacture a joined body of an aluminum nitride substrate and a copper plate.

Next, a UV curing type etching resist is applied by screen printing on the copper plate of this joined body,
An etching process is performed using a cupric chloride solution to dissolve and remove unnecessary portions of the copper plate, and further remove the etching resist by 5%.
It was peeled off with a caustic soda solution. In the bonded body after this etching treatment, since there is a residual unnecessary brazing material between the copper circuit patterns and a reaction product of the active metal component and the aluminum nitride substrate,
1 at a temperature of 60 ℃, 10% ammonium fluoride solution
It was removed by immersing it for 0 minutes.

Then, this was vacuum-packed and immersed in methanol / dry ice at -70 ° C. for 1 hour to correct the undulation.

With respect to the ceramic substrate having a metal circuit manufactured in this manner, the three-point bending strength when pressed from the heat radiation side (back surface) was measured under the conditions of a span of 30 mm and a crosshead speed of 0.5 mm / min. did. Also,
In the air, after holding -40 ° C x 30 minutes, leaving it at 25 ° C x 10 minutes, holding it at 125 ° C x 30 minutes, and letting it stand at 25 ° C x 10 minutes as a cycle, a heat cycle resistance test was conducted. The number of heat cycles when the circuit started peeling was measured. The results are shown in Table 1.

Comparative Example 1 A ceramic substrate having a metal circuit was manufactured and evaluated in the same manner as in Example 1 except that the waviness was not corrected.

[0027]

[Table 1]

[0028]

According to the present invention, it is possible to manufacture a ceramics circuit board having a metal circuit with further improved durability against heat cycles.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the principle of hysteresis.

─────────────────────────────────────────────────── --- Continuation of the front page (56) Reference JP-A-4-170374 (JP, A) JP-A-63-254031 (JP, A) JP-A-61-225047 (JP, A) JP-A-6- 164081 (JP, A) JP-A-3-250688 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H05K 3/10-3/38 C04B 37/00-37/04

Claims (6)

(57) [Claims] 1. A bonded body of a ceramic substrate and a metal plate,
A undulation correcting step of contacting the bonded body in which the metal of the bonded body is etched to form a metal circuit and / or the bonded body of the ceramic substrate and the metal circuit pattern to an atmosphere of −20 ° C. or lower. And a method for manufacturing a ceramics circuit board having a metal circuit. 2. The ceramic substrate has a thickness of 0.3 to 0.8.
2. The method for producing a ceramic circuit board having a metal circuit according to claim 1, wherein the method is an aluminum nitride substrate, a silicon nitride substrate, or an alumina substrate having a thickness of 0.3 mm, and the metal is copper having a thickness of 0.3 mm or more. 3. The metal circuit according to claim 2, wherein the ceramics substrate is an aluminum nitride substrate, which is oxidized in the atmosphere to form an oxidized surface containing alumina on the surface. A method for manufacturing a ceramics circuit board having the following. 4. The method for manufacturing a ceramics circuit board having a metal circuit according to claim 2, wherein the joined body is joined by an active metal brazing method. 5. The method for manufacturing a ceramics circuit board having a metal circuit according to claim 3, wherein the joined body is joined by an active metal brazing method. 6. The joined body is vacuum-packed and the temperature is set to −2.
The method for producing a ceramics circuit board having a metal circuit according to claim 1, wherein the method is brought into contact with methanol / dry ice at 0 to -80 ° C.