JP3342797B2 - Method for manufacturing ceramic circuit board having metal circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a ceramic having a metal circuit.
The present invention relates to a method for manufacturing a mixed circuit board .

[0002]

2. Description of the Related Art In recent years, high-performance modules such as high-power and high-efficiency inverters have been transitioning with high performance of industrial equipment such as robots and motors, and the heat generated from semiconductor elements has been increasing steadily. ing. In order to efficiently dissipate this heat, various methods have conventionally been used for large power module substrates. Especially recently, ceramic substrates with good thermal conductivity have become available,
A structure in which a metal plate such as a copper plate is bonded on a substrate to form a circuit, and then a semiconductor element is mounted as it is or after performing a process such as plating has been adopted.

[0003] Such modules were initially used for simple machine tools, but have been used for welding machines, train drives and electric vehicles in recent years, and have been subjected to more severe environmental conditions such as electric current. It has been required to increase the circuit copper thickness for increasing the density, to improve the durability against thermal shock and the like, and to further reduce the size. At present, only an aluminum nitride substrate can meet this demand.

[0004] There are various methods for joining a metal and a ceramic. 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 (for example,
177634) and a DBC method in which an aluminum nitride substrate and a copper plate whose surfaces are oxidized are heated and joined at a temperature lower than the melting point of copper and higher than the eutectic temperature of Cu-O (for example, Japanese Patent Application Laid-Open No.
-163093).

[0005] The active metal brazing method has the following advantages over the DBC method. (1) Since the processing temperature for obtaining the joined 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, the durability against heat shock and heat cycle is high.

[0006]

However, in the active metal brazing method, since the joining is performed by increasing the temperature to near the melting point of the brazing material, stress remains in the joined body, and the durability against recent heat shocks and heat cycles. Could not be satisfied, and further improvement was awaited.

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

[0008]

That is, the present invention provides an aluminum nitride substrate having an oxidized surface containing alumina by performing an oxidation treatment after a honing treatment, and then comprising zirconium or a compound thereof and titanium or a compound thereof. Using an active metal brazing material, a copper metal circuit with a thickness of 0.3 mm or more is formed on the front surface, and a copper metal radiator plate with a thickness of 0.2 mm or less is formed on the back surface, and then mechanical correction is performed. A method for manufacturing a ceramic circuit board having a characteristic metal circuit. In this case, the swell of the ceramic circuit board having a metal circuit defined by the deformation amount per unit length of 10 mm is 30 μm or less at any point, and the length of the circuit board (x
In the case where the length in the (axis) direction is L, the length in the direction intersecting with the axis (y-axis) is W, and coordinates having the origin at the center of the circuit board are set, the position indicating the maximum value of the undulation is -L / 4 ≦ x ≦ L
/ 4, −W / 4 ≦ y ≦ W / 4.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

When a metal circuit pattern or a metal plate is joined to a ceramic substrate, not all joining surfaces are joined in the same manner, and some reactions start early and some are delayed. At that time, a tensile or compressive stress is applied between a place where the reaction starts early and a place where the reaction starts late, and this becomes a residual stress at the time of joining. The portion to which the tensile or compressive stress is applied is partially deformed according to the magnitude of the stress, and remains as undulation. A large undulation means the presence of a large residual stress, and the magnitude of the residual stress can be known by examining the state of the undulation.

In the present invention, the undulation is preferably measured by a contour shape. However, the height of the circuit board from the surface plate is measured every several millimeters using a dial gauge, and a contour line is drawn. There may be.

In the present invention, it is most preferable that the amount of undulation is 0. However, if the amount of deformation per unit length of 10 mm is 30 μm or less at any point, the residual effect on the durability against heat shock and heat cycle is reduced. The effects of stress can be neglected. Further, the position showing the maximum value (apex) of the undulation is also related to the durability against heat shock and heat cycle. In the present invention, the position is preferably near the center of the circuit board. Specifically, when the length of the circuit board in the longitudinal (x-axis) direction is L, the length of the cross direction (y-axis) thereof is W, and coordinates are set with the origin at the center of the circuit board, The position indicating the maximum value of the undulation is -L / 4 ≦ x ≦ L /
4. It is necessary that −W / 4 ≦ y ≦ W / 4. If there is a position showing the maximum value of the undulation in other places, even if the amount of undulation satisfies the above value, the overall shape of the circuit board will be unstable, and the durability of the circuit board against heat shock and heat cycle will be improved. No further improvement can be expected.

The present invention provides a metal circuit having excellent durability as described above.
A method for producing a ceramic circuit board having
By checking the twist state in advance, its durability
You can know big and small.

In the present invention, a metal plate is joined to a ceramic substrate, and a metal circuit is formed by etching the metal of the joined body, or a metal circuit pattern is processed from the metal plate in advance and the metal circuit is formed on the ceramic substrate. The ceramic circuit board having the metal circuit of the present invention is manufactured by joining to form a metal circuit.The swell correction step is a step in which the metal plate and the ceramic substrate are joined, and the metal of the joined body is etched. This is performed at a stage where the metal circuit is formed and / or at a stage where the pattern of the metal circuit and the ceramic substrate are joined. Desirably, it is performed at a stage close to the final product.

In the present invention, the swell correction is performed by applying a mechanical force, and a specific method is to sandwich the upper and lower surfaces of a joined body of a ceramics substrate and a metal plate and / or a metal circuit with rollers. And a method of hitting fine particles on the surface by shot blasting or the like.

[0016] The ceramic substrate used in the present invention is nitrogen
Aluminum is the substrate, the thickness thereof is too thick thermal resistance increases, because there is no durability is too thin, it is preferably about 0.3 to 0.8 mm.

The surface properties of the ceramic substrate are important, and minute defects and dents have a great effect on the contact area with a metal plate or a metal circuit, so it is desirable that the surface is smooth. Those that have been treated are desirable. In the present invention, an aluminum nitride substrate having high thermal conductivity is desirable, and in particular, an aluminum nitride substrate having an oxidized surface containing alumina formed on the surface by performing an oxidation treatment at a temperature of about 1100 ° C. in the atmosphere is desirable.

The material of the metal circuit is copper . As the thickness of the metal circuit, it is preferable that the thickness is larger than 0.3 mm from the tendency that the current density increases in recent years. In the present invention, a circuit board having a structure in which a metal circuit is formed on the surface of the ceramic substrate, and a metal radiator plate is formed on the back surface ,
Copper is also used for the material of the metal radiator plate, and its thickness is preferably 0.2 mm or less.

A metal circuit is provided on one side of the ceramic substrate,
As a method of forming a metal heat sink on the other surface, a method of etching a joined body of the ceramic <br/> click scan board and the metal plate,
It can be performed by a method of bonding a metal circuit and / or a pattern of a metal heat sink pierced from a metal plate to a ceramic substrate, and the like. In these cases, a bonding method of the metal plate or the metal circuit pattern and the ceramic substrate includes: Active metal brazing is employed.

The metal component of the brazing material in the active metal brazing method contains silver and / or copper as a main component, and an active metal as a sub-component in order to ensure wettability with a ceramic substrate during melting. The 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 active metals include zirconium, titanium,
Hafnium, niobium, tantalum, vanadium and their compounds. Preferably, zirconium or a compound thereof is used, and particularly preferably, zirconium or a compound thereof is used in combination with titanium or a compound thereof. One example of these ratios is 1 to 7 parts by weight of active metal per 100 parts by weight of total of 69 to 95 parts by weight of silver and 5 to 31 parts by weight of copper. The joining temperature is preferably 820 to 860 ° C.

[0021]

The present invention will be specifically described below with reference to examples and comparative examples.

Comparative Example 4 96 parts by weight of aluminum nitride powder, 4 parts by weight of yttria, 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 triolate and 12 parts by weight of water were added. They were blended and mixed with a mixer. The molding speed is 1.0 / min, the molding pressure is 55-7.
Extrusion molding at 0 kg / cm ^2, 120 in far infrared
After drying at 5 ° C. for 5 minutes, degreasing was performed at 480 ° C. for 10 hours in the air, and baking was performed at 1920 ° C. for 30 minutes.
The obtained aluminum nitride sintered body was cleaned by a honing treatment on the surface, and then 60 mm × 36 mm × 0.65 mm.
mm of 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 polyisobutyl methacrylate are added and kneaded at 5 parts by weight. , Brazing material paste was adjusted. This was applied to the metal circuit surface (front surface) of the aluminum nitride substrate by screen printing to form an L-shaped pattern having a pattern ratio of 0.20, and the entire surface was applied to the heat dissipation surface side (back surface). The coating amount (after drying) at that time was 9 mg / cm ² .

Next, the surface has a size of 60 mm × 36 mm ×
A copper plate with a thickness of 0.3 mm and 60 mm on the back
A copper plate having a thickness of × 36 mm × 0.15 mm is placed in contact with the plate, heated at a temperature of 880 ° C. for 30 minutes under a vacuum of 1 × 10 ⁻⁵ Torr or less, and then cooled at a rate of 2 ° C./min. Thus, a joined body was manufactured.

A UV curing type etching resist is applied by screen printing on the obtained copper plate of the joined body of the aluminum nitride substrate and the copper plate, and then an etching process is performed using a cupric chloride solution to dissolve unnecessary portions of the copper plate. The resist was removed, and the etching resist was peeled off with a 5% sodium hydroxide solution. In the joined body after this etching treatment, there is a residual unnecessary brazing material or a reaction product between the active metal component and the aluminum nitride substrate between the copper circuit patterns.
It was immersed in a 10% ammonium fluoride solution for 10 minutes and removed.

This was further mechanically corrected by shot blasting to produce a ceramic circuit board having a metal circuit .

Comparative Example 1 A ceramic circuit board having a metal circuit was manufactured in the same manner as in Comparative Example 4 except that mechanical correction by shot blast was not performed.

[0028] It was prepared conjugate was heated 30 minutes at a temperature 950 ° C. Instead of heating 30 minutes in Comparative Example 2 Temperature 880 ° C., and except that not performed mechanical straightening by shot blasting, the ratio
A ceramic circuit board having a metal circuit was manufactured in the same manner as in Comparative Example 4 .

Comparative Example 3 Comparative Example 4 was repeated except that a joined body was manufactured at a rate of 8 ° C./min instead of 2 ° C./min after joining, and that mechanical correction by shot blasting was not performed. In the same manner as in the above, a ceramic circuit board having a metal circuit was manufactured.

Example 1 A comparative example was performed except that the aluminum nitride sintered body was subjected to a honing treatment, and then subjected to an oxidation treatment at a temperature of 1100 ° C. for 60 minutes in the air, and then the aluminum nitride substrate was processed and used. In the same manner as in Example 4 , a ceramic circuit board having the metal circuit of the present invention was manufactured.

The undulation was measured on the circuit board manufactured through the above series of processes, and the three-point bending strength when pressed from the heat radiation side was measured under the conditions of a span of 30 mm and a crosshead speed of 0.5 mm / min. did. Also,
After holding at −40 ° C. × 30 minutes, leave at 25 ° C. × 10 minutes, and further hold at 125 ° C. × 30 minutes, and then perform a heat cycle resistance test with leaving at 25 ° C. × 10 minutes as one cycle. Was measured the number of times peeling started. Table 1 shows the results.

[0032]

[Table 1] (Note: Since the dimensions of the circuit board are 60 mm long × 36 mm wide, the position (maximum coordinate) of the present invention showing the maximum value of the undulation is in the range of −15 ≦ x ≦ 15 and -9 ≦ y ≦ 9. Is.)

[0033]

According to the present invention, it is possible to manufacture a ceramic circuit board having a metal circuit with further improved durability against a heat cycle. In addition, the present invention
According to the above, the durability of the ceramic circuit board is
The undulation state of the ceramic circuit board
You can know by reading.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-254031 (JP, A) JP-A-56-169393 (JP, A) JP-A-61-225047 (JP, A) 164081 (JP, A) JP-A-3-250688 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05K 1/02 H05K 3/22

Claims (2)

(57) [Claims] An oxidation treatment is performed after the honing treatment,
After forming an aluminum nitride substrate having an oxidized surface containing alumina, using an active metal brazing material containing zirconium or a compound thereof and titanium or a compound thereof, a copper metal circuit having a thickness of 0.3 mm or more is formed on the surface, and A method of manufacturing a ceramic circuit board having a metal circuit, comprising forming a metal heat sink made of copper having a thickness of 0.2 mm or less on a back surface, and then performing mechanical correction. 2. A ceramic circuit board having a metal circuit, wherein the undulation defined by the deformation amount per unit length of 10 mm is 30 μm or less at any point, and the length of the circuit board in the longitudinal (x-axis) direction. Is set to L, the length in the direction (y-axis) intersecting with L is set to W, and when coordinates are set with the origin at the center of the circuit board, the position indicating the maximum value of the undulation is -L / 4 ≦ x ≦ L / 4. The method for manufacturing a ceramic circuit board according to claim 1, wherein -W / 4 ≦ y ≦ W / 4.