JPH09315876A - Aluminum-ceramic composite substrate and is production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve heat cycle resistance and thermal conductivity by joining a specified metalized layer on one main surface of a ceramic substrate and joining molten aluminum on the other surface. SOLUTION: One kind solder material selected from W, Mo-MnO and Ag-Cu based alloy is applied on the one main surface of the ceramic substrate 1 and burned at 800-950 deg.C under vacuum to form a metallized layer 11 having 560μm thickness. Then, after directly joining molten aluminum on the other surface of the ceramic substrate 1, the molten aluminum is solidified to obtain a metal- ceramic composite substrate. Then, an etching resist is press-fixed by heating on the surface of the aluminum material of the composite substrate, and after forming a prescribed circuit 4 by light shielding, developing and etching, an electronic mounting part 3 is formed by subjecting a surface of the circuit 4 to plating, and also a heat radiating plate 5 is joined on the metallized layer 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal-ceramic composite substrate suitable for mounting high-power electronic components such as power modules and a method for producing the same, and more particularly to an automobile or a vehicle that requires particularly excellent heat cycle resistance. An object of the present invention is to provide a composite substrate suitable for mounting electronic components for electric trains and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, as a substrate used for mounting a high-power electronic component such as a power module, a copper-clad ceramic composite substrate produced by bonding a copper plate to a surface of a ceramic substrate has been used. This composite substrate further depends on the type of ceramic substrate used and its manufacturing method.
It is divided into a copper / alumina direct bonding substrate, a copper / aluminum nitride direct bonding substrate, a copper / alumina brazing substrate, and a copper / aluminum nitride brazing substrate.

Of these, the copper / alumina direct bonding substrate is:
As disclosed in JP-A-52-37914, copper oxide is used on the surface of an oxygen-free copper plate by using a copper plate containing oxygen or by using an oxygen-free copper plate and heating in an oxidizing atmosphere. After the generation, the copper plate and the alumina substrate are superposed and heated in an inert atmosphere to generate a composite oxide of copper and aluminum at the interface between the copper plate and the alumina substrate and join the copper plate and the alumina substrate. .

On the other hand, in the case of a copper / aluminum nitride direct bonding substrate, it is necessary to previously form an oxide on the surface of the aluminum nitride substrate. For example, as disclosed in Japanese Patent Application Laid-Open No. 3-93687, about 100
After treating the aluminum nitride substrate at a temperature of 0 ° C. to generate an oxide on the surface, the copper plate and the aluminum nitride substrate are joined via the oxide layer by the above-described method.

A copper / alumina brazing substrate and a copper / aluminum nitride brazing substrate are joined between a copper plate and a ceramic substrate by using a brazing material having a low contact point.
In addition to copper, an alloying element for lowering the melting point and an alloying element for improving the wettability with ceramics are added to the brazing material to be used. For example, active metal brazing materials such as Ag-Cu-Ti are often used. Have been.

Although the copper / ceramic composite substrate is widely used as described above, there are some problems during manufacturing and practically. The most serious problem among them is a failure due to the formation of cracks inside the ceramic substrate during the mounting and use of electronic components, and electrical conduction between the front and back of the substrate.

This is because the coefficient of thermal expansion of copper is about one digit larger than that of ceramics, but in the case of bonding, when the ceramics substrate and copper are heated to close to 1000 ° C. Due to the difference in expansion coefficient, a large amount of thermal stress is generated inside the composite substrate.

Further, when mounting electronic components such as power modules, the copper / ceramic composite substrate is heated to nearly 400 ° C., and the temperature of the composite substrate constantly changes due to the use environment and heat generation during use. Then, a fluctuating thermal stress is applied to the composite substrate. Cracks occur in the ceramic substrate due to these thermal stresses.

In recent years, with the development of power modules for electric vehicles, the demand for composite substrates having excellent heat cycle resistance has been particularly increased. For example, in the case of use conditions in which temperature changes are severe and vibration is large, as in electric vehicles, It is said that the heat resistance of the composite substrate is required to be 500 times or more, but the copper / ceramic composite substrate currently used cannot meet such a demand.

The concept of using aluminum having excellent electrical and thermal conductivity similar to copper as a conductive circuit material has been known for a long time, and such a concept is described in, for example, Japanese Patent Application Laid-Open No. Sho 59-121890. Generally, a brazing method is used for joining aluminum and ceramics.
125463, JP-A-4-12554 and JP-A-4-12554
No. 18746 discloses an aluminum-ceramic substrate manufactured by a brazing method.

However, in the case of this method, there is a problem in that the bonding must be performed in a vacuum, and in the case of non-oxide ceramics, pretreatment must be performed in advance to form an oxide on the surface of the ceramics. Yes,
There were some unsatisfactory points in terms of manufacturing cost and thermal conductivity.

[0012]

While the aluminum-ceramic substrate has an excellent heat cycle resistance, the thermal conductivity and electrical conductivity of Al are smaller than that of copper. The thickness of Al on the side is 1.6
Must be doubled. Therefore, the ability to dissipate heat generated when power is applied to electronic components is inferior to that of copper clad substrates.

Therefore, it is an object of the present invention to develop a novel metal-ceramic composite substrate which is excellent not only in heat cycle resistance but also in heat conductivity.

[0014]

[Means for Solving the Problems] As a result of intensive research to solve the above problems, as compared with conventional copper-clad bonded substrates and aluminum brazed bonded substrates, aluminum molten metal is bonded and solidified on at least one surface of a ceramic substrate, Further, a metallized layer made of a silver-copper brazing material or the like is bonded to the opposite surface to a predetermined thickness (5 to 60 μm thickness), and finally a heat radiation plate made of a copper plate is bonded to the metallized layer to reduce warpage. We were able to develop a new metal-ceramics composite substrate with excellent heat cycle resistance and thermal conductivity.

That is, the first aspect of the present invention is to form a metal part made of an aluminum material for electrical conduction and mounting of electronic parts on one main surface of a ceramic substrate and to a metallization layer for joining a heat sink to the other surface. And a metal-ceramics composite substrate.

In a second aspect of the present invention, the metallization layer is W,
The present invention relates to a metal-ceramic composite substrate which is a brazing material of at least one of Mo-MnO and Ag-Cu based alloys.

The third aspect of the present invention is to use W, Mo-MnO, Ag-Cu as a metallized layer on one main surface of the ceramic substrate.
A first step for forming a kind of alloy layer selected from the group-based alloys, then a second step of joining molten aluminum to the other surface of the above substrate and then solidifying to form a composite substrate, and then the obtained composite substrate, A third step of forming a predetermined circuit by etching the surface of the aluminum material,
Next, a fourth step of plating the surface of the obtained aluminum circuit, and a method for producing a metal-ceramic composite substrate.

[0018]

The substrate used in the present invention is a ceramic substrate made of alumina, aluminum nitride, silicon carbide, zirconia or the like, glass or the like. In this case, a high-purity material is more preferable.

On one surface of the ceramic substrate, W, Mo-
5 to 60 by baking at least one or more brazing filler metal of MnO alloy or Ag-Cu alloy in the form of alloy foil or paste at 800 to 950 ° C under vacuum
The metallization is performed with a thickness of μm, preferably 10 to 50 μm.

In this case, if the thickness of the metallized layer is 5 μm or less, the wettability is poor and the adhesion to the ceramic substrate is weak, and if it is 100 μm or more, too much stress is applied during printing. When the thickness is in the above range, the thermal resistance of the final product can be reduced as much as possible, and the warpage of the composite substrate can be reduced.

When a silver-copper alloy brazing material is used as a paste among the above brazing materials, the mixing ratio of silver and copper is 55 to 85% silver and 15 to 45% copper in weight ratio. More preferably, titanium, zirconium, hafnium as an active metal, or an alloy powder containing 1 to 20 parts by weight of hydride or oxide of these and 100 parts by weight of an alloy of silver and copper is used. A total of 100 parts by volume of 15 to 30 parts by volume, 60 to 70 parts by volume of organic solvent (toluene, terpineol, etc.), and 0 to 20 parts by volume of organic binder may be used.

Further, the metal for forming the circuit in the present invention is a pure metal or alloy of aluminum, which improves conductivity and obtains softness. In this case, the higher the purity, the higher the conductivity, but on the contrary, the price becomes higher. Therefore, in the present invention, 99.9% (3N) of pure aluminum was used.

The metal and the ceramics substrate are joined by the melt joining method, whereby a composite substrate having high joining strength and few uncontacted defects can be obtained, and the aluminum nitride substrate and the silicon nitride substrate are surface-modified. It is possible to join directly without doing (second step).

Next, the metal obtained by the above-mentioned molten metal joining method
After heating and pressure-bonding the etching resist to both main surfaces of the ceramic composite substrate, only the surface of the aluminum material is subjected to light-shielding and developing treatment to form a desired pattern, and etching is performed with a ferric chloride solution to form the circuit 4. (Third step).

Among the circuits obtained in the present invention, a kind of plating selected from copper, molybdenum, nickel and the like is laminated on an aluminum material as the electronic component mounting portion 3 to obtain heat cycle resistance and thermal shock resistance. It is also possible to obtain an excellent composite substrate (fourth step).

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION The composite substrate of the present invention (hereinafter referred to as a metal-ceramic direct bonding substrate) will be described in detail below with reference to the drawings.

(Example 1)

First, 36 mm × 52 mm × 0.635 m
27.5 wt% silver, copper 27.
A brazing material paste consisting of 0 wt% and 0.5 wt% Ti was applied on the front surface and baked at 830 ° C. in a vacuum furnace to obtain a metallized layer 11 having a thickness of 20 μm (first step).

The obtained ceramics substrate 1 is shown in FIG. 3, which is an apparatus for manufacturing a metal-ceramics direct bonding substrate (principle diagram).
To insert. First, aluminum 2 having a purity of 99.9% is set in the crucible 6 having the heater 7, the lid 9 is closed, nitrogen gas is filled in the case 8, and then the guide-integrated die 10 provided in the crucible 6 is attached. The alumina substrate obtained in the first step was sequentially inserted from the inlet on the left side with the metallization 11 side facing down. A molten aluminum was brought into contact with the alumina substrate contained in the crucible 6 and then solidified on the outlet side to obtain a metal-ceramic direct bonding substrate in which an aluminum plate having a thickness of 0.5 mm was bonded to the upper surface of the alumina substrate. (Second step).

Then, an etching resist is heat-pressed onto both surfaces of the obtained direct-bonded substrate, and then only the aluminum plate on the surface is subjected to light-shielding / development treatment to form a desired pattern and etching treatment with a ferric chloride solution. Was performed to form the circuit 4 (third step).

Next, after the circuit surface is replaced with zinc, Ni plating is applied, and a copper plate having a thickness of 4 mm is bonded as a heat sink plate 5 to the metallized layer 11 on the back surface.
A target metal-ceramics composite substrate was obtained (fourth step).

When the heat cycle resistance and heat conductivity of the above-mentioned bonded substrate thus obtained were examined, a heat cycle of 1000 was obtained.
No cracks are generated even after turning, and the thermal conductivity is low,
It also had the effect that the amount of warpage of the product itself was smaller than that of conventional products.

(Example 2)

An aluminum nitride substrate (36 mm × 52 mm × 0.63) is used instead of alumina as a ceramic substrate.
5 mm) except that the same procedure as in Example 1 was performed.
When an aluminum nitride direct bonding substrate was obtained and the heat cycle resistance of this bonding substrate was examined, cracks did not occur even after 3000 times, the thermal conductivity was small, and the amount of warpage of the product itself was smaller than that of the conventional product.

(Comparative Example 1)

For comparison, the aluminum nitride substrate shown in Example 2 was used to form a copper plate having a thickness of 0.3 mm on both sides of the substrate.
A copper-clad substrate obtained by firing in a vacuum furnace at 780 ° C. through a g-Cu-Ti brazing filler paste was used, and when the heat cycle resistance was determined, cracks occurred in several tens of times, and the amount of warpage of the substrate was It was great.

[0037]

As described above, the metal-ceramic direct bonding substrate obtained by the method of the present invention has a high heat cycle resistance which cannot be obtained by the conventional composite substrate, and is used as a high power power module substrate for electric vehicles and trains. It is particularly preferable.

[Brief description of drawings]

FIG. 1 is a schematic plan view of a metal / ceramics direct bonding substrate according to the present invention.

FIG. 2 is a side view of the metal-ceramics direct bonding substrate of FIG.

FIG. 3 is a principle view of an apparatus for manufacturing a bonded substrate of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ceramics substrate 2 Aluminum 3 Electronic component mounting part 4 Circuit 5 Heat sink plate 6 Crucible 7 Heater 8 Case 9 Lid 10 Guide integrated die 11 Metallized layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C04B 41/91 C04B 41/91 B H05K 1/03 610 H05K 1/03 610D // H01L 23/14 H01L 23/14 M

Claims (3)

[Claims] 1. A ceramic substrate is provided with a metal portion made of an aluminum material for electrical conduction and mounting of electronic components, and a metallized layer for joining a heat sink is provided on the other surface of the ceramic substrate. And a metal-ceramic composite substrate. 2. The metallized layer comprises W, Mo--MnO,
The metal-ceramic composite substrate according to claim 1, which is at least one brazing material of an Ag-Cu alloy. 3. A first step of forming a kind of alloy layer selected from W, Mo—MnO and Ag—Cu alloys as a metallization layer on one main surface of a ceramic substrate, and then molten aluminum on the other surface of the substrate. Second step of solidifying into a composite substrate after joining, then, in the obtained composite substrate, a third step of forming a predetermined circuit by etching the surface of the aluminum material, and then of the obtained aluminum circuit A fourth step of plating the surface, and a method for producing a metal-ceramic composite substrate, comprising: