JPH0666533B2 - Method for manufacturing aluminum nitride substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention mainly relates to an individual semiconductor that handles high power output,
Aluminum nitride used for heat sinks of electronic devices (hereinafter
The present invention relates to a method of forming a surface layer for forming a metal layer on the surface of a substrate (referred to as AlN).

[Contents and problems of conventional technology]

Conventionally, as a method of obtaining adhesion strength between this type of AlN substrate and the metal layer, the AlN surface is chemically roughened by etching or the like, or the surface is oxidized between the AlN and the metal layer to form an intermediate layer of the alumina layer. However, when etching is used, there is a problem that the strength of the AlN substrate decreases when the degree of etching is large, and an intermediate layer of alumina is formed on the surface of AlN. In the case of non-oxide ceramics,
It is difficult to obtain an intermediate product in baking in air, and when using a photothermally conductive substrate, the intermediate layer impairs the thermal conductivity and the original performance as high thermal conductivity is lost. When heat is applied in a neutral atmosphere, there is a problem that the intermediate layer once formed may decompose.

[Object of the Invention]

In order to eliminate these drawbacks, the present invention uses a regular AlN substrate with a large amount of binder on the surface of the AlN substrate during firing of the AlN substrate.
N Adheres to the substrate surface and removes the binder during sintering to make AlN
An object is to provide an AlN substrate having excellent adhesion strength between a metal layer and AlN by forming irregularities on the substrate surface.

[Structure of Invention]

The present invention is a method for manufacturing an AlN substrate, in which a green sheet formed from AlN powder and a binder has a proportion of AlN in the range of 2 to 70 wt% and is used as an outermost layer of the green substrate. After applying the binder on at least one side and removing the binder, the Al
It is intended to form irregularities on the surface of the N substrate and to form a metal layer having high adhesive strength on the surface of the AlN substrate. That is, the present invention is a manufacturing method in which a plurality of aluminum nitride green sheets are laminated, molded and debindered, and then subjected to high temperature firing to obtain an aluminum nitride substrate. % Green sheet is prepared, placed on one side or both sides of the outermost layer of the green substrate, prebaked to remove the binder, and then baked at a high temperature to form irregularities on the surface. It is a manufacturing method of an aluminum substrate.

[Explanation by Examples]

An example of joining with a metal layer using an AlN substrate will be shown below as an example according to the present invention. Polyvinyl butyral (PVB) having a molecular weight of 70,000 to 100,000 was used as an organic binder to prepare a ceramic green sheet of each kind of powder amount. The AlN powder added at that time has an average particle size of 1.0 μm.

1. First, polyvinyl butyral was dissolved in isopropyl alcohol, and 85% by weight of AlN was gradually added to this, while stirring by hand, and then kneading with a homogenizer for 20 minutes. The viscosity at this time was 6000 to 15000 cps. Next, using a doctor blade method, a film thickness of 100 μm,
Film is formed to a width of 160 mm and the resulting sheet is 140 x 140 mm
It was punched out into a regular sheet 1.

2. Similarly, the proportion of AlN ranges from 2 to 85 wt% and is 10
Thickness 40 with different AlN powder and binder weight ratio
A green sheet 2 of μm was prepared.

As for lamination, as shown in FIG. 1, 12 sheets of 1 AlN sheet were laminated and then 1 sheet of 2 AlN sheet was laminated. This was subjected to thermocompression bonding in a mold to obtain a pressed body. The obtained pressed body was heated to 550 ° C. at a temperature rising rate of 15 ° C./hour or less in a normal pressure N ₂ gas atmosphere, and was further held at 550 ° C. for 8 hours to remove the binder. Next, firing was performed at a firing temperature of 1800 ° C. for 5 hours in a N ₂ gas atmosphere to produce a sintered body. As shown in FIG. 2, the obtained sintered body had a large number of protrusions formed on its surface. Roughness at this time is AlN filling rate 20w
The maximum surface roughness Rmax was 12 μm at t%.

Next, 2 m
Electroless Ni plating is formed to a size of mx 2 mm to a thickness of 10 μm,
A 0.7 mmφ lead wire was vertically soldered to the obtained Ni plating layer, and the vertical tensile strength was measured. The results are shown in Table 1.

As shown in Table 1, the preferable adhesion strength of 2.0 Kg / mm ² or more is obtained when the filling rate of AlN is 10 wt% to 50 wt%, and the value of 1.0 Kg / mm ² or more is 2 wt% to 70 wt%. It is obtained at the filling rate of AlN.

As shown in Table 1, when the filling rate of AlN exceeds 70 wt%, the surface of the sintered body does not show the unevenness like the sintered body by the conventional method, the average surface roughness is Ra 0.4 μm, and the maximum surface is The roughness was Rmax 3.7 μm. The adhesion strength was also the same as that of the conventional method. Next, even when the filling rate of AlN was less than 2 wt%, the effect of unevenness decreased and it was equivalent to that of the conventional method. As shown in Table 1, in the method of forming irregularities on the AlN surface phase according to the present invention, it is possible to form a metal film having a higher adhesion strength than the conventional method if the AlN filling rate is in the range of 2 to 70 wt%. Was understood. Incidentally, the present invention, as shown in the examples, is to increase the amount of binder added to AlN as a means for providing irregularities on the AlN surface, and to scatter during sintering to form irregularities on the surface. As a matter of course, not only the organic binders of the examples, but also other organic additives scattered during sintering can obtain the same effects as those of the present invention.

〔The invention's effect〕

As described above, according to the present invention, a ceramic substrate having excellent adhesion strength between the ceramic and the metal phase can be obtained by forming irregularities on the surface of the ceramic.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a ceramic sheet during thermocompression bonding. FIG. 2 shows a sintered body obtained by the method according to the present invention and an electroless material.
Sectional drawing of joining with Ni film. 1 ... Ceramics green sheet (regular). 2 Ceramics green sheet (AlN powder accounts for 2 to 70 wt%). 3 ... Press die. 4 ... Ni film. 5: Ceramics sintered body.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01L 23/15 H05K 3/38 A 7011-4E

Claims (1)

[Claims] 1. A method for producing an aluminum nitride substrate by laminating a plurality of aluminum nitride green sheets, molding and debinding them, and then performing high-temperature firing to produce aluminum nitride powder in which the proportion of aluminum nitride powder is 2 to 70 wt. % Green sheet, which is placed on one side or both sides of the outermost layer of the green substrate to remove the binder by pre-baking and then baking at high temperature to form irregularities on the surface. Substrate manufacturing method.