JPH04170374A - Method for joining aln ceramics to copper plate - Google Patents

Abstract

PURPOSE:To enable joining excellent in heat resistant impact properties by cooling the joined body of a copper plate and an AlN ceramics sintered body at two steps in the specified conditions after joining when the silver-copper eutectic solder material contg. active metal is used and the AlN ceramics sintered body is joined to the copper plate. CONSTITUTION:The silver-copper eutectic solder material contg. active metal (e.g. titanium) is used and an AlN ceramics sintered body is joined to a copper plate. After joining, this joined body is quenched at >=5 deg.C/minute temp. lowering velocity to the temp. range within 500-700 deg.C. Then it is slowly cooled at <=5 deg.C/ minute temp. lowering velocity to <=200 deg.C. Thereby since it is quenched to 500-700 deg.C from the burning temp., the component of solder material is inhibited from being diffused to the copper plate. This copper plate is prevented from being hardened. Further when the joined body is slowly cooled from this temp., primary crystal formed at a time of quenching is integrated. The thermal stress between the copper plate and AlN ceramics is relaxed by deformation of the solder material layer at this time and residual stress is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method of bonding a copper plate and Aj2N ceramics in a substrate of an electronic device.

[Prior art] When a copper plate and A42N ceramics are bonded, the difference in thermal expansion (copper 17 x 10-4/"C1A42N4~5x1
0-4/''C) is generated, and AεN has the disadvantage that cracks are likely to occur during cooling after bonding or when thermal shock is applied due to exposure to low and high temperatures in the surroundings.

[Problem to be solved by the invention]

The present invention was proposed in order to improve these drawbacks, and the present invention addresses residual thermal stress caused by the difference in thermal expansion when a copper plate and AlN ceramics are bonded at high temperature using a brazing filler metal containing an active metal and cooled. The aim is to improve thermal shock resistance by relaxing the .

[Means for Solving the Problems] In order to solve the above problems, the present invention controls the cooling process after joining a copper plate and an AffN ceramic sintered body, and uses a silver-copper eutectic solder containing an active metal. (a) When bonding a copper plate and an AβN ceramic sintered body using a
Rapid cooling at a cooling rate of ℃/min or higher.

(b) Next, it is gradually cooled down to 200°C or less at a temperature decreasing rate of 5°C/min or less.

Copper plate AβN is characterized by consisting of two steps:
This provides a method for joining ceramics.

[Function] When bonding a copper plate and an AβN ceramic sintered body using a silver-copper eutectic brazing filler metal containing an active metal,
When rapidly cooled to 00° C. to 700° C., diffusion of the brazing material component into the copper plate can be suppressed, and the copper plate can be prevented from hardening.

Then, when the material is slowly cooled from this temperature, the primary crystals formed during the rapid cooling coalesce. Due to the deformation of the brazing metal layer at that time, the copper plate and AJ2N
Thermal stress with ceramics is relaxed.

If the material is rapidly cooled from the firing temperature to 500.degree. C. or lower, the residual stress will increase and cracks will occur during cooling. Also 700℃
If quenching is stopped at a higher temperature, the wax phase components will diffuse into the steel sheet, harden the copper sheet, and reduce thermal shock resistance. Therefore, quenching is carried out at a temperature of 500°C to 700°C.

The cooling rate is 5°C/min or more, preferably 15°C/min or more. If it is less than 5° C./min, diffusion of the brazing filler metal components into the steel cannot be effectively prevented.

Next, slow cooling will be explained. The initial pieces in the brazing material layer produced by rapid cooling coalesce and become larger crystal grains, and their deformation contributes to stress relaxation. Additionally, there is enough time for stress relaxation while copper is in the plastic region at each temperature.

This coalescence of primary crystals and plastic deformation of copper are each 200℃
Since this occurs at temperatures above 200°C, the temperature range up to 200°C is slowly cooled.

The cooling rate of slow cooling is 5° C./min or less, preferably 2° C./min or less. If the cooling rate exceeds 5°C/min, sufficient coalescence of the initial product will not occur, so the cooling rate is limited to 5°C/min or less.

〔Example〕

Using 72Ag-27Cu-ITi silver-copper solder as the brazing material, a 50LLm thick brazing material layer was formed into a 0.635m thick brazing material.
A copper plate with a thickness of 0.3 mm was placed thereon, and the film was fired for 5 minutes in a vacuum for 5 minutes.

The cooling rate (PI >
Cooling at a rate of 2°C/min, 6.5°C/min, 1°C/min,
Then, the cooling rate (P2) was 10°C/200°C.
The samples were cooled at a rate of 2° C./min, 2° C./min, and 0.5° C./min, and thermal shock was applied for 10 cycles each, and the state of cracking and cracking was observed. The results are shown in Table 1.

Samples that were rapidly cooled to 650°C and then slowly cooled to 200'C exhibited excellent thermal shock resistance.

Figure 1 shows the above test piece being heated from 800°C to 650°C for 20 minutes.
°C/min, cooled at 1 °C/min then 10 °C/min to 200 °C
A microscopic photograph of the metallographic structure of the cross section of the brazing material layer of the sample cooled at a rate of 0.5° C./min and 400 times is shown. Table 2 shows the conditions. Figure 2 (a
) to (d) are explanatory diagrams of FIGS. 1(a) to (d), respectively.

In FIG. 1(d), the coalescent growth of primary crystals is clear.

[Effects of the Invention] According to the present invention, the wax phase component does not diffuse into the copper plate, and the copper plate does not harden. In addition, the primary crystals of the brazing metal layer combine with the copper plate and AJ.
Since thermal stress between 2N and residual stress is reduced, it is possible to perform bonding with excellent thermal shock resistance.

[Brief explanation of drawings]

Figures 1 (a) to (d) are micrographs with a magnification of 400 times showing the metal crystal structure of the brazing material layer, and Figures 2 (a) to (d) are micrographs shown in Figures 1 (a) to (d), respectively. It is a corresponding explanatory diagram.

Claims (1)

[Claims] 1. Copper plate and Al using silver-copper eutectic brazing filler metal containing active metal.
When joining the N ceramic sintered body, after joining, it is rapidly cooled at a cooling rate of 5°C/min or more to a temperature range of 500°C or higher and 700°C or lower, and then 5°C to 200°C or lower.
A method for joining a copper plate and AlN ceramics, characterized by slow cooling at a temperature decreasing rate of /min or less.