JPH02102548A - Thermal expansion adjusting material - Google Patents

Abstract

PURPOSE:To improve a solderability while the superior thermal expansion adaptability of an Nb layer with a ceramics layer is maintained intact by a method wherein a thermal expansion adjusting material is constituted in such a way that copper layers or copper alloy layers are respectively cladded on both surfaces of the Nb layer and the thickness ratio of the copper layer: the Nb layer: the copper layer is set at a specified range. CONSTITUTION:Copper plates or copper alloy plate 1b and 1b, whose thickness are almost equal, are respectively cladded on both surfaces of an Nb plate 1a and the plates 1a, 1b and 1b are constituted into a thermal expansion adjustable clad material (a thermal expansion adjusting material) 1. The plate thickness ratio of the copper plate: the Nb plate: the copper plate is set at a range between 1:500:1 (about 0.4% of the coating volume percentage of Cu) and 15:70:15. As this result, a layer, to which a silver solder layer 4 comes into contact, is not the Nb layer but is changed into the copper layer 1b and a difference between this silver soldering and a silver soldering with the copper layer itself is eliminated. Thereby, a significant improvement and a stabilization of a solderability can be accomplished without impairing the thermal expansion adaptability of the Nb layer with an Al2O3 ceramics layer 3.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for silver soldering between a ceramic substrate and a sealing component in a paragauge type semiconductor device, using a thermal expansion method that can suitably match the difference in thermal expansion. This relates to adjustment materials.

[Prior Art] For example, in a packaged semiconductor device, the fourth
As shown in the figure, an AJ203 ceramic substrate 3 is bonded to the casing 1- with silver solder 2, and the ceramic substrate 3
A Si chip 5 such as a power diode is bonded by solder 4 to the device.

In this case, in silver soldering between the housing and the ceramic substrate, it is heated to a high temperature of about 800 to 900 degrees Celsius, so
It is necessary to match the thermal expansion between Al2Oa ceramics and the casing. Kovar or molybdenum, whose coefficient of thermal expansion is close to that of ceramics, is generally used as the material for the casing, but materials such as niobium (hereinafter referred to as Nb) Attempts have also been made to use low expansion metals or alloys.

[Problems to be Solved by the Invention] When silver soldering the above AJ203 ceramics to Nb used as a casing, silver soldering (,
(1-28% Cu alloy, etc.), brazing not only makes the parts unstable and lacks reliability, but also leaves problems such as the risk of peeling later. Ta.

The purpose of the present invention is to eliminate the above-mentioned concerns about silver brazing, and to greatly improve thermal expansion properties while maintaining the excellent thermal expansion consistency with ceramics that Nb has. The aim is to provide materials.

[Means for Solving the Problems] The present invention clads both sides of Nb with copper or a copper alloy, and the thickness ratio of copper/Nb/copper is 15 near 0:15 to 1:50.
It is configured to have a range of 0:1.

[Effect] With the above composition ratio, it is possible to achieve significant improvement and stabilization of brazing properties by having a copper layer on the surface without impairing the thermal expansion compatibility with ceramics that Nb has. This can contribute to improving the reliability of semiconductor devices.

[Example] The present invention will be described below with reference to Examples.

In the present invention, as shown in FIG. 1, copper or copper alloy tb is coated on both sides of Nb1a with approximately the same thickness.

1b is made into a rad material 1 which can be adjusted in thermal expansion.

The reason why both sides are clad with approximately the same thickness is to prevent warping during heating and ensure thermal stability.

The reason why copper or a copper alloy is used for cladding is that copper has particularly excellent wettability and bondability with silver solder when bonded to AJ203 ceramic 3, and also has excellent thermal conductivity.

That is, by using the clad material 1 according to the present invention, the silver solder 2 comes into contact with the copper layer 1b as shown in FIG. 2 instead of Nb as in the conventional example shown in FIG. There is no difference from bonding, and combined with good thermal conductivity, a stable and excellent bond can be obtained.

FIG. 3 is an R diagram showing the change in thermal Mj tensile strength of the clad material according to the present invention obtained as described above and the AjzO3 ceramics depending on the temperature.

As can be seen from FIG. 3, from the viewpoint of thermal WB'31, the smaller the plate thickness ratio of copper in the cladding material, the closer the amount of thermal expansion thereof will be to that of ceramics. However, the plate thickness ratio of copper/Nb/copper is 1:500:1 (
If the Cu coating volume ratio is smaller than approximately 0.4%, the thickness of the copper will be insufficient, and the above-mentioned brazing will not be able to improve the properties sufficiently, and the heat resistance due to the excellent thermal conductivity of copper will be insufficient. The dissipation ability also decreases, which is not preferable.

From the above-mentioned meaning of heat dissipation, a larger copper plate thickness ratio is preferable, but as can be seen from Figure 3, as the copper plate thickness ratio increases, the amount of thermal expansion gradually increases and consistency becomes worse.

Therefore, the upper limit of the copper/Nb-copper plate thickness ratio is 15 near 0:15.

Note that the copper layer may be made of pure copper, but
Cu5n alloy, Cu-
Ag alloy, Cu-Zr alloy, Cu-P alloy, Cu-Zn
If an alloy or a Cu-AJ 20s composite material is used, brazing can improve not only the properties but also the heat resistance, which is very preferable.

Example 1: Each plate thickness of the copper layer, Nb layer, and copper layer was 10 mm by cold rolling and welding.
Copper/Nb/Copper clad material (total thickness 2.0IIIffi) so that μm: t, 98mm: 10μm
was produced. The cladding material is processed into a metal cap, and this and A1tO3 ceramics are bonded with Ag wax (Aa-
28% Cu alloy) to assemble the ceramic barrier gauge, brazing has good properties and even after cooling to room temperature, Ag
A good package was obtained without peeling of the wax.

Example 2 A heat-resistant composite material, Cu-0.1% AJ1203 composite material (softening temperature 600°C), was combined with Nb, and a three-layered cladding material was cold-rolled to have the cross-sectional shape shown in Figure 1. Rolled and pressure welded. Furthermore, after diffusion heat treatment at 800'C to ensure sufficient metal bonding, finish rolling is performed to reduce the total plate thickness to 1.0
En, Cu AJI 20s ・Nb -Cu AJ2
A clad material according to the present invention was manufactured with a thickness ratio of 0.03 to 0.02:0.96:0.02.

This clad material is processed into a metal cap, and AJ203
Ceramics and Ag solder (Ag-28% Cu alloy) were bonded at a temperature of 900°C and assembled into a multi-layer ceramic paragauge.

Brazing with Ag solder had extremely good properties, and even after cooling to room temperature, there was no cracking due to the difference in thermal expansion of AJ203 ceramics, and no peeling of the A (J solder) was observed, making it possible to obtain a good package. As a result of mounting tests, it was found that there was little variation in thermal resistance and that it exhibited good thermal conductivity.

Example 3゜0.2m thick Cu-O, t%zr alloy strip and 1.0m thick
Thick Nb strip and 0.2mm thick Cu-0.1%Zr
A 3MM clad material with a thickness of 1.0 m+ was produced by stacking three layers of alloy strips, cold rolling, and finish rolling. This clad material is used as a metal substrate and a thickness of 1
．． Ag waxing of AjzO3 ceramics in 0 city (Ag-2
2%Cu-18%Zn-5%Sn alloy), and then Si for power on AJ1203 ceramics.
A device having the structure shown in Fig. 2 was manufactured by soldering the die. In this case, AQ brazing was performed by cooling the temperature from 700°C to room temperature, but good brazing was achieved without cracking of the Al2O3 ceramics. I was able to do this.

As a result of a mounting test of this, it was possible to obtain a good surface mount metal board without solder fatigue due to heat.

Application example 1゜In the above example, a three-layer structure copper/Nb/copper clad material was produced by cold rolling welding, but the plate thickness ratio was further reduced to 1:500:1 and the plate thickness was 1.0 m. In such a case, it has been found that it is possible to manufacture the N and b plates by depositing copper with a thickness of about 2 μm on both sides using a vapor phase method including a vapor deposition method or an electroplating method.

Application example 2゜In the above example, Nb plate (purity of 99.90% or more) was used, but by using Nb-10% Cu alloy (sintered material), the copper coating thickness can be reduced, and copper Nb-10%
It has been found that it is possible to easily produce a three-layered cladding material with good adhesion between Cu sintered and rolled material and copper.

[Effects of the Invention] As described above, according to the present invention, the following excellent effects can be achieved.

(1) The slope of thermal expansion is similar to that of AJ 203 ceramics, and brazing makes it possible to obtain a material with thermal expansion consistency that prevents the ceramic from cracking or peeling even when cooled from 900°C to room temperature. can.

(2) Copper/Nb - Copper clad material has Nb workability.
It has the advantage that it is improved over a single unit, has high reliability of Ag brazing, and can improve product yield as a package component.

(3) The plate thickness composition ratio of copper/Nb/copper clad material is 1
Thermal expansion at high temperatures of 700 to 900°C can be adjusted by freely changing the ratio of 0:15 to 1:500:1.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of the cladding material according to the present invention;
Fig. 2 is an explanatory cross-sectional view showing how a semiconductor is mounted using the clad material according to the present invention as a barrier gauge material, Fig. 3 is a diagram showing the relationship between temperature and thermal expansion, and Fig. 4 is a conventional package. It is an explanatory sketch showing the implementation situation of. 1: thermal expansion adjusting material, 1 a: Nb, 1 b = copper or copper alloy, 2: silver solder, 3: A1 ceramics, two solders, 5: chip.

Claims (2)

[Claims] (1) Made of a three-layer composite material in which both sides of a niobium plate are coated with copper or copper alloy of approximately the same thickness, the ratio of copper layer, niobium layer, and copper layer is 15:70:15 (copper coating volume ratio 30%). ) to 1:
A thermal expansion adjusting material in the range of 500:1 (copper coating volume ratio 0.4%). (2) C with an alloy component added in an amount of 2% by weight or less as a copper layer
u-Sn alloy, Cu-Ag alloy, Cu-Zr alloy, Cu
-P alloy, Cu-Zn alloy or Cu-Al_2O_
2. The thermal expansion adjusting material according to claim 1, comprising a three-component composite material.