JPH02232326A - Copper material having good joinability with ceramic - Google Patents

Abstract

PURPOSE:To manufacture copper material having good joinability with ceramic without strictly executing the regulation of impurities by providing tough pitch copper contg. oxygen of specified concn. with a high purity Cu layer having specified thickness. CONSTITUTION:Tough pitch copper having 180 to 300ppm oxygen concn. and the balance Cu with inevitable impurities is provided with a high purity Cu layer of 1 to 20mu. Furthermore, in the high purity Cu layer, Cu concn. is preferably regulated to about >=99.95% and it is provided by plating treatment. In this way, a copper material having relatively smooth surface, allowing stable mounting of elements and having good joinability with ceramic can be obtd., which is useful for a ceramic-copper composite material as electronic parts.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a steel material that has good bondability with ceramics. [Conventional technology] Hybrid I is a bonded body made by bonding steel to ceramics.
It is often used in electronic parts such as C. Conventionally, these bonds have been made by printing a metal paste containing an organic binder such as molybdenum or tungsten on ceramics, then heating it in an atmospheric furnace to metallize the metal paste to form a metallized layer, and then coating the metallized layer with nickel. This was done using a complicated method that involved various steps, such as plating and then joining the steel materials by soldering. In response, a method has been developed that involves a simple process of directly bonding ceramics and copper by generating copper oxide (Cu20) at the bonding interface between ceramics and steel.
Attention has been paid. In this method, ceramics and steel are simply heat-treated in a state where they are in direct contact with each other to bond them together. As understood from the copper-oxygen binary phase diagram, Cu. It is possible to form an O liquid phase, and this is used to directly bond ceramics and steel materials. There are two methods of supplying oxygen: one using oxygen in copper (using tough pitch copper) and the other using oxygen present in the atmosphere (using oxygen-free copper), and the bonding method using tough pitch copper is generally used. ing.

Although this direct bonding method has a simpler process and various advantages compared to previous bonding methods, there are still some problems that remain to be resolved. This is because copper is heated to near its melting point and retained.
S, Fe, Si, ^8, contained around 30 ppm
Impurity elements such as Pb and Ni can significantly lower the melting point locally, causing the surface of the steel material (the surface on which the device is mounted) to become rough at the 8i edge, or similar local melting point decreases occurring at the contact surface. In some cases, the wetting area decreases and a good bond cannot be obtained. This resulted in a number of disadvantages, such as a significant drop in bonding yield, leading to increased costs, and the roughness of the copper surface, making it impossible to mount devices. Therefore, the tough pitch copper used contains the impurity elements S, Fa, Si,
, Pb, Ni, etc. must be kept below 10 ppm each, and industrially this is subject to very strict restrictions such as the furnace material of the melting furnace and operating conditions. [The problem that the invention tries to solve! ! ! ] The present invention has been made in view of the prior art as explained above, and an object of the present invention is to provide a copper material that does not require strict control of impurities such as S and has good bondability with ceramics. [Means for Solving the Problems] The gist of the present invention is to add 1 to 20 μl of high-purity Cu to tough pitch copper in which the oxygen concentration is 180 to 300 ppm, and the balance is Cu and unavoidable impurities. It exists in ceramics, which are characterized by a layered structure, and in steel materials, which have good bonding properties. [Function] The copper material having good bondability with the ceramic according to the present invention will be explained in detail below. Oxygen is an essential element for direct metal bonding with ceramics, and if the concentration is less than 180 ppm, the amount of oxygen supplied at the bonding interface will be insufficient, resulting in poor bonding.

In addition, at a concentration exceeding 300 ppm, bondability is good, but even if a high purity Cu layer is applied with a thickness of 1 to 20 μm,
The surface on which the element is mounted becomes rough (excess 02 collects at grain boundaries, increasing surface roughness). Therefore, the oxygen concentration is set at 180 to 300 ppm. At the bonding interface between the high-purity Cu layer and the ceramics,
The thickness of the high-purity Cu layer is less than lμ1, which has the effect of suppressing the local melting point decrease due to impurity elements that are unavoidably mixed in, and making the Cu20M phase sufficiently present at the interface to obtain a good bonding interface. However, the effect is small, and bondability decreases when the amount exceeds 20μ. Therefore,
The thickness of the high-purity Cu layer is 1 to 20 μm. In addition, when a high-purity Cu layer is not provided, the tough pitch surface on which the device is mounted becomes uneven due to the formation of the Gu,0 liquid phase, and the surface roughness increases significantly (RmaxlO
(μm or more), but by providing a high-purity Cu layer of 1 to 20 μm, the surface becomes relatively smooth, leading to stable quality of element mounting. In this case, the thicker the high-purity Cu layer, the better, but from the viewpoint of bondability with ceramics, surface roughness, and cost, a thickness of 1 to 20 μm is appropriate. The Cu concentration of the high-purity Cu layer is preferably 99.95% or more, and may be provided, for example, by plating.
In the case of plating, the plating may be left as is, but in order to further improve the smoothness of the surface of the material and to remove occluded gases, rolling and annealing may be performed after Cu plating. In addition, in the present invention, there is no particular limitation on the type of ceramics to be joined, but for example, ^Il20
Examples include s, ^10, .Si02, etc., and these ceramics may also be a film formed on a suitable substrate. [Example] A steel material having good bondability with ceramics according to the present invention will be explained in detail below based on its implementation. A 0.3 muat material of tough pitch steel having the ingredients and ratios shown in Table 1 was used as a test material. The ceramics are 1.5mmtX 30mmtx501ll from Alumina Trade.
I11 was used.

If the rope material to be joined is 0.3++v+tX 25
mm*x45m+aJZ was prepared by etching, and Cu plating was performed in a copper sulfate plating bath before etching.

In the bonding test, ceramics and steel were stacked and heated at 1070°C x 1 in a 100% N2 gas atmosphere (dew point -50°C).
After the 0-minute heat treatment, a visual inspection (×40) was performed, and the bondability was evaluated based on the presence or absence of blisters. In addition, the surface roughness of the steel surface was measured and the surface condition was observed using a scanning electron microscope.6 Table 2 shows the test conditions and test results.

In addition, among the results of scanning electron microscope observation of the surface of steel material bonded to ceramics, No. 1 is a representative example. l (Example) and No. 8 (Comparative example) as shown in Figure 1 (a) and (b)
It is shown in As is clear from Table 2 and Figure 1, No. 1~N
o. 6 (Example) had better bondability with ceramics than the comparative example, and the surface of the steel material on which elements and the like were mounted had excellent smoothness with RmaxX of 10 μm or less.

On the other hand, NO. 7 and no. 8 (Comparative example) is C
There is no u-plating treatment, so there is a lot of blistering, and the surface of the steel material is uneven.

No. 9, to, 11. 12 (Comparative example) is C
02 to 14 degrees is 300p with or without U-glazing
pm, and the occurrence of blisters was small, but the surface roughness was large● No. l3 14, 15 (comparative example) has a concentration of 0 and a concentration of 1. l]Oppm, and the surface roughness of the steel material surface is good regardless of the presence or absence of Cu plating, but there is a problem in bondability. No. No. 16 (comparative example) is a tough pitch steel with impurity control, and has the same bondability and surface roughness as the present invention, but in terms of industrial production, No. In order to control impurities to 18%, a considerable amount of equipment is required, leading to increased costs and decreased productivity. [Effects of the Invention] According to the present invention, there is no need to carry out extreme impurity control;
By adding a Cu plating layer to conventional tough pitch copper, it is possible to provide a steel material with good bonding properties with ceramics. This contributes to Table 1 (ppm) Table 2

[Brief explanation of the drawing]

FIG. 1(a) shows the present invention No. 1 is a scanning electron micrograph showing the state of crystal grains on the surface of a steel material directly bonded to alumina ceramics using steel material No. 1. FIG. 1(b) shows comparative example No. This is a scanning electron micrograph showing the state of crystal grains on the surface of a copper material directly bonded to an alumina ceramic using steel material No. 8. 20. : 1μju (a) Invention No. 1 (b) Comparative material No. 0.8 Figure 1

Claims (1)

[Claims] The oxygen concentration is 180 to 300 ppm, and the remainder is Cu.
1 to 20μ for tough pitch copper consisting of unavoidable impurities.
A copper material with good bondability to ceramics, characterized by having a high purity Cu layer of m.