JPS6325502B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to an aluminum package, and more specifically, to an aluminum package for a microwave amplifier using a semiconductor such as GaAsFET.

(2) Prior Art and Problems As is well known, conventional microwave amplifier package cages are manufactured from iron-based materials, mainly stainless steel. However, such packages not only have poor heat dissipation properties but also are very heavy, so these packages have recently been required to meet two challenges: weight reduction (especially necessary when mounted on aircraft); and good thermal conductivity (if this is poor, the heat generated by high-output amplifiers will cause damage to the circuit elements).

Although attempts have been made to use aluminum instead of stainless steel for the package, it has not yet been put to practical use. because,
In the case of aluminum packages, although the unique characteristics of aluminum can be utilized, such as good thermal conductivity, good heat radiation, light weight, and excellent workability, the important property of airtight sealing is This is because it cannot be guaranteed. In other words, when joining the case and cover of an aluminum package, cracks occur in the weld bead due to rapid solidification after welding, making it impossible to make the package completely airtight, as detailed below. be. Furthermore, continuous wave oscillation, a type of solid-state laser,
When welding aluminum using a YAG laser, the average output power of the laser is several
It is on the order of 100W, and since Al has a high reflectance to the laser, it is possible to melt thin objects like aluminum foil with a laser, but it is impossible to melt thick objects, so it is necessary to actually perform welding. is not possible.

It is well known that when sealing a circuit board or a package on which elements are mounted, care must be taken to avoid thermal deterioration of the elements. for that,
Sealing methods such as brazing, which require exposing the entire aluminum package to high temperatures, cannot be used here. Although it is possible to employ a welding method that locally heats the package, ordinary welding methods cannot be used. This is because aluminum, which has extremely good thermal conductivity, is selected as the package material, and therefore heat dissipation becomes too large to carry out welding. In the end, the current situation is that we have to rely on laser welding methods.
However, even if the package is sealed using this method, the good thermal conductivity of aluminum will cause the weld to cool down extremely quickly, causing cracks to form in the weld bead, and thus preventing the package from sealing. Airtightness cannot be maintained. It has been found that such cracks occur not only when pure aluminum is used as the package material, but also when aluminum alloys with excellent corrosion resistance, such as Al-Mg, are used. There is.

In addition, in order to eliminate the above-mentioned drawbacks of stainless steel, the present inventors formed the case of the package using an aluminum alloy, formed the joint part of the case and its cover from an iron-based metal, and used a laser beam to form the joint of the case and its cover. He was the first to invent and apply for a patent for airtight sealing (Japanese Patent Application Laid-Open No. 147135/1983).
However, although this aluminum alloy package can achieve its intended purpose, it is complicated in that it requires diffusion bonding of ferrous metals, such as stainless steel or mild steel, to the aluminum alloy, and also Similarly, cracks tend to occur.

(3) Object of the Invention As is clear from the above description, a drawback inherent to the conventional aluminum package is poor airtight sealability. An object of the present invention is to dramatically improve the hermetic sealability of an aluminum package without changing the basic idea of performing hermetic sealing welding of an aluminum package using a laser. moreover,
The object of the present invention is to enable the use of a low-power laser such as a continuous wave YAG laser.

(4) Structure of the Invention The present inventors have recently proposed an aluminum package in which a case and a cover, each made of aluminum or an aluminum alloy, are hermetically sealed by laser welding, and a sealed portion of the case. An intermediate layer made of a non-ferrous metal is interposed between the sealing part of the cover and the sealing part, and the intermediate layer is made into an aluminum alloy by laser welding together with the aluminum and/or aluminum alloy of the sealing part. It has been found that the above objects can be achieved with an aluminum package.

According to a preferred embodiment of the present invention, a Si layer is formed on the sealing portion of the case and/or cover of an aluminum package by a thin film forming method such as a vapor deposition method, a sputtering method, or a plasma spraying method. The cover and case are stacked with the layers sandwiched between them, and the Si layer and the aluminum and/or aluminum alloy in the sealing part are irradiated with a focused laser beam to melt that part, and the aluminum and/or aluminum alloy is melted.
This can be carried out by forming an intermediate layer made of a eutectic alloy of -Si.

According to another preferred embodiment of the present invention, a Zn plating layer having a low reflectance to a laser is formed on each of the case sealing portion and the cover sealing portion of the aluminum package using a plating method such as an electroplating method. This can be carried out by forming an intermediate layer made of an Al--Zn alloy by laser welding this Zn plating layer together with the aluminum and/or aluminum alloy of the sealing part. When the intermediate layer is formed from such an alloy, the thickness of the intermediate layer has good energy absorption, so the aluminum can be melted using a low-power laser.
Laser welding can be performed.

According to yet another preferred embodiment of the present invention, a Cu plating layer and a Ni plating layer are sequentially formed on the case sealing portion and the cover sealing portion of the aluminum package by, for example, an electroplating method. This can be carried out by laser welding this composite Cu+Ni plating layer, which has a low reflectance to laser, together with aluminum and/or aluminum alloy of the sealing part to form an intermediate layer made of Al-Cu-Ni alloy. . The results obtained are the same for the intermediate layer made of the Al--Zn alloy described above.

As is clear from the above description, in the present invention,
An intermediate layer made of a non-ferrous metal is formed using methods such as foil insertion, vapor deposition, plating, etc., and this (these) intermediate layer is melted by laser welding together with aluminum and/or aluminum alloy of the sealing part. , blend into the weld. That is, the resulting welded part becomes an aluminum alloy in which the nonferrous metal of the intermediate layer is alloyed. When the intermediate layer is thus alloyed within the weld, a significant increase in the strength of the weld can be achieved.

Any aluminum-based material can be advantageously used as the material of the aluminum package when implementing the invention. Typical aluminum-based materials include, for example, pure aluminum (for example, 1100 specified by JIS), corrosion-resistant aluminum alloy (for example, 5052 specified by JIS), and others. The materials of the case and cover of the package may be the same or different from each other, and can be arbitrarily selected from the aluminum-based materials mentioned above.

(5) Embodiments of the Invention The aluminum package of the present invention will be described with reference to the attached drawings.

FIG. 1 shows the case and cover of an aluminum package according to the invention before hermetic welding. In this state, the intermediate layer (hereinafter particularly referred to as a bonding film layer) has not yet been formed. In the illustrated case, the cover 1 and case 2 are made of pure aluminum 1100. The case 2 further has input/output terminals 3, and is also equipped with a circuit board and elements, although not shown.

FIG. 2 illustrates a method for hermetically sealing the aluminum package of the present invention by laser welding. As shown in the figure, a laser beam from a laser oscillator 4 is focused by a lens system 5 and irradiated onto a bonding film layer 6 provided between the sealing portion of the cover 1 and the sealing portion of the case 2 . This laser beam irradiation is usually carried out in an atmosphere of an inert gas such as nitrogen or argon.

FIG. 3 shows an example in which an Al--Si alloy layer is used as a bonding film layer according to the present invention. In the case shown, both the cover 1 and the case 2 were made from pure aluminum 1100. Si was deposited on the sealing portion of the cover 1 by plasma spraying. The thickness of the formed Si plasma sprayed layer 7 was 50 μm. Next, the sealing parts of the cover 1 and the case 2 were overlapped and welded by irradiating the layer 7 and its vicinity with a laser beam focused to 0.3 mm in a nitrogen gas atmosphere. Laser welding has a pulse width of 4
Welding was carried out at a welding speed of 4 mm/sec under the conditions of 15 pps, pulse rate of 15 pps, and average output of 200 W.

Using a helium leak detector, we investigated the airtightness of an aluminum package that was tightly hermetically sealed through an Al-Si alloy layer, and found that it had a high airtightness of over 10 ^-10 atm・cc/s, which is no problem in practical use. It turned out that it has. Furthermore, when the welded portion of this package was observed under a microscope, it was found that there were no cracks at all, and that high reliability was obtained. In addition, when the welded part was inspected using an XMA (X-ray microanalyzer), it was confirmed that the welded part was made of an Al-Si eutectic alloy.

FIG. 4 shows an example in which an Al--Cu--Ni alloy layer is used as a bonding film layer according to the present invention. In the case shown, cover 1 and case 2 are
Both were made from pure aluminum 1100. A film with a thickness of 10 μm is applied on each of the sealing portion of cover 1 and the sealing portion of case 2 to match the shape of these sealing portions.
A Cu layer 8 with a thickness of m and a Ni layer 9 with a thickness of 10 μm were sequentially formed by electroplating. Next, the sealing parts of the cover 1 and the case 2 were overlapped and welded by irradiating the layers 8 and 9 and their vicinity with a laser beam focused to 0.1 mm in a nitrogen gas atmosphere. The laser beam used here was a continuous wave laser beam with an average output of 300 W and a welding speed of 4 mm/sec.

Using a helium leak detector, we investigated the airtightness of the aluminum package, which was tightly hermetically sealed through a composite Cu+Ni plating layer as a bonding film layer, and found that it was 10 ^-10 atm, which poses no practical problems.
It was found that the airtightness was as high as cc/s or higher. Furthermore, when the welded portion of this package was observed under a microscope, it was found that there were no cracks at all, and that high reliability was obtained.

In the case of FIGS. 3 and 4, both the cover 1 and the case 2 are made of pure aluminum 1100, but instead, either the cover 1 or the case 2 is made of aluminum alloy 5052, or
Comparable results similar to those described above were obtained when both of these were formed from aluminum alloy 5052.

(6) Effects of the Invention According to the present invention, it is possible to provide an aluminum package for microwaves that is lightweight, stable, and highly hermetically sealed. Furthermore, a low output laser can be used for welding. Furthermore, this package can be equipped with high-power devices because the material that makes up the package has excellent heat dissipation.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing the state of the aluminum package of the present invention before hermetically sealing welding;
The figure is a conceptual diagram showing a method of hermetically sealing the aluminum package of the present invention by laser welding, FIG. 3 is a schematic diagram showing an example of using an Al-Si alloy layer as an intermediate layer, and FIG. is a schematic diagram showing an example in which an Al-Cu-Ni alloy layer is used as an intermediate layer. In the figure, 1 is a cover, 2 is a case, 3 is an input/output terminal, 4 is a laser oscillator, 5 is a lens system, 6 is an intermediate layer, 7 is a Si plasma sprayed layer, 8 is a Cu plating layer,
And 9 is a Ni plating layer.

Claims (1)

[Scope of Claims] 1. An aluminum package formed by hermetically sealing a case and a cover, each made of aluminum or an aluminum alloy, by laser welding, wherein the sealing portion of the case and the sealing portion of the cover are An aluminum package, characterized in that an intermediate layer made of a non-ferrous metal is interposed therebetween, and the intermediate layer is made into an aluminum alloy by laser welding together with the aluminum and/or aluminum alloy of the sealing part. 2. A Si layer is formed on the sealing part of the case and/or the sealing part of the cover, and the Si layer is laser welded together with aluminum and/or aluminum alloy of the sealing part to form an Al-Si alloy. An aluminum package according to claim 1, further comprising an intermediate layer of: 3. A Zn plating layer is formed on each of the sealing part of the case and the cover, and the Zn plating layer is laser welded together with aluminum and/or aluminum alloy of the sealing part to form Al-Zn.
An aluminum package according to claim 1, comprising an intermediate layer made of an alloy. 4. A Cu plating layer and a Ni plating layer are sequentially formed on the sealing portion of the case and the sealing portion of the cover, and these composite plating layers are heated with a laser beam together with aluminum and/or aluminum alloy of the sealing portion. An aluminum package according to claim 1, wherein the aluminum package is welded to form an intermediate layer made of an Al--Cu--Ni alloy.