JP2000077551A - Electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic device having an insulating substrate which will produce no cracks, when a metal cover is welded to the metallized metal layer of the insulating substrate by an electron beam to extremely improve the hermeticity of a box containing an electronic component to extremely satisfactory state and hence capable of operating the electronic component normally stable for a long time. SOLUTION: An electronic device has an insulating substrate 1, having a mounting portion 1a on which an electronic component 3 is mounted and a frame-like metallized metal layer 5 attached thereto, so that it surrounds the mounting portion 1a, an electronic component 3 mounted on the mounting portion 1a of the insulating substrate 1, and a metal cover 2 welded to the metallized metal layer 5 of the insulating substrate 1 via a brazing material therebetween by a beam welding to hermetically seal the electronic component 3 with the insulating substrate 1. The insulating substrate 1 has thermal conductivity of 15 W/m.K or less at 100 deg.C and is not heated to a high temperature which will produce cracks, to effectively prevent cracks from being produced due to thermal shocks.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic device in which electronic components such as a piezoelectric vibrator and a semiconductor element are hermetically housed in a container formed of an insulating base such as ceramics and a metal lid.

[0002]

2. Description of the Related Art Electronic components such as a piezoelectric vibrator and a semiconductor element are air-tightly accommodated in a container for accommodating the electronic components to become an electronic device as a product.

[0003] Among these electronic devices, the one with the highest reliability is made of ceramics such as an aluminum oxide sintered body, and has a mounting portion in which electronic components are mounted in the center of the upper surface and a mounting portion in the outer peripheral portion of the upper surface. Electronic components are hermetically sealed inside a container comprising an insulating base having a metal frame attached so as to surround it, and a metal lid joined by seam welding to the metal frame attached to the insulating base. It is a sealed type. In this type of electronic device, an electronic component is mounted on a mounting portion of an insulating base, and then a metal lid is mounted on a metal frame attached to the insulating base. It is manufactured by rolling while a pair of roller electrodes of a seam welding machine are in contact with each other, flowing a large current for welding between the roller electrodes, and seam-welding a metal lid to a metal frame.

In this type of electronic device, the metal frame attached to the insulating base has a frame-shaped metallized metal layer applied to the outer periphery of the upper surface of the insulating base so as to surround the mounting portion. At the same time, the metallized metal layer is plated with a nickel plating layer, and then brazed to the metallized metal layer via a brazing material such as silver brazing.

[0005] In this type of electronic device, ceramics constituting an insulating base on which electronic components are mounted are excellent in electrical insulation, heat resistance, and environmental resistance. Since the metal lid is welded, the airtight reliability of the container is extremely high.In addition, when the metal lid is seam-welded to the metal frame, the heat of seam welding causes the outer periphery of the metal lid and the metal frame The parts are applied locally and are not transmitted to the mounting part of the insulating base much, so that the electronic components housed inside are not easily damaged by heat when joining the metal lid to the insulating base. There are good advantages.

However, this type of electronic device is
After the electronic components are mounted on the mounting part of the insulating base, when the metal lid is seam-welded to the metal frame attached to the insulating base, the roller electrode of the seam welding device is mechanically rolled. Since the moving speed of the roller electrode is as slow as at most 3 mm / sec, it takes a long time of about several seconds to seam-weld a metal cover of 3 mm square to the metal frame, for example, resulting in low productivity. Was.

Furthermore, since a metal frame is required as a base metal for seam welding a metal lid to an insulating base, the height of the electronic device is increased by that much and the cost is increased. It also had the disadvantage that it would be.

In view of the above, a ceramic insulating base having a mounting portion for mounting an electronic component at the center of the upper surface and a metallized metal layer having a thickness of about 10 to 20 μm surrounding the mounting portion at the outer peripheral portion of the upper surface is provided. After preparing a container comprising a lid body and mounting electronic components on the mounting portion of the insulating base,
An electronic device in which electronic components are hermetically sealed inside a container made of an insulating substrate and a metal lid by electron beam welding a metal lid to a metallized metal layer of the insulating substrate via a brazing material. Proposed.

In this type of electronic device, the metallized metal layer of the insulating substrate is coated with nickel plating to a thickness of 2 to 5 μm, and a metal lid is formed on the nickel-plated metallized metal layer. After that, the electron beam is irradiated on the upper surface of the metal lid while moving the electron beam along the frame-shaped metallized metal layer by a magnetic field, and the thermal energy of the irradiated electron beam By melting the brazing material corresponding to the portion irradiated by the electron beam,
The metal lid and the insulating base are joined.

According to such an electronic device, since the electron beam is irradiated while being moved by the magnetic field, the electron beam can be moved at a high speed of about 300 mm / sec or more. Since it can be welded to the metallized metal layer of the insulating base in a very short time of less than seconds, the productivity is extremely excellent.

Furthermore, since a metal frame is not required as a base metal for welding, the height of the electronic device can be reduced accordingly, and the cost is low.

[0012]

However, in an electronic device in which electronic components are hermetically accommodated in a container in which this type of metal lid is joined by electron beam welding, the metal lid is formed of a metallized metal of an insulating base. When an electron beam is welded to a layer, heat generated by the electron beam is transmitted to a portion of the insulating substrate corresponding to the portion irradiated with the electron beam, and this portion receives a thermal shock that locally becomes high in a very short time, For this reason, a crack may be formed in a portion of the insulating substrate corresponding to the portion irradiated with the electron beam. When such cracks are formed, the cracks are repeatedly subjected to temperature changes in the external environment for a long period of time, and thus progress to the outside of the insulating base. There has been a problem that normal and stable operation cannot be performed over a period.

The present invention has been devised in view of the above problems, and has as its object to prevent cracks in the insulating substrate when the metal lid is electron-beam welded to the metallized metal layer of the insulating substrate. Another object of the present invention is to provide an electronic device that can operate the electronic components housed therein in a normal and stable manner for a long period of time by making the container housing the electronic components extremely airtight.

[0014]

According to the present invention, there is provided an electronic device comprising: a mounting portion on which an electronic component is mounted on an upper surface; and an insulating base having a frame-shaped metallized metal layer attached to surround the mounting portion; The electronic component mounted on the mounting portion of the insulating base is joined to the metallized metal layer of the insulating base by electron beam welding via a brazing material, and the electronic component is bonded to the insulating base. An electronic device comprising a metal lid hermetically sealed, wherein the insulating substrate has a thermal conductivity at 100 ° C. of 15 W / m · K or less.

According to the electronic device of the present invention, the insulating base material
Since the thermal conductivity at 0 ° C. is as low as 15 W / m · K or less, when the metal lid is electron-beam-welded to the metallized metal layer of the insulating substrate, heat from the electron beam is not easily transmitted to the insulating substrate.

As a result, the insulating substrate does not reach such a high temperature that cracks are generated, and as a result, cracks are effectively prevented from being generated in the insulating substrate due to the thermal shock of the electron beam.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an electronic device according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view showing an example of an embodiment of an electronic device according to the present invention. In FIG.
2 is a metal lid, and 3 is an electronic component.

The insulating base 1 is made of a ceramic such as an aluminum oxide sintered body or an aluminum nitride sintered body, and has a recess A for accommodating the electronic component 3 in the center of the upper surface thereof. The bottom surface of the concave portion A forms a mounting portion 1a for mounting the electronic component 3, and the mounting portion 1a
Has an electronic component 3 mounted thereon.

If the insulating substrate 1 is made of, for example, an aluminum oxide sintered body, an appropriate organic binder and a solvent are added to aluminum oxide and raw material powders of silicon oxide, magnesium oxide, calcium oxide, etc. The ceramic green sheet is formed by adopting a doctor blade method or a calender roll method, which is well known in the art, and thereafter, a plurality of ceramic green sheets are subjected to appropriate punching and laminated at a high temperature. It is manufactured by firing.

Further, a metallized wiring layer 4 made of a sintered metal powder such as tungsten or molybdenum, which extends from the upper surface of the mounting portion 1a to the lower surface of the insulating substrate 1, is formed on the insulating substrate 1.

The metallized wiring layer 4 functions as a conductive path for electrically leading each electrode of the electronic component 3 to the outside. Electrodes of the electronic component 3 are electrically connected to the upper surface of the mounting portion 1a via, for example, a conductive adhesive. The portion of the metallized wiring layer 4 extending to the lower surface of the insulating base 1 is electrically connected to a wiring conductor of an external electric circuit board (not shown) via, for example, solder.

The metallized wiring layer 4 is formed by applying a metal paste obtained by adding a suitable organic binder or solvent to a metal powder such as tungsten to a ceramic green sheet serving as the insulating substrate 1 in a predetermined pattern by a conventionally known screen printing method. By printing and applying this and baking it together with the ceramic green sheet to be the insulating substrate 1, the insulating substrate 1 is attached and led out in a predetermined pattern from the upper surface to the lower surface of the mounting portion 1a.

The metallized wiring layer 4 is preferably provided with a metal having excellent corrosion resistance such as nickel and gold and excellent wettability with solder to a thickness of 1 to 20 μm by plating on the exposed surface. In addition, oxidation corrosion of the metallized wiring layer 4 can be effectively prevented, and the connection between the metallized wiring layer 4 and the wiring conductor of the external electric circuit board can be strengthened. Therefore, it is preferable that a metal having excellent corrosion resistance and excellent wettability with solder, such as nickel and gold, be applied to the surface of the metallized wiring layer 4 to a thickness of 1 to 20 μm by plating.

A frame-shaped metallized metal layer 5 having a width of about 0.4 mm is formed on the outer peripheral portion of the upper surface of the insulating base 1 so as to surround the mounting portion 1a. The metal cover 2 is joined to the metallized metal layer 5 by electron beam welding with a brazing material 6 interposed therebetween.

The metallized metal layer 5 functions as a base metal for joining the metal cover 2 to the insulating base 1 and is made of a sintered metal powder such as tungsten or molybdenum.
The metallized metal layer 5 is formed by adding a metal paste such as tungsten to a suitable organic binder or a solvent and mixing the resulting metal paste on a ceramic green sheet serving as the insulating substrate 1 by a conventionally known screen printing method. A predetermined thickness and a predetermined pattern are printed and applied in advance, and this is
By firing together with the ceramic green sheet to be formed, a frame shape is formed on the upper surface of the insulating substrate 1 so as to surround the mounting portion 1a.

The metallized metal layer 5 is preferably provided with a metal having excellent corrosion resistance, such as nickel or gold, and excellent wettability with the brazing material 6 in a thickness of 1 to 20 μm by plating on the surface thereof. In addition, the metallized metal layer 5 can be effectively prevented from being oxidized and corroded, and the metallized metal layer 5 and the metal lid 2 can be strongly welded to each other through the brazing material 6. Therefore, the metallized metal layer 5
The surface of is coated with a metal having excellent corrosion resistance, such as nickel or gold, and excellent wettability with the brazing material 6 by a plating method of 1 to 20 μm.
m.

The metal lid 2 bonded to the metallized metal layer 5 is made of, for example, an iron-nickel alloy or an iron-nickel alloy.
The insulating base 1 is made of a metal such as a nickel-cobalt alloy or a non-magnetic metal such as titanium or copper / aluminum, and is joined to the metallized metal layer 5 of the insulating base 1.
And the electronic component 3 is hermetically sealed.

The metal lid 2 and the metallized metal layer 5 of the insulating substrate 1 are joined by electron beam welding, for example, by attaching the flat metal lid 2 to the metallized metal layer 5.
After the brazing material 6 is placed and placed on the metal cover 2 and preheated to a temperature of about 100 ° C., an electron beam having a diameter of about 0.1 to 0.2 mm is applied to the upper surface of the metal lid 2 by a magnetic field. Irradiation is performed while moving along the metallized metal layer 5, and the heat by the electron beam is transmitted to the lower surface of the metal lid 2 to melt the brazing material 6.

When the metal cover 2 and the metallized metal layer 5 of the insulating substrate 1 are joined by electron beam welding, preheating to a temperature of about 100 ° C. in advance causes slight thermal shock due to the electron beam. In order to soften it.

When the metal cover 2 is made of a non-magnetic metal, the metal cover 2 is not magnetized by being affected by an external magnetic field or rubbing against an external member. When welding by beam welding, the irradiation position of the electron beam does not shift due to the magnetic force of the metal lid 2, and the upper surface of the metal lid 2 is accurately irradiated with the electron beam and firmly joined. Can be.

In the present invention, the insulating substrate 1
It is important that the thermal conductivity at 100 ° C. is 15 W / m · K or less.

The insulating substrate 1 has a thermal conductivity at 100 ° C.
When the metal lid 2 is joined to the metallized metal layer 5 of the insulating base 1 preheated to about 100 ° C. by electron beam welding, the metal lid 2 is difficult to conduct heat at 15 W / m · K or less. Even when the electron beam is irradiated on the upper surface of the substrate 2, the heat generated by the electron beam is hardly transmitted to the insulating base 1, so that the insulating base 1 does not reach a high temperature at which cracks occur. As a result, it is possible to effectively prevent the occurrence of cracks in the insulating substrate 1 due to the thermal shock of the electron beam, and to make the container including the insulating substrate 1 and the metal lid 2 extremely airtight.
The electronic components 3 housed therein can be operated normally and stably for a long period of time.

Further, since heat is hardly transmitted to the insulating substrate 1 and a large amount of heat energy by the electron beam does not escape to the insulating substrate 1 side, welding is performed by reducing the energy of the electron beam for melting the brazing material 6. be able to.

In order to reduce the thermal conductivity of the insulating substrate 1 at 100 ° C. to 15 W / m · K or less, for example, the following method may be used. Since the higher the purity of the ceramic, the higher the thermal conductivity, the lower the purity, the lower the thermal conductivity. Since the thermal conductivity increases as the crystal grain size of the ceramics increases, the thermal conductivity can be reduced by reducing the size of the raw material particles and suppressing the grain growth by keeping the firing temperature low. The thermal conductivity can be reduced by adding an additive that forms a solid solution in the ceramics, for example, iron oxide or chromium oxide for alumina ceramics. The more voids (voids) in the ceramic, the lower the thermal conductivity.

When the thermal conductivity at 100.degree. C. exceeds 15 W / m.K, the insulating base 1 is placed on the
When the upper surface of the metal lid 2 is irradiated with an electron beam when joining the metallized metal layer 5 of the insulating substrate 1 preheated to a temperature of about 5 ° C. by electron beam welding, a large amount of heat due to the electron beam is transmitted to the insulating substrate 1. As a result, the portion of the insulating substrate 1 corresponding to the position where the electron beam is irradiated becomes extremely hot, and the insulating substrate 1 is liable to crack. Therefore, the thermal conductivity of the insulating substrate 1 at 100 ° C. is specified to be 15 W / m · K or less.

The brazing material 6 disposed between the metal lid 2 and the metallized metal layer 5 is made of a silver-copper alloy or a gold-tin alloy / lead-
Tin alloy, aluminum-silicon alloy, copper-zinc alloy,
It is made of a silver-copper-phosphorus alloy, a silver-indium-tin alloy, or the like, and functions as a bonding material for bonding the metal lid 2 to the metallized metal layer 5. That is, the heat generated by the electron beam applied to the upper surface of the metal lid 2 at the time of joining by the electron beam welding is transmitted to the lower surface of the metal lid 2, and the brazing material 6 is melted by receiving this heat, and The cover 2 is made of the metallized metal layer 5 of the insulating base 1.
To join.

When the brazing material 6 is disposed between the metal lid 2 and the metallized metal layer 5, the brazing material 6 is coated on the lower surface of the metal lid 2 in advance in order to improve the workability of the arrangement. It is preferable to keep it on.

Thus, according to the electronic device of the present invention, an electronic device in which the electronic component 3 is housed with high hermetic reliability inside the container including the insulating base 1 and the metal lid 2 can be obtained.

[0040]

EXAMPLE As an insulating substrate, an alumina raw material powder having an average particle size of 2 μm and a sintering aid composed of silicon oxide, magnesium oxide and calcium oxide were used. As shown in Table 1, the purity of alumina was 91 to 93%. Chromium oxide was added in the range of 0.5 to 3% by weight and calcined at a temperature of 1600 ° C. to make the thermal conductivity at 100 ° C. different, 3 mm long × 2 mm wide. × An insulating substrate made of an aluminum oxide sintered body having a thickness of 0.5 mm was prepared. A frame-shaped tungsten metallized metal layer having a width of 0.4 mm and a thickness of 10 μm whose outer periphery coincides with the outer periphery of the insulating substrate is formed on the outer peripheral portion of the upper surface of the insulating substrate, and a nickel plating layer is electrolytically plated on the metallized metal layer. 25 samples were prepared for each sample.

Next, a silver solder having a thickness of 10 μm was clad on the lower surface of each of these samples in a vacuum to a length of 3 mm.
A metal lid made of an iron-nickel-cobalt alloy having a width of 2 mm and a thickness of 0.1 mm is placed and preheated to a temperature of about 100 ° C., and then 4 mA · 120 W is applied to the upper surface of the metal lid. An electron beam having a diameter of 0.2 mm was irradiated at a speed of 250 mm / sec while moving along the metallized metal layer at an output of, and the metal lid was electron-beam welded to the metallized metal layer via a silver solder.

Thereafter, the metal lids bonded to these samples were dissolved and removed with nitric acid, and the presence or absence of cracks in the insulating substrate was visually inspected.

Table 1 shows the results. In Table 1, Sample No. 1 is a comparative example for comparison with the present invention, and is a sample outside the scope of the present invention.

[0044]

[Table 1]

As shown in Table 1, for samples Nos. 2 to 6 having a thermal conductivity at 100 ° C. of 15 W / m · K or less within the range of the present invention, no cracks were found on the insulating substrate. I couldn't. On the other hand, cracks were observed in all of the samples of Sample No. 1 which is a comparative example outside the scope of the present invention.

The present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the scope of the present invention.

[0047]

According to the electronic device of the present invention, the insulating substrate
Since the thermal conductivity at 100 ° C. is as low as 15 W / m · K or less, when the metal lid is joined to the metallized metal layer of the insulating substrate by electron beam welding, heat from the electron beam is not easily transmitted to the insulating substrate. As a result, the insulating substrate is not heated to such a high temperature as to cause cracks, and as a result, cracks are effectively prevented from being generated in the insulating substrate due to the thermal shock of the electron beam. The electronic components hermetically housed inside the container can be normally and stably operated for a long period of time.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of an embodiment of an electronic device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Insulating base 1a ... Mounting part 2 ... Metal lid 3 ... Electronic parts 5 Metallized metal layer 6 ... Brazing material

Claims (1)

[Claims] An insulating substrate having a mounting portion on which an electronic component is mounted on an upper surface, a frame-shaped metallized metal layer attached so as to surround the mounting portion, and mounted on the mounting portion of the insulating substrate. The electronic component and a metal lid that is joined to the metallized metal layer of the insulating base by electron beam welding via a brazing material and hermetically seals the electronic component with the insulating base. An electronic device comprising: an insulating substrate having a thermal conductivity of 15 at 100 ° C.
An electronic device having a W / m · K or less.