JPS60254753A - Mounting package of eprom chip - Google Patents

Abstract

PURPOSE:To improve heat resistance and moisture resistance, by coating EPROM chips, which are mounted on a ceramic wiring substrate with a metal cap comprising sapphire having a window in an airtight manner. CONSTITUTION:A metallized layer 8, which is formed by burning molybdenum, tungsten paste or the like, and a nickel and gold plated layer 9 are laminated and formed sequentially at the peripheral part of a ceramic wiring substrate 6 so as to surround mounting parts of EPROM chips 7. On the nickel and gold plated layer 9, a cap 11 made of Cobal, which comprises a thin plate 10 of sapphire and has ultraviolet-ray transmitting window, is bonded by solder 12 in an airtight manner. As the metallic cap, sapphire and the metal, whose thermal expansion coefficient is approximately equal to that of the ceramic substrate, are used. Therefore, moisture resistance and resistance against heat shock can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a package in which an EPROM chip is mounted on a ceramic wiring board.

[Technical background of the invention and its problems J] [A FROM chip mounting package is constructed by covering the EPROM hermetically with an ultraviolet-transparent glass plate in order to erase the written memory data by irradiating it with ultraviolet rays. ing.

FIG. 2 shows such a conventional EPROM mounting package, in which a ceramic ring 3 is bonded with an adhesive 4 on a ceramic wiring board 2 on which an EPROM chip 1 is mounted, and an ultraviolet transmitting glass 5 is bonded on top of the ceramic ring 3. It is configured by adhering with agent 4.

Note that as the adhesive 4, an organic adhesive such as an epoxy resin is generally used.

By the way, organic adhesives such as epoxy 1, which have been conventionally used to bond the ceramic ring 3 and the ultraviolet-transmissive glass 5, are not completely airtight, so the package constructed in this way is moisture resistant. There was a drawback of lack of sex.

In addition, such adhesives have a large difference in thermal expansion coefficient from glass and ceramics, so the usable temperature is 70°C or higher.
There was also the drawback that it was limited to about 0.

Therefore, the conventional EPROM chip package is
For example, MI, which requires even stricter moisture resistance and temperature characteristics.
It was impossible to satisfy L standards and the like.

[Object of the Invention] The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide an EPROM chip mounting package that has dramatically improved heat resistance and moisture resistance.

[Summary of the invention] That is, the EPROM chip mounting package of the present invention has the following features:
It is characterized in that an EPROM chip mounted on a ceramic wiring board is hermetically covered with a metal cap having a window made of sapphire.

[Embodiment of the Invention] FIG. 1 is a cross-sectional view of an embodiment of an EPROM chip mounting package of the present invention.

In FIG. 1, a plurality of EPROM chips 7 are mounted on a ceramic wiring board 6. As shown in FIG.

On the periphery of the ceramic wiring board 6, a metallized layer 8 made of molybdenum or tungsten paste, etc., and a nickel and gold plating layer 9 are laminated in order surrounding the EPROM depth 7 mounting area.

On this nickel and gold plating layer 9, a cap 11 made of Kovar and having an ultraviolet transmitting window made of a thin sapphire plate 10 is hermetically bonded with solder 12.

In addition, the Kovar cap 11 and the ceramic wiring board 6
The bonding may be performed by first silver-brazing the Kovar weld ring onto the ceramic wiring board 6 using the method described above, and then laser welding the Kovar cap 11 thereon.

The thin sapphire plate 10 described above has a punched hole in the center of the Kovar cap 11 and its peripheral edge is recessed.
It is fixed to the Ricovar cap 11 by joining this concave portion.

To join the Kovar cap 11 and the sapphire thin plate 10, a metallized layer made of tungsten paste or the like and a nickel plating layer are formed in advance on the periphery of the sapphire thin plate 10 in this order, and then the sapphire thin plate 10 is connected to a punched hole in the Kovar cap 11. This is done by placing it on the concave part and attaching silver solder 13 to it.

Note that, as shown in this embodiment, resistance to heat shock is improved by using a metal cap such as Kovar, which has approximately the same coefficient of thermal expansion as the sapphire or ceramic substrate.

In the embodiment shown in FIG. 1, an example was explained in which an ultraviolet transmitting window made of one large thin sapphire plate 10 was provided on the upper center surface of the cap 11 made of Kovar, but the present invention is not limited to such an embodiment. each EP, not the
A plurality of sapphire windows may be formed corresponding to the ROM.

FIG. 3, in which parts common to those in FIG. 1 are given the same reference numerals, shows such an embodiment.
A punching hole large enough to irradiate each EPROM chip 7 with ultraviolet rays is provided on the top surface of each EPROM chip 7, and a thin sapphire plate 10 is inserted into each of the punching holes, similar to the embodiment shown in FIG. This is an example of an airtight joint.

For example, in a package in which a large number of EPROM chips are mounted two in close proximity, the EPROM
The number of sapphire windows may be changed as appropriate, such as providing one sapphire cap for two chips.

In this way, one of the ultraviolet transmitting windows made of a thin sapphire plate
When the size of the particles is reduced, resistance to heat shock is further improved.

[Effects of the Invention] As explained above, in the EPROM chip mounting package of the present invention, the ultraviolet transmitting window is formed of sapphire that can be soldered with silver, so that heat resistance and moisture resistance can be significantly improved. Furthermore, since sapphire has a small difference in coefficient of thermal expansion from ceramic or Kovar, it has significantly improved resistance to heat shock. In particular, when the metal cap is made of C or Kovar, which has a coefficient of thermal expansion almost equal to that of sapphire, reliability against heat shock can be sufficiently maintained in the temperature range of -55°C to +150°C.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an embodiment of an EPROM chip-mounted package of the present invention, FIG. 2 is a cross-sectional view of a conventional EPROM chip-mounted package, and FIG. 3 is a cross-sectional view of an EPROM chip-mounted package of another embodiment of the present invention. FIG. 1.7... EPROM chip 2.6... Ceramic wiring board 4...
...Adhesive 8...Metalized layer 9...
...Nickel and gold plating layer 10...
・・・・・・Sapphire thin plate 11・・・・・・・・・
・・・Kobar Cap Representative Patent Attorney Sa Suyama - Figure 3

Claims (3)

[Claims] (1) An EPROM chip mounting package characterized in that an EPROM chip mounted on a ceramic wiring board is hermetically covered with a metal cap having a window made of sapphire. (2) The EPROM chip mounting package according to claim 1, wherein the metal cap is made of Kovar. (3) The window made of sapphire is constructed by sequentially forming a metallized layer and a nickel plating layer around the punched hole in the Kovar cap, and then silver-brazing a thin plate of sapphire onto the vine plating layer. An EPROM chip mounting package according to claim 1 or 2.