Package for microwave IC

Abstract: A microwave IC package comprises a base (1) and a plurality of cavities (2a) and (2b) for mounting IC chips (5a) and (5b), the cavities (2a) and (2b) being formed on the base (1). Also provided on the base (1) are terminals (4a), (4b), (8a), (8b) and (8c) which are connected to said IC chips by wire bonding. The cavities (2a) and (2b) are separated from each other by a grounded conductor (3A). Due to the separation, isolation between the input and the output of the IC package is improved.

Description: Field of the Invention The present invention relates to a package for a semiconductor integrated circuit, for example, which operates in a high-frequency band of several tens MHz or over. Description of the Prior Art Fig. 4A is a plan view showing a conventional metal base type package while Fig. 48 is a sectional view taken along the line C - C of Fig. 4A. Referring to Figs. 4A and 4B, in a microwave IC package 30, space 2 for mounting IC chip (referred to as "cavity" hereinafter) is provided on a metal base 1 while a metal ring 3 for shielding is fixed through a mount 3a of insulating material to the metal base 1, surrounding the cavity 2. On the right and left sides of the cavity 2, microstrip-shaped feedthroughs 4a, 4b are formed. The feedthroughs 4a, 4b are formed by patterning a conductor, such as gold and the like, to form microstrip lines on dielectrics of ceramic or the like, and they extend from opposite ends of the metal base 1 under the mount 3a until they reach the cavity 2. The feedthrough 4a is used as an RF terminal for input while the feedthrough 4b is used as an RF terminal for output. Similarly, on a dielectric of ceramic or the like DC terminals 8a, 8b, 8c are formed by patterning a conductive material, such as gold and the like, in the direction orthogonal to the shaft line of the feedthroughs 4a, 4b. A single or a plurality of high-frequency IC chips are attached to the cavity 2; Fig. 5 shows an example when two high-frequency IC chips are mounted. In this example, high-frequency IC chips 5a, 5b are fixed on the cavity 2 by means of soldering, using adhesive agent or the like, and connected with each other by wire 9 while each of them is connected to the feedthroughs 4a, 4b and the DC terminals 8a, 8b, 8c in the similar way. For those connections, ribbon bond or the like may be employed instead of the wire bond. In a configuration of the above-mentioned microwave IC package, since the feedthrough 4a for input and the feedthrough 4b for output are opposite to each other and close to each other with the cavity 2 interposed therebetween, part of an input signal from the feedthrough 4a for input may leak immediately to the feedthrough 4b for output without passing to the high-frequency IC chips 5a, 5b; hence, there is the disadvantage that isolation between the input and output of the package 30 deteriorates and an excellent switching device cannot be obtained. US-A-4868639 discloses a microwave IC package which has a base and a plurality of cavities on the base for mounting IC chips, a conductor on the base partitioning off the cavities, and a terminal on the base, connected to the chips. The purpose of the disclosed arrangement is to reduce cost by eliminating soldering. US-A-4901041 discloses a microwave IC package comprising a low-pass filter, with a housing connected to ground. An object of the present invention is to provide a microwave IC package which, in a simple configuration, effects good isolation between input and output terminals. According to the present invention there is provided a microwave IC package as specified in Claim 1. Preferred embodiments are set out in the dependent claims. In a microwave IC package of the present invention, provided with a shield of at least one ground conductor or one dielectric having a plurality of throughholes between feedthroughs for input and output, isolation between the input and the output is greatly improved; therefore, an input signal from an input terminal never leaks immediately to an output terminal, and thus, an excellent switching device can be obtained. These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings, in which Fig. 1A is a plan view showing a preferred embodiment of a microwave IC package according to the present invention while Fig. 1B is a sectional view along the line A - A of Fig. 1A; Fig. 2 is a plan view of the microwave IC package of Fig. 1A with a high-frequency IC chip packaged therein; Fig. 3A is a plan view of another preferred embodiment of the microwave IC package according to the present invention while Fig. 3B is a sectional view along the line B - B of Fig. 3A; Fig. 4A is a plan view showing a conventional microwave IC package while Fig. 4A; and Fig. 5 is a plan view showing the conventional microwave IC package with a high-frequency IC chip packaged therein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Now, preferred embodiments according to the present invention will be described with reference to the accompanying drawings. Fig. 1A is a plan view showing a first preferred embodiment of a microwave IC package according to the present invention while Fig. 1B is a sectional view along the line A - A of Fig. 1A. Since like reference numerals denote corresponding parts to those in Figs. 4 and 5, the explanation on them is omitted. A microwave IC package in this embodiment is formed of components almost identical with those for a conventional package 30. A cavity includes separate cavities 2a and 2b. A metal ring 3 has a partition 3A in the center portion for shielding the cavities 2a and 2b from each other, and the metal ring 3 is fixed through a ceramic mount 3a to a metal base 1. Between the cavities 2a and 2b, a feedthrough 4c is formed extending under the mount 3a. Fig. 2 is a plan view showing the microwave IC package shown in Fig. 1A with high-frequency IC chips attached therein. Two high-frequency IC chips 5a and 5b are fixed to the cavities 2a and 2b, respectively, by means of soldering, using adhesive agent or the like, and they are connected to feedthroughs 4a, 4b, 4c and DC terminals 8a, 8b, 8c by wire 9. For such connections, ribbon bonding or other means may be employed instead of the wire bond. The metal ring 3 is connected to the DC terminal 8a by wire 9a. When the package is attached to another device, the DC terminal 8a is connected to a ground circuit of the device. In this embodiment, there are two separate cavities and the ground conductor 3A intervenes between them; hence, isolation between the feedthrough 4a for input and the feedthrough 4b for output is extremely improved. While a metal-base and metal-ring type package has been explained in the above first embodiment, another (second) preferred embodiment employing a multi-stratum dielectric package will be explained. Fig. 3A is a plan view showing a microwave IC package of the second preferred embodiment while Fig. 3B is a sectional view along the line B - B of Fig. 3A. In Figs. 3A and 3B, a microwave IC package 20 has dielectric layers 6a, 6b, 6c overlaid with one another in the order from the uppermost on a metal base 1, and two portions of the lowermost layer 6c define cavity 2a' or 2b' in their respective exposed surfaces which are obtained by opening the dielectric layer 6b . The dielectric layer 6a is formed around the cavities 2a' and 2b' so that it separates these two cavities from each other. In this embodiment, there is not particularly provided any feedthrough, but microstrip lines 22a , 22b, 22c are formed by patterning gold, for example, to form microsrips directly on the dielectric layers 6b. One of the microstrip lines 22a and 22b formed on the surface of the exposed dielectric layer 6b serves as an input terminal, and the other serves as an output terminal. A plurality of throughholes 7 are provided for each of dielectric layers 6a, 6b, 6c so that the surround each of the cavities 2a' and 2b' . More specifically, the plurality of throughholes 7 are provided at the portion which separates the cavities 2a' and 2b' from each other. This structure assures a shielding effect. In this way, in the second embodiment, there are two separate cavities in a multi-stratum dielectric type package while a dielectric partition with a plurality of throughholes is formed between them; therefore, RF terminals for input and output are shielded from each other, and there is an effect that isolation between the input and the output is extremely improved similar to the first embodiment. Furthermore, while a metal package base is employed in the second embodiment similar to the first embodiment, a package base may be formed of dielectric material and the whole package may be structured of dielectric layers to obtain the similar effect. While an example in which two separate cavities are provided has been described in the previously mentioned first and second preferred embodiments, there may be provided three or more cavities which are all divided by partitions of ground conductors or dielectrics with throughholes; and naturally, isolation between the input and output is further increased. While the invention has been shown and described in detail, the foregoing description is in all aspects illustrative and not restrictive.

Claims: A microwave IC package, comprising: a base (1) having a plurality of sites (2a, 2b; 2a', 2b') provided on a main surface thereof for mounting IC chips; an input terminal (4a; 22a) provided on said main surface of said base (1) and connected to at least one first chip mounted on at least one first site of said plurality; an output terminal (4b; 22b) provided on said main surface of said base (1) and connected to at least one second chip mounted on at least one second site of said plurality of sites; and shielding means (3A; 6a, 7) provided on the said base (1), between the said first and second sites; characterized in that said sites are cavities on said base, said input terminal (4a; 22a), said first cavity (2a; 2a'), said second cavity (2b; 2b'), and said output terminal (4b; 22b) are aligned in series, and electrical connecting means (4c; 22c) on the base interconnect the chips at the first and second cavities and extend past the shielding means. A microwave IC package in accordance with claim 1, wherein said shielding means includes a ground conductor (3A) provided on a dielectric (3a) between said first and second cavities (2a, 2b). A microwave IC package in accordance with claim 2, further comprising a metal ring (3) disposed on an insulating stand (3a) which is provided on said input terminal (4a) and said output terminal (4b), for being electrically insulated from said input terminal (4a) and said output terminal (4b) and surrounding said plurality of cavities (2a, 2b), wherein said ground conductor (3A) is formed as a unity with said metal ring (3). A microwave IC package in accordance with claim 1, wherein said base is metal and said shielding means comprises a dielectric (6a) provided on said main surface of said base, said dielectric (6a) partitioning off said first and second cavities (2a', 2b') and having a number of throughholes (7), which are helpful to attain a shielding effect. A microwave IC package in accordance with claim 4, further comprising: at least two dielectric layers (6b, 6c) provided between said dielectric (6a) and said base, wherein the upper of said dielectric layers (6b) has a plurality of openings to form said plurality of cavities (2a', 2b'). A microwave IC package in accordance with claim 5, wherein said input terminal (22a) and said output terminal (22b) are formed on an exposed portion of said dielectric layer (6b) having said plurality of openings. A microwave IC package in accordance with claim 4, wherein said dielectric (6a) includes a dielectric layer (6a) provided so as to surround said plurality of cavities (2a', 2b') individually, said dielectric layer (6a) having said throughholes (7) arranged so as to surround said plurality of cavities (2a', 2b') individually.

Inventors: KATOH TAKAYUKI, KATOH, TAKAYUKI, Katoh, Takayuki, c/o Mitsubishi Denki K.K.
Applicants: MITSUBISHI ELECTRIC CORP, MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1991
Main classification: H01L23
IPC codes: H01P3, H01L23, H01L25, H01P1