JPH06236937A - Package for microwave semiconductor device - Google Patents

Abstract

PURPOSE:To transmit a microwave signal without its loss and to attenuate an inessential signal by a method wherein short stubs in the specific length of respective microwave-signal wavelengths are installed at individual end parts of input/output terminals. CONSTITUTION:A die area 7 on which a chip 4 is mounted is formed in nearly the central part of a ceramic substrate 2, and a grounding pare 8 which comes into continuity with the die area 7 is installed on its rear part. Lead frames 9 are connected to the grounding plate 8 via short stubs 1 whose length is nearly (2n+1)/4 times as long as a microwave-signal wavelength to be used, and static electricity or the like which is input from outer lead wires 10 is discharged by the grounding plate 8 via the short stubs 1. Thereby, it is possible to prevent the semiconductor chip 4 at the inside from being destroyed, and it is possible to reduce the noise of a microwave semiconductor device after the chip 4 has been mounted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monolithic microwave integrated circuit.
t, hereinafter abbreviated as MMIC), etc., for the structure of a package for mounting a microwave semiconductor device.

[0002]

2. Description of the Related Art In recent years, packages intended for mounting semiconductor device chips in the microwave band (hereinafter simply referred to as "chips") have been developed in terms of material and structure in view of high integration, multi-functionality and high speed of chips. Is undergoing a major transformation.

In terms of materials, for example, in consideration of heat generation of the chip, a ceramic material such as SiC or AlN having excellent heat dissipation and thermal conductivity and a coefficient of thermal expansion almost the same as that of the chip material is used. The structure is also such that, for example, in the case of a flat package, a plurality of lead wires made of a high-conductivity thin film brazed around a small thin plate having a substantially square shape have a substantially uniform length with respect to the central chip. In some cases, the impedance matching is facilitated and the transmission loss is reduced.

As a more general structure, input / output terminals designed to have impedance matching in a wide band from direct current to high frequency and to reduce transmission loss are formed on a ceramic surface. Then, wiring between these input / output terminals and each part of the chip or external terminals allows the microwave signal to propagate through an electronic circuit including the chip.

[0005]

As described above, the conventional package is designed to have a structure that can be used in a wide band, and therefore, the microwave semiconductor device having the chip mounted thereon cannot be mounted on another mother board or the like. When static electricity is accumulated in the wiring members of the motherboard or other electronic components that make electrical connection when connecting with other electronic components, the static electricity is introduced into the package through the lead wires, and the package concerned There was a problem that the chip inside was electrostatically destroyed.

The present invention has been made in view of the above problems, and an object thereof is to provide a microwave semiconductor device package having a structure for protecting an internal chip from electrostatic breakdown.

[0007]

The structure of the present invention for achieving the above object is a microwave semiconductor device package having an input / output terminal through which a microwave signal propagates. It is characterized in that a short stub having a length of approximately (2n + 1) / 4 times (n is an integer) the microwave signal wavelength is provided.

According to another structure of the present invention, a microwave semiconductor device chip is formed in a flat plate shape in a substantially central portion thereof, and a lead frame for electrically connecting the chip and an external lead wire is formed on a back surface portion thereof. In the microwave semiconductor device package, a short stub having a length of approximately (2n + 1) / 4 times (n is an integer) the microwave signal wavelength to be used is provided at the tip of the lead frame.

In each of the above structures, the grounding destination of the short stub is the ground potential, and is the die area for mounting the chip or a predetermined metal pattern electrically connected to the die area.

[0010]

[Function] The short stub is one of the transmission lines connected in the middle of one transmission line whose load end is short-circuited, and the length to the load end is the wavelength of the used microwave signal ( When it is 2n + 1) / 4 times (n is an integer), the impedance seen from the connection point is infinite, that is, it is in an open state (see Japan Packaging and Publishing Association, "Design and Implementation of High Frequency Circuits", p43-p47). ). Therefore, if a short stub having such a length is provided at the input / output terminals, it becomes difficult for the microwave signal of the frequency to be transmitted to the short stub, so that there is almost no transmission loss and impedance matching is easy. Become. On the other hand, for a signal of a component other than the frequency, the impedance seen from the connection point has a predetermined value. Therefore, the signal of the unnecessary frequency is attenuated by this short stub and the transmission signal is filtered.

Further, if the package has a flat plate shape, it is not necessary to prepare a special space for the short stub, although it depends on the operating frequency, and in terms of performance, the ground potential of the die area is small. Since the filter is designed to be extremely stable, stable filter performance can be obtained.

When the grounding destination of the short stub is a die area of ground potential or a predetermined metal pattern,
There is no accumulation of static electricity and it does not affect the chips inside the package.

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1A is a side sectional view of a flat package according to an embodiment of the present invention, and FIG. 1B is a rear view. In the figure, 1 is a short stub, 2 is a ceramic substrate, 3 is a cap, 4 is a chip, 5 is an internal lead wire, 6 is a lead terminal, 7 is a die area, 8 is a ground plate, 9 is a lead frame, and 10 is an outside. Represents a lead wire.

The short stub 1 has a length of a wavelength which is ¼ times that of the microwave signal used, and one end thereof is electrically connected to the ground plate 8 and the other end thereof is electrically connected to the lead frame 9. . Further, the lead frame 9 is electrically connected to the external lead wire 10 and the internal lead wire 5 via the lead terminal 6 and the conductive member.

As the ceramic substrate 2, an alumina flat plate having a thickness of 400 μm is used, and holes (via holes) for penetrating a conductive member are formed at the locations where the die area 7 and the lead terminals 6 are formed. .

The die area 7 mounts the chip 4 at the time of mounting and is electrically connected to the ground plate 8 via a conductive member. The ground plate 8 may have a rectangular shape as shown, a grid pattern for shielding the die area 7, or another metal pattern.

In the flat package having this structure,
The impedance when the ground plate 8 is viewed from the point A in FIG. 1A exhibits infinity for the used frequency component and a predetermined value for the other signal components determined by the frequency of the signal. That is, regarding the used frequency component of the microwave signal guided from the external lead wire 10, the short stub 1
Since it is not propagated toward, there is almost no transmission loss and impedance matching is ensured. On the other hand, a signal having a component other than the frequency, for example, a noise component or static electricity is attenuated by the short stub 1, so that the transmission signal is filtered. At the same time, this signal is discharged at the ground plate 8. Therefore, components such as static electricity and noise do not propagate to the internal lead wires 5, so that the chips 4 are not affected and electrostatic breakdown is prevented.

FIG. 2 is a characteristic test equivalent circuit diagram of the microwave semiconductor device package according to the present embodiment. The negative terminal of the 50 Ω pure resistance signal source 20 is connected to the ground line AGROUND, and 12 [V] from the positive terminal. GHZ] microwave signal to the input terminal of the microstrip line 21. The output of the microstrip line 21 is branched into two via a point A, one of which is guided to the positive terminal of the measuring instrument 22 and the other of which is guided to the input terminal of the short stub 23. Measuring instrument 2
Reference numeral 2 is a 50Ω pure resistance measuring instrument, and its negative terminal and the output terminal of the short stub 23 are ground line AGROUND, respectively.
It is connected to the.

The microstrip line 21 and the short stub 23 are formed on an alumina substrate having a thickness of 40 μm and have a relative permittivity εr 9.6 and a conductance 4.1E.
It consists of a dielectric thin film of 7 and the former is 1000 [μm] long
And the width is 400 [μm] and the latter is 2500 [μm]
And the width is 400 [μm]. The thickness of each dielectric film is 8 [μm].

With this configuration, S-parameter characteristics and VSWR
When the (standing wave ratio) transition was measured, the results are shown in FIGS.
A filter characteristic diagram such as is obtained. The vertical axis of FIG. 3A is S21 (output side impedance), which is shown as a dB value when the maximum value is 0. The vertical axis of FIG. 3B indicates the voltage standing wave ratio VSWR on the signal source 21 side of FIG.
It is 1.

Referring to these figures, S21 is the maximum at the use frequency 12 [GHZ], and its value is-.
It was 0.018 dB. Also, VSWR1 at this time
Was the minimum and its value was 1.033. In addition, V
The value of SWR1 can be obtained by the following equation when the input impedance is S11.

[0023]

[Equation 1]

Thus, the operating frequency (12 [GHZ
]), Since the presence of the short stub 23 can be ignored, the microwave signal can be transmitted with almost no loss in the used frequency, and the impedance matching can be realized. On the other hand, since signals of frequencies other than that are filtered, noise reduction of the microwave semiconductor device after chip mounting can be achieved.

Further, in the package having the structure shown in FIG. 1, it is not necessary to prepare a special space for the short stub 1, so that the present invention can be implemented by a slight design change of the existing package. Moreover, in this type of package, the ground potential of the die area 7 is usually designed to be extremely stable, so that a stable filter performance can be obtained.

In this embodiment, the example of the flat package has been described, but the present invention can be similarly applied to other flat-plate packages such as a pin grid array package and a chip carrier, and the above effects can be obtained. . Further, the length of the short stub 1 (23) may be substantially the impedance (2n + 1) of the wavelength of the microwave signal to be used because the impedance viewed from the point A in FIG.
/ 4 times (n is an integer).

Further, the present invention can be applied to a package having an input / output terminal which is intended for wide band use. In this case, by providing the short stub 1 (23) at each end, the filter effect is obtained and impedance matching is facilitated.

[0028]

As described in detail above, according to the present invention, at each end of the input / output terminal through which the microwave signal propagates,
Since short stubs each having a length of approximately (2n + 1) / 4 times the microwave signal wavelength (n is an integer) are provided, the frequency of the microwave signal to be used can be transmitted with almost no loss, but static electricity or the like is unnecessary. The signal is attenuated or discharged by the short stub, and it is difficult to transmit the signal inside the package. As a result, destruction of the internal semiconductor chip is prevented, and the conventional problems are solved.

According to the present invention, the microwave semiconductor device chip is mounted in a substantially flat shape in the central portion thereof, and a lead frame for conducting the chip and the external lead wire is formed on the back surface portion of the microwave. In the package for the wave semiconductor device, the above-mentioned short stub is provided at the tip of the lead frame, so that the above-mentioned effect becomes more remarkable and the amount of design change of the conventional structure becomes smaller than that in the case of the above-mentioned structure.

By setting the grounding destination of the short stub to a die area having a ground potential or a predetermined metal pattern electrically connected to the die area, an unnecessary signal is immediately discharged, and the characteristics of the filter are improved. In addition to being stable, there is an effect that noise of the microwave semiconductor device after chip mounting is reduced.

[Brief description of drawings]

1A is a side sectional view of a flat package according to an embodiment of the present invention, and FIG. 1B is a rear view thereof.

FIG. 2 is a diagram showing an equivalent circuit of a characteristic test of the flat package of the present embodiment.

FIG. 3A is a S-parameter characteristic obtained by the above test, and FIG. 3B is a diagram showing VSWR transition.

[Explanation of symbols]

1 ... Short stub, 2 ... Ceramic substrate, 3 ... Cap, 4 ... Chip (microwave semiconductor device chip), 5 ...
Internal lead wire, 6 ... Lead terminal, 7 ... Die area, 8 ...
Ground plate (predetermined metal pattern), 9 ... Lead frame,
10 ... External lead wire.

Claims (3)

[Claims] 1. A package for a microwave semiconductor device having an input / output terminal through which a microwave signal propagates, wherein each end of the input / output terminal has approximately (2n + 1) / 4 times (n) the wavelength of the microwave signal. Is a short stub whose length is an integer). 2. A microwave semiconductor device having a flat plate-like shape on which a microwave semiconductor device chip is mounted, and a lead frame for electrically connecting the chip and an external lead wire is formed on a back surface of the plate. A package for a microwave semiconductor device, wherein a short stub having a length of approximately (2n + 1) / 4 times (n is an integer) the wavelength of the microwave signal used is provided at the tip of the lead frame. 3. The grounding destination of the short stub is a ground potential and is a die area for mounting the chip or a predetermined metal pattern electrically connected to the die area. Item 3. The microwave semiconductor device package according to Item 1 or 2.