JP2001102471A - High-frequency semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To diminish a difference in characteristic impedance of a line conductor of a high-frequency semiconductor element after sealing with a metallic lid from that before the sealing in a high-frequency semiconductor device. SOLUTION: The high-frequency semiconductor device is provided with a substrate 11 comprising a mounting 11a for a high-frequency semiconductor element 13 on its upper plane, the high-frequency semiconductor element 13 mounted on the substrate 11a and comprising a line conductor 14, a frame body 12 junctioned with the substrate 11 for surrounding the mount part 11a, a high-frequency input and output part 15 arranged so as to penetrate the frame body 12, and a lid 20 junctioned with the upper surface of the frame body 12. As for the lid 20, upper surface earth conductors 22 are formed on the upper surface of a dielectric plate 21, and lower surface earth conductors 23 are formed on the lower surface except a part 24 which faces to the line conductor 14 of the high-frequency semiconductor element 13. Also, through conductors 15 for passing the conductor 22 and 23 there through are arranged inside the device. A characteristic impedance of the line conductor after sealing can be restrained from changing and a difference in a high-frequency characteristic can be diminished.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency semiconductor device used for communication equipment or sensors using microwaves or millimeter waves.

[0002]

2. Description of the Related Art Conventionally, an electronic component such as a high-frequency semiconductor circuit operating in a microwave or millimeter-wave band has a circuit mounted inside a housing of a high-frequency package having a housing made of a dielectric material such as metal or ceramic. From the viewpoint of physical or electrical protection, the housing opening is sealed with a metal lid by brazing or the like, so that it is configured as a high-frequency semiconductor device that can be put to practical use.

As a form of such a high-frequency semiconductor device, for example, as shown in an exploded perspective view in FIG. 5, a high-frequency semiconductor element is provided inside a high-frequency package housing 1 having a metal housing 1 as a high-frequency semiconductor element. A ground conductor is provided on the lower surface, and a semiconductor circuit board 2 having a wiring portion on the upper surface is accommodated by joining the solder by soldering or the like. Are connected by a gold wire 5 or the like, and a metal lid 6 made of an iron-nickel-cobalt alloy or the like is sealed by brazing to an opening of the housing 1 in general.

[0004]

However, in the above-described high-frequency semiconductor device, the distance between the line conductor 3 and the metal cover 6 in the wiring portion on the upper surface of the semiconductor circuit is determined as the state after sealing. 1, the wall of the housing 1 is usually designed to be as low as possible in order to suppress unnecessary resonance in the internal space of the housing 1.
And the metal lid 6 as the upper ground conductor, the impedance of the line conductor 3 differs between the state in which the upper space is open and the state after the sealing. As a result, there is a problem that desired high-frequency characteristics cannot be obtained.

The present invention has been made in view of the above-mentioned problems in the prior art, and has as its object to improve the impedance characteristics of a line conductor of a high-frequency semiconductor element in a sealed state so that the sealed state and the upper space can be improved. It is an object of the present invention to provide a high-frequency semiconductor device capable of reducing a difference in high-frequency characteristics from a state in which is opened.

[0006]

According to the present invention, there is provided a high-frequency semiconductor device comprising: a substrate having a mounting portion for a high-frequency semiconductor element on an upper surface; a high-frequency semiconductor element having a line conductor mounted on the mounting portion; A frame joined on the substrate so as to surround the mounting portion, a high-frequency input / output section provided through the frame, and a lid joined to an upper surface of the frame. In this lid, an upper surface ground conductor is formed on the upper surface of the dielectric plate, and a lower surface ground conductor is formed on the lower surface except for a portion facing the line conductor of the high frequency semiconductor element, and the upper surface ground conductor is formed inside. A through conductor for conducting between a conductor and the lower surface ground conductor is provided.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to a high-frequency semiconductor device of the present invention, a substrate having a mounting portion for mounting a high-frequency semiconductor element on an upper surface, and a frame joined to the substrate so as to surround the mounting portion And a high-frequency input / output unit provided through the frame, and a lid joined to the upper surface of the frame to seal a housing composed of the substrate and the frame. In the semiconductor device, the lid body is formed with an upper surface having a ground conductor formed on the entire surface, a lower surface ground conductor formed in a range except a portion opposed to the line conductor of the high-frequency semiconductor element, and the upper and lower surfaces of the inside are grounded. By using a dielectric plate in which a through conductor such as a via conductor formed in the area where the conductor exists is disposed, the line conductor of the high-frequency semiconductor element is suppressed while suppressing an increase in the volume inside the housing. Upper ground conductor ( In this it is possible to increase the distance to the top ground conductor). Therefore, in order to suppress unnecessary resonance in the internal space of the housing, the housing wall is usually designed to be as low as possible, and in a conventional high-frequency semiconductor device, a metal lid which is a line conductor and an upper ground conductor in a state after sealing is used. And the impedance of the line conductor of the high-frequency semiconductor element is different between the state in which the upper space is opened and the state after sealing, respectively, compared with the case where the impedance of the line conductor of the high-frequency semiconductor element is different. High frequency characteristics can be improved by suppressing fluctuations in the impedance of the conductor. As a result, the difference in characteristics between the sealed state and the state in which the upper space is opened can be reduced, so that the high-frequency semiconductor device can guarantee the characteristics of the high-frequency semiconductor element alone even after sealing.

Hereinafter, the present invention will be described in detail with reference to the drawings. It should be noted that the present invention is not limited to the following examples, and changes and improvements may be made without departing from the gist of the present invention.

FIG. 1 is an exploded perspective view showing a part of a high-frequency semiconductor device according to an embodiment of the present invention.
FIG. 2 is a sectional view taken along line AA ′ in FIG.

In these figures, 11 is a substrate made of metal, 11a is a mounting portion of the high frequency semiconductor element 13 provided on the upper surface of the substrate 11, and 12 is bonded on the substrate 11 so as to surround the mounting portion 11a. It is a frame made of metal.
The frame 12 constitutes a housing made of metal. Reference numeral 13 denotes a high-frequency semiconductor element having a line conductor 14, and here, a ground conductor (not shown) is provided on the lower surface of the semiconductor circuit board 13a.
Shows the case where the line conductor 14 is formed on the upper surface.

Reference numeral 15 denotes a notch 12a formed on the side wall of the frame 12.
And a high-frequency input / output unit provided through the frame 12, for example, a dielectric substrate 16 and a line conductor 17 formed on the upper surface of the dielectric substrate 16 and a line conductor on the upper surface of the dielectric substrate 16. It comprises a dielectric wall member 18 sandwiching and joining a part of 17. Then, the line conductor 17 of the high-frequency input / output unit 15 and the line conductor 14 of the high-frequency semiconductor element 13 are electrically connected via a bonding wire 19 such as a gold wire.

Reference numeral 20 denotes a lid joined to the upper surface of the frame 12, and the high-frequency semiconductor element 13 is mounted on a mounting portion 11a on the substrate 11, and includes a container comprising the substrate 11, the frame 12, and the lid 20. The high-frequency semiconductor device is housed in an airtight manner inside.

In the lid 20, reference numeral 21 denotes a dielectric plate serving as a base material of the lid 20, reference numeral 22 denotes an upper surface grounding conductor formed on the upper surface of the dielectric plate 21 so as to cover almost the entire surface thereof, and reference numeral 23 denotes a dielectric plate. 21 is a lower surface ground conductor formed on the lower surface of 21. This bottom conductor 23
Is the part of the high-frequency semiconductor element 13 facing the line conductor 14
Except for 24. Numeral 25 denotes a through conductor such as a via conductor which is formed inside the dielectric plate 21 so as to penetrate the dielectric plate 21 and conducts the upper ground conductor 22 and the lower ground conductor 23. Usually, a plurality of through conductors 25 are provided in order to bring the upper ground conductor 22 and the lower ground conductor 23 into a good ground condition in terms of high frequency, and the lower ground conductor 18 is provided on the lower surface of the dielectric plate 21 by a high frequency semiconductor element. 13 is formed excluding the part 24 facing the line conductor 14, and each lower surface ground conductor 23
Are provided so as to conduct with the upper surface ground conductor 22.

According to such a high-frequency semiconductor device of the present invention, the lower surface of the lid 20 is located in a range excluding the vicinity of the portion 24 which is immediately above the line conductor 14 of the high-frequency semiconductor element 13 opposed thereto. Since the grounding conductor 23 is formed, the grounding conductor arranged by the lid 20 above the line conductor 14 includes a portion directly above the line conductor 14 in the upper surface grounding conductor 22 formed on the upper surface of the lid 20. Plays a role in opposition to the line conductor 14. At this time, the electrical distance between the line conductor 14 and the top ground conductor 22 is due to pass through the dielectric plate 21 which is the base material of the lid 20 in the middle of the path.
Compared with the case where the case is sealed with a metal lid as in the conventional case, when the height of the housing wall (frame body 12) is the same,
This corresponds to an increase in the electrical distance between the ground conductor and the ground conductor (the top ground conductor 22). As a result, the electromagnetic field conditions for the high-frequency signal of the high-frequency
Since the upper portion of the line 14 can be made closer to an open state, the transmission characteristics of the line conductor 14 in the high-frequency semiconductor element 13 mounted inside the housing composed of the substrate 11 and the frame 12 also 14 It is possible to approach the characteristics evaluated with the upper part open.

Further, increasing the electrical distance between the line conductor 14 and the upper grounding conductor requires the substrate 11 and the frame 12
This makes it easier to generate unnecessary resonance inside the housing or the surface wave on the line conductor 14 of the high-frequency semiconductor element 13 mounted inside the housing, but in the present invention, the line conductor on the lower surface of the lid 20 14 Near the top (part 2 above)
In addition to 4), a lower surface ground conductor 23 is formed, and the lower surface ground conductor 23 has a structure in which the lower surface ground conductor 23 is electrically connected to the upper surface ground conductor 22 by a through conductor 25 penetrating the lid 20. While the majority of the housing opening is shielded by the ground conductor 23, the upper surface ground conductor 22 and the line conductor 14
It is possible to secure an electrical distance with
While suppressing an increase in the volume of free space inside the housing composed of the substrate 11 and the frame 12, the line conductor 14 and the upper ground conductor 22
It has a structure that can secure an electrical distance necessary for grounding the device.

The substrate 11 in the high-frequency semiconductor device of the present invention
The frame 12 is preferably made of a metal, for example, a metal material such as an iron-nickel-cobalt alloy. It should be noted that instead of those made of these metals, those obtained by applying a conductor coating such as a metallized metal layer on the surface of a base material of a dielectric material may be used.

As the high-frequency semiconductor element 13, as long as it has the line conductor 14 on the upper surface, in addition to the above-described semiconductor circuit board 13a having the line conductor 14 formed on the upper surface, various wiring parts can be used. Can be used.

As a material of the dielectric plate 21 serving as a base material of the lid 20, for example, a ceramic material such as alumina ceramics and mullite ceramics, an inorganic dielectric material such as glass ceramics, or PTFE (polytetrafluoroethylene). Organic resin-based dielectric materials such as glass epoxy and polyimide are used.

The thickness of the dielectric plate 21 may be appropriately set according to the required characteristics based on the frequency of the high-frequency signal used by the line conductor 14 and the relative permittivity of the dielectric material of the dielectric plate 21. .

The upper surface ground conductor 22 and the lower surface ground conductor 23 formed on the lid 20 are made of a metal material for a high-frequency line conductor, for example, Cu, MoMn + Ni + Au.W + Ni + Au.Cr.
+ Cu ・ Cr + Cu + Ni + Au ・ Ta2N + NiCr
+ Au.Ti + Pd + Au.NiCr + Pd + Au or the like, and is formed by a thick film printing method, a metallizing method, various thin film forming methods, a plating method, or the like. Further, a member formed by joining a conductive member such as a metal foil through a metallized metal layer or the like may be used. The thickness of the upper ground conductor 22 and the lower ground conductor 23 may be set to an appropriate thickness as a high-frequency ground conductor. For example, the thickness is set to about 5 μm for a thin film and about 20 μm for a thick film.

Further, a through conductor 25 disposed inside the dielectric plate 21 and conducting between the upper ground conductor 22 and the lower ground conductor 23 includes:
By forming via conductors, through-hole conductors, or the like, or by embedding rod-shaped metal members, it is only necessary to form a necessary number at necessary places so as to obtain a desired high-frequency good grounding state. . For example, as the material of the through conductor 25, various conductive materials can be used as long as they can be formed by a process applicable to the dielectric plate 21 of the base material of the lid 20. Also, the cross-sectional shape of the through conductor 25 can be various shapes such as a circle and a rectangle,
The size is not particularly limited as long as the size can satisfy the condition of the interval between the through conductors 25. Also,
The distance between the through conductors 25 is 1/4 in the operating frequency band
It is desirable that the wavelength be equal to or less than the wavelength because a good grounding state can be obtained. Further, it is better to increase the number of the through conductors 25 as much as possible within the range in which they can be arranged.

[0022]

Next, a specific example of the high-frequency semiconductor device of the present invention will be described.

First, a metal housing having a length × width × thickness of 3.0 mm × 2.2 mm × 0.45 mm and a thickness of 0.5 mm inside the housing is provided by a substrate and a frame made of an iron-nickel-cobalt alloy. And a length x width x thickness of 2.0 mm x
1.2 mm x 0.2 mm alumina ceramics (relative permittivity
9.6) Length x width x thickness is 2.0 mm x 0.22 m on the top surface of the substrate
A microstrip line substrate for characteristic comparison and evaluation formed by forming a line conductor of a microstrip line of m × 5 μm was mounted by soldering. Next, the length × width × thickness is 4.0 mm × 2.2 mm × 0.2 m on the upper surface of the frame opening.
Metallized tungsten metallization with a thickness of about 10 μm on the whole surface of the upper surface of a dielectric plate made of alumina ceramics having a relative dielectric constant of 8.8 m and a region excluding a region with a width of 0.4 mm centered on the longitudinal center line of the lower surface. Layer thickness 2
A via conductor having a diameter of 100 μm, made of tungsten for forming an upper ground conductor and a lower ground conductor by depositing a 6 μm Ni + Au plating layer and penetrating the dielectric plate to conduct the upper ground conductor and the lower ground conductor. To
A lid having a structure in which the center-to-center spacing is 400 μm and formed so as to be arranged at a position 50 μm from the end of the lower surface ground conductor 23 is joined with AgCu brazing to produce a high-frequency semiconductor device A of the present invention. did.

As a comparative example, a case made of the same metal as described above and a microstrip line substrate for characteristic comparison and evaluation as a high-frequency semiconductor element were used. X 4.0 mm x 2.2 mm x 0 thickness.
A conventional high-frequency semiconductor device B was manufactured by similarly joining a metal lid made of a 2 mm iron-nickel-cobalt alloy. Furthermore, using the same metal housing as above and a microstrip line substrate for characteristic comparison and evaluation as a high-frequency semiconductor element, the upper surface of the opening of the frame of the housing is opened without joining the lid. Semiconductor device C was manufactured.

For each of these high-frequency semiconductor devices A, B and C, the transmission characteristics of the microstrip line of the microstrip line substrate for comparison and evaluation mounted on the inside of the metal casing were evaluated by a network analyzer measurement. The impedance and propagation constant of the strip line were determined. These results are shown in FIGS.

FIG. 3 is a diagram showing the characteristic of the characteristic impedance Z ₀ with respect to the frequency of the microstrip line inside the metal casing in each of the high-frequency semiconductor devices A to C. The horizontal axis represents the frequency (unit: GHz). The vertical axis represents the characteristic impedance Z ₀ value (unit: Ω), and the characteristic curves A to C show the frequency characteristics of the high-frequency semiconductor devices A to C, respectively. As can be seen, the characteristic impedance of the high-frequency semiconductor device A of the present invention is:
Compared with the characteristic impedance of the conventional high-frequency semiconductor device B employing the sealing structure, the high-frequency semiconductor device C in which the upper portion of the metal housing is opened without being joined by the lid.
The impedance of the line conductor has a value closer to the characteristic impedance of the line conductor even in the state after the lid is joined and sealed after sealing.

FIG. 4 is a diagram showing the characteristics of the propagation constant β with respect to the frequency of the microstrip line inside the metal casing in each of the high-frequency semiconductor devices A to C. The horizontal axis represents the frequency (unit: GHz). The vertical axis represents the propagation constant β (unit: rad / m), and the characteristic curves A to C show the frequency characteristics of the high-frequency semiconductor devices A to C, respectively. As can be seen, the propagation constant is not different between the high-frequency semiconductor devices A and C, and according to the high-frequency semiconductor device A of the present invention, the electrical length of the line conductor of the high-frequency semiconductor element is guaranteed even after the lid is sealed. It was confirmed that it was done.

From the above results, in the high-frequency semiconductor device of the present invention, the upper surface grounding conductor is formed on the upper surface of the dielectric plate as the cover.
A lower surface ground conductor is formed on the lower surface except for a portion facing the line conductor of the high-frequency semiconductor element, and a through conductor that conducts between the upper surface ground conductor and the lower surface ground conductor is provided inside. By sealing the high-frequency semiconductor element, it is possible to increase the distance to the ground conductor above the line conductor while suppressing the generation of unnecessary resonance or surface waves and suppressing the increase in volume inside the housing. ,
As the state after the sealing, the distance between the line conductor and the lid in the wiring portion on the upper surface of the high-frequency semiconductor element as in the conventional case is designed to be as small as possible to suppress unnecessary resonance in the internal space of the case. Frame conductor), but the line conductor in the state where the upper space is open due to the short distance between the line conductor and the upper ground conductor as in the case of the conventional metal lid, and in the state after sealing. Compared to the case where the impedance of the line conductor differs, it is possible to improve the impedance characteristic of the line conductor in the sealed state by increasing the electrical distance between the line conductor and the upper surface ground conductor opposed thereto. It was confirmed that the high-frequency semiconductor device having good line conductor impedance characteristics even after stopping was obtained.

It should be noted that the above is only an example of the embodiment of the present invention, and the present invention is not limited to the embodiment. Various modifications and improvements may be made without departing from the gist of the present invention. No problem.

[0030]

According to the high-frequency semiconductor device of the present invention, a substrate having a mounting portion for a high-frequency semiconductor element on an upper surface, a high-frequency semiconductor element having a line conductor mounted on the mounting portion, and the substrate A frame joined to surround the mounting portion, a high-frequency input / output section provided through the frame, and a lid joined to the upper surface of the frame, In this lid, an upper surface ground conductor is formed on an upper surface of a dielectric plate, and a lower surface ground conductor is formed on a lower surface except for a portion opposed to the line conductor of the high-frequency semiconductor element. Since the through conductor for conducting the lower surface grounding conductor is provided, the distance between the line conductor and the lid in the wiring portion of the high-frequency semiconductor element is determined by the distance inside the housing as a state after sealing. Suppress unwanted resonance in space Therefore, the height of the housing wall (frame) is designed to be as low as possible, but the distance between the line conductor and the upper ground conductor is close as when using a conventional metal lid. The impedance of the line conductor does not differ between the state where the upper space is open and the state after sealing, and the upper surface conductor at the upper part of the line conductor facing this while suppressing the increase in volume inside the housing Since the electrical distance of the line conductor can be increased, the impedance characteristics of the line conductor of the high-frequency semiconductor element in the sealed state can be improved, and the high-frequency semiconductor device having good impedance characteristics of the line conductor in the sealed state Becomes

As described above, according to the present invention, the impedance characteristics of the line conductor of the high-frequency semiconductor element in the sealed state are improved, and the difference in the high-frequency characteristics between the sealed state and the state in which the upper space is opened is reduced. A high-frequency semiconductor device capable of performing the above-mentioned steps can be provided.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a part of a high-frequency semiconductor device according to an embodiment of the present invention, and is partially transparent.

FIG. 2 is a sectional view taken along line A-A 'in FIG.

FIG. 3 is a diagram illustrating characteristics of a characteristic impedance Z ₀ with respect to a frequency of a microstrip line in a metal housing in a high-frequency semiconductor device.

FIG. 4 is a diagram showing characteristics of a propagation constant β with respect to a frequency of a microstrip line in a metal housing in a high-frequency semiconductor device.

FIG. 5 is an exploded perspective view showing an example of a conventional high-frequency semiconductor device.

[Explanation of symbols]

11 ···· Substrate 11a ···· Mounting section 12 ····· Frame 13 ············································ High-frequency input / output section 20: lid 21: dielectric plate 22: top ground conductor 23: bottom ground conductor 24: line conductor 14 of high frequency semiconductor element 13 25 ・ ・ ・ ・ ・ The through conductor

Claims (1)

[Claims] 1. A substrate having a mounting portion for a high-frequency semiconductor element on an upper surface, a high-frequency semiconductor element having a line conductor mounted on the mounting portion, and joined to the substrate so as to surround the mounting portion. Frame, a high-frequency input / output unit provided through the frame, and a lid joined to the upper surface of the frame, wherein the lid is an upper surface of the dielectric plate. And a through conductor for conducting the upper ground conductor and the lower ground conductor therein, except that a lower ground conductor is formed on a lower surface of the high frequency semiconductor element except for a portion facing the line conductor. A high-frequency semiconductor device, wherein: