JP2000357755A - Package for high-frequency device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate reflection of a signal due to impedance mismatching at a bonding part and thereby improve transmission characteristics, by extending the top end of a coaxial connector close to a semiconductor chip in a package cavity and forming a pad for wire-bonding on the center core and on the outer conductor, respectively. SOLUTION: A coaxial cable 32 is mounted on a package from its outside via a coaxial connector 30. The coaxial connector 30 is extended to the package inside to form a top end member 50 with the center core 34 and the outer conductor 42 of the connector. The top end of the center core 34 of the connector is connected to a semiconductor chip 12 of a high-frequency device by a bonding wire 24. In the output side, the signal is transmitted from the semiconductor chip 12 to an external terminal via a substrate transmission line 52. By such means, reflection of a signal due to impedance mismatching at the bonding is eliminated, thereby improving the transmission characteristics of the overall line.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a package for a high-frequency device used in the optical / telecommunications field, and more particularly to a package for a high-frequency device with improved transmission efficiency of a high-frequency signal.

[0002]

2. Description of the Related Art FIG. 1 is a schematic explanatory view showing a cross section of a conventional package structure accommodating a high-frequency device. In the figure, a semiconductor chip 12 is accommodated in a package body (hereinafter simply referred to as a package) 10 entirely made of metal, and an external signal input to the semiconductor chip 12 and an external signal output are transmitted through a transmission line. Substrate insulator 1
The operation is performed via external leads 18 and 20 through conductor circuits provided in 4 and 16, respectively. In the example shown, the printed circuit board (P
WB) 22 is connected to one external lead 18. Code 24
Denotes a bonding wire, and 26 denotes a support base on which the semiconductor chip 12 is mounted.

In a package 10 made entirely of metal as shown in FIG. 1, a convex insulator 14 is used as a transmission line substrate for a wiring (high-speed signal line) through which a high-frequency signal such as 2.5 GHz passes. , 16 are employed. In this case, on the input side, the printed circuit board 22 is
A convex insulator provided through the above wiring and package
Connected to the wiring on 14. Then, a signal is transmitted to the inside of the package through the wiring on the convex insulator. The same applies to the output side.

However, as the frequency further increases and the frequency of the signal approaches, for example, about 10 GHz, especially at the connection between the external lead and the wiring on the convex insulator of the package,
Since the amount of signal reflection increases due to the influence of characteristic impedance mismatch and the like, the structure shown in FIG. 1 causes a large loss, and the signal can be transmitted to the inside or outside of the package at a high transmission rate. It becomes difficult.

Therefore, in a package for handling signals in such a frequency band, a coaxial connector is attached to the package in advance as shown in FIGS. A structure that eliminates the influence of the above has been proposed.

FIG. 2 is a schematic explanatory view showing a form of connection between a coaxial cable and a package in a conventional package with a coaxial connector, and FIG. 3A is an enlarged view of a part of FIG. b) is an enlarged schematic sectional view of only the coaxial connector.

The package is a coaxial connector.
1. Except for having 30, it is the same as the package structure of FIG. 1, and in FIGS. The output side of the signal shown in FIG. 2 is provided with the convex insulator as shown in FIG. 1, but it goes without saying that the input side of the signal may have the same configuration.

In FIG. 2, a coaxial cable 32 is attached to the package body 10 via a coaxial connector 30, and FIG.
As is clear from the enlarged views of (a) and (b), the connector inner core 34 constituting the distal end of the coaxial connector 30 extends inside the package together with the insulator 36 provided therearound. Such a connector inner core 34 is directly connected to a wiring on a transmission line substrate 38 provided in advance in the package by a conductor paste. In the drawing, the joining portion 40 made of the conductor paste is shown in black. This transmission line board
The wiring on 38 is connected to a high-frequency device such as the semiconductor chip 12 by a bonding wire 24 at the other end.

[0009]

However, even with a package with a coaxial connector having such a structure, it is difficult to transmit a high-frequency signal with low loss while suppressing reflection.

That is, in the conventional example as described above, the coaxial connector 30 is installed on the metal side wall of the package body 10, and the connector inner core 34 of the coaxial connector 30 is connected to the transmission line substrate 38 inside the package. However, at the junction between the end of the coaxial connector that receives the coaxial cable inside the package and the transmission line substrate inside the package, signal reflection occurs due to characteristic impedance mismatch, so it is necessary to obtain sufficient characteristics. It is difficult.

In addition, a brazing material such as AuSn is used for joining the tip of the inner core of the coaxial connector to the transmission line substrate, but it is difficult to perform such joining while maintaining positional accuracy. It is.

It is an object of the present invention to provide a high-frequency device package for electronic equipment used in the field of optical / telecommunications, which will have higher and higher frequencies in the future. A more specific object of the present invention is to provide a high-frequency device package that can transmit a signal with a high transmission efficiency even with a high-frequency signal having a frequency of 10 GHz or more.

[0013]

Means for Solving the Problems The present inventor has conducted various studies to solve the above problems, and has completed the following invention.

That is, the present invention relates to a package to which a coaxial connector for connecting a coaxial cable is attached, wherein the distal end of the coaxial connector on the package side is composed of a connector inner core and an outer conductor, and this distal end is packaged. A high-frequency device package extending into the cavity.

According to a preferred aspect of the present invention, a wire bonding pad is formed on each of a connector inner core and an outer conductor constituting the distal end portion of the coaxial connector extending into the cavity of the package. You may.

That is, according to the present invention, the coaxial connector is extended to the inside of the package, and the extended portion, that is, the end portion, is connected to the inner conductor of the connector and the outer conductor coaxially provided around the outer periphery of the connector via an insulator. In this case, the tip of the inner core of the connector is directly connected to the semiconductor chip. Therefore, the number of connection portions from the external coaxial cable to the internal device is reduced, and problems such as impedance mismatch of the connection portion can be avoided in advance.

Further, according to the present invention, as described above, a wire bonding pad is formed on each of the connector inner core and the outer conductor constituting the distal end of the coaxial connector extended into the cavity of the package. Connection with a high-frequency device is further facilitated.

That is, when the grounding pads are provided on the left and right sides of the pad provided on the inner core of the connector (signal line) or on the outer conductor (grounding line) side on one side, preferably at symmetrical positions, the grounding pad is provided. In this case, the change in the distribution of the electromagnetic field from the pad in the inner core of the connector to the pad for grounding can be reduced as compared with the case where only one side is used.

[0019]

Next, the operation and effect of the present invention will be described in more detail with reference to the drawings showing an embodiment of the present invention.

FIG. 4 is a schematic explanatory view of a package according to the present invention. FIG. 4 (a) is a plan view and FIG. 4 (b) is a longitudinal sectional view. 1 to 3 are denoted by the same reference numerals.

4 (a) and 4 (b), the coaxial cable 32
Is attached to the package from the outside via the coaxial connector 30. In the case of the present invention, the coaxial connector 30 extends to the inside of the package. Therefore, the inner core of the connector
The outer conductor 42 and the outer conductor 42 constitute a distal end portion 50 therein. At this time, the connector inner core 34 is connected to the semiconductor chip 12 which is a high-frequency device by the bonding wire 24 at the tip. In the illustrated example, on the output side of the signal, the signal is sent from the semiconductor chip 12 to the external terminal 54 via the transmission line substrate 52 by wire bonding, but also on the output side, the coaxial connector according to the present invention as described above. May be provided. The connector inner core 34 is made of an electric conductor, and is insulated from an outer conductor 42 also made of an electric conductor. The outer conductor 42 may extend from the package side wall.

As described above, according to the present invention, the inner core of the coaxial connector is directly coaxial and directly connected to a high-frequency device such as a semiconductor chip, so that an intermediate circuit can be omitted. Problems such as characteristic impedance mismatch in the circuit can be minimized, and a decrease in transmission rate is hardly observed. In this example, an example is shown in which a coaxial connector is provided only on the signal input side, but the signal output side may be similarly configured.

FIG. 5 shows another modification.
5 (a) is a partial longitudinal sectional view of a connection portion of the coaxial connector of the package, FIG. 5 (b) is a transverse partial sectional view thereof, and FIG. 5 (c) is a schematic perspective view of a distal end portion of the coaxial connector. Yes,
FIG. 5D is a schematic sectional view of the same.

In the case of FIG. 5, the outer conductor 42 of the coaxial connector is used.
Also, the pad portion for wire bonding for the ground line is formed symmetrically. That is, FIG.
Shows a longitudinal sectional view, in which a wire bonding pad 58 is provided at the tip of the connector inner core 34. As is clear from FIG. 5 (b), the outer conductor 42 is similarly provided with a wire bonding pad. There are 60 provided.

The pads 58 and 60 are formed in advance on the inner core 34 and the outer conductor 42 of the connector. However, in some cases, the coaxial connector may be attached to the package and then attached by, for example, brazing.

According to this aspect, the inner core of the coaxial connector is coaxial until immediately before connection to the semiconductor chip, so that the transmission efficiency is improved even with a higher frequency.

In the present invention, the connection between the coaxial cable and the coaxial connector, the form of attachment between the coaxial connector and the package, and the like may be performed, for example, in the same manner as the conventional one, and are not particularly limited.

[0028]

As described above, according to the present invention, the distal end of the coaxial connector is extended to the vicinity of the semiconductor chip in the package cavity, and the inner and outer cores of the connector constituting the distal end of the coaxial connector are extended. Form a wire bonding pad with the conductor (for grounding). This allows
The joint between the transmission line substrate and the tip of the inner core of the coaxial connector as seen in a conventional package with a coaxial connector is eliminated, and signal reflection due to impedance mismatch at this joint is eliminated.

As a result, not only the transmission characteristics of the entire line are improved, but also the following excellent benefits are obtained. (i) According to the present invention, the connection between the end of the coaxial connector and the transmission line substrate is eliminated, the transmission line substrate itself can be omitted, and the structure becomes simpler. (ii) It is possible to improve the transmission efficiency of signals with a frequency of 10 GHz or more, and obtain a package that can sufficiently cope with higher frequencies in the field of optical / telecommunications in the future.

Therefore, according to the present invention, it is possible to obtain a package having a simpler structure and easier to manufacture, and is particularly promising for a high-frequency device for handling a signal of a high frequency of 10 GHz or more, and is in the field of optical / telecommunications. The practical significance of the present invention is great.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing a cross section of a conventional package structure.

FIG. 2 is a schematic explanatory view showing the same cross section of a conventional package structure with a coaxial connector.

FIGS. 3A and 3B are enlarged views of a tip portion of a coaxial connector having another conventional package structure.

FIGS. 4 (a) and 4 (b) are schematic illustrations of a structure of a package with a coaxial connector according to the present invention, which are a plan view and a sectional view, respectively.

5 (a), 5 (b), 5 (c) and 5 (d) are a longitudinal sectional view and a transverse sectional view, respectively, of a connection portion at a tip end of a coaxial connector in a package with a coaxial connector according to the present invention. It is the perspective view and sectional drawing of a front-end | tip part.

Claims (3)

[Claims] 1. A package to which a coaxial connector for connecting a coaxial cable is attached, wherein a distal end of the coaxial connector on the package side is provided so as to surround the inner core of the connector via an inner core of the connector and an insulator. A high-frequency device package comprising: 2. The high-frequency device package according to claim 1, wherein a wire bonding pad is formed on each of an inner core and an outer conductor of the connector constituting the tip portion in the package. 3. The high-frequency device package according to claim 1, wherein the inner core of the connector and the semiconductor chip housed in the package are directly connected by wire bonding.