JPH05218279A - Lead fixing structure of high frequency package - Google Patents

Abstract

PURPOSE:To shorten a wire, evade eccentricity, and stabilize characteristic impedance, by interposing specified material whose permitivity is nearly equal to that of air between a part or the whole part of a small diameter part and a lead, in a lead fixing structure wherein a small diameter lead is inserted and glass is interposed between a large diameter part and the lead. CONSTITUTION:A package 20 composed of conductive material (e.g. iron-nickel- cobalt alloy) has a box structure. The upper side faces the package inside, and the lower side faces the package outside. In the package 20, a through hole 21 which penetrates the inner surface and the outer surface of the package 20 is formed, which is provided with a small diameter part 21a and a large diameter part 21b. The small diameter part 21a is opened toward the inside of the package, and the large diameter part 21b is opened toward the outside of the package. The outer diameter of a lead 22 is smaller than the inner diameter of the small diameter part 21a. Material whose permitivity is lower than that of glass 23 of the large diameter part 21b is used as specified material 24 of the small diameter part 21a. Since expandable resin, e.g. GORE-TEX contains a lot of air bubbles, its permitivity is lower than that of glass.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead mounting structure for a high frequency device package.

[0002]

2. Description of the Related Art Generally, a package for a high frequency device is assembled by enclosing an inert gas in a metallic package. The package has a shielding effect and prevents ingress of moisture etc. to improve durability. By the way, the signal transmission to such a high frequency device is
Through the lead inserted in the through hole of the package,
Glass is used to seal the leads and the through holes. That is, in FIG. 4, the lead 3 is inserted along the axis of the through hole 2 penetrating both surfaces (the inner surface and the outer surface of the package) of the package 1, and the through hole 2 is sealed with the glass 4.

The lead 3 and the through hole 2 form a distributed constant line having a characteristic impedance (for example, 50 ohms). The magnitude of the impedance depends on the frequency of the signal, the dielectric constant of the glass 4, and the inner diameter φ _{L of the} through hole 2. Depends on. here,
The inner diameter φ _L of the through hole 2 is required to be as small as possible. This is because, as shown in FIG. 4, since the wire 6 connecting the tip of the lead 3 and the electronic circuit 5 becomes long in proportion to φ _L , the deterioration of the high frequency characteristics in this wire portion,
That is, mismatching increases.

Therefore, the present applicant has previously proposed "a coaxial line of a package for a high frequency element" (Japanese Patent Application No. 3-3).
No. 39856, filed on November 27, 1991). As shown in FIG. 5, the technology of this prior application is based on the through hole 8 of the package 7.
The small-diameter portion 8a and the large-diameter portion 8b are formed on the glass, the large-diameter portion 8b is sealed with the glass 9, and the small-diameter portion 8a serves as a space portion.

According to this, when the semiconductor element is hermetically sealed, an inert gas such as nitrogen or argon can be introduced into the small diameter portion 8a, and a distributed constant line can be formed using this inert gas as an insulator. .. Generally, the dielectric constant of gas such as air is smaller than that of glass (for example, the dielectric constant of air is 1.
From 0), the inner diameter φ _S of the small diameter portion 8a of the through hole 8 can be made smaller than the inner diameter φ _{L in} the case of glass.
The length of 1 can be shortened to suppress the influence of mismatching.

[0006]

However, in the technique of the prior application, the inner diameter of the small diameter portion of the through hole is smaller than the inner diameter φ _{L in} the case of glass due to the dielectric constant of the inert gas introduced into the small diameter portion. It is effective in that it can shorten the wire, but since the lead is not held securely in the small diameter part, the lead may be tilted due to vibration during wire bonding, etc. There is room for improvement, such as deviation from the axis), and changes in the characteristic impedance.

Therefore, it is an object of the present invention to shorten the wire and ensure the retention of the lead to stabilize the characteristic impedance.

[0008]

In order to achieve the above-mentioned object, the present invention has a small-diameter portion facing the inside of a package made of a conductive material and a large-diameter portion facing the outside of the package. In a lead mounting structure of a high-frequency package, in which a lead having a diameter smaller than that of the small diameter portion is passed through a through hole having and a glass is interposed between the large diameter portion and the lead, a part of the small diameter portion or It is characterized in that a predetermined material having a dielectric constant close to that of air is interposed between the whole and the lead.

[0009]

In the present invention, the lead in the small diameter portion is held by a predetermined material having a dielectric constant close to that of gas such as air. Therefore, the inner diameter of the small diameter portion is reduced depending on the dielectric constant of the predetermined material, and the wire length is shortened.

Further, due to the holding effect of the predetermined material, positional deviation of the leads caused by external vibration during assembly or during use as a semiconductor device is reliably avoided. Furthermore, if a predetermined material having a melting point higher than that of glass is used, the predetermined material can be press-fitted at the same time as the glass sealing.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a first embodiment of a lead mounting structure for a high frequency package according to the present invention. In FIG. 1, 2
Reference numeral 0 is a partial cross section of a package that houses an optical device such as a laser light emitting element, an ultra high frequency amplifier, and the like. The package 20 made of a conductive material (for example, iron-nickel-cobalt alloy) has a box structure, and the upper side of the drawing faces the inside of the package and the lower side of the drawing faces the outside of the package.

The package 20 is provided with a through hole 21 penetrating the inner and outer surfaces thereof, and the through hole 21 has a small diameter portion 21a opening to the inside of the package and a large diameter portion 21b opening to the outside of the package. And have. 22 is
The leads 22 are inserted so as to match the central axes of the small diameter portion 21a and the large diameter portion 21b, and the outer diameter of the lead 22 is smaller than the inner diameter of the small diameter portion 21a. Further, 23 is a glass sealed in the large diameter portion 21b, 24 is a predetermined material press-fitted into the small diameter portion 21a, and the predetermined material 24 having a dielectric constant lower than that of the glass 23 is used. ..
For example, a foam resin such as GORE-TEX has a lower dielectric constant (4-9 depending on the component) of the glass 23 because it contains many bubbles, and is close to the dielectric constant of a gas such as air (about 2). ) Is preferred.

In such a structure, the opening diameter of the through hole 21 inside the package (that is, the inner diameter of the small diameter portion 21a).
φ _S is determined by the frequency and the characteristic impedance of the signal transmitted by the lead 22 and the dielectric constant of the predetermined material 24, and is smaller than that in the case of glass sealing (see φ _{L in} FIG. 4). Therefore, the electronic circuit 25 inside the package and the lead 22 can be brought close to each other by the difference between φ _L and φ _S , and the wire 26 can be shortened to suppress the influence of mismatching.

Moreover, the lead 22 is made of the predetermined material 24.
Since the lead 22 can be reliably held, eccentricity of the lead 22 caused by external vibration during assembly or during use as a semiconductor device can be avoided, and the lead 22 is always held in the correct position to stabilize the characteristic impedance. be able to. It should be noted that the present invention is not limited to the above-mentioned embodiments, and various modifications can be considered within the intended scope.

For example, as shown in FIG. 2 of the second embodiment, only the vicinity of the opening of the small diameter portion 21a is sealed with the thin plate 30, or as shown in FIG. 3 of the third embodiment, the small diameter portion. The open end of 21a may be sealed with the flanged cap 31. These thin plate 30 and collar cap 31 are
The same material as the predetermined material 24 of the embodiment, that is, a material having a dielectric constant close to that of a gas such as air is used.

[0016]

According to the present invention, the wire can be shortened, the lead can be securely held, eccentricity can be avoided, and the characteristic impedance can be stabilized.

[Brief description of drawings]

FIG. 1 is a sectional view of a first embodiment.

FIG. 2 is a sectional view of a second embodiment.

FIG. 3 is a sectional view of a third embodiment.

FIG. 4 is a sectional view of a conventional example.

FIG. 5 is a cross-sectional view of a conventional example according to the prior application.

[Explanation of symbols]

 20: Package 21: Through hole 21a: Small diameter part 21b: Large diameter part 22: Lead 23: Glass 24: Predetermined material

Claims (1)

[Claims] 1. A lead having a diameter smaller than the small diameter portion is inserted into a through hole having a small diameter portion facing the inside of the package made of a conductive material and opening, and a large diameter portion facing the outside of the package. In a lead mounting structure of a high-frequency package which is configured to pass through and through which glass is interposed between the large diameter portion and the lead, a predetermined material having a dielectric constant of air close to a part or all of the small diameter portion and the lead is provided. High frequency package lead mounting structure characterized by being interposed.