JPH09283648A - Surface mounting type hermetic package - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the entire height of a package to a low level and improve hermetic property, by fitting and sealing a glass into an inner space of a ring- shaped stem made of ceramics and symmetrically sealing a pair of metal leads in the glass. SOLUTION: A stem 2 made of ceramics is formed in a rectangular ring shape, and a glass 7 is fitted and sealed in an inner space 4 opened on the inner side of the stem 2. Since the ceramics is an insulator, no insulating material layer needs to be formed on the bottom of the stem 2 and therefore the entire height may be restrained to 0.7-0.9mm. Also, the inner side of the stem 2 has a step-like shape with a lower part protruding inward, thereby ensuring a large contact surface between the stem 2 and the glass 7 in fitting and sealing the glass 7 into the inner space 4. Thus, even when the entire height of the stem 2 is restrained to a low level, sufficient sealing strength and hermetic property may be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an airtight package for holding a piezoelectric element such as a crystal oscillator, a semiconductor element or the like, and more particularly to a surface mount type airtight package which is directly surface-mounted on a printed circuit board without holes.

[0002]

2. Description of the Related Art A surface mount type airtight package for holding a piezoelectric element such as a crystal oscillator or a semiconductor element in an airtight manner and directly surface-mounting it on a printed circuit board without a hole is shown in FIG. .

A pair of through holes 3 and 3 are provided symmetrically in a stem 2 of a thick flat plate made of metal such as Kovar, and metal leads 8 and 8 are provided in the through holes 3 and 3 via glass 7 and 7. It is sealed.

The metal leads 8 and 8 are projected on the upper surface of the stem 2, and the supporters 9 and 9 are welded to the projected portions, and the crystal oscillator 10 is supported on the supporters 9 and 9.

The metal leads 8 and 8 penetrate the glass 7 and 7 from the upper surface of the stem 2, are bent outward at the bottom surface of the stem 2 and extend along the bottom surface of the stem 2, and have a holeless printed circuit board (not shown). The metal leads 8 and 8 are soldered on the predetermined positions of and can be directly surface-mounted.

It should be noted that the metal leads 8 and 8 extending along the bottom surface of the stem 2 do not come into direct contact with the stem 2, and only the metal leads 8 and 8 are mounted even when mounted on a printed circuit board without holes. Is in contact with the printed circuit board, and an insulating material layer 11 such as resin is formed on the bottom surface of the stem 2 so that the central portion of the bottom surface of the stem 2 does not contact the printed circuit board.

A welding flange 21 is integrally formed at the lower end of the stem 2. The welding flange 21 and the cap flange 31 are overlapped with each other, and a welding electrode is applied from above and below to perform resistance welding. To form a surface-mounted airtight package 1.

[0008]

In recent years, there has been an increasing demand for a surface mount type airtight package which can be directly surface mounted on a printed circuit board without a hole. For such a package, the total height is kept as low as possible. It is strongly desired to form

In the above-mentioned conventional surface mount type airtight package, the stem is made of metal such as Kovar,
An insulating material layer such as resin must be formed on the bottom surface of the stem as a means for preventing the metal lead from coming into contact with the bottom surface of the stem, and as a means for preventing the central portion of the bottom surface of the stem from coming into contact with the printed circuit board. Therefore, the total height of the package is increased by the amount of this insulating material layer.

Further, if the total height of the package is made low, the total length of the metal lead becomes short, so that a sufficient distance cannot be secured between the metal lead and the glass, and the airtightness of the package may deteriorate.

An object of the present invention is to provide a surface mount type airtight package which can keep the overall height of the package low and is excellent in airtightness.

[0012]

In order to achieve the above object, in the present invention, in a surface mount type airtight package which is directly surface mounted on a printed circuit board without holes, glass is provided in an inner space of an annular stem made of ceramic. Since a pair of metal leads are symmetrically sealed in the glass by fitting and sealing, the overall height of the package can be kept low.

Further, the metal lead is embedded in the glass on the upper surface of the stem, extends outward from the vicinity of the center of the upper surface of the stem toward the outside, and is bent downward at a predetermined position to penetrate the glass. Then bend outwards at the bottom of the stem,
Since it extends to the end of the stem along the same plane as the bottom surface of the stem, it is possible to obtain a package having excellent airtightness.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is a surface-mounting airtight package which is directly surface-mounted on a printed circuit board without a hole, in which glass is fitted into an internal space of an annular stem made of ceramic and sealed. And a pair of metal leads are symmetrically sealed in the glass. Since ceramic is an insulator, there is no problem even if the metal leads extending along the bottom surface of the stem come into contact with the bottom surface of the stem. Also, there is no problem if the stem body directly contacts the printed circuit board without holes during mounting. Therefore, it is not necessary to form an insulating material layer on the bottom surface of the stem, and the total height of the package can be kept low.

Further, since ceramic is excellent in strength and has a good sealing strength with glass, it is possible to maintain the same strength and airtightness of the stem body as those of a metal stem.

According to a second aspect of the present invention, the metal lead extends from the vicinity of the center of the stem upper surface toward the outside while being embedded in the glass on the upper surface of the stem, along the upper surface of the stem, and at a predetermined position. Bend downwards to penetrate through the glass,
The stem is bent outward at the bottom surface and extends along the bottom surface of the stem to the end of the stem. According to this, the required total length of the metal lead can be maintained even if the overall height of the stem is kept low, so that the sealing distance between the metal lead and the glass can be secured.

According to the third aspect of the present invention, the portion of the metal lead extending over the upper surface of the stem is formed thicker than the portion of the metal lead extending over the bottom surface of the stem. It is what According to this, it is possible to prevent the glass from being damaged when the supporter is welded to the metal lead.

In the invention according to claim 4 of the present invention, when the glass is fitted and sealed in the internal space of the stem, the stem has a shape such that the area of the portion where the inside of the stem comes into contact with the glass is wide. It has been formed. According to this, since the contact area between the stem and the glass can be sufficiently secured, the sealing strength between the stem and the glass can be increased and the airtightness can be sufficiently maintained.

According to a fifth aspect of the present invention, a flange for welding is provided on the upper surface of the stem so as to project outward from the upper surface of the stem and extend over the entire circumference of the stem. According to this, even if the stem is made of ceramic, the stem and the cap can be easily sealed by resistance welding.

In the invention according to claim 6 of the present invention, the welding flange is bent downward at the end portion on the stem side and is embedded and sealed in the glass. According to this, it is possible to secure a sufficient sealing strength without integrally molding the stem and the flange, and it is possible to maintain the airtightness of the package.

According to the seventh and eighth aspects of the present invention, the welding flange is provided with a convex portion over the entire circumference of the welding flange, and the outer periphery of the convex portion is formed slightly smaller than the inner diameter of the cap. is there. According to this, during cap welding, the cap can be easily positioned, and at the same time, splash of welding dust can be prevented from adhering to the supporter, the crystal oscillator, and the metal leads inside the package.

Further, the stress generated at the time of cap welding can be absorbed to prevent the glass from being damaged.

(Embodiment 1) FIG. 1 is a sectional view of an airtight package for a crystal unit which is directly surface-mounted on a printed circuit board without holes.

The stem 2 made of ceramics is formed in a rectangular annular shape in a plan view (not shown), and a glass 7 is fitted and sealed in an internal space 4 inside the stem 2. Since ceramic is an insulator, it is not necessary to form an insulating material layer on the bottom surface of the stem 2, and in this example, the total height could be suppressed to 0.7 to 0.9 mm.

Further, in comparison with the conventional metal stem, the sealing strength and the airtightness of the stem were comparable to each other, and the reliability as an airtight package could be maintained.

The inside of the stem 2 has a so-called step-like shape in which the lower part thereof protrudes inward, and the inner space 4
Stem 2 and glass 7 when the glass 7 is fitted and sealed
Since a large contact area is ensured, sufficient sealing strength and airtightness can be obtained even if the overall height of the stem 2 is kept low.

In the present embodiment, the contact surface of the stem 2 with the glass 7 is formed stepwise, but the present invention is not limited to this, and the same effect can be obtained by forming the contact surface in a shape that increases the contact area. it can.

The metal leads 8, 8 have a flat plate shape, and the metal leads 8, 8 are provided on the glass 7 surface on the upper surface of the stem 2.
Reference numeral 8 extends from near the center of the stem 2 toward the outside along the upper surface of the stem 2. The metal leads 8 and 8 are embedded in the glass 7 so as to project upward from the glass surface by 0.1 to 0.3 mm. The supporters 9 and 9 welded onto the metal leads 8 and 8 are attached to the crystal oscillator. Supports 10.
In this way, since the metal leads 8 and 8 extend along the upper surface of the stem 2, a wide welding area with the supporters 9 and 9 can be secured, so that the welding strength is excellent and the crystal resonator is reliably supported. it can.

The metal leads 8, 8 extending to the upper surface of the stem 2 are bent downward in the middle, penetrate the inside of the glass 7, and are bent outward at the glass 7 surface of the bottom surface of the stem 2. , As it is, extends along the same plane as the bottom surface of the stem 2 to the end of the stem 2. Therefore, the required total length of the metal leads 8 and 8 can be obtained even if the total height of the package is kept low, and a sufficient sealing distance between the metal leads 8 and 8 and the glass 7 can be secured, resulting in sufficient airtightness. Can be kept. In this embodiment, the total length of the metal leads 8 and 8 is 2.0 to 3.5 mm.

The metal leads 8, 8 extending on the upper surface of the stem 2 are formed thicker than the metal leads 8, 8 extending on the bottom surface of the stem 2. Therefore, the glass 7 is not damaged when the metal leads 8, 8 on the upper surface of the stem 2 and the supporters 9, 9 for supporting the crystal unit 10 are welded. In the present embodiment, the metal leads 8, 8 on the top surface of the stem 2 have a thickness of 0.15 to 0.2 mm, and the metal leads 8, 8 on the bottom surface of the stem 2 have a thickness of 0.1 to 0.15.
mm.

A welding flange 21 made of Kovar is provided on the periphery of the upper surface of the stem 2 on the same plane as the upper surface of the stem 2 from the end of the stem 2 toward the outside from 0.1 to 0.5 mm.
It is provided so as to project.

The welding flange 21 is bent downward at the end on the side of the stem 2, and the bent portion is the stem 2.
It is embedded and sealed in the glass 7. Note that this sealing is performed at the same time as the metal leads 8 and 8 are sealed to the stem 2.

A convex portion 6 is formed on the entire circumference of the welding flange 21. The inner diameter of the cap 5 is positioned by the outer periphery of the convex portion 6, and the welding flange 21
The cap flange 31 is overlaid, and resistance welding electrodes are applied from above and below to perform resistance welding and sealing.

In the above description, an example of a surface mount type airtight package for a crystal unit has been described, but the present invention is not limited to this, and a semiconductor device package can be similarly implemented.

[0035]

As described above, according to the present invention, since the stem is made of ceramic, which is an insulator, it is not necessary to form an insulating material layer on the bottom surface of the stem, and the total height of the package can be suppressed.

Further, since a large contact area between the stem and the glass is secured, a strong sealing strength and sufficient airtightness can be obtained.

Further, since the metal leads are bent and a sufficient glass sealing distance is secured, the airtightness of the package can be kept good.

Further, since the portion of the metal lead to which the supporter is welded is formed thick, the glass is not damaged during welding.

Further, since the stem and the cap can be sealed by resistance welding, the package cost can be provided at a low cost.

Further, since the welding flange is bent downward at the end on the stem side and is embedded and sealed in the glass, the welding flange and the stem can be firmly fixed and airtight. An excellent package can be provided.

Further, since the convex portion is formed on the welding flange, positioning of the cap can be facilitated when the stem and the cap are welded, and the splash generated during resistance welding causes the supporter, the element and the lead. Since it does not adhere to the package and can absorb the stress generated during welding, the reliability of the package itself can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a surface mount type airtight package showing an embodiment of the present invention.

FIG. 2 is a sectional view of a conventional surface mount type airtight package.

[Explanation of symbols]

 1 Package 2 Stem 3 Through Hole 4 Internal Space 5 Cap 6 Convex 7 Glass 8 Metal Lead 9 Supporter 10 Crystal Resonator 11 Insulating Material Layer 21 Welding Flange 31 Cap Flange

Claims (8)

[Claims] 1. In a surface-mounting type airtight package which is directly surface-mounted on a printed circuit board without holes, glass is fitted and sealed in an inner space of an annular stem made of ceramic, and a pair of metal leads are symmetrically arranged in the glass. A surface mount type airtight package characterized by being sealed. 2. The metal lead extends from near the center of the stem upper surface toward the outside while being embedded in the glass on the upper surface of the stem, along the stem upper surface, and bends downward at a predetermined position. 2. The surface mount airtight package according to claim 1, wherein the surface mount type airtight package penetrates through the glass, bends outward at the bottom surface of the stem, and extends along the bottom surface of the stem to the end of the stem. . 3. A portion of the metal lead extending to the upper surface of the stem is formed thicker than a portion of the metal lead extending to the bottom surface of the stem. The surface mount type airtight package according to claim 2. 4. The stem is formed in a shape such that an area of a portion where the inside of the stem and the glass come into contact with each other is widened when the glass is fitted and sealed in the inner space of the stem. The surface mount type airtight package according to claim 1. 5. The surface mount type airtight package according to claim 1, wherein a welding flange is provided on an upper surface of the stem so as to project from a peripheral end of the stem and extend over the entire circumference of the stem. 6. The surface mount type airtight package according to claim 5, wherein the welding flange is bent downward at an end portion on the stem side and is embedded and sealed in the glass. 7. The surface mount type airtight package according to claim 5, wherein the welding flange is provided with a convex portion over the entire circumference of the welding flange. 8. The surface mount type hermetic package according to claim 7, wherein an outer circumference of the convex portion is slightly smaller than an inner diameter of the cap.