JP2943689B2 - Surface mount type airtight package - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art A surface mount type airtight package which holds a piezoelectric element such as a quartz oscillator or a semiconductor element in an airtight manner and is directly mounted on a printed circuit board without holes is known, for example, as shown in FIG. .

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

The metal leads 8, 8 protrude from the upper surface of the stem 2, and supporters 9, 9 are welded to the protruding portions to support the crystal unit 10 on the supporters 9, 9.

The metal leads 8, 8 penetrate through the glass 7, 7 from the top surface of the stem 2, bend outward at the bottom surface of the stem 2, extend along the bottom surface of the stem 2, and extend along the bottom surface of the stem 2, not shown. The metal leads 8, 8 are soldered on the predetermined positions, so that they can be directly surface-mounted.

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

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, and a welding electrode is applied from above and below by resistance welding to form the stem 2 and the cap 5. To form a surface-mounted hermetic package 1.

[0008]

In recent years, there has been an increasing demand for a surface-mounted hermetic package which can be directly surface-mounted on a printed circuit board without a hole. However, for such a package, the overall height must be kept as low as possible. It is strongly desired to form

In the above-mentioned conventional surface mount type airtight package, since the stem is made of metal such as Kovar,
An insulating material layer such as a resin must be formed on the bottom surface of the stem to prevent the metal lead from contacting the bottom surface of the stem and to prevent the center of the bottom surface of the stem from contacting the printed circuit board. For this reason, the overall height of the package is increased by the amount of the insulating material layer.

Further, if the overall height of the package is reduced, the total length of the metal leads is shortened, so that a sufficient distance between the metal leads and the glass cannot be secured, and the airtightness of the package may be reduced.

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 has excellent airtightness.

[0012]

In order to achieve the above object, the present invention provides a surface mount type airtight package which is directly surface mounted on a printed circuit board without a hole. Since the pair of metal leads is sealed in the glass and symmetrically sealed in the glass, the overall height of the package can be reduced.

The metal lead extends along the upper surface of the stem from the vicinity of the center of the upper surface of the stem to the outside while being embedded in the glass on the upper surface of the stem, and is bent downward at a predetermined position to penetrate through the glass. And bend outward 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, a package having excellent airtightness can be obtained.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is directed to a surface mount type airtight package which is directly mounted on a printed circuit board without a hole, and glass is fitted into the inner space of a ceramic annular stem. And a pair of metal leads sealed symmetrically in the glass. Since ceramic is an insulator, there is no problem if the metal leads extending along the bottom surface of the stem come into contact with the bottom surface of the stem. Further, there is no problem even 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 overall height of the package can be reduced.

Further, ceramics are excellent in strength and have good sealing strength with glass, so that the same strength and airtightness of the stem main body as the metal stem can be maintained.

In the invention according to a second aspect of the present invention, the metal lead extends from the vicinity of the center of the upper surface of the stem to the outside and extends along the upper surface of the stem while being embedded in the glass on the upper surface of the stem. To bend downward and penetrate through the glass,
It is bent outward at the bottom of the stem and extends along the bottom of the stem to the end of the stem. According to this, even if the overall height of the stem is kept low, the required overall length of the metal lead can be maintained, so that the sealing distance between the metal lead and the glass can be ensured.

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

According to the invention described in claim 4 of the present invention, when the glass is fitted into the inner space of the stem and sealed, the stem is shaped so that the area of the portion where the glass contacts the inside of the stem is increased. It has been formed. According to this, since the contact area between the stem and the glass can be sufficiently ensured, 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 welding flange is provided on the upper surface of the stem so as to protrude outward from the upper surface of the stem and extend over the entire periphery 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 on the stem side, embedded in glass, and sealed. According to this, sufficient sealing strength can be ensured without integrally forming the stem and the flange, and the airtightness of the package can be maintained.

According to the seventh and eighth aspects of the present invention, the welding flange is provided with a projection over the entire periphery of the welding flange, and the outer periphery of the projection is formed slightly smaller than the inner diameter of the cap. is there. According to this, at the time of cap welding, the positioning of the cap can be easily performed, and at the same time, the splash, which is welding dust, can be prevented from adhering to the supporter, the crystal unit, 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 cross-sectional view of an airtight package for a crystal unit directly mounted on a printed board without holes.

A plan view (not shown) of the stem 2 made of ceramic is formed in a rectangular ring shape, and a glass 7 is fitted into and sealed in an internal space 4 opened inside the stem 2. Since ceramic is an insulator, there is no need to form an insulating material layer on the bottom surface of the stem 2, and in this embodiment, the overall height could be suppressed to 0.7 to 0.9 mm.

In comparison with the conventional metal stem, the sealing strength and airtightness of the stem were not inferior to each other, and the reliability of the airtight package could be maintained.

The inside of the stem 2 has a so-called stair-like shape in which the lower part protrudes inward.
2 and glass 7 when glass 7 is fitted into and sealed
Therefore, 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 in a stepped shape. However, the present invention is not limited to this, and a similar effect can be obtained by forming the stem 2 into a shape having a large contact area. it can.

The metal leads 8 and 8 have a flat plate shape, and the metal leads 8 and 8
8 extends from the vicinity of the center of the stem 2 to the outside along the upper surface of the stem 2. The metal leads 8, 8 are embedded in the glass 7 so as to protrude 0.1 to 0.3 mm above the glass surface, and supporters 9, 9 welded on the metal leads 8, 8 are attached to a crystal oscillator. Supports 10.
As described above, since the metal leads 8 extend along the upper surface of the stem 2, a large welding area with the supporters 9 can be secured, so that the welding strength is excellent and the crystal oscillator is reliably supported. it can.

The metal leads 8 extending on the upper surface of the stem 2 are bent downward in the middle, penetrate the glass 7, and are bent outward on the glass 7 surface on the bottom surface of the stem 2. , And extends to the end of the stem 2 along the same plane as the bottom surface of the stem 2 as it is. For this reason, even if the total height of the package is kept low, the required total length of the metal leads 8 and 8 can be obtained, and the sealing distance between the metal leads 8 and 8 and the glass 7 can be sufficiently ensured. Can be kept. In the present embodiment, the total length of the metal leads 8 is set to 2.0 to 3.5 mm.

The metal leads 8 extending on the upper surface of the stem 2 are formed thicker than the metal leads 8 extending on the bottom surface of the stem 2. Therefore, the glass 7 is not damaged when the metal leads 8 on the upper surface of the stem 2 and the supporters 9 for supporting the crystal unit 10 are welded. In the present embodiment, the metal leads 8 on the upper surface of the stem 2 have a thickness of 0.15 to 0.2 mm, and the metal leads 8 on the lower 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 substantially same plane as the upper surface of the stem 2 from the end of the stem 2 toward the outside by 0.1 to 0.5 mm.
It is provided so as to protrude.

The end of the welding flange 21 on the stem 2 side is bent downward.
Embedded in the glass 7 and sealed. The sealing is performed at the same time as the metal leads 8 are sealed to the stem 2.

The welding flange 21 is provided with a projection 6 over the entire circumference. The inner diameter of the cap 5 is determined by the outer circumference of the projection 6 and the welding flange 21 is formed.
And a cap flange 31 are overlapped, and a resistance welding electrode is applied from above and below and sealed by resistance welding.

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

[0035]

As described above, according to the present invention, since the stem is made of ceramic which is an insulator, there is no need to form an insulating material layer on the bottom of the stem, and the overall height of the package can be suppressed.

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

Further, since the glass lead has a bent shape and a sufficient glass sealing distance is secured, the hermeticity of the package can be kept good.

Further, since the thickness of the portion where the supporter of the metal lead 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 reduced.

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 airtightness can be secured. Excellent package can be provided.

Further, since the projection is formed on the welding flange, the positioning of the cap can be facilitated when the stem and the cap are welded, and the splash generated at the time of resistance welding is reduced by the supporter, the element and the lead. Since it is possible to absorb the stress generated at the time of welding without adhering to the package, the effect of improving the reliability of the package itself can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a surface-mounted hermetic package showing an embodiment of the present invention.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Package 2 Stem 3 Through hole 4 Internal space 5 Cap 6 Convex part 7 Glass 8 Metal lead 9 Supporter 10 Crystal oscillator 11 Insulating material layer 21 Welding flange 31 Cap flange

Continued on the front page (58) Fields surveyed (Int.Cl. ⁶ , DB name) H01L 23/04 H01L 23/02 H03H 9/02 H03H 9/10

Claims (8)

(57) [Claims] 1. A surface-mounted hermetic package which is directly surface-mounted on a printed circuit board without a hole, wherein glass is fitted into an inner space of an annular stem made of ceramic and sealed, and a pair of metal leads are symmetrically disposed in the glass. A surface-mount type airtight package characterized by sealing. 2. The metal lead extends along the stem upper surface from near the center of the stem upper surface to the outside while being embedded in the glass on the upper surface of the stem, and bends downward at a predetermined position. 2. The surface-mounted hermetic package according to claim 1, wherein the package extends through the glass, bends outward at the bottom of the stem, and extends to the end of the stem along the bottom of the stem. . 3. A portion of the metal lead extending on an upper surface of the stem is formed to be thicker than a portion of the metal lead extending on a bottom surface of the stem. The surface mount type airtight package according to claim 2. 4. When the glass is fitted into the internal space of the stem and sealed, the stem is formed in such a shape that the area of the portion where the glass contacts the inside of the stem increases. The surface-mounted hermetic package according to claim 1, wherein: 5. The surface-mounted hermetic package according to claim 1, wherein a welding flange is provided on an upper surface of the stem so as to protrude from a peripheral end of the stem and extends over the entire periphery of the stem. 6. The surface-mounted hermetic package according to claim 5, wherein the welding flange is bent downward at an end on the stem side and is embedded and sealed in the glass. 7. The surface mount type airtight package according to claim 5, wherein a convex portion is provided on the welding flange over the entire circumference of the welding flange. 8. The surface-mounted hermetic package according to claim 7, wherein the outer periphery of the projection is slightly smaller than the inner diameter of the cap.