JP2007311434A - Stem for electronic device, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stem for electronic devices for preventing thermal shock that the temperature of a base surface abruptly rises due to the radiant heat of melted solder in packaging from occurring, and preventing the glass hemispherical section of stand-off glass from falling off due to shear. <P>SOLUTION: By forming an Sn-Pb coating 5 on the surface of the base 1 excluding sealing glass 3 and the glass hemispherical section 2a of the stand-off glass 2 as a thermal buffer film, an increase in temperature near the surface of the base 1 can be suppressed even if the radiant heat of molten solder 7 is brought onto the surface of the base 1 via a packaging substrate 6, thus preventing cracks from being generated with a glass corner 2b as a starting point and preventing the glass hemispherical section 2a from falling off due to shear. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a stem for an electronic device and a method for manufacturing the same, and relates to a technique related to the stem for an electronic device having a stand-off glass.

  2. Description of the Related Art Conventionally, some electronic device stems used for a base portion of an electronic device have a standoff glass. This is formed by projecting standoff glass on the lower surface (mounting substrate side) of the base of the stem for the electronic device, and when the electronic device is mounted on the mounting substrate or the like, the standoff glass is brought into contact with the mounting substrate. Thus, the base of the stem for the electronic device is mounted at a certain distance from the mounting substrate so that the base portion of the electronic device does not directly contact the mounting substrate.

  Conventional stems for electronic devices include those disclosed in Patent Document 1 and Patent Document 2, for example. 2A and 2B show an example of a conventional stem for an electronic device, in which FIG. 2A is a perspective view seen from the mounting substrate side, and FIG. 2B is a cross-sectional view showing a state in which the electronic device stem is mounted on the mounting substrate. (C) is principal part sectional drawing.

  In FIG. 2, 100 is a base, 100a is a lead-through hole, 100b is a stand-off through-hole, 101 is a stand-off glass, 101a is a glass hemisphere, 101b is a glass corner, 101c is a glass column, and 102 is a seal. The attached glass (insulating glass), 103 (103a) are leads, 104 is a mounting substrate, 104a is a land, and 105 is solder.

  As shown in FIG. 2A, the stem for the electronic device has leads 103 at the four corners of the base 100. One of these leads 103a is called an earth lead for establishing electrical continuity with the base 100. The lead 103a is inserted through the lead through hole 100a of the base 100 and brazed (not shown). It is fixed to the base 100.

  The other three leads 103 are called insulating leads, and are placed through the lead through holes 100a of the base 100 and sealed with the sealing glass (insulating glass) 102 to the lead through holes 100a. It is fixed to the base 100.

  In the vicinity of each lead 103 at the four corners of the base 100, a stand-off glass 101 is disposed so as to fill the stand-off through hole 100b, and the glass hemispherical portion 101a of the stand-off glass 101 is disposed on the outer surface of the base 100 (on the mounting substrate side). ) Protruding. The glass hemisphere 101a swells to a diameter larger than the inner diameter of the stand-off through hole 100b.

  As shown in FIG. 2B, a land 104a is disposed in the through hole 104b of the mounting substrate 104, and the land 104a is formed to extend from the inner surface of the through hole 104b to the main surface of the mounting substrate 104. Yes.

  In a state where the stem for the electronic device is mounted on the mounting substrate 104, the glass hemispherical portion 101a abuts on the mounting substrate 104, the lead 103 is inserted through the through hole 104b of the mounting substrate 104, and the land 104a and the lead 103 are connected to the solder 105. It is joined with.

  According to this configuration, the glass hemispherical portion 101 a protruding from the base 100 abuts on the mounting substrate 104, so that the electronic device stem that forms the base portion of the electronic device (not shown) is formed between the base 100 and the mounting substrate 104. It is mounted on the mounting substrate 104 with a gap corresponding to the glass hemispherical portion 101a in between.

  Here, a method of sealing the standoff glass 101 in the standoff through hole 100b of the base 100 will be described. The base 100 is made of an iron-based alloy such as iron-nickel. The base 100 is assembled in a jig with a soft glass tablet inserted into the stand-off through hole 100b of the base 100.

  Next, the base 100 together with the jig is passed through a sealing furnace to heat the base 100 and the glass tablet. The melted glass fills the stand-off through hole 100b of the base 100 and rises hemispherically on the substrate mounting surface side of the base 100 to form a glass hemispherical portion 101a. When the temperature falls after passing through the sealing furnace, the glass is solidified to form the standoff glass 101, and the base 100 tightens the standoff glass 101 due to the difference in thermal expansion coefficient between the glass and the metal. The force acts, and the stand-off glass 101 is sealed in the stand-off through hole 100b by a so-called compression type mechanical stress. The base 100 is usually plated with nickel having a thickness of about 1 to 5 μm for the purpose of preserving.

  In the electronic device stem described above, the glass hemispherical portion 101 a of the stand-off glass 101 has an outer diameter larger than the inner diameter of the stand-off through hole 100 b of the base 100. Therefore, a glass corner portion 101b is formed along the opening edge of the standoff through hole 100b at the boundary between the glass columnar portion 101c that seals the standoff through hole 100b and the glass hemispherical portion 101a of the standoff glass 101. Is done.

  The mechanical stress concentration described above occurs on the glass corner portion 101b, and cracks are generated from the glass corner portion 101b as a starting point due to shear stress. In the worst case, the glass hemispherical portion 101a of the stand-off glass 101 is glass. The columnar part 101c may be sheared and dropped off.

In order to solve this problem, there has been a device in which the shape of the base is devised in order to alleviate the stress concentration on the stand-off glass. This configuration is shown in FIG.
As shown in FIG. 3A, the base 100 is provided with a protruding peripheral edge portion 100c around the opening of the stand-off through hole 100b. The protruding peripheral edge portion 100c is formed as a ring-shaped protrusion on the outer surface (mounting substrate side) of the base 100 so as to surround the opening of the stand-off through hole 100b. The protruding peripheral edge portion 100c was formed so that the outer peripheral diameter (ridge line portion) thereof matched the outer diameter size of the glass hemispherical portion 101a. Further, the corner portion of the inner wall surface of the projecting peripheral edge portion 100c was chamfered.

  Alternatively, as shown in FIG. 3 (b), there is one in which a thin-walled protruding peripheral portion 100c is formed by forming a concave groove 100d around the opening of the stand-off through hole 100b of the base 100.

3A and 3B, the protruding peripheral edge portion 100c is formed with a thin metal thickness, so that the base 100 is formed at the corner portion of the stand-off through hole 100b. The shear stress applied to the stand-off glass 101 can be relaxed. For this reason, the single unit of the stem for the electronic device was able to obtain a certain effect in preventing cracks and dropout of the glass hemispherical portion 101a.
JP-A-5-62518 Japanese Patent No. 2658886

  However, when the electronic device stem having the conventional configuration described above is incorporated into an electronic device to form a base portion of the electronic device and mounted on a mounting substrate or the like by a method such as solder flow, the molten solder is electronically transmitted through the mounting substrate. There was a problem of radiating radiant heat on the surface of the device stem.

  Unlike the heating by heat conduction through the atmosphere or the like, this radiant heat rapidly raises the surface of the object that receives the radiation. For this reason, the base 100 of the stem for the electronic device is in a state of receiving a thermal shock, and stress is concentrated on the surface portion of the base 100. This stress acts as a shear stress on the glass hemispherical portion 101a, and is caused by cracks and shear. It may cause dropout.

  The present invention solves the above-described conventional problems, and stress is not generated intensively on the surface portion of the metal base even when exposed to radiant heat from the solder when mounted on the mounting substrate. Therefore, an object of the present invention is to provide a stem for an electronic device that does not cause cracking or dropping in the glass portion and a method for manufacturing the stem.

  In order to solve the above-described problems, the stem for an electronic device according to the present invention is provided with a stand-off glass protrusion on the first main surface of the base made of metal, and the first main main body except for the stand-off glass protrusion. A thermal buffer film made of a metal having a lower thermal conductivity than the metal is formed on the surface.

  With the configuration described above, when mounting the stem on the mounting substrate with the first main surface facing the mounting substrate, the temperature rise near the surface of the first main surface of the base due to the radiant heat from the molten solder is thermally buffered. The film suppresses.

  The base is an iron-based alloy, and the thermal buffer film is a Sn—Pb film. The heat buffer film preferably has a film thickness of 3 to 20 μm, and the action of the heat buffer film can be ensured at this film thickness.

  The method for manufacturing a stem for an electronic device according to the present invention includes an assembling step of forming a standoff glass protrusion on the first main surface of the base, and at least a first step excluding the standoff glass protrusion after the assembling step. And a plating step of forming a thermal buffer film made of a metal having a lower thermal conductivity than the metal on the exposed surface of the main surface.

  In the assembly step, a glass tablet obtained by compressing and pre-baking glass powder and a binder is inserted into the through-hole of the base incorporated in the assembly jig, and the base is passed through the sealing furnace together with the assembly jig. Furnace and heat the base and the glass tablet, seal the through-holes with molten glass and form protrusions on the first main surface side, and in the plating step, Sn-Pb film that forms a thermal buffer film 3 Or a film thickness of 20 μm.

  As described above, according to the present invention, when mounting on a mounting board, even if the heat of the molten solder brings radiant heat to the first main surface side surface on the mounting board side of the base via the mounting board, By covering the base surface with a metal thermal buffer film with a lower thermal conductivity than the base metal, it is possible to suppress rapid temperature rise in the vicinity of the base surface, and glass cracks and glass hemispherical shedding may occur. It can be set as the stem for electronic devices which does not generate | occur | produce.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1A is a cross-sectional view of a stem for an electronic device according to an embodiment of the present invention, and FIG. 1B is a cross-sectional view of the electronic device stem mounted on a mounting substrate.

  1A and 1B, 1 is a base, 1a is a first through hole, 1b is a second through hole, 2 is a stand-off glass, 2a is a glass hemispherical part, 2b is a glass corner part, 2c Is a glass columnar part, 3 is a sealing glass (insulating glass), 4 is a lead, 5 is a Sn-Pb coating, 6 is a mounting substrate, 6a is a land, 6b is a through hole, and 7 is a molten solder.

  As shown in FIG. 1 (a), a base 1 made of an iron alloy such as iron-nickel has a standoff glass 2 sealed in a first through hole 1a that forms a standoff through hole. The glass 2 includes a glass columnar portion 2c that seals the first through-hole 1a, and a glass hemispherical portion 2a that bulges and projects in a hemispherical shape on the first main surface side that forms the outer surface (mounting substrate side) of the base 1. The glass hemisphere 2a is formed to have an outer diameter larger than the inner diameter of the first through hole 1a.

  The base 1 has a lead 4 inserted through a second through hole 1b forming a lead through hole sealed with a sealing glass (insulating glass) 3, and a glass hemispherical portion 2a of the standoff glass 2 and a sealing glass. A Sn—Pb film 5 that forms a thermal buffer film is formed on the surfaces of the first and second main surfaces and the side end surfaces of the base 1 except 3.

  As shown in FIG. 1B, the mounting substrate 6 on which the stem for the electronic device is mounted has a land 6a formed in a through hole 6b through which the lead 4 is inserted. The land 6a is formed from the inner surface of the through hole 6b. The main surface of the mounting substrate 6 extends.

  When mounting the electronic device stem on the mounting substrate 6, the lead 4 is inserted into the through hole 6 b of the mounting substrate 6, and the glass hemisphere 2 a and the mounting substrate 6 are brought into contact with each other to mount the electronic device stem on the mounting substrate. The molten solder 7 is flowed to the main surface on the opposite side which is not mounted on the mounting surface of the mounting substrate 6, that is, not opposed to the base 1.

  With this configuration, even if the molten solder 7 brings radiant heat to the surface on the first main surface side of the base 1 facing the mounting substrate 6 through the mounting substrate 6, it is made of an iron-based alloy such as iron-nickel. The Sn—Pb film 5 having a lower thermal conductivity than the base 1 covers the surface of the base 1, so that the Sn—Pb film 5 acts as a thermal buffer film and the temperature near the surface of the base 1 is rapidly increased. Suppress.

  For this reason, as shown in FIG. 1 (a), no crack is generated even in the glass corner portion 2b that is most likely to be the starting point of the crack, and when the stem for the electronic device is mounted on the mounting substrate 6, the molten solder flow Even if it performs, the drop by the shearing of a glass crack or the glass hemisphere part 2a does not generate | occur | produce.

  Here, when the film thickness of the Sn—Pb film 5 is preferably 3 to 20 μm, more preferably 5 to 15 μm, a sufficient effect as a thermal buffer film can be obtained. The reason is as follows. That is, the Sn—Pb film 5 is insufficient in action as a thermal buffer film when the film thickness is less than 3 μm. Further, when the film thickness exceeds 20 μm, the Sn—Pb film 5 is formed in a state where it climbs up to the glass hemispherical part 2 a or the glass part of the sealing glass 3, and the Sn—Pb film 5 peels off from the glass part. May cause damage to the action of the thermal buffer film.

  In addition, as embodiment of this invention, although the material of the base 1 was demonstrated as an iron-type alloy, it is not limited to this, In relation with the glass to be used, the thermal expansion coefficient of glass and a metal is Any metal may be used as long as a force that tightens the base 1 on the glass due to the difference works.

  Moreover, although demonstrated using Sn-Pb membrane | film | coat 5 as a thermal buffer film, it is not limited to this, If it is a metal membrane | film | coat with the heat conductivity lower than the base 1 and the effect of a thermal buffer is acquired, good. For example, when the base 1 is iron-nickel, it may be Pd, Cr, or the like.

  Furthermore, although the case where the Sn-Pb film 5 which is a heat buffer film is formed on all the surfaces of the base 1 except the glass hemispherical portion 2a of the standoff glass 2 and the sealing glass (insulating glass) 3 has been described, However, the present invention is not limited to this, and it may be formed at least on the first main surface of the base 1 that is a surface that receives the radiant heat from the molten solder 7.

  A method for manufacturing such a stem for an electronic device will be described with reference to FIG. First, in the assembly process, a glass tablet is inserted into the first through hole 1a and the second through hole 1b of the base 1. This glass tablet is obtained by compressing and pre-baking glass powder and a binder, and the glass tablet inserted into the first through hole 1a has a cylindrical shape having a predetermined volume and is inserted into the second through hole 1b. The glass tablet to be made has a cylindrical shape.

Then, the lead 4 is inserted into the hole of the cylindrical glass tablet inserted into the second through hole 1b of the base 1, and the base 1 in this state is incorporated into an assembly jig made of carbon.
Next, the base 1 together with the assembly jig is passed through a sealing furnace, and the base 1 and both glass tablets are heated to about 1000 ° C. to melt the glass tablets. The glass tablet inserted into the first through-hole 1a is melted to seal the first through-hole 1a and form a protrusion on the first main surface side, and becomes the stand-off glass 2 after solidification. The glass tablet inserted into the second through hole 1b seals the second through hole 1b and seals the lead 4 as the sealing glass (insulating glass) 3 to the second through hole 1b.

  In the plating step after this assembly step, an Sn—Pb film 5 having a thickness of 3 to 20 μm is formed on the exposed surface of the base 1, that is, the surface excluding the glass hemispherical portion 2a of the standoff glass 2 and the sealing glass 3. .

  Here, for the purpose of preserving as a pre-process of the assembling process, a single layer or multilayer base plating containing nickel or the like may be applied to the entire surface including the inner surfaces of the first through hole 1a and the second through hole 1b of the base 1. good. In the plating process, the lead 4 and part of the base 1 may be masked as necessary to selectively perform plating.

  The present invention is useful as a stem for an electronic device, and is particularly suitable for an electronic device stem having a stand-off glass.

(A) is sectional drawing of the stem for electronic devices in embodiment of this invention, (b) is sectional drawing which shows the mounting state of the stem for electronic devices (A) is a perspective view of a conventional stem for an electronic device, (b) is a cross-sectional view showing a mounting state of the stem for the electronic device, and (c) is a cross-sectional view of a main part of the stem for the electronic device. (A) is sectional drawing of the conventional stem for electronic devices, (b) is sectional drawing of the other conventional stem for electronic devices.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base 1a 1st through-hole 1b 2nd through-hole 2 Stand-off glass 2a Glass hemisphere part 2b Glass corner part 2c Glass columnar part 3 Sealing glass (insulating glass)
4 Lead 5 Sn-Pb Film 6 Mounting Board 6a Land 6b Through Hole 7 Molten Solder 100 Base 100a Lead Through Hole 100b Stand-Off Through Hole 100c Projecting Peripheral Edge 100d Groove 101 Stand-off Glass 101a Glass Hemisphere 101b Glass Corner Part 101c Glass column part 102 Sealing glass (insulating glass)
103 Lead 104 Mounting board 104a Land 104b Through hole 105 Solder

Claims (8)

A standoff glass protrusion is provided on the first main surface of the base made of metal, and a heat buffer film made of a metal having a lower thermal conductivity than the metal is formed on the first main surface except for the protrusion of the standoff glass. A stem for an electronic device. The electronic device stem according to claim 1, wherein the first main surface is mounted facing the mounting substrate. The stem for an electronic device according to claim 1, wherein the metal is an iron-based alloy. The stem for an electronic device according to any one of claims 1 to 3, wherein the thermal buffer film is a Sn-Pb film. 5. The stem for an electronic device according to claim 4, wherein the Sn—Pb film has a thickness of 3 to 20 μm. An electronic apparatus using the stem for an electronic apparatus according to claim 1. An assembly process of forming standoff glass protrusions on the first main surface of the base, and after the assembly process, at least the exposed surface of the first main surface excluding the standoff glass protrusions is more thermally conductive than the metal. And a plating process for forming a thermal buffer film made of a metal having a low rate. In the assembling process, a glass tablet obtained by compressing and pre-baking glass powder and a binder is inserted into a through-hole of the base incorporated in the assembling jig, and the base is passed through a sealing furnace together with the assembling jig. The base and the glass tablet are heated, the through-holes are sealed with molten glass, and projections are formed on the first main surface side. In the plating step, an Sn—Pb film that forms a thermal buffer film is 3 to 20 μm. The method for manufacturing a stem for an electronic device according to claim 7, wherein the stem is formed to have a thickness of 10 mm.

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