JPH0442933Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to a leadless diode.

2. Description of the Related Art In accordance with the recent demand for high-density mounting of electronic components on printed circuit boards, there is a tendency for leadless electronic components, in which lead wires are omitted from the component body, to be frequently used. A typical leadless type diode is one in which a pair of electrodes sandwiching a semiconductor pellet of the diode are sealed with a glass sleeve, and a specific example thereof will be described below with reference to FIG.

In the diode 1 shown in FIG. 7, 2 is a semiconductor pellet, 3 and 4 are a pair of electrodes that sandwich the semiconductor pellet 2, and 5 is a glass sleeve that is welded to the outer periphery of the electrodes 3 and 4 to hermetically seal the semiconductor pellet 2. be. The pair of electrodes 3 and 4 are made by cutting a wire made of a steel layer coated with an iron-nickel wire and forming a volition layer into a predetermined length. It consists of heads 3b, 4b formed with a large diameter, and cylindrical parts 3a, 4.
A glass sleeve 5 is welded to the outer periphery of the cylindrical portions 3a, 4a while holding the semiconductor pellet 2 between the end faces of the cylindrical portions 3a and 4a.

Such a diode 1 is manufactured as follows using, for example, jigs 6 to 8 as shown in FIG. The jigs 6 to 8 are made of stainless steel, for example, and are composed of a lower jig 6, an intermediate jig 7, and an upper jig 8. The intermediate jig 7 has a hole 10 for storing and holding the glass sleeve 5 in a portion facing the recess 9. After supplying the electrode 4 to the recess 9, the intermediate jig 7 has a hole 10 for storing and holding the glass sleeve 5. A glass sleeve 5 is then supplied onto the head 4b of the electrode 4, and the semiconductor pellet 2 and the cylindrical portion 3a of the other electrode 3 are inserted into the glass sleeve 5. The upper jig 8 has a recess 11 on the lower surface for storing and holding the head 3b of the electrode 3 protruding from the glass sleeve 5, and a guide hole 12 passing through the top surface of the recess 11. A weight 13 is placed on the electrode 3 and presses the electrode 3 against the semiconductor pellet 2 with a predetermined load. The diode 1 shown in FIG. 7 is manufactured by heating the whole in the state shown in FIG. 8 and welding the glass sleeve 5 to the outer peripheral surfaces of the cylindrical parts 3a, 4a of the upper and lower electrodes 3, 4.

Problems to be Solved by the Invention In the diode 1, when the glass sleeve 5 is welded to the outer peripheral surface of the cylindrical portions 3a, 4a of the electrodes 3, 4, the end surface of the glass sleeve 5 is It may come in contact with and stick to the surface. In this way, the end surface of the glass sleeve 5 and the electrode head 3b,
If the end surface of glass sleeve 5 is stuck,
Due to the difference in coefficient of thermal expansion between the electrodes 3 and 4, stress is generated in the diametrical direction at the end surface of the glass sleeve 5 during cooling after sealing, and this stress causes cracks in the end surface of the glass sleeve 5, resulting in airtightness. was sometimes damaged.

Therefore, when sealing the glass sleeve 5, the end surface of the glass sleeve 5 and the heads 3b, 4b of the electrodes 3, 4
Although a gap is provided between the glass sleeve 5 and the electrode heads 3b and 4b to prevent the glass sleeve 5 from coming into direct contact with the electrode heads 3b and 4b, this is difficult to implement in practice. Since the glass sleeve 5 is placed on the top 4b of the lower electrode 4, the glass sleeve 5 adheres firmly to the head 4b of the lower electrode 4, resulting in a high crack occurrence rate at the lower end surface of the glass sleeve 5. This makes it difficult to improve yield and reliability.

In addition, even if the columnar electrode does not have a head, an external electrode is formed by a solder layer on the electrode end surface, so if heat is applied after the external electrode is formed, the difference in thermal expansion coefficient between the solder layer and the glass sleeve As a result, stress is generated in the diametrical direction at the end surface of the glass sleeve during cooling, and this stress may cause cracks in the end surface of the glass sleeve, impairing airtightness.

Therefore, an object of the present invention is to provide a leadless diode with good yield and reliability in which the occurrence of cracks at the end face portion of a glass sleeve is reduced.

Means for Solving the Problems The present invention fixes the glass sleeve to the outer periphery of a pair of columnar electrodes that sandwich a semiconductor pellet in the glass sleeve, and also attaches a glass made of resin to the end surface of the glass sleeve. The above object is achieved by a diode characterized in that an intermediate layer having poor wettability is formed, and a conductive layer is formed on the intermediate layer and on the end surface of the electrode exposed from the glass sleeve. This is what I did.

Function A structure in which an intermediate layer with poor wettability with glass is formed on the end face of a glass sleeve sealed around the outer periphery of a pair of electrodes, and a conductive layer as an external extraction electrode is formed on top of the intermediate layer. Even when multi-layered with copper, solder, etc., the intermediate layer prevents the conductive layer from adhering to the end surface of the glass sleeve, thereby preventing the occurrence of cracks at the end surface of the glass sleeve.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 to 6.

FIG. 1 is a cross-sectional view of the diode 14 according to the embodiment of the present invention, and FIG. 2 is a side view thereof.
1 is a semiconductor pellet of a diode, 16 and 17 are a pair of cylindrical electrodes that sandwich the semiconductor pellet 15, and 18 is a glass sleeve welded to the outer peripheral surfaces of the electrodes 16 and 17. Reference numerals 19 and 19 indicate an intermediate layer made of resin that is formed on both end surfaces of the glass sleeve 18 and has poor wettability with glass; 20 and 20 indicate intermediate layers 19 and 19 on both ends of the glass sleeve 18;
Electrodes 16 and 17 exposed from glass sleeve 18
A conductive layer of copper or the like is deposited on the end faces of the 21, 21 are solder layers formed on the conductive layers 20, 20 by a plating method, a vapor deposition method, etc., and are used as external electrodes.

The pair of electrodes 16 and 17 are made of a uniform wire of the same length, and both are fixed to the glass sleeve 18 at a position slightly inside both ends of the glass sleeve 18. Sealing with the glass sleeve 18 is performed using a lower jig 2 made of stainless steel as shown in FIG. 6, for example.
2. Using the intermediate jig 23, the upper jig 24, and the weight 25, it is carried out as follows. The lower jig 22 has a convex portion 26 having a smaller diameter than the electrodes 16 and 17 on its flat upper surface, and the intermediate jig 23 has a hole 27 in a portion opposite to the convex portion 26 into which the glass sleeve 18 is inserted.
The glass sleeve 18 is supplied from this hole 27 onto the periphery of the protrusion 26 of the lower jig 22, and then one electrode 16, the semiconductor pellet 15, and the other electrode 17 are sequentially supplied into the glass sleeve 18. . The previously supplied electrode 16 is placed on the convex portion 26,
The semiconductor pellet 1 is lifted up by a certain distance from the lower end surface of the glass sleeve 18 and placed on this electrode 16.
The upper end surface of the other electrode 17 that presses the glass sleeve 18 is located at a position lower than the upper end of the glass sleeve 18 by a predetermined distance. The electrode 1 is placed on the upper jig 24 located on the intermediate jig 23.
A guide hole 28 is provided in a portion facing the electrode 7 , and a weight 25 inserted into the guide hole 28 is placed on the electrode 17 . When the state shown in FIG. 6 is maintained and the whole is heated, the glass sleeve 18 is welded to the outer peripheral surfaces of the upper and lower electrodes 16, 17, and a diode sub-assembly body 29 as shown in FIG. 3 is obtained. It will be done.

For such a sub-assembled body 29, the present invention first coats both end surfaces of the glass sleeve 18 with a resin having poor wettability with glass to form the intermediate layers 19, 19. Form. Since the end surfaces of the glass sleeve 18 protrude from the end surfaces of the electrodes 16, 17, the intermediate layers 19, 19 can be easily formed by a stamp coating method or the like. Next, as shown in FIG.
Conductive layers 20, 20 are formed by plating copper or the like on 9 and the exposed end surfaces of electrodes 16, 17. The conductive layers 20, 20 may be formed by laminating multiple layers of metal such as silver or gold. After that, conductive layers 20,2
0, solder layers 21, 21 are formed.

Such conductive layers 20, 20 and solder layers 21, 2
1, even if stress due to heat is generated between the end surface of the glass sleeve 18 and the solder layers 21, 21, the intermediate layers 19, 19 having poor wettability with glass are interposed on the end surface of the glass sleeve 18. This absorbs the stress and prevents cracks in the glass sleeve 18.

Note that the end surface of the glass sleeve 18 and the electrodes 16,1
The positional relationship of the end faces to the glass sleeve 18 is not limited to the above embodiment, and the present invention can be similarly applied even if the end faces of the electrodes 16 and 17 slightly protrude from the end face of the glass sleeve 18.

Effects of the invention According to the invention, the intermediate layer formed on the end surface of the glass sleeve greatly suppresses the occurrence of cracks in the glass sleeve, further improving the airtightness of the glass sleeve, and producing high-yield and highly reliable diodes. can be provided.

Further, since the intermediate layer is formed only on the end surface of the glass sleeve, it does not need to be a conductive member and may be made of a resin material, is inexpensive, and can be easily applied using a stamp coating method or the like. Furthermore, the electrode can be easily soldered by a conductive layer formed on the intermediate layer and the end face of the columnar electrode.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views and side views showing one embodiment of the diode according to the present invention, FIGS. 3 to 5 are cross-sectional views of the diode shown in FIG. 1 at various manufacturing steps, and FIG. 2 is a partial sectional view of a sealing jig for manufacturing the diode shown in FIG. 1. FIG. Figure 7 is a cross-sectional view of a conventional leadless diode, and Figure 8 is a cross-sectional view of a conventional leadless diode.
It is a partial sectional view of the sealing jig which manufactures the diode of a figure. 15... Semiconductor pellet, 16, 17... Electrode, 18... Glass sleeve, 19... Intermediate layer,
20... Conductive layer.

Claims (1)

[Scope of utility model registration request] The glass sleeve is fixed to the outer periphery of a pair of columnar electrodes that are housed with semiconductor pellets sandwiched between them, and an intermediate layer made of resin and having poor wettability with glass is formed on the end surface of the glass sleeve. A diode characterized in that a conductive layer is formed on the intermediate layer and on the end surface of the electrode exposed from the glass sleeve.