JPH0442932Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field This invention relates to a leadless diode mounted on a printed circuit board or the like.

2. Description of the Related Art With the recent demand for high-density mounting of electronic components on printed circuit boards, leadless electronic components, in which lead wires are omitted from the component body, are increasingly being 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. 5, 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 composite wire having a volition layer formed on a copper layer coated with an iron-nickel wire into a predetermined length, and each has a cylindrical portion 3a, 4a and one end thereof formed by crushing. 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 sandwiching the semiconductor pellet 2 between the end faces of the glass sleeve 5a.

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.
has a recess 9 on its upper surface for storing and holding one electrode 4 of the diode 1 with its head 4b facing down, and the intermediate jig 7 has a hole 10 in a portion facing the recess 9 for storing and holding the glass sleeve 5. After supplying the electrode 4 to the recess 9, the head 4 of the electrode 4 is inserted through the hole 10.
A glass sleeve 5 is supplied onto the electrode 3b, 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. In this state shown in Fig. 6, heat the entire glass sleeve 5.
are welded to the outer peripheral surfaces of the cylindrical portions 3a, 4a of the upper and lower electrodes 3, 4, thereby manufacturing the diode 1 shown in FIG.

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 poor airtightness. There were times when it was 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
A space is provided between the glass sleeve 5 and the electrode heads 3b and 4b to prevent the glass sleeve 5 from directly contacting the electrode heads 3b and 4b, but this is difficult to implement in practice, especially when the lower electrode is sealed. Since the glass sleeve 5 is placed on the lower electrode 4, the glass sleeve 5 is firmly adhered to the head 4b of the lower electrode 4, resulting in a high rate of crack occurrence at the lower end surface of the glass sleeve 5, which is the cause of the diode. This makes it difficult to improve manufacturing 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 coefficient of thermal expansion of the solder layer and glass sleeve will change. Due to this difference, 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, resulting in loss of 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 provides a diode in which a glass sleeve is fixed to the outer periphery of a pair of columnar electrodes that are housed in a glass sleeve with a semiconductor pellet sandwiched therebetween.
A conductive layer made of aluminum and having poor wettability with glass was formed on the end face of the glass sleeve and the exposed end face of the columnar electrode, and a solder layer was formed thereon via an intermediate metal layer that easily adhered to aluminum and solder. This is a diode characterized in that the above object is achieved.

Effect: The end face of the glass sleeve sealed around the outer periphery of the pair of electrodes and the conductive layer formed on the end face of the electrode have poor wettability with glass, so cracks may occur at the end face of the glass sleeve. This can improve the yield of diodes.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

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.
16 is a semiconductor pellet of a diode, 16 and 16 are cylindrical electrodes formed by a pair of diamond wires that sandwich the semiconductor pellet 15, and 17 is a pair of electrodes 16 and 16.
A glass sleeve is welded to the outer peripheral surface of the semiconductor pellet 15 to hermetically enclose the semiconductor pellet 15 therein. Reference numerals 18 and 18 designate conductive layers that are deposited on both end surfaces of the glass sleeve 17 and the exposed end surfaces of the electrodes 16, 16 by vapor deposition, thermal spraying, or the like, and are made of aluminum, which has poor wettability with glass. Further, 19, 19 are conductive layers 18,
An intermediate metal layer such as copper is laminated on the intermediate metal layer 18 by a vapor deposition method or the like, and 20, 20 is a solder layer formed on the intermediate metal layer 19 by a plating method or the like, and is used as an electrode for each part.

Since solder is difficult to adhere to aluminum, the intermediate metal layers 19, 19 are formed of aluminum and copper, which easily adheres to solder, to complete the laminate of each layer of aluminum, copper, and solder on the end surfaces of the electrodes 16, 16. Make it.

The diode 14 is manufactured as shown in FIGS. 3 and 4. That is, using a jig (not shown) made of stainless steel or the like, a pair of electrodes 16, 16 holding a semiconductor pellet 15 as shown in FIG.
A sub-assembled body 21 is obtained in which a glass sleeve 17 is welded to the outer peripheral surface of the sub-assembled body 21. Next, conductive layers 18, 18 and intermediate metal layers 19, 19 are sequentially laminated on both end faces of this sub-assembled body 21, thereby obtaining a sub-assembled body 22 as shown in FIG. Thereafter, by forming solder layers 20, 20 on both end faces of this sub-assembled body 22, the diode 14 shown in FIG. 1 is manufactured.

The conductive layer 18 in such a diode manufacturing process,
Intermediate metal layers 19, 19 and solder layer 20 after 18,
In the manufacturing process No. 20, the end surface of the glass sleeve 17 is coated with conductive layers 18, 18 having poor wettability with glass.
Therefore, even if stress due to heat occurs between the end surface of the glass sleeve 17 and the solder layers 20, 20, this stress is absorbed by the conductive layers 18, 18.
Therefore, the incidence of cracks in the end face portion of the glass sleeve 16 is greatly reduced.

Effects of the invention According to the invention, the occurrence of cracks at the end face portion of the glass sleeve is significantly suppressed, the airtightness of the glass sleeve is further improved, and a leadless diode with high yield can be provided.

Furthermore, the conductive layer made of aluminum is inexpensive and can be easily formed on the end face of the glass sleeve and the columnar electrodes by vapor deposition, thermal spraying, or the like.

In addition, the conductive layer made of aluminum has poor wettability with glass and has the function of preventing glass cracks, and its poor solderability is compensated for by the solder layer formed on top of it via an intermediate metal layer. The solderability during mounting is good.

[Brief explanation of the drawing]

1 and 2 are a cross-sectional view and a side view including a partially cut-out portion showing one embodiment of the diode according to the present invention, and FIGS. 3 and 4 show the steps of manufacturing the diode shown in FIG. 1. FIG. FIG. 5 is a sectional view of a conventional leadless diode, and FIG. 6 is a partial sectional view of a sealing jig for manufacturing the diode shown in FIG. 15... Semiconductor pellet, 16... Electrode, 17
...Glass sleeve, 18...Conductive layer.

Claims (1)

[Scope of utility model registration request] In a diode in which the glass sleeve is fixed to the outer periphery of a pair of columnar electrodes that sandwich a semiconductor pellet in the glass sleeve, the end face of the glass sleeve and the exposed end face of the columnar electrode have wettability with glass made of aluminum. A diode characterized by forming an inferior conductive layer and forming a solder layer thereon via an intermediate metal layer that easily adheres to aluminum and solder.