JPS59224150A - Glass mold type semiconductor device - Google Patents

Abstract

PURPOSE:To solder a semiconductor pellet to the flat surface of an electrode, by using the electrode, which comprises a core material whose main component is copper and a tube material whose main component is an alloy of iron, nickel, and cobalt that is bonded to said core material metallurgically, thereby eliminating humidity resisting problem with respect to leads. CONSTITUTION:An electrode 6 comprises a core material 6a of copper including slight amount of zirconium and a tube material comprising 30wt% nickel, 14.5wt% cobalt, 0.45wt% manganese, and iron as a remainder material, which are metallurgically sintered. Since machining can be readily performed, an end surface, to which a silicon pellet is soldered, can be readily made flat. In order to prevent the diffusion of the copper component of the core material into the silicon pellet 1 by the heating at the time of soldering or burning of glass, or in order to prevent the deterioration of characteristics of the silicon pellet 1 caused by the formation of the alloy, it s recommended that a shielding film made of nickel or titanium is provided on the main surface of the silicon pellt, which is not shown in the Figure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a glass mold type semiconductor device, particularly to an electrode structure of an axial lead type diode.

[Background of the invention]

Generally, this ridge diode has the structure shown in FIG. That is, a brazing filler metal 2 mainly composed of aluminum is placed on the amphiphilic surface of the silicon pellet L with the p0 junction J exposed on the side surface.
Glue an electrode 3 of yodimolybdenum or tungsten,
The surrounding area is sealed with glass 4. The electrode 3 is preliminarily provided with a lead 5 whose main component is copper. Glass 4 is p
This subassembly is used to stabilize and seal the surface of the n-junction J, and after a so-called subassembly in which a silicon pellet 1 is brazed and clamped to an electrode 3 is prepared, a glass slurry made by kneading glass powder and water is poured into this subassembly. It is molded by coating the surrounding area and firing it.

Molybdenum or tungsten has a hot broom tensile coefficient similar to that of silicon or glass. It is effective as an electrode material because it does not generate excessive thermal stress at the bonded part and has excellent thermal conductivity and electrical conductivity, but it has poor workability and is difficult to use on the flat surface to which silicon pellets 1 are soldered. The flatness is low, and the adhesion to the lead 5 is poor, and even if special percussion welding is performed, the welded portion may be corroded by moisture, so it cannot be said to have sufficient moisture resistance.

Therefore, materials to replace molybdenum or tungsten are being developed, but all of them have a larger coefficient of thermal expansion than molybdenum or tungsten.

For example, the thermal stress σ acting on the bond between the electrode and the glass is expressed by the following formula.

σ=ΔT(αG−α,) ...(1)Δ
T Temperature change during firing α G Coefficient of thermal expansion of Ni glass α・: Coefficient of thermal expansion of electrode In order to reduce thermal stress σ, coefficient of thermal expansion α of the electrode. If it cannot be reduced, the temperature change ΔT during glass firing is reduced. In other words, it would be sufficient to use a glass with a low transposition temperature, but in reality, glass with a sufficiently low transposition temperature has not been obtained due to considerations such as the coefficient of thermal expansion αG and the surface stabilization function.

Therefore, the electrode materials that have been developed to date to replace molybdenum or tungsten are
I couldn't say it was sufficient.

[Purpose of the invention]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a glass mold type semiconductor device which can solve the problems caused by using molybdenum or tungsten electrodes and which can be mass-produced.

[Summary of the invention]

The present invention, which achieves the above object, is characterized by comprising a core material mainly composed of copper and a cylindrical material mainly composed of an iron-nickel-cobalt alloy metallurgically bonded to the core material. It consists in using electrodes. The semiconductor slab is brazed to the end face parallel to the cross section of this electrode, and the leads are bonded to the core material.

[Embodiments of the invention]

The present invention will be explained below based on the embodiment shown in FIG.

In FIG. 2, the same or equivalent parts as shown in FIG. 1 are given the same reference numerals.

6 is an electrode according to the present invention, which is made of a copper core material 6a containing a small amount of zircon, 30 wt% nickel, and 14.5 Wtl.
The tube material 6b is made of cobalt of 0.45 wt%, manganese of 0.45 wt%, and the balance iron.

The core material 6a and the cylinder material 6b are metallurgically bonded.

That is, the shape of the electrode 6 is obtained by cutting the material obtained by HW wire drawing into a predetermined size.
A silicon pellet 1 is brazed to the end face parallel to the cross section. Since cutting and processing can be easily performed, the end face to which the silicon pellet is to be brazed can be easily flattened.

Although not shown, in order to prevent the properties of the silicon pellet 1 from deteriorating due to diffusion or alloying of the copper component of the core material into the silicon pellet 1 due to heating during brazing or glass firing, the silicon pellet 1 is It is preferable to provide a shielding film of nickel, titanium, etc. on the main surface.

The lead 5 is welded to the core material 6a in advance.

Since both are of the same type of metal, the welding strength is high and the bond has excellent moisture resistance.

The thermal expansion coefficient of the core material 6a in the temperature range of 30 to 6001 T is 20X10-'/lr, and that of the cylindrical material 6b having the above composition is 7.6xto-'/c. Due to the shrink-fitting effect of the cylindrical material 6b, the coefficient of thermal expansion of the stain pole 6 in the cross-sectional direction is approximately equal to that of the cylindrical material 6b. On the other hand, in the axial direction, the shrink fit effect of the cylindrical member 6b does not work, and the coefficient of thermal expansion is a composite of both.

FIG. 3 shows an example. The figure shows the coefficient of thermal expansion as a curve when heated to each temperature. The solid line in the figure is for the composition according to the present invention, and the parameters are the cross-sectional area of the core material 6a relative to the cross-sectional area of the electrode 6 expressed in φ.

For comparison, the dotted line indicates the coefficient of thermal expansion of an electrode having a similar structure in which an alloy consisting of 60 wt% iron and 40 Wtq6 nickel is used as the cylindrical material and the area ratio of the core material is 48 inches.

According to Figure 3, the axial coefficient of thermal expansion of the electrode with the tube material mainly composed of iron-nickel-cobalt is lower than that of the electrode with the tube material mainly composed of iron-nickel-cobalt at the same temperature. It is clear that it is quite small. It is also clear that when the temperature exceeds around 300C, the smaller the core area ratio, the smaller the thermal expansion coefficient.

FIG. 4 shows the relationship between the average coefficient of thermal expansion of the electrode at 30 to 600 C and the core area ratio when a tube material having a self-composition of 1 is used.

According to FIG. 4, it is clear that as the core material area ratio increases, the uniform heating + y tensile coefficient increases.

In a region where the area ratio is 20% or less, the change in the coefficient of thermal expansion is small, the thermal conductivity is inferior to molybdenum, and it no longer functions as an electrode. Moreover, when it exceeds 60%, the thermal expansion coefficient increases rapidly, and the thermal expansion coefficient of copper (=zoxto-' /
Since it approaches C), an area ratio of 20 to 60 inches is effective.

For comparison, the thermal expansion coefficient of molybdenum is shown in FIG. 4, and compared to molybdenum, the thermal expansion coefficient of the electrode according to the present invention is large.

On the other hand, when looking at glass materials, the dislocation temperature is 500C.
There are glasses on the market that are smaller than that, so
As is clear when considered in conjunction with FIG. 3, the electrode according to the present invention generates little thermal stress between the electrode and the glass even when the glass is fired, and can be put to practical use.

That is, evaluation of the temperature characteristics of glass is performed at three temperatures: softening point, dislocation point, and yield point. These are all natural logarithmic values of the viscosity η, and the temperature can be quantitatively determined. The transposition temperature is defined by the temperature at which togη=13.3, is the lowest temperature, and is the temperature at which glass starts to flow. In general, glass firing is performed at a temperature lower than the transition temperature12.
Efforts have been made to carry out the process at a high temperature of 0 to 180C to sufficiently lower the viscosity of the glass and improve its wettability with the silicon pellets 1 and electrodes 6. In the cooling process after firing the glass, the viscosity of the glass is low in the region above the transposition temperature, and no stress remains inside the glass because it is close to a liquid state.

Therefore, commercially available glass having a transition temperature of around 500'c or lower can be used as a molding material since the coefficient of thermal expansion of the electrode of the present invention is small in this temperature range.

〔Effect of the invention〕

As explained above, according to the present invention, since an electrode is used instead of molybdenum or tungsten, there is no problem of moisture resistance with the lead, and the semiconductor pellet is brazed to the flat surface of the electrode. Since this electrode can be easily obtained, it is also suitable for mass production.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing a conventional axial lead type SOJ lath molded diode, Fig. 2 is a cross-sectional view of an axial lead type glass molded diode showing an embodiment of the present invention, and Fig. 3 is a cross-sectional view showing an axial lead type glass molded diode used in the present invention. FIG. 4 is a diagram showing the relationship between the core area ratio and the average coefficient of thermal expansion of the electrode used in the present invention. l... Silicon pellet, 2... Brazing filler metal, 4...
Glass, lead...lead, 6...electrode, 6a...core material, 6b...tube material. Agent Patent Attorney Akio Takahashi y a r5on-1 [z]

Claims (1)

[Claims] 111. In a glass-molded semiconductor device in which an electrode with leads is brazed on the bidirectional surface of a semiconductor pellet and the surrounding area is molded with glass, the electrode is made of iron metal that has been metallurgically bonded to a core material whose main component is copper. A glass mold type semiconductor device characterized in that it is made of a cylindrical material whose main components are nickel-cobalt. 2. In item 1 above, the tube material is an alloy consisting of 30 wt% nickel, 14.5 wt% cobalt, Q, 45 wt% manganese, and the remainder iron, and the core material has a cross section with respect to the electrode. A glass mode semiconductor device characterized in that the area ratio is 20 to 60%. 3. In the above item 1, the glass has a transition temperature of 500C.
A glass-molded semiconductor device characterized in that it is close to or lower than that.