US 3117179 A
Description (OCR text may contain errors)
Jan. 7, 1964 E. G. BROWN 3, 7, 79
TRANSISTOR CAPSULE AND HEADER THEREFOR Filed July 24; 1959 ELMER G. BROWN INVENTOR.
ATTORNEYS United States Patent 3,117,179 TRANSHSTUR CAPSULE AND HEADER THEREFQR Elmer G. Brown, Mountain View, Caliii, assigzror, by mesne assignments, to Cievite Corporation, @levmand, 011150, a corporation of Ohio Filed July 24, 1959, Ser. No. 829,36t1 1 Claim. (Ci. 174--2) This invention relates generally to a transistor capsule suitable for high power transistors.
When semiconductive devices are employed at relatively high powers, it becomes ne essary to provide means tfCi conducting away or removing heat generated in the device. in general, most semiconductive devices are encapsulated in one manner or another. in certain instances, a heat transfer fluid such as transformer oil is placed within the capsule and serves to provide a medium for conducting heat away from the device. in other instances, the device is mounted in intimate contact with a metal header.
in one particular type of capsule, a copper heat sink is secured to the metal header to provide a relatively high heat capacity. The use of both a header and sink is necessary since it would be relatively diflicult to provide leads which extend into the capsule by conventional techniques. it is difficult to provide a lead-in through a copper header because of the diilerences in thermal expansion between the copper and the insulator, such as glass, surrounding the lead. The forces which arise destroy the vacuum seal.
it is, therefore, a general obgieot of the present invention to provide an improved transistor capsule and header assembly therefor.
it is another object of the present invention to provide a novel copper header and lead-in.
it is still a further object of the present invention to provide a transistor capsule which includes a header which is relatively inexpensive to manufacture and which provides a reliable seal between the lead-in assembly and .eader.
These and other objects of the invention will become more clearly apparent from the following description when taken in conjunction with the accompanying drawing.
Referring to the drawing:
FIGURE 1 is an elevational view in section of a transistor capsule in accordance with the present invention; and
FIGURE 2 is a sectional view taken along the line 2--2 of FEGURE 1.
Referring to the figures, the capsule includes a header assembly designated generally by reference numeral 11 and a cover 12 suitably secured thereto. The header assembly includes a copper or other igh heat capacity metal header 13. T he header may have secured on one surface a lead 14. The header is bored 16 to receive one or more lead-in assemblies designated generally by the reference numeral 17.
The lead-in assembly includes a metallic cylindrical sleeve 18 and an insulating material 19 in the form of a head which supports the lead 21 within the sleeve and spaced from the metallic walls. The material forming the sleeve 18 should have a thermal expansion corre sponding to that of the insulating material 19 whereby a suitable vacuum seal may be formed between the two parts. The insulating material 19 extends over a limited length of the sleeve, as indicated. The remaining portion of the sleeve is free. A rim 22 may be formed on the free end. Tie sleeve is inserted in the bore of the header and the free end is suitably sealed to the surface 23 of the header. Any differential erpansion between the header and the lead-in does not destroy the seal between the insulating material and sleeve. It will only serve to move the free end of the sleeve. By way of example, the lead-in assembly may include a Kovar lead and sleeve with a glass supporting and sealing bead. Glass to metal seals made with Kovar are relatively easy to make. The lead-in assembly can then be secured at the free end of the sleeve to a copper header.
The semiconductive device 26 may be mounted on the upper surface and the lead 21 bent over to maize contact with the upper surface. As illustrated, the device 26 is a two terminal device with electrical connection made to the spaced surface. evices having more layers may be encapsulated by providing more leaddn assemblies of the type described. The device is encapsulated by inserting the cap 12 over the device and welding around the lower peripheral edge 27. A suitable brazing ring 2% may be provided to facilitate welding.
Thus, it is seen that there is provided a capsule and a header therefor which is of improved design. The header itself may be made of high heat capacity, high conductance material and serve to directly receive the semiconductive device. The seal formed is a competent seal which is effected a minimum amount by differential expansion since the lead-in assembly is made of materials which have substantially the same coefficients of expansion. The only connection between materials having different coefficients of expansion is the top of the free end of the sleeve forming part of the assembly and, therefore, allows some movement without destroying the seal.
A capsule for transistors and the like comprising a metal header having a predetermined thickness, at least one cylindrical hole extending between the surfaces of said header, a semiconductive device carried on one surface of said header, at least one wire lead disposed in electrical contact with said device extending through said hole, a sleeve disposed about a portion of said lead, insulating material for supporting said lead in said sleeve, said insulating material disposed entirely within said sleeve and extending only partially along the interior len th of said sleeve whereby said sleeve has one end free of said insulating material, said free end having a narrow lip encircling the perimeter thereof and supporting said sleeve in spaced relation from said header within said hole, said sleeve having a length which is less than said predetermined thickness whereby the sleeve and insulating material are disposed entirely within said hole.
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