Page 67 - Power Electronics Handbook

60 Power semiconductor devices
Plastic packages such as TO220 are relatively inexpensive, easy to
mount, and the epoxy used gives a good hermetic seal.
The stud-type encapsulation is shown in Figure 1.36, for a thyristor. with
the dice hard soldered into the package, although compression bonding
could be used instead. The dice is soldered to the base and encapsulated in
ceramic, usually a top metal being used which is welded to the header.
An important consideration in high-frequency applications is the
package, which must have low stray capacitance and good cooling
properties, Figure 1.36(g) showing one type of package which can be used
for high-frequency transistors. Twin-emitter leads are used, which gives
symmetry of board layout when devices are combined for greater power.
The leads are low-inductance strip lines, which can interface to microstrip
lines used in UHF-VHF equipment. Beryllium oxide forms the dice
insulator, since it has good thermal conductivity and the dice is located
onto a copper stud which is bolted to a heatsink.

1.16 References

Bush, S. (19%) Thirtysomething, Electronics Weekly, 26 January, pp. 21-22.
Finkelstein, W. and Mondelli, A.A. (1995) Ion beam lithography - a paradigm shift in
technology, Semiconductor Internationul, May, pp. 55-58.
Goodenough, E (1994) DMOSFETS, IGBs switch high voltage, Electronic Design, 7 November,
pp. 95-105.
IR (1992) IGBT characteristics, Internationul Rectifier Application Nore AN-983A, pp.
1-12.
Jeong, H.J. et al. (1994) The future of optical lithography, Solid State Technology, April. pp.
39-47.
Levenson. M.D. (1995) Extending optical lithography to the gigabit era, Solid Stare
Technology, February, pp. 57-64.
Rosen, A. and Zutavern, E (1994) High-Power Optically Activated Solid-state Switches,
Artech House.
Singer, P. (1995a) CVD technology trends, Semiconductor International, February, pp.
55-62.
Singer, P. (1995b) Trends in ion implantation, Semiconductor Internationul, August, pp.
58-64.