1. Thermal Equivalent Circuit for a Transistor

2. Junction Temperature Case TemperatureHeat Sink Temperature Ambient Temperature

3. Thermal Resistance from Junction to Case Thermal Resistance from Case to Heat Sink Thermal Resistance from Heat Sink to Ambient Total Average Power Loss

5. Motorola MS-10 Heat Sink

6. Performance Under Forced Air Flow

7. Thermal Characteristic in Free Air

8. Top View of MS-10 Heat Sink

9. Hole Pattern for a TO-3 Case

10. Mica Insulator

11. Thermal Resistances for Mica Insulators

13. Clip-On Heat Sinks

14. Thermal Performance

15. Thermal Resistance for Clip-On

16. Bond-On Extrusions for DIP Packages

17. Thermal Performance

18. Thermal Resistances for Bond-On

19. Example TO-220 case style dissipating 5 watts R JC = 3.0  C / Watt (from device spec) T Jmax = 150  C T Amax = 50  C Find the proper heat sink to keep the junction temperature from exceeding 150  C in natural convection.

20. Need to determine a value for R CS – depends on the mounting technique. If the device is mounted without an insulator, but only with Thermalcote, (silicone grease), check page 57, Figure 9 for TO -220 case style.

21. R CS = 1  C/W No Insulator Use Thermalcote

23. Thermalloy P/N 6030 Temperature rise above ambient@ 5 Watts Power Dissipation = 66  C

24. Thermal Resistance R SA As long as R SA is less than 16  C/W, the requirement is met.

25. Thermalloy P/N 6030