This sort of information seems to be unusually difficult to obtain, either on the web or elsewhere, and I have had great difficulty in getting thermal resistance data from anywhere - although as you shall see as you read on, I have managed it. Terms such as 'thermal resistance' and '☌ / Watt' are a little daunting for the uninitiated, and the purpose of this article is to explain how thermal transfer works, from the transistor die until it is finally dispersed into the atmosphere. The design of heatsinks, or to be more exact for most builders, the selection of a suitable heatsink, is not difficult once the basics have been mastered. The material here is the result of a lot of hard work, research, personalĮxperience and (what should be) common knowledge. I have had a lot of additional information supplied by readers (you know who you are, and thank you for your input). You would be surprised how much I learned while researching and writing this material, and

read all of this article - not just the bit you think you need. If the devices are hot and the heatsink is cold, then you haven't mounted the devices properly, or you used an inappropriate mounting technique (such as silicone washers for a transistor dissipating high power). Much of this article concentrates on the mounting techniques, and if you get that wrong, it won't matter how good your heatsink is. The bigger and better the heatsink you use, the lower the operating temperature of the devices mounted on it, provided you take great care to ensure that the interface between the device(s) and heatsink are as good as you can achieve. There Is No Such Thing As A Heatsink That's Too Big A point I have made in several articles and projects needs to be reiterated here . What are the essential requirements? Which things make the biggest difference? These questions may not have occurred to many readers, but they are very important to ensure the long term reliability of your projects. There are many misunderstandings and misconceptions about transistor mounting. This article is essential reading for anyone who uses heatsinks in audio, and the same principles apply for power control, RF and CPU cooling, as well as many other applications in electronics.

15.1 - Thermal Conductivity Of Various Materials.

11.2 - Further Reductions of Thermal Resistance.

7 - Case to Heatsink Thermal Resistance.

6 - Junction to Case Thermal Resistance.

4 - Measuring Heatsink Thermal Resistance.

2n 3055 transistor