heat sink and shunt

HEAT SINKS AND HEAT SHUNTS
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When transistors carry high currents they generate a lot of heat internally, which can destroy the transistor.

A heat sink is a way of removing this heat.
It is a metal plate with fins which act as radiators of the heat.
The transistor is bolted to the sink usually with some heat conducting paste smeared between them.

Often the case of the transistor is internally connected to the collector.
Therefore the transistor must be electrically isolated from the sink.
This is done by using transistor mounting kits consisting of thin mica washers and plastic mounting bushes.
These must be fitted correctly or the sink will not do its job correctly.

When components are being soldered to printed circuits, heat from the iron can travel up the lead and damage the component.
The heat shunt is clipped to the lead,and absorbs this heat protecting the component from damage.
Having said that, most components today are well able to handle high temperatures without use of a shunt.
There are a few special components which require use of a shunt.