AN1004
Application Notes
Figure AN1004.4 through Figure AN1004.6 show additional
examples of acceptable heat sinks.
Incorrect
(A)
Correct
Figure AN1004.4
Examples of PC Board Mounts
Heat Sink
Printed
Circuit
Board
(B)
Lead Bending Method
Figure AN1004.2
When bending leads in the plane of the leads (spreading), bend
only the narrow part. Sharp angle bends should be done only
once as repetitive bending will fatigue and break the leads.
B
A
The mounting tab of the TO-202 package may also be bent or
formed into any convenient shape as long as it is held firmly
between the plastic case and the area to be formed or bent. With-
out this precaution, bending the tab may fracture the chip and
permanently damage the unit.
Figure AN1004.5
Vertical Mount Heat Sink
Several types of vertical mount heat sinks are available. Keep
heat sink vertical for maximum convection.
Heat Sinking
Use of the largest, most efficient heat sink as is practical and cost
effective extends device life and increases reliability. In the illus-
tration shown in Figure AN1004.3, each device is electrically iso-
lated.
Heat Sink
Figure AN1004.6
Examples of Extruded Aluminum
When coupled with fans, extruded aluminum mounts have the
highest efficiency.
Heat Sinking Notes
Care should be taken not to mount heat sinks near other heat-
producing elements such as power resistors, because black
anodized heat sinks may absorb more heat than they dissipate.
Figure AN1004.3
Several Isolated TO-220 Devices Mounted to a
Common Heat Sink
Some heat sinks can hold several power devices. Make sure that
if they are in electrical contact to the heat sink, the devices do not
short-circuit the desired functions. Isolate the devices electrically
or move to another location. Recall that the mounting tab of Tec-
cor isolated TO-220 devices is electrically isolated so that several
devices may be mounted on the same heat sink without extra
insulating components. If using an external insulator such as
mica, with a thickness of 0.004", an additional thermal resistance
of 0.8° C/W for TO-220 or 0.5° C/W for TO-218 devices is added
to the RθJC device rating.
Many power device failures are a direct result of improper
heat dissipation. Heat sinks with a mating area smaller than the
metal tab of the device are unacceptable. Heat sinking material
should be at least 0.062" thick to be effective and efficient.
Note that in all applications the maximum case temperature (TC)
rating of the device must not be exceeded. Refer to the individual
device data sheet rating curves (TC versus IT) as well as the indi-
vidual device outline drawings for correct TC measurement point.
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AN1004 - 2
©2002 Teccor Electronics
Thyristor Product Catalog
TECCOR [ TECCOR ELECTRONICS ]
