
AN1004
Application Notes
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+1 972-580-7777 
AN1004 - 2
2002 Teccor Electronics
Thyristor Product Catalog
Figure AN1004.2
Lead Bending Method
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.
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.
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.
Figure AN1004.3
Several Isolated TO-220 Devices Mounted to a 
Common Heat Sink
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 (T
) 
rating of the device must not be exceeded. Refer to the individual 
device data sheet rating curves (T
C
 versus I
T
) as well as the indi-
vidual device outline drawings for correct T
C
 measurement point.
Figure AN1004.4 through Figure AN1004.6 show additional 
examples of acceptable heat sinks.
Figure AN1004.4
Examples of PC Board Mounts
Figure AN1004.5
Vertical Mount Heat Sink
Several types of vertical mount heat sinks are available. Keep 
heat sink vertical for maximum convection.
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.
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 R
θ
JC
 device rating.
Incorrect
(A)
(B)
Correct
Heat Sink
Heat Sink
Printed
Circuit
Board
B
A