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I am using a TIP120 Darlington transistor in a through-hole (specifically TO-220) package, in a very simple application which does not generate much heat.

I remember reading that the metal tab at the top is only for connecting to an optional external heat sink.

Due to a design dimensional issue (unforeseen!), I need to reduce the height of this package in my case.

Can you cut the metal tab off without any effect on the functionality of the component?

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  • \$\begingroup\$ Why you did'nt use a transistor with lower power dissipation in another package i.e. TO-126? \$\endgroup\$ – GR Tech Jan 10 '15 at 19:23
  • \$\begingroup\$ @GRTech: Just circumstantial really! I happened to have this lying around, and am trying to put something together quickly. \$\endgroup\$ – boardbite Jan 10 '15 at 19:43
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I have done it, but I would never ship anything like that out.

I suggest clamping the "waste" end of the TO-220 in a vise firmly and sawing it with a fine tooth hacksaw blade, not allowing anything to touch the epoxy.

Shearing would be much faster and neater, but I fear it would distort the metal and cause the part to become more unreliable than necessary.

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  • \$\begingroup\$ +1, sticking the waste end in the vise, is how I cut all electronics components. \$\endgroup\$ – George Herold Jan 11 '15 at 0:23
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Removing the tab does not affect the functionality of the device, except for power dissipation. In fact, the SMT "DPAK" package is essentially that.

However, the manner in which you remove the tab may create excessive stresses on the device that will adversely affect its reliability. If you try to shear it off or bend it over, you may cause some separation between the epoxy and the metal. If you try to saw or grind it off, you may heat up the device excessively. So be careful, and be prepared for failure.

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