I've recently acquired some LM2596T-5.0 3A buck converters. They are TO-220-5L packages with bent leads similar to this image:

TO-220-5L Bent

I have seen other TO-220-5L components with straight leads like this:

TO-220-5L Straight

My question is whether there is a good reason why they are bent (arcing, magnetic interference, etc) or is it just to make mounting easier, or some other reason. The bent lead don't work very well on breadboards or prototype boards so I have straightened them and then fanned them out a bit so they will fit but I just wondered if this would cause me a problem at some point.

  • 3
    \$\begingroup\$ Just a guess, but for higher currents, you want thicker PCB traces and that is easier when the pins are further apart (hence staggering them). It also leads to 0.1" pitch pins (though the second row is staggered by 0.05" from the other). \$\endgroup\$ – Tom Carpenter Aug 21 '15 at 2:37
  • \$\begingroup\$ @TomCarpenter: I thought that might have been the case when I ordered them but it turns out the leads are thinner (not narrower in width but thinner) than any TO-220 package I have ever used (78XXs, TIP120s, etc) and neither row seems to be spaced to fit a standard 0.1" pitch breadboard or prototype board without bending them apart slightly -- especially, as you mention, the back row. \$\endgroup\$ – ThatAintWorking Aug 21 '15 at 2:43
  • \$\begingroup\$ Interesting. Thinner isn't necessarily an issue (easier to bend?) as the distance is short, and internally the bond wires will be much thinner anyway. It is interesting that they don't fit 0.1" - I've come across ones that do before (bar the back row of course). Maybe those were 7 pin ones, can't remember. \$\endgroup\$ – Tom Carpenter Aug 21 '15 at 2:52
  • \$\begingroup\$ You're right, they are 0.134" for that part as per the Package Drawing \$\endgroup\$ – Tom Carpenter Aug 21 '15 at 2:54

There are 2 reasons for the bent leads: 1, more design area for the PCB; 2, easier to install or less error, since there is only one orientation that will fit.

  • \$\begingroup\$ Note: the second point is also known as Poka-yoke. \$\endgroup\$ – Franklin Yu Jun 22 '16 at 22:56

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.