TO-247 metal pad shape

[Circlotron]

Here's a pic of a ST branded TO-247 dual schottky diode. Nothing special at all. The question is, why is the edge of the metal pad such a complicated shape? Some other manufacturers have a simple rectangle. The sides almost look like they have had a TO-220 punched out. What about the top corners? Any ideas?

[Muttley Snickers]

It would appear that the designer had a fire hydrant fetish or something, this in turn begs the question of what's up with the burn marks on the legs ?.   

[djQUAN]

what's up with the burn marks on the legs ?.   

It is shiny solder. Dark part appears to be the photographer's hair.

[Circlotron]

Shiny tinned leads.
Dark part is a reflection of the black plastic phone case.
Hair? I wish... 

[SeanB]

Probably a requirement for the production machinery, wanting a shape that would be easy for the automatic machinery to align within the feed line, so the assembly of the dies would be done perfectly each time, and then the bonder would get the pads attached to the die after the epoxy cure or the soldering operation. Then the final pressure encapsulation fills in all the voids and attaches the leads, then a final punch strips the leadframe from the device, and then another automatic grip passes the leads through a tinning bath for long reliability, then into the tubes for shipping after a quick functional test and a labelling operation.

[T3sl4co1l]

IIRC, a lot of the ones I've broken open also have features on the inner face: a coined profile around the edge, or a bumpy texturing on the surface.

IGBT, from IR, I think?



(It's a co-pack, so the shiny rectangle is the antiparallel diode, which was shattered when the device cracked.  The larger square, more easily visible by the outline impression it left on the plastic, is the IGBT die.  It exploded in arc flash, hence the molten glob on the plate.)

Tim

[djQUAN]

Hair? I wish... 

The shapes I would think are dependent on the punch dies.
The semicircles on left and right of the mounting hole (front side) are parts of the front mold that push the copper tab to the back of the mold for the exposed copper pad.
The shapes in the back are in such a way that the plastic case could flow behind some parts of the copper tab to keep it together better. If you smash it and analyze the copper tab you'll see what I mean.
That's what I think about them