LM4780TA (Non Insulated Type)
 

hi guys,
take look at the back of the chips (LM4780TA)
the metal plate seem tarnish. is this normal?

http://img852.imageshack.us/img852/1...4780taback.jpg

same goes for LM4702CTA
http://img850.imageshack.us/img850/4...702ctaback.jpg

thank you.

shoudl be more careful with word.
i mean non-isolated

I doubt anything is wrong with them. As long as you got them from a legit supplier that you know supplies authentic chips, don't worry about it. I have plenty of ICs laying around with similar "tarnish". If it's bothering you, get some rubbing alcohol and a Q-tip.

Though the casing on the second ones do look a little odd...

hi,
yes i got it from a legit supplier locally.
thanks for the assurance.

the casing on the second one are from LM4702CTA.

anyone from the semiconductor packaging industry please do help to comment from the manufacturing point of view.

thank you.

I wouldn't try much aggressive cleaning of the heat transfer surface.

If you're going too aggressive with sandpaper or a file or something, while you'll make the surface shiny, it's easy to take off more material from the edges, and make a convex surface with less effective heat transfer area.

Maybe some steel wool, but it looks pretty normal to my eye.