It has been a while before I posted something useful. On my search for obscure chips, I came around another interesting Chinese chip (which I don’t reveal yet). The chip was advertised as a cheap drop-in replacement for a American IC so I suspected it would be a clone. I wanted to look inside the chip to check if that is true.
For my post about the SWM050 I used the decap service from DirtyPCBs.com. The process was quite straightforward and the result was not hires pictures but there was enough to see . Browsing the internet it revealed the decapping process is quite easy; you need lots of personal protection gear, some acid, glasswork and a heat source.
First a note of precaution: boiling (or warm) acids are dangerous and eat easily through carbon based material like your clothing and skin. Always wear safety goggles, (acid resistive) gloves, long sleeves and easily to remove clothes. Also observe the recommendations by the manufacturers safety data sheets (SDS). The SDS for sulphuric acid is here and others can be found through google. Please read them carefully and obey them!
I choose to use sulphuric acid as the acid as it seems to do the job great, but is not as fumy and aggressive as nitric acid. I had a low wattage (55W) boiling plate and this combination gave almost no fumes. To minimize the fumes even more I had the beaker cover by another glass and performed the decapping outside.
I didn’t rush the procedure and the whole decapping process toke about one hour and this is the reward:
It doesn’t have any markings of the chip it is suppose to replace, so at least it is a own design (can still be a clone). I haven’t got a microscope yet to verify that or look better at the die. If you have a recommendations for a microscope, please share them in the comments.