Just had to use my tip I invented a while back. This time a SIL IC with the lettering side of the IC 2 mm from a large block cap. Would have required 3 hours taking boards apart and back together to desolder just to read.
Used a 1mm steel rod covered with some turns of PTFE for the "rubbing" and pulling a length of PTFE around the IC through the gap to take the image. I urge everyone to give it a try, so it is impressed on memory for when needed, its just like magic
How to read unreadable IC/transistor lettering Yes, just like magic. I could not read 3 of the 5 characters on a heat damaged TOP66 power transistor. I wondered if a sort of "brass rubbing" would work. I just happened to have some plumber's PTFE tape to hand ( nominal 0.05 to
0.08 mm thick). Laid a piece over the power tranny, rubbed with a finger nail, and the missing characters came up like magic. As the characters remained on the PTFE, as an image , I realised you could use this technique to read IC lettering where it is imppossible to read, because of constrictions and inability to introduce an inspection mirror or even just where you cannot get the illumination at just the right angle to read. You need access space enough to introduce a piece of PTFE and then rub it with the wooden end of a small artist's brush, or similar, wrapped in some of the PTFE, so it rubs easily without dragging. Don't rub too firmly because you want the relief print to show as clear and the rest of the PTFE becoming translucent rather than the original white. Remove and read with a backlight or against something matt black. Maybe a couple of attempts to get a clear image in all parts of the label. May even be worth trying on reverse-engineering-proofed, rubbed off, IC lettering. Useful for indistinct moulding logos / lettering etc on small plastic parts, gives some contrast.-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on