STmicro: Same component marks, different marking method? - Page 1
Forum section: electronics / general

author: AndrejaKo
author_rank: Frequent Contributor
timestamp: July 08, 2013, 07:48:01 pm
content: Hi guys!I just wanted to ask if anyone here ever got STmicro components which have exactly the same marking text on them, but have been marked using different methods?I got 3 (now obsolete) TDA7231As which haveTDA7231AGA923ST PHLwritten on them. One of the chips was behaving strangely (but I can't rule out possibility of me killing it) and two seem to be working fine.The strange one (after looking with a microscope) seems to have been laser engraved, while the two which work fine seem to have text printed on them (I can see paint on the surface of the chips). All 3 have thin grooves running along the longer side of the DIP8. The strange one seems to have much smoother surface texture, while the two working ones have numerous cavities on their surface. The strange one has much deeper top side mark than the other two.So I wanted to ask is something like this common?I mean, I don't want to say that I think that the strange one is fake, but it looks fake to me.

author: c4757p
author_rank: Super Contributor
timestamp: July 08, 2013, 07:53:02 pm
content: I don't think I've ever seen an ST chip with a smooth surface.Pictures?

author: AndrejaKo
author_rank: Frequent Contributor
timestamp: July 08, 2013, 07:54:52 pm
content: Sorry, can't make them at the moment. My cell-phone camera is terrible and my regular camera isn't here.Actually, I'll see if I can use a scanner to scan the surface of the chips in great enough detail.

author: c4757p
author_rank: Super Contributor
timestamp: July 08, 2013, 08:02:27 pm
content: That would be awesome, if reflections off the smooth one aren't a problem.

author: AndrejaKo
author_rank: Frequent Contributor
timestamp: July 08, 2013, 08:24:35 pm
content: Sorry, the best my scanner can do is 600 DPI and the result is attached. The suspected fake is on the left, working one is on the right. The left one's inscription in real world looks grayish while the right one's is yellowish.

author: c4757p
author_rank: Super Contributor
timestamp: July 08, 2013, 08:32:17 pm
content: At a glance, right looks like a usual ST part, left looks cheap.

author: Stonent
author_rank: Super Contributor
timestamp: July 08, 2013, 10:22:34 pm
content: Is there anything on the bottom? Also the legs look different.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: July 08, 2013, 10:26:14 pm
content: Bear in mind that big companies have multiple fabs, and multiple packaging facilities,probably with different equipment so it's quite possible you may see the same chip with different cosmetics.

author: AndrejaKo
author_rank: Frequent Contributor
timestamp: July 09, 2013, 12:54:42 pm
content: Both chips have blank circle on the bottom. The strange chip has circle of greater diameter than the correctly working one.I'm aware that companies have different fabs and just the cosmetic differences wouldn't be all that surprising to me, but it's the combination of exactly the same markings and performance that I find strange. In fact, using image search, I couldn't find photos of two same looking TDA7231AsI mean, I'd expect that if two different fabs/packaging houses were making same chip, the package would have at least some sort of identification mark showing from where it came from, but I can't rule out the possibility that they could in fact be the same.I guess that 923 here would be date code, maybe 2009, 23rd week? This leaves GA and PHL uncounted for. Some manufacturers have documents explaining how exactly their packages are marked, but I can't find a similar document for STmicroelectronics.

author: Stonent
author_rank: Super Contributor
timestamp: July 09, 2013, 02:01:51 pm
content: Phl would usually be Philippines.

author: Monkeh
author_rank: Super Contributor
timestamp: July 09, 2013, 05:03:03 pm
content: ST parts can vary in appearance quite a bit. For example: