Fake Alpha and Omega semi parts? - Page 1
Forum section: electronics / beginners

author: umkumiut
author_rank: Contributor
timestamp: February 04, 2019, 05:26:57 pm
content: Hi All,I bought two Li-Ion protection modules from ebay and the main MOSFETs look suspicious to me on one of them.Both are for 2 cells in series and have balance circuits too.The first one looks decent to me (blue soldermask). It is rated for 10A, uses 2x2 MOSFETs to switch the load with the marking "D514" and the logo of Alpha and Omega semi.1st module:https://imgur.com/a/rzAXm9CThe second has the suspicious looking parts (green soldermask). The module itself should handle 20A. The main switching MOSFETs have the logo of the AOS again, with the marking "D472". However, it looks like that the original markings have been grinded off and then they were marked by laser again. Compared with the MOSFETs of the other board, the texture of the molding is pretty different.2nd module:https://imgur.com/a/i15hoU9https://imgur.com/a/keVY0GFhttps://imgur.com/a/scsFg3gWhat do you think? Does it really worth faking an AOS part?Would you trust it?

author: mvs
author_rank: Frequent Contributor
timestamp: February 04, 2019, 05:52:17 pm
content: Quote from: umkumiut on February 04, 2019, 05:26:57 pmWhy not? Its a popular brand in Asia. You can measure RDSon and take decision based on numbers (Vds can not be an issue here), or just replace it with proper MOSFET you can trust.BTW AOD472 is obsolete, a bit strange decision to use it in production and/or to fake it.

author: Tomorokoshi
author_rank: Super Contributor
timestamp: February 04, 2019, 06:03:13 pm
content: Likely fake. Sanded and lasered. Notice the rough edges along the perimeter of the top surface.As for:Quote from: mvs on February 04, 2019, 05:52:17 pmObsolete parts almost appear to be targeted for this type of fake. It makes the supplier of the fake become very attractive to the company purchasing a part they otherwise can't get.

author: wraper
author_rank: Unknown
timestamp: February 04, 2019, 06:06:23 pm
content: 100% sanded.

author: mvs
author_rank: Frequent Contributor
timestamp: February 04, 2019, 06:29:28 pm
content: Quote from: Tomorokoshi on February 04, 2019, 06:03:13 pmYes, in case of some custom/special parts it make sense. But MOSFET are quite generic parts, there is almost no effort to pickup replacement.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 04, 2019, 06:30:50 pm
content: Quote from: umkumiut on February 04, 2019, 05:26:57 pmIf you have to ask, then:The answer is yes.You can safely assume that. Doesn't matter how you feel about the situation, doesn't matter the particulars. If anything, you should be looking for reasons, or tests, that can prove it'snotfake!This is a boringly common question here, with a boringly common answer. It should be stickied, or something...(but nobody reads stickies so I guess that wouldn't matter).Tim

author: Daixiwen
author_rank: Frequent Contributor
timestamp: February 05, 2019, 08:45:41 am
content: I have dealt with fake MOSFets on battery protection circuits before, so there is a market for this. Power MOSFets have usually long lead times, so sometimes the PCB manufacturer can have the good idea to go through a broker instead of the regular distributor.I have seen cases with rejected MOSFets that were relabeled, and also complete fakes, with a much smaller die placed in a D2PACK chip.Compare the RDSon between the two boards, it is usually much higher on fakes.