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I have recently bought a FT2232H mini module breakout board. When I tried to connect it to a computer via usb nothing happened, either on windows or linux. For the latter I checked that the devices listed in lsusb are unchanged. I also checked with two different computers and two different usb wires.

Then I noticed that there is some white dust around all the soldered pins of the chip: enter image description here enter image description here

What is this dust ? Is it related to aging of the breakout board (it's written 2010 on the board, not sure if this is related to design or manufacturing) ? And could this make shortcuts among the pins and be the reason of the chip failure ?

Ratbert
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    I want to say that's some sort of flux residue, but I'm not sure enough to make that an answer. – Hearth Feb 07 '19 at 21:20
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    Was about to make the same comment. Try *gently* cleaning it with a toothbrush and (pure) alcohol. – Huisman Feb 07 '19 at 21:24
  • Flux residue would be my guess also. You can safely try shifting it with a liberal amount of isopropyl alcohol and a lightweight lint-free cloth. –  Feb 07 '19 at 21:24
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    I wonder if that pad-pad short in the first picture is intentional – W5VO Feb 07 '19 at 21:51
  • The two pins right of the one connected to the via are shortened by a blob of solder, and it does not look intentional.. – sweber Feb 07 '19 at 23:34
  • @W5VO, the short is probably not intentional because it is on top of the IC pins .... i would expect the pads to be shorted if it was intentional ..... but hey, you never know – jsotola Feb 08 '19 at 02:17

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That looks like residue from something like safewash water based flux remover. Or residue from washing after using a water soluable flux. The residue is only in places where surface tension would hold water. I'd liberally wash the board in isopropanol (or a similar not-to-strong organic polar solvent) and then blow the gunk-disolved in solvent out with a decent compressed air lance (make sure it doens't have an oiler).

It might or might not be the cause of your misery. The circuit most likely to be compromised would be the crystal oscillator. I'd check your board is getting power, and then I'd check it's crystal is ticking. (If you don't have a scope an old shortwave radio is ideal for checking that)

james
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