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Original question:

TM4C129ENCPDT: Problem with an external 32.768 kHz crystal oscillator

TM4C129ENCPDT: the pin of TM4C129 become green

user4973896
Expert 1555 points
Part Number: TM4C129ENCPDT

I find that the tm4c129encpdt on  the board which  the client sent back   became  green  as below。 can  somebody tell me  why？

  • 0
    Genius 3850 points

    wouldn't your client be in the best position to tell you what happened?

  • 0
    Guru 55913 points

    Roach or other bugs contaminates pins - seen this many times in past mostly destroy traces on PCB. Otherwise perhaps soda pop was spilled on gold plated pins?

  • 0 in reply to Genatco
    Guru 117855 points

    B.P. (just) may have 'broken new ground' w/this one!

    Are the MCU pins (really) gold plated?

    And - if that's so - is not gold (deliberately chosen) as it superbly resists 'oxidation/corrosion?'

    Copper is 'known' to 'turn green' due to simple oxidation. It is highly likely that (some) contaminate (possibly an 'imperfect' soldering or board-cleaning process) has produced this effect.    Staff's 'eagle eye' detects that this MCU appears to have been 'removed' from its assembled pcb - which 'removes' the ADDED CLUES - which such BOARD EXAMINATION (not just a single chip) would provide!   (i.e. how far did this contamination/oxidation physically 'spread' - what else & other areas - were impacted?

    No report of board/device performance arrived - nor of the 'operating environment'  (sub-surface, marine use - perhaps?)      That's of (some) consequence - is it not?    

    Chip and/or Board Assembly ABUSE - or subject to severe moisture-laden environment (while improperly protected) (i.e. encapsulant-free) all may trump (other) explanations...

  • 0
    TI__Guru 72500 points

    As listed in Appendix A of the datasheet, the leads are copper with Nickle, Paladium and  Gold layers on top (CU NIPDAU). As CB1 mentioned, copper will oxidize green. From the picture I cannot determine if the green color is oxidized copper or a containment left on the leads from solder flux or something else. As Danny F mentioned, knowing what happened to the parts might help, (storage, age, solder process, removal process). Why do yu ask? Was there a continuity problem before the devices were removed from the board? Here is the plating depth of different metals:

  • 0 in reply to cb1_mobile
    Guru 55913 points
    There be white gold on them there pins. Notice the green goo all around as if pins floating in some kind of caustic bath.

    Ever see a single or several leaky electrolytic caps destroy a perfectly good PCB/chips? Our VHS Sharp slim cam PCB had similar damage. Tried to save replacing most all leaky caps but failed to see the PCB was being attacked by cap oil of all things! Paid over grand QVC '93, one reason to save the dang thing besides it was a good friend. Now sitting in the corner collecting dust next to the Sony handy cam, hardly ever use it but neither one had any conformal coating like typical mobile modules might be expect to have.
  • 0 in reply to Genatco
    Guru 117855 points

    BP101 said:
    There be white gold on them there pins

    Was not that phrase, 'Gold in them 'thar'  hills (or now, pins)?     (we need to insure 'accuracy' of our historical references - do we not?

    Your 'leaky electrolytic' (or similar) registers as 'far more likely' than (earlier) - 'multi-legged, fast/shifty, escape-artist' creatures.

    The curious wording, 'MCU becomes green' - seems to suggest that the MCU - uniquely and 'on its own'  (i.e. without (any) external influence) - became so corroded.

    When posters provide the bare minimum of data - especially when omitting the 'particularly vital' (i.e. the 'rest of the pcb') - my suspicions (naturally) rise!     (Why go thru the trouble of 'removing the MCU?' ... What if that 'green-plague' - extended far beyond 'just' the MCU? ... Might that be of great 'inconvenience' - to the 'failed MCU claim?)

    Improper - possibly (even) acid-based solder flux - or board 'cleaner' - or some 'after assembly assault' - rapidly climbs - this 'green-tinged', Suspect List!

  • 0 in reply to cb1_mobile
    Expert 1555 points
    yes，I MEET TWO QUESTION before i remove the chip，one is go to websit “e2e.ti.com/.../704552”
    the other is “e2e.ti.com/.../687279"
  • 0 in reply to user4973896
    Guru 117855 points

    Your first link is 'dead' ... second provides NO INDICATION of the, 'Cause of pin corrosion.'     (JTAG issue (only) is described - which bears NO RELATION whatsoever - to MCU  corrosion!)

    Many questions were asked regarding your board's handling - operating environment - and 'correctness of processing & assembly.'     Not one was answered - that's 'telling' - is it not?

    No one here can (ever) recall vendor's MCU suffering such fate - by itself - when handled & processed properly.     As the vendor agent noted (in his reply) ... 'what happened to your parts?' ... minus that KEY INFO - your posting has little chance of being understood  - even less ... of  being resolved...

  • 0 in reply to cb1_mobile
    Expert 1555 points
    I have another question is on website "e2e.ti.com/.../704552"
  • 0 in reply to user4973896
    Guru 117855 points
    To (possibly) assist you - the GROUP here requires (some) detail from you! (not so much - more (diverting) questions...)