[oshug] Parallella: spare chips

Omer Kilic omerkilic at gmail.com
Wed Oct 31 15:45:13 UTC 2012


Hi Jason,

On (30/10/2012 14:53), Jason Flynn G7OCD wrote:
> On 30/10/2012 08:25, Andrew Back wrote:
>> The Adapteva website says these are "324-ball 15x15mm flip-chip BGA"
>> [1] but doesn't mention the pitch? Perhaps it's implicit — my
>> knowledge of BGA devices goes as far as appreciating that they are
>> difficult for hobbyists to work with.
>
> I wouldn't be put off this. There are many back-street
> workshops that routinely remove, re-ball and resolder
> BGAs on laptop motherboards, without damaging any of
> the adjacent devices. Worst case, you could employ one
> of these.

You can also watch people on Youtube fixing their Xbox problems by 
'reflowing' chips using tea candles, that seems to work too :)

As you've mentioned, these are 'back-street' methods and I don't know 
about you but worrying about whether my BGA has been reflowed properly 
or not is the last thing I want while bringing up a complex design.

That said, I could get access to our SMT lab at the University which has 
the necessary equipment (sans a paste station but we can improvise) to 
deal with this if anyone wanted to go ahead with this. We could have 
another OSHUG trip to Canterbury for some SMT fun and beer!


> PCB manufacturing houses often do assembly, the board
> house I use would cost you about £20 each to put 8
> devices down professionally.

That is a cracking deal, would you mind sharing the details of that 
board house, off the list if you'd prefer?


> As for testing, I would stick with a JTAG boundary
> scan (what it was designed for) rathet than x-raying
> as x-rays can damage certain technologies.

Good point.


Cheers,
Omer.



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