[oshug] Parallella: spare chips

Alan Wood folknology at gmail.com
Tue Oct 30 09:11:26 UTC 2012


With these classes of chips one normally has to use machine placement,
as hand placement can't easily be relied upon to be accurate enough.
One normally outsources this rather than trying to make the prototypes
at home, after placement most are x-rayed in order to check bonding
and proper alignment as a pure visual inspection is not good enough.
In terms of pads/balls 0.8mm pitch was common on BGA but it varies and
newer flip chips can go down to 0.4mm pitch, but without datasheets
and land patterns its difficult to make any concrete assumptions apart
from the obvious machine placement recommended. The packages are not
what I would coin as home assembly friendly, but that's to be expected
with the number of pins we are talking about here.

regards
Al

On Tue, Oct 30, 2012 at 8:25 AM, Andrew Back <arback at computer.org> wrote:
> Hi Jeremy,
>
> On 29 October 2012 15:16, Jeremy Bennett <jeremy.bennett at embecosm.com> wrote:>> Hi all,
>>
>> For those who haven't seen, Parallella got funded on KickStarter - a
>> total of just under $900k raised. For those who would like to hear more,
>> I'll be talking about the project at OSHUG on 15th November.
>>
>> As part of my reward package, I'll receive 8 Epiphany III (16-core) bare
>> chips in December. I have neither the skills or facilities to use these,
>> so I am open to any OSHUG suggestions for putting them to a good use.
>> I'm sure some of you have both the skills and facilities to do something
>> creative with them.
>
> 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. In any case, if it were 1mm or
> higher it seems you could get a small four layer board done fairly
> cheaply [2], and perhaps this could just do breakout and be used to
> hook one up to an FPGA dev board. However, from a quick calculation it
> looks like the pitch has to be 0.8mm or under.
>
> Wondering if Omer, Sukkin, or Al have any ideas, as they've far more
> experience with this sort of thing ...
>
> As a last resort we could try the "quit whining and solder" technique :o)
>
>   http://eds.dyndns.org/~ircjunk/images/bga-adapt2.jpg
>
> Best,
>
> Andrew
>
> [1] http://www.adapteva.com/products/silicon-devices/e16g301/
> [2] http://siliconexposed.blogspot.de/2012/07/bga-process-notes.html
>
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