[oshug] Parallella: spare chips

Alan Wood folknology at gmail.com
Tue Oct 30 12:07:03 UTC 2012


PS I am speaking to some folks to see if we can get some help building
a prototype with these

regards
Al

On Tue, Oct 30, 2012 at 9:11 AM, Alan Wood <folknology at gmail.com> wrote:
> 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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