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  #11  
Old 04-20-2008, 02:01 AM
Reactive Reactive is offline
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A 'stock' adapter for proto typing. Why produce custom PCBs until we get a known working unit? A simple SOIC to DIP adapter is all that's needed to work on a bread board for instance and MUCH cheaper.

Maybe even a PLCC to DIP adapter also for the CPLD. Then all custom surface mount for the production PCB.
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  #12  
Old 04-20-2008, 03:25 AM
Grant Stockly Grant Stockly is offline
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I guess I was thinking we'd use a TFQP CPLD...

I guess I have a different opinion, since 3 overtime hours would pay for the prototype and I couldn't wire a bread board in 3 hours.
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  #13  
Old 04-20-2008, 05:30 AM
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True, wiring a bread board would take some time but do you really think it's a good idea to produce a PCB without any testing first? I could just see a $150-ish expense for PCBs that don't work and then we still need to fight wiring and soldering which would now take even longer. I just normally get something on the bench working first, then start to translate the breadboard to CAD or schematic. Or am I making this a bigger production then it needs to be? It is really small and should be pretty simple I would assume. I guess what I'm asking is do you guys feel confident as creating PCBs without any testing first? I'm all for it then. I just know what happens when I don't do any testing - I end up having really cool but expensive PCB coasters for my desk. ;-)

I do like TQFP though! I just assumed PLCC for wiring convenience.
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  #14  
Old 04-20-2008, 06:03 AM
Grant Stockly Grant Stockly is offline
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Sure. I just had a run of 10 PCBs which required 3 jumper wire fixes. Two were due to not proof reading a schematic. It wouldn't have mattered at all but two address lines were switched on a flash chip. That messed up the "knock-knock" sequence used to unlock the flash for writing. The other jumper wire was to add something that I didn't think of when I ordered it.

BUT, since it was a run of 10 I saved $150 or so against a prototype...so I guess it depends...
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  #15  
Old 04-20-2008, 07:02 AM
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Three wires isn't too bad. It could just be a real pain to fix or rewire a proto PCB with all SMT compared to bread board. Of course a proto without a solder mask would probably be a good way to go just in case a rewire or jumper is needed. I always forget the mask is an option. ;-)
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  #16  
Old 04-20-2008, 07:58 AM
Grant Stockly Grant Stockly is offline
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When I was testing one of my boards I found out DigiKey sent me the wrong parts. So I had to use a DIP version. Check out what I had to do.

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  #17  
Old 04-20-2008, 02:39 PM
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Oh geeze! Yeah, that's exactly what I'm hoping to avoid. All in all, that's not too bad though. Don't you just love Bell Wire? ;-) I use it all the time too.

Anyway, you're call I guess. If you guys feel that it's a simple enough project where starting with a PCB is a good idea then I'm with you. I've just been there were I need to change the wiring and have to cut and wire traces. With 12 mil tracks it's not too bad, just a pain. 8s get a little hairy though.
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  #18  
Old 04-20-2008, 09:52 PM
rgjones rgjones is offline
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http://www.solder.net/services/estimate.asp

using their estimator - they charge $11.25 per mounted BGA device whch is the best I have seen so far - just surfing the web.
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  #19  
Old 04-20-2008, 10:01 PM
rgjones rgjones is offline
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Interesting Powerpoint presentation on BGA's

http://www.pcblibraries.com/download...ions%20PPT.pdf

also

http://www.adcom.co.il/pcb%20layout/..._Placement.pdf

Last edited by rgjones; 04-20-2008 at 10:12 PM.
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  #20  
Old 04-21-2008, 01:50 AM
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So anyone have an idea as to a specific SDRAM IC to use?
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