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Re: BGA soldering



Mike Murphree wrote:

>>However  in space a socket is not going to be any use.
>>
>>If anyone has had any  experience of small scale prototyping BGA's onto
>>PCBs without resorting to  third party commercial operations, I'd be
>>glad of any tips.
>>
>>I'm fine  hand soldering the 0.4 and 0.5mm QFP's, but I'm not sure how
>>to go about  dealing with BGA packages.
>>    
>>
>
>Searching for: BGA toaster reflow    will turn up a number of hits on
>Google.  The other problem is alignment, most places use X-ray systems to
>verify part alignment and solder quality.  If you're building it for a
>space application, you probably want this done anyway.
>  
>
Most folks I've seen that have built toaster oven style reflow ovens for 
their SMT work have liked them, but said they're far from perfect.  
They're doing SMT work, but rarely BGA because the buggers are really 
hard to align in a home shop and virtually impossible to test or check, 
other than to just power them up and see if you let the smoke out.

A commercial shop with a commercial reflow oven (and as Mike mentions, a 
proper way to check for errors after the device is attached) is probably 
much more prudent for anything going to space.

>You can't hand solder what you can't see/reach.  BGA packages use little
>solder balls underneath the IC package (didn't we spend years trying to
>get rid of that problem?) to attach to the PCB.
>  
>
The guys that came up with the idea of modifying the "cook" cycles of 
cheap toaster ovens to mimic the much more stringent and controlled 
environments on commercial reflow ovens -- that's pretty dang neat 
ingenuity.  But truly, I wouldn't trust it for something that *has* to 
work.  Get professional help with BGA's if you have to use them. 

Amateur BGA soldering just leaves too much margin for error for 
something you can't get at to try to fix later on.  Does the component 
have a non BGA equivalent?  BGA usually gets you the most bang for the 
buck when it comes to space vs. pin-count, but is really hard to work 
with on hobbiest/amateur boards.  Is there another high pin-density 
package that your device is available in?

Next question, but this starts to head off into the stuff I do not know 
about satellite building... could you have the chip put on a 
daughterboard assembly that's small with a cable and header 
professionally built and then just attach that to your board? 

I know this adds mechanical complexity and something that could 
break/not work, but if you absolutely had to use the BGA and had to keep 
the production costs super-cheap... it's a thought.  Probably a dumb 
one.   There's probably some generic design rule against doing that on 
birds, and I am just a hobbyist.

Nate WY0X
----
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