[eagle] Re: BGA Tools

Matt Ettus matt at ettus.com
Mon Jan 15 18:37:44 PST 2007


Lyle Johnson wrote:
>> Besides, I wouldn't send out a single BGA-containing board to my
>> TERRESTRIAL customers without having it X-Ray scanned first to check the
>> connections.  I certainly wouldn't send one into space without a
>> scan. Are you planning on purchasing an XRay machine as well?
>
> No, no plans on an X-ray machine, Matt.    High-volume manufacturers
> of boards with BGAs dont; X-Raythem either.

Not true at all.  EVERY SINGLE board with a BGA on it from ANY of the
contract manufacturers I use is XRayed.  Even the bargain-basement guys
who I wouldn't trust with a valuable BGA do it.  It isn't even
optional.  You don't have to request it, you don't have to pay extra for
it, they automatically XRay EVERY SINGLE BGA board, no matter what.  The
cost is negligible.

> Once you get the thermal profiles worked out, it makes reliable
> connections.
>
> The equipment comes with a test board for 4 positions, and 4 BGA
> devices that contain a pattern of jumpers so that you can determine
> when it is in fact properly soldered down.  This helps to calibrate
> the thermal profiles.

There is a very big difference between making electrical contact and
making a good solid physical joint.  And calibration means that most
chips will be properly placed the first time.  It doesn't mean ALL will
be placed properly.

>
> This is the same machine JPL used to place the BGAs in the Spirit and
> Opportunity rovers.  Not sure if they X-rayed these or not, but it is
> the same exact placement tool set.  In fact, Zephyrtronics includes a
> NASA report on how to use the machine for reliable placements.

I'd bet my life that JPL XRayed them.  In fact, I'd bet they XRayed them
several times -- once after assembly, once after thermal vac tests, once
after a shake test, and then once again for good measure.

To repeat, I wouldn't send a single BGA-containing board out to a
customer without an XRay, and the only risk to me would be roundtrip UPS
charges.

I know you've sent a lot more satellites into orbit than I have, so you
have a lot of experience with this.  But I have to say that anybody
sending a BGA into space without XRaying it first is absolutely nuts.  I
don't care if Werner von Braun himself said otherwise.

Matt



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