Tamir,

the best way to find out what happened is to send the failed components to
the manufacturer for a failure analysis. Thy will tell you right away if you
baked enough the parts.

The prime suspect is the humidity. Most likely, the baking did not remove it
all from the BGAs and they pop-corned. You should check the humidity level
in your production area. Besides that, how long the boards have been kept
outside between the baking and the reflow of the new BGA? If it's one week
and you have high humidity, you shouldn't investigate more.

Regards,
Ioan

> -----Original Message-----
> From: Tamir Ben Shoshan [SMTP:[log in to unmask]]
> Sent: Wednesday, May 30, 2001 10:21 AM
> To:   [log in to unmask]
> Subject:      [TN] BGA's failure during rework process.
>
> Hi,
>
> The board's type I am dealing with is 3.8 mm thick with 28 layers made of
> GETEK raw material. The BGA's rework process had been defined as followed:
> Baking the boards for 24 hours at 125C, remove the defected component with
> the BGA's rework station, clean the component's area, paste printing,
> locate
> the component on the pads and pass it through the reflow oven under the
> same
> profile definition as the first assembly (because of a big board size- 17"
> X
> 18" and thickness we found out that this process is better then local
> profile).
> On each board 6 BGAs should be replaced (version upgrade). After replacing
> the BGAs with the above process few other BGAs components were fail in
> away
> that implementing force on the component makes it work properly. The X ray
> inspection didn't show anything wrong with any of the solder joint. After
> replacing the suspected components the boards pass all the functional
> test.
> The failed components were plastic BGA.
> Does any one familiar with that phenomena, I appreciate any help or
> advise.
>
> Best Regards,  Tamir.
>
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