If your customer requires inspection of all BGA you will have to purchase
and X-ray laminography system. Very expensive about 650K for a new one.
Good luck
Hector Valladares
SMT Staff Engineer
Honeywell Space Systems
-----Original Message-----
From: Lefebvre, Scott [mailto:[log in to unmask]]
Sent: Friday, October 19, 2001 4:39 PM
To: [log in to unmask]
Subject: [TN] FW: double sided BGAs Re-work
The question I have is how do you rework the board if one of the BGAs should
fail
with out effecting the other component on the back side.
Scott
-----Original Message-----
From: Gaby Bogdan [mailto:[log in to unmask]]
Sent: Wednesday, October 17, 2001 10:03 AM
Subject: Re: double sided BGAs
Concerning the difficulty to analyze the solder joints by X-ray, I have seen
that the best method to improve the testability is to design the outer
layers in such a manner that the BGA pads on one side are shifted between
the pads on the other side.
If your circuits are so, it is possible to check each BGA separately.
Check the artwork.
If not, you must have at least the possibility to rotate the circuit during
inspection.
Gaby
----- Original Message -----
From: "Larry Koens" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, October 17, 2001 6:32 PM
Subject: [TN] double sided BGAs
> Dear TechNet,
> My company has been asked to bid on assembling a board that would have
> two BGAs on the topside and two more BGAs mirrored on the bottomside.
> That is, they will be directly across from each other on both sides. I
> never done them on both sides. So far, everything that I have done has
> been on one side only. Has anyone done them on both sides before?
>
> I am figuring xray will be a problem as after the second side is
> placed, because the pads/balls will mirror each other on both sides.
> Would I be able to tell the difference between the two BGA connections?
> Suggestions?
>
> Will I need to epoxy the first side BGAs so they would not drop off
> during my second reflow? Wouldn't I need to epoxy them after first
> reflow so that the balls could collapse?
>
> Thanks,
> Larry Koens
> SMT Manufacturing Engineer
> E.I. Microcircuits
> Mankato, MN
>
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