I agree it should not be a problem. I have built a lot of boards with large BGAs on both sides using lead free paste. Just make sure you do your cross sectioning to make sure you have the right ball shape afterwards.
At first I thought you were going to say you had to put a BGA through wavesolder.....
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ioan Tempea
Sent: Friday, April 01, 2011 11:30 AM
To: [log in to unmask]
Subject: Re: [TN] BGA on Solder Side
Hi Leif Erik,
I wouldn't worry, the bigger the pin count the more stable to BGA (more balls = more surface tension). I have built tons of boards with many upside down BGAs, some even having metal top. No issue. LF solders have higher surface tension than SnPb and this can only help even further.
Regards,
Ioan Tempea, ing.
Ingénieur Principal de Fabrication / Senior Manufacturing Engineer
T | 450.967.7100 ext.244
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N'imprimer que si nécessaire - Print only if you must
-----Message d'origine-----
De : Leif Erik Laerum [mailto:[log in to unmask]]
Envoyé : April-01-11 2:11 PM
À : [log in to unmask]
Objet : [TN] BGA on Solder Side
Technetters,
We are faced with a design that puts 2 BGAs on the solder side of a
board. It will therefore go through reflow on the bottom when building
the other side. The BGA is 19 x 19 mm 484 balls .8mm pitch. Av Weight
1.3302 g. This is a lead free design. I seem to have seen a paper on
the subject discussed on technet, but the archives do not work for me
right now.
We have done thousands of boards with BGAs on both sides, but always
small ones with max ball count at 84. We have never one this size. Any
experiences out there that you can share? Do's and don'ts? I can tack
the corners of the BGA with SMT adhesive, but I would rather not if I
can avoid it.
--
Leif Erik Laerum
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