My initial question was whether we could switch to using Pb free wire
solder for hand-soldering operations on our production floor, even
though our production products are still using stuffed boards that were
populated with SnPb solder paste.
This would be for installing things like connectors, shields, or doing
rework, etc. BGA's are never soldered by hand.
Then when the products start switching to Pb free, we don't have to
worry about controlling two types of solder on the production floor. Pb
free product assemblers would just use the standard wire solder - Pb
free - already available to them.
Related question (probably already answered in the archives, but..).
Can Pb BGA's be soldered with Pb free solder paste? I would think the
balls would fully collapse, since they melt at a lower temperature.
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Tempea, Ioan
Sent: 18-Nov-05 8:03 AM
To: [log in to unmask]
Subject: Re: [LF] Antw: [LF] Mixed processes and components
Guenter,
the metallurgy should be OK under what conditions: SnPb soldering
temperatures (210C to 220C), lead-free soldering temperatures (around
240C), or does not matter?
Besides, I have heard of another beast out there: BGAs with mixed solder
balls (part of the balls are SnPb and the rest Pb-free). What can we
expect from these ones?
Thanks,
Ioan
> -----Original Message-----
> From: Leadfree [SMTP:[log in to unmask]] On Behalf Of Guenter Grossmann
> Sent: Friday, November 18, 2005 8:37 AM
> To: [log in to unmask]
> Subject: [LF] Antw: [LF] Mixed processes and components
>
> We published a characterisation study in Soldering and Surface Mount
Technology Vol17 about LF BGAs soldered with SnPb. Well I stated that
from the metallurgy side i didn't see any reason why this shouldn't
work. Looking at the presentation of David (beautiful pictures by the
way) I am glad to see that the rupture due to thermal cycling is not
along the SnPb / LF interface. There is a rupture along the pad on the
PCB. Well, to be provocative, somewhere the joint has to let go.
Usually at the weakest point which seems to be the solder/pad interface.
Does a LF BGA soldered with LF solder withstand the 2000 cycles that are
mentioned as a minimum ?
>
> Guenter
>
>
> EMPA
> Swiss Federal Laboratories for Materials Testing and Research Centre
> for Reliability Guenter Grossmann, Senior Engineer
>
> 8600 Duebendorf
> Switzerland
>
> Phone: xx41 1 823 4279
> Fax : xx41 1 823 4054
> mail: [log in to unmask]
>
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