Nope. QQS-571E is not appropriate here either. QQS571E does contain
recommended impurity levels for at least one Pb-free alloy (Sn96) but if
my memory serves me correctly, it is primarily a purchasing spec for
tin/lead alloys.
In light of there even being so much debate & discussion concerning the
long performance of SAC alloys as compared to 63/37, I can't see how any
industry body is willing to write a spec covering the manufacturing
induced impurities and their acceptable levels. Some impurities may be
rather obvious (ie., S, P As, Al,) but determining the acceptable level
of say Cu over the whole range of SAC alloys will be considerably more
challenging.
I suspect these impurity limit levels will not be reliably set until
some years after the industry transitions to more of a lead-free
manufacturing base.
Rich K / KEDS
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Edwin Louis
Sent: Friday, January 21, 2005 7:37 AM
To: [log in to unmask]
Subject: Re: [TN] Lead-free Wave Solder Pot Impurity Levels
What about Federal Specification QQS-571?
-----Original Message-----
From: Leland Woodall [mailto:[log in to unmask]]
Sent: Friday, January 21, 2005 6:26 AM
To: [log in to unmask]
Subject: [TN] Lead-free Wave Solder Pot Impurity Levels
Hi Folks,
I have a small dilemma here. There is a standard for eutectic solder
pot impurity levels, but I can't seem to find one for lead-free. Is
there such an animal?
Everything I've researched on the Web shows only recommendations, namely
from Alpha and AIM. Those two have slight disagreements.
At least they provide something, and that is impressive.
It also appears that the major concern is processing problems versus
product reliability. If copper content gets too high, the wave solder
viscosity becomes too high and bogs down the mechanical parts of the
machine.
When things get out of whack, can I expect reliability problems as well?
What levels of impurities would cause premature joint failure,
specifically?
Are we too new to this, and have tests not yet been agreed upon? Is IPC
addressing the issue?
Any help you could provide would be sincerely appreciated.
Offline comments are welcomed.
Many, many thanks,
Leland Woodall
Quality Coordinator
Keihin Carolina System Technology, Inc.
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