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From: Rob Borenstein
Subject: Re: ASSY: Low Tin Level in Wave Solder
Greetings Techneters,
Could someone please explain the adverse effects of having a solder pot
slightly skewed from the eutectic point, as is the case with Steve's pot-2?
Do we get bridging, insufficient barrel fill, cold solder joints? Has anyone
correlated an increase in wave fallout to solder pot metallurgy?
Thanks in advance,
Date: 03 Jan 97 16:32:11 -0500
From: "Aric Parr" <[log in to unmask]>
To: "[log in to unmask]" <[log in to unmask]> (Return requested)
Subject: Re: ASSY: Low Tin Level in Wave Solder
Resent-Message-ID: <"4lKp31.0.l3K.4BPpo"@ipc>
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Tin oxidizes faster than lead. This means that dross has a higher tin
content than the solder in the pot.
In a previous job, with a very high dross machine, we regularly added
tin to the bath.
Have the dross production and dross composition from that machine
checked and compare it with that of the other machines. The tin is
probably coming from the dross.
High antimony alloys were used to reduce this differential. I notice
that you are using an antimony free alloy.
______________________________ Reply Separator
_________________________________
Subject: ASSY: Low Tin Level in Wave Solder
Author: [log in to unmask] at internet
Date: 1/3/97 3:41 PM
Good Day Everyone!
We just got our solder analysis back (it's from a lab that everyone uses)
for our wave solder pots, and we have one wave solder pot that's low in Tin...
61.4% to be exact. The recommendation is to add 4.3 lbs. of pure Tin for each
100 lbs. of solder to return it to the nominal 63%.
My question is; just how in tarnation did we get one wave solder pot low
on
Tin? It don't make sense...we use the same bar solder in all our machines, we
wave solder basically the same kinds of products in all of our machines. By
that
I mean we don't have one line waving only gold plated boards all the time, or
only OSP coated PCB's all the time, etc.. so what gives?
This is the very first time that I've ever had a solder analysis come
back
and tell me to put pure Tin into the pot...this is weird. I've had nickel get
a
little high before, but that's about it. We've got three machines and all of
the
analysis looks like this:
Pot-1 Pot-2 Pot-3
Tin 62.4% 61.4% 62.7%
Lead Balance Balance Balance
Antimony <0.005% <0.005% <0.005%
Copper 0.039% 0.048% 0.033%
Gold 0.017% <0.003% <0.003%
Silver <0.001% <0.001% 0.002%
Aluminum <0.001% <0.001% <0.001%
Arsenic <0.010% <0.010% <0.010%
Bismuth 0.001% 0.001% <0.001%
Cadmium <0.001% <0.001% <0.001%
Indium <0.005% <0.005% <0.005%
Iron <0.003% <0.003% <0.003%
Nickel 0.006% 0.005% 0.004%
Zinc <0.001% <0.001% <0.001%
The analysis was conducted according to specifications in IPC-S-815B. As you
can
see, Pot-2 is the "slacker" tin-wise. The only noticable difference that I can
see between the other two is that the copper content is just a tad
higher...does
that have anything to do with anything? Looking at the tin content on the
other
two pots, they're just barely above the limit which is 62.4%-63.6%...is my bar
solder vendor starting to get tight with the Tin? Any light that anybody can
shed on this would be 'preciated...
__\/__
. / ^ _ \ .
|\| (o)(o) |/|
#------.OOOo----oo----oOOO.-----#
# Steve Gregory #
# SMT Process Engineer #
# The SMT Centre Incorporated #
# [log in to unmask] #
#________________Oooo.__________#
.oooO ( )
( ) ) /
\ ( (_/
\_)
Robert Borenstein Phone:(416) 448-5607
Dept 110, Celestica Fax: (416) 448-4736
Process Engineering Internet: [log in to unmask]
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