Sasha,
As stated by an earlier contributor, the tin rises to the top (more or less) and this is where the operators remove the dross along with solder. Just my guess, not fact. The tin drop is empirical observation over many (20+) years of being intimate with wave soldering. Always, when an analysis came back "off eutectic" tin was added. 100%, never saw one go the other way!
Have a safe and happy holiday!
Regards,
Ed Popielarski
QTA Machine
27291 Jardines
Mission Viejo, Ca. 92692
Phone:949-581-6601
Fax: 949-581-2448
Cel: 949-337-2578
WWW.QTA.NET
"Thank God for America...
before it's too late!"
----- Original Message -----
From: Sasha Miladinovic
To: TechNet E-Mail Forum. ; Ed Popielarski
Sent: Thursday, December 04, 2003 10:17 AM
Subject: Re: [TN] SnPb Solder pot composition
Ed,
I like Your declaration about "cold" joints... :) I had a minor war i a earlier life with a Q-department about the definition.. :)
I'm not sure it any of us is right or wrong, but why would be Tin that drops?
Isn't it density and temparature that is the governing factors in this case?
Enyone outthere that can explain this? :)
*************************************************************************
Sasha Miladinovic - Production Engineering
Amersham Biosciences, PCB Production, Umeå
Tel: +46 (0) 90 150 232
Fax: +46 (0) 90 138 372
E-mail: [log in to unmask]
*************************************************************************
Ed Popielarski <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
2003-12-04 18:40
Please respond to "TechNet E-Mail Forum."; Please respond to Ed Popielarski
To: [log in to unmask]
cc:
Subject: Re: [TN] SnPb Solder pot composition
Yordan,
Deviation from 63/37 can cause increased solder shorts in a wave soldering
machine. At 63/37 (eutectic) the melt point is minimum, and there is no
plasticus range. As you drift from there the melt point increases and the
plastic range increases. This is why hand solder is preferred at 60/40...
there IS plastic range and makes it easier to judge the joint as you solder.
This is also the main cause of "frosty" joints (I hate to say "cold" since
it is a very inaccurate term).
Another thought to add to the mix is the accuracy of the lab. I recommend
using either Alpha Metals or Kester to do the analysis (Type C which is the
"whole enchilada" variety) and perhaps to rule out other variables discussed
in other's postings, take a few samples, from the static part of the pot,
from the wave after running at temperature, etc. If all the samples come
back relatively the same, then you are good to go, but if one or two stand
out, there could be something worth looking into.
Additionally, (yes, another variable) the tin is usually the element that
drops, not the lead. This has me wondering as well. Why?
Have a safe and happy holiday!
Regards,
Ed Popielarski
QTA Machine
27291 Jardines
Mission Viejo, Ca. 92692
Phone:949-581-6601
Fax: 949-581-2448
Cel: 949-337-2578
WWW.QTA.NET
"Thank God for America...
before it's too late!"
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