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Reasons for pitted solder join


#1

Greetings to the list.

I was wondering if anyone knew why pitted solder joins occur?
Specifically in silver. Is it from overheating, poor solder join (and
therefore greater amount of solder required), bad solder…

Thank you
Eileen


#2

In my experience, solder pits tend to be caused by one (or several)
of the following:

  1. Dirty solder/dirty piece (fingerprints, grease, dirty or
    insufficient flux, oxidization)
  2. Poor contact points
  3. Poor quality solder
  4. Overheating/heating solder directly instead of piece

Hope that helps with the troubleshooting :slight_smile:
Kieran


#3

This is a great list, but I would also like to add contaminated/
dirty flux…

Christine
www.christinebossler.com


#4
I was wondering if anyone knew why pitted solder joins occur?
Specifically in silver. Is it from overheating, poor solder join
(and therefore greater amount of solder required), bad solder... 

Silver absorbs lots of oxygen when molten, the oxygen comes out when
it solidifies. In the case of your silver solder overheating, keeping
it hot too long and overly wide joints all contribute to visably
pitted joints. So tight joints, and working fast with just enough
heat will reduce the probability of pits in the joint.

James Binnion
James Binnion Metal Arts


#5
This is a great list, but I would also like to add contaminated/
dirty flux.. 

This can contribute but oxygen absorption is the main culprit. But
for any soldering operation clean metal, clean solder and clean flux
should be standard practice. if you don’t follow the clean, clean,
clean rule you are asking for a variety of troubles not just pitted
joints.

Jim

James Binnion
James Binnion Metal Arts


#6

Hi Eileen,

The most probable cause is overheating the solder. Try getting the
piece up to heat before presenting the solder. You can also heat
from the opposing side of the metal afterwards and draw the solder
through the seam. This will help eliminate the porous spots in the
joint since the solder travels towards the heat.

Mark


#7

Add one more. Quenching into hot pickle. A freshly soldered joint is
a very fragile and tender connection and until it cools and
solidifies, it is should be treated with care. Throwing a freshly
soldered joint into a hot acid bath can create minute fractures and
pits into your solder.

Wait 10 seconds and allow your solder to do its job. What’s the
rush? Ten seconds in air and a cooling cycle in room temp water and
then pickle will create a strong bond.

As a tip, I usually keep a loop around my neck to inspect a
completed solder operation. What you see with your naked eye is a
completely different world when scrutinized under magnification.
Sometimes I think I have totally nailed a good solder operation, and
then viewed under a loupe, I go EEK!

Karen christians


#8

Thank you to all who responded. I don’t quench in hot pickle - in my
first class, someone threw their hot piece into the pickle and I
copped a lungful of acid fumes. Not a good experience and certainly
one I wouldn’t care to repeat :slight_smile:

Jim, I read that silver can absorb up to 200% its weight in oxygen
(when molten) and releases it as it cools. In the case of Sterling
silver, the copper reacts with the absorbed oxygen which is where
firescale can occur. Isthis your experience/understanding? I always
mean to check this statement- it was written back in the 1950’s.

Thank you
Eileen


#9
I read that silver can absorb up to 200% its weight in oxygen (when
molten) and releases it as it cools. In the case of Sterling
silver, the copper reacts with the absorbed oxygen which is where
firescale can occur. Isthis your experience/understanding? I
always mean to check this statement- it was written back in the
1950's. 

Well I believe it is 200% its volume not weight, otherwise it would
get quite heavy when molten :slight_smile: But regardless it will absorb huge
amounts of oxygen when molten and that gas comes out when it cools.
And yes this is the source of much of the firestain in sterling
castings.

Jim

James Binnion
James Binnion Metal Arts