LEAD-FREE HAND SOLDERING - FAQ - Cooper Hand Tools

Division Headquarters
P.O. Box 728
Apex, NC 27502-0728
1000 Lufkin Road
Apex, NC 27539
Phone: (919) 387-0099
Fax: (919) 387-2560
LEAD-FREE HAND SOLDERING - FAQ
QUESTION: Can we expect a solder joint to look the same after hand soldering
with lead-free solder?
ANSWER: One of the first things we notice when soldering with lead-free solder, is a dull
appearance on the surface. Actually, industry standards have allowed a matte surface for
years. However, a matte surface is not common. Many times it was the result of a slow cool
down involving large mass parts or thick multi-layer boards or even high temperature solder.
Chip soldered with Tin-Lead Alloy Through hole joint with Lead-Free Alloy
Lead-free alloys often go beyond dull and surface appearance may actually be
grainy. Inspectors will have to adapt their thinking away from smooth, bright
and shiny and realize that rejecting a grainy lead-free joint could be just as
bad as accepting a defect.
In revision "D" of both IPC-A-610 and J-STD-001 it says: "The primary difference
between the solder connections created with processes using tin-lead and
processes using lead-free alloys is related to the visual appearance of the
solder." It goes on saying: "Acceptable lead-free and tin-lead connections may
exhibit similar appearances but lead-free alloys are more likely to have:
• Surface roughness (grainy or dull)
• Different wetting contact angles
All other solder fillet criteria are the same."
QUESTION: Do we have to adjust our hand soldering techniques to work with leadfree?

Division Headquarters
P.O. Box 728
Apex, NC 27502-0728
1000 Lufkin Road
Apex, NC 27539
Phone: (919) 387-0099
Fax: (919) 387-2560
ANSWER: When making the move to lead-free, a common mistake is to turn up the
soldering tool temperature. This can be dangerous. Operators are surprised to find that
most of their through-hole and surface mount components can be soldered at or below
700°F. This is especially important when using no-clean flux.
When the iron temperature to the point of charring the flux, a defect is created and cleaning
is required. Instead of starting with a higher tip temperature, the operator can try watching
for wetting at a given temperature and decide if the process can be done in a reasonable
dwell time. Pre-heating reduces reflow time the risk of heat-related damage.
QUESTION: What changes are necessary in soldering tool maintenance when working
with lead-free solder?
ANSWER: One of the bigger challenges in working with lead-free solder is proper
maintenance of the solder tools. High percentages of tin in the lead-free alloys will have a
harmful effect on the tools. Iron tips and solder pots will degrade at a faster rate which will
affect the thermal transfer capability. Some equipment will have to be replaced and more
attention given to maintaining the quality of the soldering iron tips.
Operator training in using the correct methods will pay huge dividends. Operators should
immediately develop the habit of tinning the tip after the soldering operation as well as using
distilled water for solder sponges. Tip tinners and polishing bars may be used as a regular
part of iron maintenance.
QUESTION: What changes are necessary in soldering tool design/performance when
working with lead-free solder?
ANSWER: Soldering irons and stations will require the capacity to bring the joint to
sufficient temperature rapidly and hold that temperature with minimal recovery time. More
powerful tools will do the job better just like a car engine with more horsepower will pass
quicker and climb hills easier.
Besides having the necessary power, the optimal soldering tool will also possess very
efficient heat transfer to the work. This efficient heat transfer, plus sufficient power, will
ensure that recovery rates are very fast and will not slow down operations when moving
from joint to joint. In addition dwell time on the PCB will be minimized.

Division Headquarters
P.O. Box 728
Apex, NC 27502-0728
1000 Lufkin Road
Apex, NC 27539
Phone: (919) 387-0099
Fax: (919) 387-2560
Efficient delivery of the heat to the joint depends on a number of factors:
• Adequate power from the heater
• Proximity of the heater to the working end of the tool
• Thermal efficiency in delivery of the heat to the joint (geometry and tip/heater materials)
• Some means of quickly sensing the need for delivery of more heat (location of sensor)
• Accurate control of the tools temperature (microprocessor control with no overshoot).
Submitted by: Photos courtesy of:
Robert Markovsky Ken Moore
Cooper Hand Tools Omni Training
www.cooperhandtools.com/weller www.omnitraining.com