22
Manual assembly
and rework
Larger tips with a greater surface
area increase the rate of heat
transfer to the joint
Control the process,
control the costs
Manual soldering is largely performed as a final assembly function, when the intrinsic
value of a populated PCB is at its highest. This means accurate process control is
essential to reduce the risk of scrapping
and soldering is a familiar made, which in turn relies on an and the need for process control is Brown, explained: “Unlike
H
assembly process, which applied understanding of the basics of paramount to optimise yields. conventional irons, heat is not stored
means many manufacturers soldering. Furthermore, as the use of So, the task of the soldering iron is in the tip. It is applied directly from
fail to appreciate the miniaturised, fine pitch components to provide the right amount of thermal the heater to the joint. This provides a
importance of process and multi-layer boards continues to energy to heat a joint and melt the reduced tip temperature that
control and how it affects the cost as grow, so does sensitivity to thermal solder according to the shape, size increases tip life, reduces solder
well as the quality of hand soldering. damage during hand soldering. and thermal load of each joint on a consumption, decreases tip oxidation
Compounding the issue, soldering The problem is exacerbated by board. As larger joints require more and improves joint integrity.”
irons are often regarded as lead-free solders with higher heat, it is normal practice to hold the A second characteristic of SmartHeat
commodity products where price, processing temperatures and iron’s tip against them longer, however technology is that by exploiting a natural
rather than performance, is used to potentially more dangerous levels of by exposing the PCB and component magnetic phenomenon, the irons are
distinguish one product from another. heat from the soldering iron. These to elevated temperatures for longer engineered to self-regulate tip
The performance of a solder joint is
factors have made hand soldering increases the risk of thermal damage. temperature to within ±1ºC of a set
dictated primarily by how well it is
modern assemblies a challenging task point, regardless of thermal load. As a
The task in hand
result, the iron tip has a constant
One way to achieve this goal without
temperature during soldering and should
subjecting board or components to
not overshoot the desired temperature.
thermal shock is to use different sized
In the production environment, this
tips. Larger tips with a greater surface
combination of rapid tip heating with
area increase the rate of heat transfer
accurate regulation eliminates
to the joint.
operator desire to increase the iron
Repetitive soldering can also drain
tip temperature to compensate for
heat from the iron and slow
slow soldering. In fact, SmartHeat
production. Conventional irons have a
systems have no operator adjustment
thermocouple in the tip that responds
controls and require zero calibration
as the tip temperature drops.
by production staff.
Consequently, the iron temperature
can lag behind demand and extend
Eliminating variables
the time needed to raise the joint to The reality is that conventional
soldering temperature. The problem is soldering irons become increasingly
exacerbated if the assembly non-viable in modern production
comprises large components. environments if the final quality of the
OK International’s SmartHeat joints relies almost totally on the skill
technology offers an alternative of the operator. Establishing a high
solution. While conventional irons yield, low-cost hand soldering
supply constant power to the tip process relies on the soldering
with varying tip temperature, technology employed and its ability
SmartHeat keeps the tip temperature to maintain process control and
constant, rather than the power remove operator influence.
supplied to it.
Accurate regulation eliminates operator desire to increase the iron tip European product marketing
temperature manager at OK International, Craig
www.okinternational.com
November/December 2008 Electronics Assembly
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