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SolderTip #45: Manual Soldering vs Wave Soldering

Question:  We assemble simple through hole circuit boards. What are the main factors to consider when shifting from hand soldering to wave soldering? What factors should be used to justify continuing to hand solder vs. switching to wave soldering?

Answer: Manual soldering is a very unique process with many variables and people being one of them. To make consistent joints every time all the time, the people have to be trained continuously and the equipment and materials have to be monitored as well.

The second part of this is volume. A manual solder joint takes about one to three seconds to make, plus depending upon the flux type used must be cleaned. A wave solder system will solder the joints more quickly and consistently than any manual soldering operator.

For example a board with a length of 6” and a width of 4” and a quantity of 100 joints will take a manual operator 3 sec per joint, which equates to 300 seconds or 5 minutes. If a wave solder system is design to have a conveyor speed of 5 feet per minute and the contact on the wave is 1 inch, that particular board will be soldered in 6 seconds. Therefore depending upon the volume of solder joints being created the decision to be made has to consider cost versus volume.

For the cost analysis, one must consider, the forecasted volume, the cost of materials, the space needed within the facility to accommodate either system, as the wave solder system will have a footprint which has to be considered. The other issue is the cost of the solder to fill the solder pot, which is or can be substantial when starting a mass soldering process, along with the cost of the installation, such as air, power, venting etc. All of this versus more benches and soldering irons for the operators, which include salaries, and all the other ancillary cost of employees such as benefits and none of the variable have been eliminated.