An engineer has applied SPC to a process for soldering electronic components to printed circuit boards. Through the use of
u charts and Pareto analysis, he has established statistical control
of the flow solder process and has reduced the average number
of defective solder joints per board to around 1%. However,
since the average board contains over 2,000 solder joints, even
1% defective presents far too many solder joints requiring
rework. The engineer would like to reduce defect levels even
further; however, since the process is in statistical control, it is
not obvious what machine adjustments will be necessary.
The flow solder machine has several variables that can be
controlled. They include: