The present control method therefore relies on the operator to apply a set of
heuristic rules based on measurements of the process
quality metric;. One problem is that the operators evaluate
the performance and set the parameters according to their
individual experience and process expertise. Additionally,
operators may set parameters differently over time due to
fatigue. distractions, etc. Experimentation with actual
product samples and hardware is necessary to adjust the
parameters to meet the process requirements.