Page 149 - Six Sigma for electronics design and manufacturing

Six Sigma for Electronics Design and Manufacturing
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tions; for example, a placement defect that can cause multiple ter-
minations defects. This can skew the termination data. Decisions
have to be made and training programs offered to operators in or-
der to follow guidelines on apportioning and analyzing defects ac-
cording to source.
4.3.7 Example and discussion of implied Cpk in IC
assembly line defect projections
Figure 4.4 is an example of a portion of an IC fabrication line. Only a
few operations are shown in order to demonstrate the utility of using
Cpk-based analysis for the line. This analysis can be used to deter-
mine defect projections for all different IC types that are made by the
line, based on the number of manufacturing steps required by the IC
for each operation. Note that by using the Cpk approach, the 1.5
shift of the average to the specification nominal is not considered in
the defect calculations.
For each operation, several attributes are shown by rows in Figure
4.4 to classify their quality:
The process specification. Each operation is characterized by one-
or two-sided implied specifications that cause defects to occur when
they interact with the variability of the process. This information is

Z
f(–z)

96.48% Z

Figure 4.4 IC assembly line Cpk example.