Page 133 - Six Sigma for electronics design and manufacturing

Six Sigma for Electronics Design and Manufacturing
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The issues of calculating FTY have become important in light of the
increase in subcontracting the manufacturing of high-technology elec-
tronic products. Project teams and their leaders need accurate esti-
mates of new product yields to plan and budget for test and trou-
bleshooting equipment and personnel. In addition, management
needs to benchmark potential suppliers in terms of their manufactur-
ing quality. The results have been beneficial in several categories,
and will be further highlighted in this chapter:
By rolling up the yields of its various product components and man-
ufacturing operations, the total product yield can be estimated.
Project teams are thus able to manage carefully where additional
resources are needed in terms of improving particular designs or
manufacturing capabilities. By using these yield estimates, the
new product team can also increase the accuracy of the new prod-
uct cost estimates.
Design for manufacture (DFM) principles, as championed by manu-
facturing engineers, can be emphasized to the design team in order
to increase the FTY of new products, since a direct relationship can
be made between the two concepts.
FTY yield calculations can influence the focus of quality improve-
ment teams.
Yield calculation can clarify the best test strategy for reducing the
overall test and troubleshooting costs.
In this chapter, the issues of yield and test strategy will be exam-
ined in a hierarchy of steps:
1. Determining units of defects
2. Determining manufacturing yield on a single operation or a part
with multiple similar operations
3. Determining design or manufacturing yield of multiple parts with
multiple manufacturing operations or design specifications
4. Determining overall product testing strategy

4.1 Determining Units of Defects
The basic definition of a defect is one that is based on the Poisson dis-
tribution. The defect rate, or defects per unit (DPU), is calculated
based on defects, opportunities, and units. Defects are any deviation
of the product functions that causes customer dissatisfaction or non-
conformance to specifications. Units are the number of parts, sub-
assemblies, assemblies, or systems that are inspected or tested. Op-