Page 217 - Six Sigma for electronics design and manufacturing

Six Sigma for Electronics Design and Manufacturing
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1. Through-hole (TH) components, which have leaded terminals to at-
tach them to holes drilled in the PCBs.
2. Surface mount technology (SMT) components, which are leadless
or have low-profile leads to attach them to the surface of the PCBs.
3. Printed circuit materials, which can include single and multilayer
plated-through PCBs as well as one sided, nonplated holes.
These components have different footprints (spacing), production
rates, assembly equipment investment, and required support.
PCB layout offers a clear choice of faster development time versus
fabrication costs. Two layers or several levels of multilayer fabrication
technology are some of the alternatives presented in the PCB layout
phase. As the layer count decreases, there is a proportional effect on
the cost and reject rate of PCB fabrication, but an inverse relationship
to the time required to completely lay out a complex electronic design.
Fabrication strategy is dependent on the desired physical and elec-
trical characteristics of the PCBs, as well as the maturity of the de-
sign and the time required for completion. Multiple alternatives are
available such as PCB materials, layer count, hole and line specifica-
tions, and construction technologies. Many design engineers are not
aware of these choices and do not fully understand the cost–benefit
ratios of each.
PCB assembly strategy is influenced by the selection of the compo-
nent technology in the design phase and the machine complement on
the production floor. The chosen technology dictates a particular set of
assembly operations. Several levels of manual versus automatic pro-
duction processes can be used, depending on the physical electronic
components chosen for the design.
Test strategy allows for logical and physical interconnection be-
tween the PCBs and the test systems. Additional target test points
and test circuits influence both the layout timing and the physical
constraints of the design.
6.3.1 Relating quality data to manufacturing six sigma
or Cpk levels
There are many steps in the manufacture of printed circuit boards
(PCBs). They include the preparation of the components and the fab-
ricated PCB, the placement of the components or their insertion into
predetermined locations on the PCBs, and the attachment of the com-
ponents to the PCBs through the application of solder joints.
In order to control the quality of manufacturing the PCBs, some of
these steps have their own recommended specifications from the
equipment and material suppliers. However, a direct relationship of