September 2014 • The PCB Design Magazine 55
HDI PWB RELIABILITy continues
In conclusion, the use of HDI PWB reli-
ability in lead-free applications is a dual-edged
sword. The copper interconnections are more
prone to a breakdown and the material is
more prone to damage. That is not to say
that robust PWBs cannot be made, but there
is a challenge in producing them. One must
test the interconnect and the material in order
to confirm robustness in a given application.
PCBDESIGN
Figure 10: Adhesive delamination. Figure 11: Cohesive crack.
Figure 12: Crazing with a CAF failure.
Paul reid's career in PCB fab-
rication and reliability testing
spans 35 years. One of his spe-
cialties is producing technical
animations of failure modes
induced by thermal excursions,
giving him insight into the mechanisms of
circuit board failure. reid is now retired. To
contact the author, click here.
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