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inspection equipment. As evidenced
Figure 9: LSC to BGA solder ball gap height from assembly lot 1.
Figure 10: LSC to BGA solder ball gap height from assembly lot 2.
Figure 11: LSC to BGA solder ball gap height from assembly lot 3.
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by Figures 9-11, Cpk values across
the three assembly lots all exceed
the automotive target of ≥1.67. This
high-margin process capability paves
a pathway for a robust and defect-free
SMT assembly that aligns with an
automotive mindset as required from
automotive Tier 1 suppliers.
Summary
LSCs are critical passive components
utilized to reduce package impedance
as their inherent closer proximity to
the chip increases capacitance, thereby
enabling crosstalk mitigation. The
combination of low-profile LSCs and
being automotive-qualified based on
AEC-Q200 specifications, are not
widespread within flip-chip packaging,
which limits their use to BGA pitches
less than or equal to 0.8mm because of
clearance issues with the PCB.
A SMT design of experiment (DoE)
was carried out based on five different
component placement options to
determine if a minimum gap height
between the LSC and the PCB surface
of 100µm can be achieved. T his
comprehensive study was done in order
to understand the impact of clearance
height between the LSC and PCB as
a function of commonly-used SMT
component placement conditions. SMT
conditions were based on the most
frequently used methods for pick and
place, which involve using placement
speed and package thickness to release
the component to the PCB. The SMT
DoE evaluation was performed on the
following five different component
placement options:
• Slow speed means minimum force
in the 2-3N apply on the package;
• Medium speed means a force in the
4-5N range;
• Fast speed means a force in the
6-9N range;
• Component released after touching
the PCB surface ( program in
package total thickness); and
• C o m p o n e n t r e l e a s e d a f t e r
submerged 0.05-0.075mm into the
solder paste (i.e., program in actual
package thickness with additional
0.05mm).
Multiple cross-sectional analyses
p e r f o r m e d a n d v e r i f i e d t h a t a
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