Page 58 - Chip Scale Review_March April_2022-digital

Figure 4: Thickness of a LSC. Figure 5: Gap height between a LSC and a PCB.

issues like solder bridging and non-wets among all splits. gap height between the LSC and the PCB. Figure 5 shows
Based on cross-sectional analysis, all commonly used SMT the gap height or distance between the LSC and PCB.
placement conditions met the clearance target of 100µm. Figure 6 shows a scatterplot comparing the relationship
Figure 2-4 provide a pictorial of the outputs (i.e., as between the BGA standoff and gap between the LSC
referenced in Table 1) being measured via cross-sectional and PCB, where Figure 7 illustrates a moderate positive
analysis of FCBGA parts assembled to the PCB. Figure 2 correlation is observed based on the same relationship
illustrates the FCBGA package mounted to the PCB, where between BGA standoff and gap between the LSC and PCB.
the FCBGA substrate, LSC, and PCB are annotated. Based on this relationship, further assembly optimization
Figures 3 and 4 show measurements of solder thickness and LSC thickness control can be tuned to drive at
between the flip-chip substrate BGA pad and the LSC and stronger positive correlation.
the LSC thickness, respectively, which contributes to the

Figure 6: Moderate positive correlation between the gap height that is between an LSC and a PCB, and between the BGA standoff height.

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