STDA022 January   2026 MSPM0L1305

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Background
  6. 3Procedure
  7. 4Assessment Methods and Results
    1. 4.1 Initial Data Collection
    2. 4.2 BLR With In Situ Monitoring
    3. 4.3 BLR Without In Situ Monitoring
  8. 5Summary of Results
  9. 6Conclusion
  10. 7Acknowledgements
  11. 8References

4.1 Initial Data Collection

After being soldered to PCBs, three of the units in the SON style of configuration were cross-sectioned to measure the solder joint thickness and SEM images were taken to examine the solder fillet formation. The solder joint measurements are summarized in Figure 4-1. All the solder joint thickness values for a given unit averaged 50μm or greater, which is in line with guidance from IPC-7351 on preferable and reliable solder joint thickness [4].

XM0L1305SRTRR MSPM0L1305 T0 Solder Joint Measurements of Units In the SON Style of Configuration Without Any Stress Testing Figure 4-1 T0 Solder Joint Measurements of Units In the SON Style of Configuration Without Any Stress Testing

The solder joints in Figure 4-2 and Figure 4-3 show no anomalies and are representative cross-sectional images for 100µm and 200µm overhangs.

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Figure 4-2 Cross Sections of Leads Soldered With a 100μm Overhang Without Any Stress Testing
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Figure 4-3 Cross Sections of Leads Soldered With a 200μm Overhang Without Any Stress Testing
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Partial fillets and low to no side-wetting angles were commonly seen in the solder joints. However, these appearances do not necessarily indicate inferior performance. More information on this concept is discussed in the following section where board-level reliability is assessed.