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36 DESIGN007 MAGAZINE I FEBRUARY 2024 standard ENIG/ENEPIG finishes but still con- tributing slight signal loss compared to immer- sion silver and OSP. One of the concerns for nickel-free finishes is the solder joint reliability with removed or greatly reduced nickel diffusion barrier layer thickness. is article will address this concern and focus on various solder joint reliability testing, including high-speed ball shear, drop shock, and solder joint reliability electromi- gration tests. Work Program As mentioned in Part 1, the test candidate surface finishes selected are: • Standard ENEPIG (4 µm electroless nickel/0.1 µm palladium/0.05 µm gold) • Standard ENIG (4 µm electroless nickel/0.05 µm gold) • in EN ENEPIG (0.2 µm electroless nickel/0.1 µm palladium/0.05 µm gold) • Ultra-in EN ENEPIG (0.1 µm electroless nickel/0.1 µm palladium/ 0.05 µm gold) • EPIG (0.1 µm palladium/0.05 µm gold) • Silver-Gold (0.15 µm silver/0.05 µm gold) • Immersion Silver (0.3 µm) • OSP (0.4 µm) As mentioned in the introduction, the fol- lowing tests were performed: • High-speed ball shear • Drop shock evaluation • Solder joint electromigration Aer the data was collected, it was summa- rized, and a decision matrix was constructed to allow designers to compare performance requirements against each surface finish's capa- bilities. Experimental Methodology High-Speed Ball Shear Test Ball shear tests were performed to evaluate the solder joint reliability. Testing was done on ball grid array (BGA) test coupons with solder mask defined pads with solder resist openings at 250 µm. e ball shear test at low- speed shear conditions (0.3–0.5 mm sec) were reported in Part 1 2 . In this article, only high- speed ball shear data is presented. It was tested at 1000 mm/sec and the spacing between the shear head and board surface was 20 µm. Drop Shock Test e dummy CTBGA84 components were used for the drop shock test. e drop shock table height and striking surface were adjusted to obtain a half-sine shock pulse with 1500 Gs and 0.5 msec peak, following the JESD22-B111 standard. Failures were defined as a drop of 1V or more in the applied potential for at least 0.5 msec, based on the IPC/JEDEC-9706 stan- dard, being detected and recorded using a high- speed data acquisition system. e interval plot of the drop shock performance are presented. Solder Joint Electromigration Test Solder joint electromigration is a phenome- non that can occur in electronic devices where electrical current flowing through solder joints causes metal atoms to migrate, leading to the degradation or failure of the joint 3 . Electromi- gration is influenced by several factors, includ- ing the magnitude and direction of the current, the temperature, the composition of the solder alloy, as well as the microstructure of the joint. Higher current densities, higher temperatures, and the presence of defects or impurities in the solder can accelerate electromigration. To study the effects of the various surface finishes on electromigration, the current and tempera- ture were fixed at 5A and 100°C. SAC 305 sol- der alloys were used for the test. Results and Discussion High-speed Ball Shear Test e high-speed ball shear test was done at 1000 mm/sec using the DAGE 4000HS instru- ment. e ball grid array (BGA) with 250 µm