FSC-5178 FIGURE 1. PHOTOGRAPHS OF FRONT AND BACK OF SUB-PANEL AFTER SOLDER PASTED WITH SAC305 AND REFLOWED a). Front side of sub-panel b). Back side of sub-panel

FSC-5178 FIGURE 2. MAGNIFIED VIEW OF FRONT SIDE OF TI +5V GATE DRIVE DISCRETE DUT CARD Rev 2-T AFTER SOLDER PASTED WITH SAC305 AND REFLOWED

FSC-5178 FIGURE 3. MAGNIFIED VIEW OF Q1, Q2, AND Q3 FOOTPRINTS WITH ‘PURPLE” DISCOLORATION A B C See Fig. 22 D

FSC-5178 FIGURE 4. MAGNIFIED VIEW OF OTHER FEATURES ON CARD THAT DON’T HAVE “PURPLE” DISCOLORATION

FSC-5178 FIGURE 5. MAGNIFIED VIEW OF OTHER GOLD PLATED EDGE FINGERS

FSC-5178 FIGURE 6. XRF SPECTRUM OF PLATED EDGE FINGERS PCB Surface Finish is Electrolytic Gold / Nickel

FSC-5178 FIGURE 7. 3D SURFACE PLOT OF XRF MEASUREMENT OF ELECTROLYTIC GOLD (Au) PLATING THICKNESS XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX

FSC-5178 FIGURE 8. 3D SURFACE PLOT OF XRF MEASUREMENT OF ELECTROLYTIC GOLD (Au) PLATING THICKNESS XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX

FSC-5178 FIGURE 9. FREQUENCY DISTRIBUTION OF XRF MEASUREMENT OF ELECTROLYTIC GOLD ON EDGE FINGER

FSC-5178 FIGURE 10. FREQUENCY DISTRIBUTION OF XRF MEASUREMENT OF ELECTROLYTIC GOLD ON EDGE FINGER

FSC-5178 FIGURE 11. FREQUENCY DISTRIBUTION OF XRF GOLD MEASUREMENT ON BACK SIDE DISCRETE COMPONENT PADS

FSC-5178 FIGURE 12. FREQUENCY DISTRIBUTION OF XRF NICKEL MEASUREMENT ON BACK SIDE DISCRETE COMPONENT PADS

FSC-5178 FIGURE 13. XRF SPECTRUM OF SOLDER ON Q3 FOOTPRINT PCB Solder Consistent with SAC305

FSC-5178 FIGURE 14. XRF SPECTRUM OF NON-WET PORTION OF Q3 FOOTPRINT Corner of Q3 footprint is Electrolytic Nickel/Gold

Leading edge “wave” is consistent with SAC305 that has lots of Au dissolved in it FSC-5178 FIGURE 15. XRF SPECTRUM OF LEADING EDGE ‘WAVE” AT CORNER OF Q3 FOOTPRINT

FSC-5178 FIGURE 16. XRF SPECTRUM OF “PURPLE” AREA ON Q3 FOOTPRINT

FSC-5178 FIGURE 17. PURPLE DISCOLORATION IS EASILY REMOVED WITH DILUTE MURIATIC ACID a). Upper left corner of Q3 pad b). Upper left corner of Q3 pad after cleaning with dilute (~3%) muriatic acid

FSC-5178 FIGURE 18. MAGNIFIED VIEW OF PURPLE AREA AFTER REMOVAL WITH DILUTE MURIATIC ACID Area Dispensed with SAC305 Solder Paste Purple area appears to be loaded with Intermetallic needles

FSC-5178 FIGURE 19. CROSS SECTION OF Q2 FEATURE ON TI DUT CARD See Fig. 20

a). Q2 cross section (25x) b). Q2 cross section (500x) c). Q2 cross section (1000x) Electroless Nickel (ENi) Copper Feature SAC305 Solder ENi SAC305 Solder Sn-Ni IMC FSC-5178 FIGURE 20. MAGNIFIED VIEWS OF Q2 FEATURE CROSS SECTION

a). 45° view of Q2 cross section (10x) b). Q2 cross section (50x) c). Q2 (500x) d). Q2 (500x) e). Q2 (500x) FSC-5178 FIGURE 21. MAGNIFIED VIEWS OF Q2 FEATURE CROSS SECTION SLIGHTLY FURTHER INTO Q2 SAC305 Solder ENi Vendor Cu Plated Cu Purple No Purple

A FSC-5178 FIGURE 22. FEATURE Q3 EXCISED FOR SEM/EDS ANALYSIS B C Corner of Q3 cut to fit in SEM D

FSC-5178 FIGURE 23. SEM AND OPTICAL IMAGE OF Q3 SAMPLE USED FOR SEM/EDS ANALYSIS A B C A B C a). SEM Image b). Optical Image D D See Fig. 24

A B C FSC-5178 FIGURE 24. MAGNIFIED SEM IMAGE OF Q3 SAMPLE USED FOR SEM/EDS ANALYSIS D

SEM/EDS isn’t a good technique to analyze thin discoloration on surfaces but it is the only analytical tool we have. We used a low kV (10kV) to minimize penetration depth The high Au (90.3%) on area ‘C’ indicates ENIG not wet with solder which agrees with optical yellow color. The high Au (11.5%) on area ‘D’ indicates that the leading edge of the solder wave that is flowing out from where the solder paste was deposited dissolves Au from the ENIG as it wets and flows outward making the Au concentration higher at the leading edge. The slightly higher O at the purple colored area ‘B’ (2.0%) and purple colored area ‘D’ (1.7%) may indicate that the purple discoloration may be a very thin oxide. The high Sn at area ‘A’ (79.7%) and area ‘B’ (86.2%) and area ‘D’ (78.3%) as well as Ag at area ‘A’ (3.3%) and area ‘B’ ( 1.7%) and area ‘D’ (1.9%) indicate there is certainly SAC solder on those surfaces. Auger or XPS would be a better surface analysis technique but we don’t have them. SEM/EDS Analysis Comments