a). front side of sub-panel
DESCRIPTION
b). Back side of sub-panel. a). Front side of sub-panel. FSC-5178 FIGURE 1. PHOTOGRAPHS OF FRONT AND BACK OF SUB-PANEL AFTER SOLDER PASTED WITH SAC305 AND REFLOWED. - PowerPoint PPT PresentationTRANSCRIPT
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 10030 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
BC
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
Series1
Series3
Series5
40414243
44
45
46
47
48
49
50
1 2 3 4 5 6 7 8 910
Go
ld (
Au
) T
hic
kn
es
s -
(mic
roin
ch
es
)
TEMP-1 Edge Finger Matrix (10x5)
3D Surface Plot of XRF Gold (Au) Measurements
49-50 48-49 47-48 46-47 45-46
44-45 43-44 42-43 41-42 40-41
FSC-5178 FIGURE 7. 3D SURFACE PLOT OF XRF MEASUREMENT OF ELECTROLYTIC GOLD (Au) PLATING THICKNESS
X XXXX
X XXXX
X XXXX
X XXXX
X XXXX
X XXXX
X XXXX
X XXXX
X XXXX
X XXXX
Series1
Series3
Series5
0255075
100125150175200225250275300325
1 2 3 4 5 6 7 8 9 10
Nic
ke
l (N
i) T
hic
kn
es
s -
(mic
roin
ch
es
)
TEMP-1 Edge Finger Matrix (10x5)
3D Surface Plot of Electrolytic Nickel (Ni) XRF Measurements
300-325 275-300 250-275 225-250 200-225
FSC-5178 FIGURE 8. 3D SURFACE PLOT OF XRF MEASUREMENT OF ELECTROLYTIC GOLD (Au) PLATING THICKNESS
X XXXX
X XXXX
X XXXX
X XXXX
X XXXX
X XXXX
X XXXX
X XXXX
X XXXX
X XXXX
FSC-5178 FIGURE 9. FREQUENCY DISTRIBUTION OF XRF MEASUREMENT OF ELECTROLYTIC GOLD ON EDGE FINGER
0
5
10
15
20
25
30
35
40
45
50
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Nic
ke
l Pla
tin
g T
hic
kn
es
s -
(mic
roin
ch
es
)
Frequency Distribution - (%<)
Gold (Au) Thickness
TEMP1 Au ESTRA1 Au
FSC-5178 FIGURE 10. FREQUENCY DISTRIBUTION OF XRF MEASUREMENT OF ELECTROLYTIC GOLD ON EDGE FINGER
0
25
50
75
100
125
150
175
200
225
250
275
300
325
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Nic
ke
l Pla
tin
g T
hic
kn
es
s -
(mic
roin
ch
es
)
Frequency Distribution - (%<)
Nickel (Ni) Thickness
TEMP1 Ni ESTRA1 Ni
0
1
2
3
4
5
6
7
8
9
10
11
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Go
ld (
Au
)Th
ickn
ess
-(m
icro
inch
es)
Frequency Distribution - (%<)
Gold (Au) Thickness on Non-Gold Finger Features
FSC-5178 FIGURE 11. FREQUENCY DISTRIBUTION OF XRF GOLD MEASUREMENT ON BACK SIDE DISCRETE COMPONENT PADS
0
20
40
60
80
100
120
140
160
180
200
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Nic
ke
l(N
i) Th
ickn
ess
-(m
icro
inch
es)
Frequency Distribution - (%<)
Nickel (Ni) Thickness on Non-Gold Finger Features
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
SAC305 Solder
ENi ENi ENi
Vendor Cu Vendor CuVendor Cu
Plated Cu Plated CuPlated Cu
Purple
Purple
No Purple
A
FSC-5178 FIGURE 22. FEATURE Q3 EXCISED FOR SEM/EDS ANALYSIS
BC
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
AB
C
AB
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
Area A Area B Area C Area DSn 79.7 86.2 1.4 78.3Ag 3.3 1.7 0.0 1.9Au 8.5 6.2 90.3 11.5Cu 5.9 2.3 5.6 4.9O 1.6 2.0 0.3 1.7Al 0.2 0.4 0.7 0.6Si 0.4 0.5 1.4 0.6C 0.5 0.6 0.4 0.6
SEM/EDS Analysis Quantification (WT%)Element
• 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