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