6. • Advantage of Ag plating
Introduction
High reflection
High speed application
• Skin effect
2
ρ: Resistivity of conductor
ω:angular frequency (2πf)
μ: absolute permeability
δ: Skin depth
63% signal contained!
Ag has the lowest resistivity
μ=4π×10-7(亨利/公尺)
Reference: National Central University
0
10
20
30
40
50
60
70
80
90
100
350 400 450 500 550 600 650 700 750
reflectionrate(%)
Wave length(nm)
Ag
Cu
Au
Pd
Ni
Thermal conductivity (20℃) (w・m-1・k-1) Electrical resistivity (300K) (n Ω・m)
Ag Au Cu Ni Pd
429 318 401 91 72
Ag Au Cu Ni Pd
15.9 22.1 16.8 69.3 105.4
6
8. Advantages of ENES
No discolor by heat treatment
For applications of the eutectic gold-tin alloy
Good mechanical properties
Good coverage as normal ENIG
Solder joint reliability is good
Reflection rate
Reflection rate >95% at visible light
Wire bonding
Wire bonding be used when Ag thickness >0.4um
8
9. Process Temp.(oC) Plating con.
Cleaner 50 5 min
Micro Etching 30 1 min
Acid Rinse R.T. 1 min
Pre-dip R.T. 1 min
Activator R.T. 1 min
Post dip R.T. 1 min
EL-Ni 80 3-5 um
Activator 50 1 min
EL-Ag 40 0.2-1.5 um
Anti-tarnish 50 1min
Uyemura ENES Process
It is necessary to rinse after each process, except for pre-dip.
The condition of cleaner and post-dip could be adjusted for different substrates.
The thickness of EL-Ni and EL-Ag could be applied for reliability test and reflection rate.
Cu
Activated Pd
Cu Cu
Ni
Ag
Ni
9
10. Ni：5um, Ag:0.4-0.8um
KONICA MINOLTA CM-3700d, di:8°, SCI, SAV(3×5mm)
1 2 3
5
1:1 1:10 1:100
Big Pad
4
Small pad
0.32 0.29 0.31 0.30 0.30
4.87 4.92 5.02 4.85 4.90
0.001
0.01
0.1
1
10
1 2 3 4 5
Ag Ni
1min
3min
5min
As-plate
350 400 450 500 550 600 650 700 750
50
55
60
65
70
75
80
85
90
95
100
Reflection rate
Uniform Thx.
Discolor checking
350oC for 5min
Uniform of Ag thickness as
plating.
There are no significant
discolor after heat treatment
Retard Ni diffusion
Reflection rate > 95%
The number of point
10
Characters of ENES
Wavelength (nm)
Reflectionrate(%)
11. Cu
Ni(P)
Ni(P)
Cu
Ni(P)
Cu
Ni(P)
Ni(P)
Cu
Ni(P)
Ni(P)
Cu
Cu
Ni(P)
0.2 μm Ag
5 μm 5 μm
5 μm 5 μm5 μm
1 reflow
3 reflow
SAC305
0.4 μm Ag 0.8 μm Ag
• No Detachment of IMC are
observed after 3 times reflow.
Cu
Ni(P)
(Cu,Ni)6Sn5
SAC 305
Cu
Ni(P)
(Ni,Cu)3Sn4
SAC 305
(Cu,Ni)6Sn5
Non-spalling Spalling
IMC determination
Cu
Ni(P)
11
SAC305SAC305
12. Requirement for ENEPES process
Retard Ni
diffusion to
Ag layer
Reflection
rate
Solder joint
reliability
Wire bonding
reliability
12
solder layer
Al substratePCB
Ag plating
3.2 mm
19 mm
2.2 mm
1.65 mm
0.5 mm
Ag plating
1 2 3 4
13. Process Temp.(oC) Plating con.
Cleaner 50 5 min
Micro Etching 30 1 min
Acid Rinse R.T. 1 min
Pre-dip R.T. 1 min
Activator R.T. 1 min
Post dip R.T. 1 min
EL-Ni 80 3-5 um
EL-Pd 50 0.02-0.1 um
EL-Ag 40 0.2-1.5 um
Anti-tarnish 50 1min
Uyemura ENEPES Process
Cu
Activated Pd
Cu Cu
Ni
Pd
Ag
Ni
It is necessary to rinse after each process, except for pre-dip.
The condition of cleaner and post-dip could be adjusted for different substrates.
The dipping time of EL-Ni, EL-Pd and EL-Ag could be adjusted for required thickness. 13
14. Relation of heat treatment and Ni diffusion
0
5000
10000
15000
20000
0 200 400 600 800
Intensity
Depth(nm)
Pd
Ag
Ni
0
5000
10000
15000
20000
0 200 400 600 800
Intensity
Depth(nm)
Pd
Ag
Ni
0
5000
10000
15000
20000
0 200 400 600 800
Intensity
Depth(nm)
Pd
Ag
Ni
0
5000
10000
15000
20000
0 200 400 600 800
Intensity
Depth(nm)
Pd
Ag
Ni
ENEPES =5/0.02/0.2um
No heated
ENEPES =5/0.02/0.8um
No heated
ENEPES =5/0.02/0.2um
Heated (300 deg C-30min.)
ENEPES =5/0.02/0.8um
Heated (300 deg C-30min.)
ENEPES can retard the diffusion of Ni into the Ag layer after heat treatment .
14
No
Heated
Heated
Ag:0.8umAg:0.2um
15. 15
Reflection rate
As-plate
Ni：5um, Pd:0.03um, Ag:0.2-1.5um
KONICA MINOLTA CM-3700d, di:8°, SCI, SAV(3×5mm)
50
55
60
65
70
75
80
85
90
95
100
350 450 550 650 750
reflectionrate(%)
Wavelength(nm)
NPR-4(6um)/as-plate
0.2um
0.5um
0.8um
1.2um
1.5um
We are considering that it is necessary to be over 0.2 um for reflection rate.
When Ag thickness is thicker, the reflection is increased at visible light.
16. Solder joint reliability
Reflow1
0.2um 0.3um 0.4um 0.5um 0.8um
Ball pull no significant differences (~2183g)
Ball shear no significant differences (~927g)
HSBS no significant differences (~1327g)
Reflow3
0.2um 0.3um 0.4um 0.5um 0.8um
Ball pull no significant differences (~2131g)
Ball shear no significant differences (~913g)
HSBS no significant differences (~1213g)
Reflow5
0.2um 0.3um 0.4um 0.5um 0.8um
Ball pull no significant differences (~2055g)
Ball shear no significant differences (~902g)
HSBS no significant differences (~1131g)
It is recommended that Ag > 0.2 um for good solder joint.
solder ball: SAC305(diameter:500um)
Ball shear strength is the average of 15 points. (shear speed: 170 um/s)
HSBS strength is the average of 15 points. (shear speed: 1 m/s) (Dage 4000-Schmidt)
16
17. Wire bonding reliability
Pull
point
A
B
C
D
E
Pull speed: 170um/sec
It is possible to bond on ENEPES by
optimizing the thickness of Ag.
K&S 4700AD
Good bonding
0%
20%
40%
60%
80%
100%
0.2um 0.3um 0.4um 0.5um 0.2um 0.3um 0.4um 0.5um
RSD-4 ENIG ENEPIG RSD-4 ENIG ENEPIG
as-plate 175deg.C-16hr
Failuremode
A B C D E
8.7 9.2
8.1 8.2
2.7
10.0
6.5 6.4 6.7
7.3
0.0
8.3
0
2
4
6
8
10
12
14
Pullstrength(g)
Average
17
20. 27.3 28.1
27.6
0.1
0.1
SAC305 Sn0.7Cu
Sn Ag Cu
Sn : Ag : Cu= 0.283 : 9.187 : 0.107 (Dollars(USA)/g)
reference:鉅亨網期貨(2012,9,4)
Cost Issue
The Ratio of Gold and Silver
Sn07Cu Solder replaces for
SAC305 on FC(C4 zone)
(Dollars(USA)/particle)
20
About final finish type :
Ag replace Au Cost down≒97%of gold
(the same thickness)
≒ 1600Dollars(USA)/OZ
≒30Dollars(USA)/OZ
21. Ref: T.Y. Lee, W.J. Choi, and K.N. Tu ”
Morphology, kinetics, and thermodynamics of
solid-state aging of eutectic SnPb and Pb-free
solders (Sn–3.5Ag,Sn–3.8Ag–0.7Cu and Sn–0.7Cu)
on Cu “J. Mater. Res., Vol. 17, No. 2, Feb 2002
Phase diagram of Sn–Ag–Cu
SAC305
More Ag addition
Ag concentration in solder
Plate-type
21
22. Ag concentration in solder
Ag
4-2434
Ag
-424
Ag/solder
ρ10X)107.53π(])10π[(37.5
3
4
ρ10X)105.37π(
C
Solder type SAC305 Sn0.7Cu
Critical Ag thickness (μm) 0.18 μm 1.27 μm
Critical CAg/solder 0.5% 3.5%
• The effect of electroless Ag thickness : Solder
Pd
CuNi
Ag
75 μm
75 μm
Cu X μm
According to Ag concentration in solder, the critical Ag thickness is only 0.18um
for SAC305, but 1.27um for Sn0.7Cu.
CAg/solder: Concentration of Ag in solder(wt.%)
ρ : density of SAC305 7.4 (g/cm3), density of Sn0.7Cu 7.3 (g/cm3)
ρAg : density of Ag 10.49 (g/cm3)
X: thickness of Ag (μm)
22
24. ENES ENEPES
Advantages
No discolor by heat treatment
Solder joint is good
Reflection rate
W/B
Retard Ni diffusion
Solder joint is excellent
Reflection rate
W/B
Drawbacks
IMC become spalling until 5
reflow
Can’t W/B if Ag is thinner
than 0.4 um
So far so good
Thickness
Ni 3-5 um
Ag 0.2-1.5 um
Ni 3-5 um
Pd 0.02-0.1 um
Ag 0.2-1.5 um
Comprehensive
estimate
Cu
Ni-P
Ag
Cu
Ni-P
Pd-P
Ag
Summary Comparison of each process
24
Reliability
Reflection
Cost Down
Uniform
Thx.
Retard Ni
Diffusion
Reliability
Reflection
Cost Down
Uniform
Thx.
Retard Ni
Diffusion
