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8th European Pulse Plating Seminar2nd March 2018, Vienna
Steiger G
alvano
techniqu
e SA
Estopp
ey‐Reb
er group
Guidelines for setting the useful range of Pulse Plating parameters
Jean-Claude Puippewww.steiger.ch
Steiger G
alvano
techniqu
e SA
Estopp
ey‐Reb
er group
Le rôle des impulsions de courant en électrocristallisationJean‐Claude Puippe
Diss. No 6225, ETH Zurich, 1978
Prof. Dr. Norbert IblDirecteur de thèse
V = L W Hjm = jpTon
Steiger G
alvano
techniqu
e SA
Estopp
ey‐Reb
er group
Limiting factors of Pulse Plating parameters
The lower limit of the pulse duration depends on the capacity effects of the electrical double layer at the electrode.
The upper limit of the pulse duration depends on the mass transport of electroactive ions through diffusion at the electrode.
Steiger G
alvano
techniqu
e SA
Estopp
ey‐Reb
er group
jc = C dηa/dt
Capacity effects
Steiger G
alvano
techniqu
e SA
Estopp
ey‐Reb
er group
No damping of faradic current
small damping of faradic current
strong dampingof faradic current
Flattening of faradic current
Capacity effects
c
d
Steiger G
alvano
techniqu
e SA
Estopp
ey‐Reb
er group
Computation of charging time tc of double layertc = time required for the faradic current to reach 99% of jpThe charging time is segmented in increments corresponding to 1 mV steps. Within one step, the faradic current can beconsidered as constant. It is readjusted according to Butler Volmer equation for each step.
jc = dQ / dt = C da/dt
djF = ‐ djC (for galvanostatic pulse)
jF = jo (exp(αzFηa/RT) – exp((1‐ α)zFηa/RT))
tn = C ((an ‐a(n‐1)) / (jFn – jF(n‐1))) ln (jC(n‐1) / jCn)
tc = ∑ tn from jF = 0 till jF = 0.99 jp
Steiger G
alvano
techniqu
e SA
Estopp
ey‐Reb
er group
(1) ln (aj ot
c/C) (2) ln
(aj ot
d/C)
For loading rate 99% (JF = 0.99 jp )
and for jp/jo > 100, td = 7 tc
Dimensionless representation of tc and td as a function of the ration jp / jo , where a = nF/RT and (�n = 1; T = 289 °K; C = 50 µF/cm2 )
Steiger G
alvano
techniqu
e SA
Estopp
ey‐Reb
er group
Computation of charging time of double layer
For the following conditions:
JF = 0.99 jpJp / jo > 100
C = 50 µF / cm2
n = 1
tc = 0.017 / jp and td = 0.120 / jpwhere tc and td are given in [ms] and jp is given in [A/cm2]
Steiger G
alvano
techniqu
e SA
Estopp
ey‐Reb
er group
Degree of flattening � of faradiccurrent as a function of Ton / tcΔ = jc / jm
Δ For Δ = 0.1,Ton / tc should be >5
Steiger G
alvano
techniqu
e SA
Estopp
ey‐Reb
er group
Lower limits of Pulse Plating parameters
The lower limits of Ton and Toff which are dictated by the charging and discharging time of the electrical double layer.
For a degree of flattening (jc/jm) Δ < 0.1,Ton > 5 tc and Toff > td . Therefore,
Where Ton and Toff are given in [ms] and jp in [A/cm2]
Ton > 0.085 / jp and Toff > 0.12 / jp
Steiger G
alvano
techniqu
e SA
Estopp
ey‐Reb
er group
Mass transport limitations through diffusion
Steiger G
alvano
techniqu
e SA
Estopp
ey‐Reb
er group
Distance to cathode, x
Concen
tration at th
e electrod
e, c Diffusion layer under DC conditions
Steiger G
alvano
techniqu
e SA
Estopp
ey‐Reb
er group
Distance to cathode, x
Concen
tration at th
e electrod
e, c Double diffusion layer under
Pulse Plating conditions
Steiger G
alvano
techniqu
e SA
Estopp
ey‐Reb
er group
Distance to cathode, x
Concen
tration at th
e electrod
e, c Relaxation rate of the pulsating
diffusion layer: Ce’/Co
�p
�N
Ce’/Co = 1 – jm/jL
Steiger G
alvano
techniqu
e SA
Estopp
ey‐Reb
er group
∂CA / ∂t = DA (∂2CA / ∂x2)
Concentration profile in transient state according to the 2nd Fick law
Steiger G
alvano
techniqu
e SA
Estopp
ey‐Reb
er group
Under potentiostatic conditions:
= D t
Under galvanostatic conditions:
= 2 D t /
Transition time for galvanostatic pulses
= D Ce’2(n F)2 / 4 jp2
Particular solutions Fick II equation
Steiger G
alvano
techniqu
e SA
Estopp
ey‐Reb
er group
The upper limit of Ton is dictated by the transition time . In order to stay away from the mass transport control, to avoid hydrogenevolution and therefore a strong drop of currentefficiency, Ton has to be set bellow
It should however be enhanced that in somecases, as for instance in alloy deposition, it maybe necessary to reach the transition time of one species in order to promote the deposition of other species.
Ton <
Upper limit of the on time Ton
Steiger G
alvano
techniqu
e SA
Estopp
ey‐Reb
er group
Considering mass transport limitations, Toff has no upper limit but a lower limit in order to allow the pulsating diffusion layer to reach a high relaxion rate. The concentration at the electrode Ce’ at the beginning of each pulse should be close to the bulkconcentration CoFor δN >> δp , the relaxation rate Ce’/Co = 1 – jm/jL
Mass transport limitationsof the off time Toff
Steiger G
alvano
techniqu
e SA
Estopp
ey‐Reb
er group
Excel table of «allowed» pulse parameters
Steiger G
alvano
techniqu
e SA
Estopp
ey‐Reb
er group
Examples of Pulse Plating aplicationsin the experimental physics
Requirements for the experimental physics:
High conductivity : RRR > 250High purity of cooating for non degasingLow roughness even for high thicknessesabove 100 µm
the only way to obtain the requestedspecifications is to apply Pulse Plating
Cuivrage intérieur de 416 dipôles de 9.58 m et 214 quadripôles de 3 m pour le ring de l’accélérateur HERA (6.3 km) du DESY à Hamburg
Argentage 60 µm des antennes du JET pour le chauffage du plasma thermonucléaire par irradiation d’ondes électromagnétiques à radiofréquence
100 µm Copper plating of 900 BPM components for the LHC at CERN
Steiger G
alvano
techniqu
e SA
Estopp
ey‐Reb
er group
Cuivrage de BPM pour le LHC, CERN
IN MEMORIAM our Passed President Prof Pietro Cavalotti and our regretted colleguesProf Chris Raub, Prof Nicolas Spyrellis, Prof V.N. Kudryavtsev, Prof M. Froment,Prof Jan Przyluski, Prof St. Rashkov, Prof E. Budevski, Prof A. Despic
Steiger G
alvano
techniqu
e SA
Estopp
ey‐Reb
er group
Thank you for your attention