Electrolytic Migration of Ag-Pd Alloy Wires with Various Pd
and TUNG-HAN CHUANG
1.—Institute of Materials Science and Engineering, National Taiwan University, Taipei 106, Taiwan.
2.—Wire Technology Co., LTD, Taichung 432, Taiwan. 3.—Department of Materials Engineering,
Ming Chi University of Technology, Taipei 243, Taiwan. 4.—e-mail: email@example.com.
5.—e-mail: firstname.lastname@example.org. 6.—e-mail: email@example.com. 7.—e-mail:
firstname.lastname@example.org. 8.—e-mail: email@example.com
During Ag ion migration in an aqueous water drop covering a pair of parallel
Ag-Pd wires under current stressing, hydrogen bubbles form ﬁrst from the
cathode, followed by the appearance of pure Ag dendrites on the cathodic wire.
In this study, Ag dendrites with a diameter of 0.2–0.4 lm grew toward the
anodic wire. The growth rate (v) of these dendrites decreased with the Pd
content (c) with a linear relationship of: v ¼ 10:02 À 0:43 c. Accompanying the
growth of pure Ag dendrites was the formation of a continuous layer of crys-
O particles on the surface of the anodic wire. The deposition of
such insulating Ag
O products did not prevent the contact of Ag dendrites
with the anodic Ag-Pd wire or the short circuit of the wire couple.
Key words: Ag ion migration, Ag-alloy bonding wires, Pd and Au additions,
water drop test
The phenomenon of Ag ion electrolytic migration
was observed in silver thick ﬁlm for the interconnec-
tion of hybrid microelectronics several decades ago.
Krumbein reported the failure mode of Ag ion migra-
tion, wherein the colloidal ‘‘staining’’ occurs at the
anode and Ag dendrites grow from the cathode to
anode to cause the short circuit of electronic devices.
Vu proposed a mechanism for the deposition of
colloidal silver on the anode as
: (1) the Ag conductor
at the anode is dissolved into Ag ion in water under
current stressing; (2) accompanying the formation of
hydrogen bubbles at the cathode, the OH
and move toward the anode; (3) the OH
ions to create AgOH products, which then
decompose on the anode to form Ag
O deposits; and (4)
a hydration reaction takes place, causing the Ag
deposits to form AgOH and then decompose as Ag
ions. Krumbein further explained that, during Ag
dendrite growth, Ag
ions migrate from the anode
toward the cathode and are reduced to Ag spikes at
localized sites on the cathode. The Ag
predominately reduced at the tips of the Ag spikes
due to the high current density there, leading to the
growth of Ag whiskers toward the anode.
Many researchers have proposed that silver elec-
trolytic migration can be inhibited by adding Pd to the
Naguib and MacLaurin reported that
the Ag ion migration rate decreased by approximately
100 times when the Pd content in Ag thick ﬁlm was
increased from 10% to 19%.
Lin et al. further showed
that Ag ion migration could be completely prevented in
Ag thick ﬁlm alloyed with 30% Pd.
that, through the potentiodynamic polarization
method, the anodic formation of PdO on Ag-Pd thick
ﬁlm blocked the formation and migration of Ag ions.
Gagne further presented an exceptional result of ‘‘dry’’
migration for Ag-Pd conductors covered with a lead-
in contrast to the phenomenon of
electrolytic Ag migration in water or humid environ-
ments reported by other researchers.
(Received July 19, 2017; accepted March 6, 2018;
published online March 19, 2018)
Journal of ELECTRONIC MATERIALS, Vol. 47, No. 7, 2018
2018 The Minerals, Metals & Materials Society