Chemistry Reference
In-Depth Information
(CHCl
3
), then rinsed with this same solvent for 1 min. During the spin-on process,
the chloroform evaporates spontaneously and leaves a palladium-based thin film
whose thickness depends on the spin-speed used and number of drops of solution
deposited on the substrate.
Both laboratory-made and commercial Ni and Cu plating baths were used in
the present study. The laboratory-made Ni plating bath contained NiSO
4
·6H
2
O
(0.14 M), NaH
2
PO
2
·H
2
O (sodium hypophosphite) (0.09 M), lactic acid (0.27 M)
and operated at pH 5 and 85°C. The laboratory-made Cu plating bath contained
five parts of the following solution CuSO
4
·5H
2
O (0.28 M), KNaC
4
H
4
O
6
·4H
2
O
(0.6 M), NaOH (0.14 M) and EDTA (0.03 M) and one part of formaldehyde
HCHO 37% and operated at pH 12 and room temperature. In addition, commer-
cial Europlate Ni 520 electroless nickel (Frappaz, Neyron, France) and Enplate
Cu 872 electroless copper (Enthone-OMI, France) baths were employed accord-
ing to manufacturer's instructions. In all these cases, sodium hypophosphite and
formaldehyde were the reducing agents present in the Ni and Cu plating baths, re-
spectively. These agents are required to reduce Ni
2+
and Cu
2+
ions to Ni
0
and Cu
0
state, respectively.
2.2. Characterization techniques
XPS analyses were performed with a Riber SIA 200 spectrometer using a non-
monochromatic Al K
α
photon source and a take-off angle of 65° with respect to
the sample surface. Spectra were referenced to the C 1s signal at a binding energy
of 285.0 eV characteristic of the C
H bonds.
Adhesion of thin metal films to their substrates was first characterized using a
simple adhesive tape peel test (cross-cut tape test according to ASTM D 3359). In
addition, a stretch deformation test (also known as fragmentation test) was employed
in conjunction with electrical measurements in order to distinguish the influence of
the polymer surface conditioning. For this purpose, dog-bone shape metal-PI sys-
tems were strained under uniaxial elongation at a constant strain rate of 0.05 mm
min
-1
using a DY 25 Adamel Lhomargy machine. Some details about the approach
using electrical measurements can be found in recent papers [33, 40, 41].
−
C and C
−
3. RESULTS AND DISCUSSION
3.1. Surface “activation” through plasma or VUV-assisted techniques and
chemisorption of Pd-based species
Figure 1 represents schematic diagrams of the different preparation processes: (A)
which are conventionally used, and (B) which were explored in our laboratory to
make the surfaces of polymers and polymer-based materials catalytically active
towards the electroless metallization [22-33]. Note that the first experiments car-
ried out in the afore-mentioned works were mainly performed with laboratory-
made Ni plating baths.
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