New developments in the adhesion promotion of electroless Ni or Cu films to polyimide substrates - Polyimides and Other High Temperature Polymers - page 293

the sensitization / activation two-step procedure. More interesting for the topic un-
der investigation is the fact that palladium is attached in a large amount (~ 1.5 at.%
in this experiment) on the NH 3 -plasma treated surface (Fig. 2, spectrum (d)). Note
again the complete absence of adsorbed tin species in this case.
Before drawing some conclusions from the afore-described experiments, we
must add that:
(i) the presence of palladium traces on PI substrates which are O 2 plasma-
treated and then immersed in a simple acidic PdCl 2 solution results from the pres-
ence of nitrogen atoms naturally available at the sample surface. In addition, this
statement is supported by the fact that polymer materials containing no nitrogen
atoms in their chemical structure do not adsorb, under similar conditions, any pal-
ladium species [22-24].
Figure 2. XPS survey spectra of Kapton ® HN substrates: (a) ethanol cleaned, (b) the same as (a) af-
ter plasma treatment in NH 3 (working pressure: 100 mTorr; flow-rate: 100 sccm; treatment time: 1
min), (c) the same as (b) after a simple “activation” process (immersion in an acidic PdCl 2 solution),
and (d) the same as (b) after the two-step sensitization / activation process (immersion successively
in acidic SnCl 2 and PdCl 2 solutions). Note that the abscissa scale (energy scale) is associated with
the bottom spectrum (a). Other spectra are shifted for sake of convenience.