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Embedded trace plating
For embedded fine-line plating we
used an electrolyte branded as Systek
ETS as described in Table 1. The test
panels used were carriers with photo
imaged dry-film patterns on them with
a thickness of 25µm. Each test panel
went through a pre-clean cycle of 1min
acid cleaner, 1min rinse, and 1min 10%
sulfuric acid before plating in the acid
copper containing the electrolyte.
Table 2 describes an example of
Figure 2: Cross sections of fine lines from the plating process with soluble anodes. the influence of anode type on plating
uniformity for fine lines and vias in
VCP equipment using the electrolyte
system previously described. Panels
were plated at 1.5 ASD, for 60min
t o obt ai n a copp e r t h ick ne ss of
approximately 20µm. The plated
height variation between fine lines of
5µm or 7µm width to the larger pads
was measured from cross sections as
shown in Figures 2 and 3. When the
equipment was operated with soluble
anodes, this variation between fine
Figure 3: Cross sections of fine lines from the plating process with insoluble anodes. lines and pads was 1.4µm for the panel
that had 5µm linewidth, and 2.19µm
suppressed and the microprofile will be continuous plating (VCP) equipment for the panel that had a 7µm linewidth.
diminished if a leveler is present. Proper in high-volume production conditions. When the equipment was operated with
additive selection and control are crucial Tight control was kept over all additive insoluble anodes, the plated height
to obtain plating uniformity and desirable components through cyclic voltammetry variations between fine lines and pads
physical properties of electroplated stripping (CVS) analysis. were all below 1.0µm for both 5µm
copper. In addition to selection and
optimization of additives, anode type,
virgin makeup solution (VMS), and
plating current density also have to be
taken into consideration for their effect on
plating performance.
Evaluation of commercial
electroplating for FOPLP
In the following sections, we examine
the plating capability of a commercial
embedded trace plating electrolyte system.
The plating processes we describe were
designed for panel-level packaging boards Table 2: Anode type influence on the performance in fine-line and pad variation for embedded trace plating.
that are up to 2 to 3 layers thick. We also
show the results of adapting this same
electrolyte system for 2-in-1 RDL plating
by varying the concentration of the copper
and acid in the VMS. Performance was
evaluated by measuring plating uniformity
and coplanarity of both fine lines, pads,
and filling of microvias on panel-level
type substrate. We compare the effect Table 3: Plated height variations between fine lines and pads within unit, as well as within panel.
of soluble versus insoluble anodes on
plating uniformity and examine the grain
structure of the deposit by XRD and
FIB-SEM imaging. The plating for the
samples shown was conducted in vertical
Table 4: Plated height variations between fine lines and pads when vias were filled.

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