Sputtered Metal Coatings
and UV Coatings—
By Don Parent his article describes the recent capacity and new process technology
T merging of 3-dimensional
metal coating and UV coating
of plastic parts into a single in-line
that will provide suppliers with a high
quality product, while at the same
time being environmentally friendly.
production process. An integrated, Sputtered metal coatings combined
in-line approach to product ﬁnishing with UV-cured basecoats and topcoats
solves many of the most pressing provide that solution. Sputtering
manufacturing issues. The result is emits no VOCs and produces no toxic
reduced costs, improved quality and chemicals, either directly or indirectly.
simpliﬁed operation. It is a clean and dry process.
Today, many plastic products have
metallic ﬁnishes. (Figure 1) While What is a PVD Sputtering?
many of these metallic ﬁnishes have PVD sputtering is a proven
traditionally been applied through “metallizing” technology that’s been
electroplating, vacuum metallizing used in semiconductor, CD/DVD and
(also known as Physical Vapor consumer products manufacturing for
Deposition or PVD) is rapidly gaining many years. It produces a high-quality
favor due to its clean process and metal layer with excellent adhesion
lower costs. and ﬁlm quality.
Sputtering is a vacuum process
The Metallizing Market in which atoms from a solid metallic
Demand for decorative vacuum target are ejected from that target
metallized coatings is increasing surface by bombardment with high-
worldwide. There is a need for new energy ions. (Figure 2) Those ejected
Metallic ﬁnishes on a variety of plastic products
22 RADTECH REPORT NOVEMBER/DECEMBER 2008
characteristics of the part may also
Figure 2 be modiﬁed by the type of topcoating
used. Coating choices might include
Cathode operation schematic matte and gloss ﬁnishes, various colors,
and different textures that are usually
dictated by the product designer.
Ultraviolet light-curable basecoatings
and topcoatings are ideal for this
process because they cure very quickly
and require minimal ﬂoor space for
the curing equipment. UV-curable
basecoats and topcoats also provide
high quality ﬁnishes with minimal or
no VOC emissions. Water or solvent
diluted UV-curable coatings contain
very low levels of VOCs and provide
an ideal surface upon which to deposit
a metal coating as well as performing
well as a protective top coat.
metal atoms travel unimpeded through ﬂawless. Without the basecoating, Solvent-free, 100% “solids” UV
the vacuum chamber and are deposited any imperfection in the base plastic coatings contain virtually no VOCs.
on the plastic substrate to be coated. becomes very visible with a thin Since nothing is lost during the
The target material can be any type reﬂective metallic coating over it. application process, solvent-free
of metal or metal alloy. Most plastic The vacuum deposited metal coatings may be reclaimed and re-used
parts are decorated using aluminum. layer is approximately 100 nm thick efﬁciently. The result is very high
PVD sputtering is capable of depositing or approximately the thickness of coating utilization rates and lower
100% aluminum as well as aluminum 1/1000th of a human hair. To protect costs per part. And there are no costs
alloys with equal ease. Alloys are often this extremely thin layer of metal from associated with the management of
used to provide corrosion resistance scratching or abrasion, or to provide VOC emissions and no VOC controls
or to change the color or look of chemical resistance, a UV topcoating are required. Further, no solvent
the sputtered metallic surface. For is applied after metallization “ﬂash-off” oven is needed to drive off
example, some copper alloys produce for durability. The ﬁnal surface the solvent. The result is a smaller
coatings that closely mimic the look
of gold. Other metals or metal alloys
such as stainless steel and chrome may
also be used. Basecoat, metal layer and topcoat
Base and Top Coatings for
Metallized Plastic Surfaces
When a vacuum metallized layer
is applied to a smooth plastic surface,
that surface becomes reﬂective just
light like a mirror. (Figure 3) Unless
the mold and the resultant surface
of the plastic part made in that mold
are of extremely high quality, a UV-
curable base coating is required to hide
surface imperfections. The basecoating
(applied prior to metallization) helps
make the reﬂective metal coating look
NOVEMBER/DECEMBER 2008 RADTECH REPORT 23
Integrated in-line process
overall system size, lower energy (Figure 4) An integrated in-line in front of drying or curing systems.
consumption and lower costs. process will provide, by far, the highest In contrast, traditional vacuum
product quality at the lowest cost. metallizers are “batch” vacuum
Batch vs. In-Line Metallizing It is important to understand deposition chambers that cannot be
Vacuum metallizing and UV-cured that basecoating and topcoating are readily integrated with a continuously
basecoating and topcoating can be by design “in-line” or continuous moving conveyor. As a result, parts
implemented as a complete process processes. A conveyor transports must be removed by hand from the
by either: (1) using the traditional and rotates the plastic parts in a (continuous) topcoating conveyor,
approach (as separate processes) or continuous manner in front of spray loaded manually into the (batch)
(2) as an integrated in-line process. guns that apply the coating, and then metallizer and then moved again by
hand loading, back on the (continuous)
conveyor for topcoating.
Figure 5 With batch metallization processes,
Batch metalization process “work-in-process” (WIP) part
storage between each process is a
necessary reality and results in a part
“Vulnerability Window” of hours or
even days. (Figure 5) In contrast,
when basecoating, metallizing and
topcoating are merged as a single
in-line process, the “Vulnerability
Window” can be as short as minutes
with the result being reduced scrap
and improved quality in addition to
lower labor cost. (Figure 6)
The part “Vulnerability Window”
Figure 6 can be described as the period of
time between process steps when
Integrated in-line metalization process the parts are handled by operators,
transferred from one ﬁxture to
another, or exposed to the surrounding
environment where they might be
contaminated with dust or damaged.
For metallizing and coating, the
“Vulnerability Window” starts when
parts enter the basecoating line and
ends when the topcoating is cured.
With a true in-line process, the
“Vulnerability Window” is minimized.
24 RADTECH REPORT NOVEMBER/DECEMBER 2008
Integrated in-line coating system
Integrated molding / no UV basecoat
An in-line metallizer transforms Implementation Example: can eliminate basecoating. A fully
this process from “continuous-batch- Single Chain-On-Edge integrated system is the result.
continuous” into an uninterrupted true An in-line metallizer integrates (Figure 8)
in-line process, eliminating the handling with a single Chain-On-Edge line and
of parts between the coating and offers virtually no process latency or Summary
metallizing steps, thereby minimizing work-in-process. (Figure 7) In-line metallizing is a key enabling
the part “Vulnerability Window.” In technology that solves the inherent
addition, an in-line metallizer minimizes Implementation Example: problems of batch processing by
labor costs and inventory, simpliﬁes Integrated Molding, No Basecoat facilitating interconnection of
logistics, and reduces ﬂoor space Integrating injection molding basecoating, metallizing and topcoating
required for the process. with metallizing and topcoating in a manner not previously possible.
NOVEMBER/DECEMBER 2008 RADTECH REPORT 25
All-new ILT490 belt radiometer.
The best just keeps getting better and better.
The ILT490 now joins the ILT400
with even more powerful features.
◆ Measurement spectrum matches
industry standard IL390C (250-400nm)
◆ NIST - traceable calibration
◆ Built-in re-chargeable batteries
◆ Integrated exposure (J/cm2)
◆ Peak irradiance (W/cm2)
◆ Intensity profiling with auto-scale
◆ Baseline profile memory
Call 978-818-6180 or visit us on the Web at
10 Technology Drive
Peabody, MA 01960
NIST Traceable Light Measurement
Systems and Sources
ISO 9001:2000 Divisions
Issues that are driving the shift back
Figure 9 to “local” or in-house metallizing:
• Electroplating costs are increasing
Tabular comparison of batch vs. in-line
and have environmental
• RoHS (Restriction of Hazardous
Substances) regulations are
increasingly making electroplating a
less attractive solution.
• Offshore manufacturing logistics
are complex and costly.
• Rising fuel prices have dramatically
increased shipping costs.
• Offshore manufacturing quality is
inconsistent and difﬁcult to control.
• Old batch metallizing processes are
Plastic part metallizing was once once again an attractive business
labor intensive. ◗
a thriving U.S. industry using batch proposition. For this to succeed,
processing; however, that work is now however, metallizing and coating must —Don Parent is president of
done mostly offshore. Growing demand be re-invented—it cannot be done the D2 Inline Solutions, located in
in Asia, combined with increasing way it was done 30 years ago. In-line Scarborough, Maine.
shipping and energy costs and integration of basecoating, metallizing
other factors, make local metallizing and topcoating is the solution.
26 RADTECH REPORT NOVEMBER/DECEMBER 2008