26 Industrial Laser Solutions MAY/JUNE 2015 www.industrial-lasers.com
a larger process fiber), the beam deliv-
ery (varying the collimator and/or objective focal lengths) and process parameters used such as pulse duration and/or
pulse energy (i.e. peak power), or rela-
tive position of focus plane vs. work-piece
FIGURE 2 shows scanning electron
microscopy (SEM) images of ~90µm
exit holes drilled using the multimode
QCW fiber laser in 381µm-thick AlN,
at a rate of over 100 holes/s.
Similar results are obtained
for 381µm-thick alumina
with typical entrance of
~100µm in diameter,
and ~70µm in diameter for the exit for over
20,000 holes/part in packaging
Typical positional accuracy
achieved is within ±5µm over
an area of 150 × 150mm, with
the hole diameter variation better than 15%
of nominal hole size for 100% of the holes.
Both periodic and non-periodic hole pat-
terns can be machined at high speed with
high positional and dimensional accuracy, by using external encoder-based
A similar setup used for drilling can also
be used for high-speed scribing on these
ceramics, where a single pulse is used
to machine a blind hole into the material,
with an appropriate pulse-to-pulse spacing needed to allow for a follow on breaking operation.
FIGURE 3 shows scribing of alumina
(99.6% Al203) and AlN 381µm thick, both
at a speed of 300mm/s, and using a pulse
d u r a t i o n below 50µs. Scribing of alu-
mina 635µm thick can be done using a longer pulse duration around 100µs at a speed
of 200mm/s with individual pulses each
leading to a depth over 350µm.
Cutting with QCW fiber laser
The QCW fiber laser also allows for high-
speed and -quality cutting of ceramics with
no dross or chip-out. High-speed cutting
of 635µm-thick alumina was demonstrated
at 140mm/s using the single-mode QCW
laser, while 381µm-thick alumina was cut
at a linear speed of
250mm/s (FIGURE 4). A
coating was applied
prior to the process and
helping to protect from
spatter and recast.
demonstrate why the
QCW fiber laser is dis-
placing the CO2 laser
in the machining of
ceramics such as alu-
mina and AlN, allowing
for higher throughputs
and, because it can
easily be focused to
spot sizes below 50µm
in diameter, machining
of smaller vias and finer structuring. On
the other hand, compared against short-er-pulse-duration lasers operating in the
nanosecond or picosecond regime, the
QCW laser often allows for much higher
throughput due to its higher
removal rates, while still achieving adequate machining quality.
Recently, cutting of sapphire has
been the focus of considerable attention because of its use in mobile phones.
FIGURE 5 shows some of the typical shapes
cut for the consumer electronics market
using the QCW fiber laser.
Thicknesses up to several millimeters
can be cut at reasonably high speeds
with good cut quality, avoiding cracks
and chip-out and with an average surface
roughness typically below 2µm (FIGURE 6).
Sapphire parts with thicknesses of 0.4, 1,
and 3mm thick were cut at speeds around
12, 9, and 3mm/s, respectively, with final
speeds depending on geometry and quality requirements.
Depending on the material and the appli-
cation, process development establishes
which laser and laser technique is better
suited to meet manufacturing goals, thus
allowing for specification of equipment
options. In addition to required machining
quality, including dimensional and posi-
tional specifications, additional considerations for high-volume manufacturing
include throughput needs as well as cost
FIGURE 5. Examples of various shaped
parts cut in sapphire with a QCW fiber
laser as used for consumer electronics.
FIGURE 4. High-speed cutting of alumina (99.6% Al203) with a thickness of 381µm at 250mm/s. (a) represents
the top view of the entrance, (b) is the top view of the exit, and (c) is the side view of the cut wall.