www.industrial-lasers.com MAY/JUNE 2015 Industrial Laser Solutions 37
For example, one
large medical device
transitioned from a
manual to a laser pro-
cess for producing
stainless steel guide-
wires used in intra-
tional devices. The
wire, with a diame-
ter similar to that of a
human hair, is coated
with an organic mate-
rial that makes it compatible for use in humans. This organic coating
material must then be stripped away from the microscopic metal core
wire to enable connection to the guidewire’s distal end.
The new laser process consistently and precisely strips away
the organic material coating from the component’s metal core
wire, which enables subsequent assembly operations performed
to the unit in downstream processes. Far less operator-depen-
dent than the method it replaces, the new process takes only seconds to complete, whereas the previous process took about 8 min.
Throughput rose by 250 percent, with an additional increase in yield.
In electronics, the higher volume of parts dictate automated
removal techniques; however, the basic premise is that the same—
either chemical, mechanical, or a combination of both—can be
used. As wire diameters decrease, there is less control of insulation removal of these processes, with potential issues of damaging the conductor and wire deformation.
Picking the right laser
A number of different lasers can be used for wire stripping, depend-
ing upon the particular wire diameter, insulation material (polyim-
ide, Pebax, polyethylene terephthalate [PE T], nylon, fluoropolymers,
The sealed CO2 laser should always be considered first. With a
wavelength of 10,604nm, the CO2 laser is readily absorbed by every
polymer so it will work to a certain degree, regardless of what insu-
lation material is used. Also, the CO2 laser is not readily absorbed
by metals, so when
all the insulation is
removed and the
laser impinges on
the exposed wire, it
has little effect for a
relatively long time.
This allows the com-
pletion of the pro-
cess to the required
tolerances on the
and provides a large
processing window. In addition, the CO2 laser is the most cost-ef-
fective in terms of dollars-per-watt power. FIGURE 2 shows a poly-
imide wire that has been stripped using a CO2 laser.
The removal of the material is done more by thermal degrada-
tion, so heat input can be an issue if the wire diameter is small. This
may result in wire distortion and potential cutting or the insulation
can be overheated, causing discoloration and burr formation. (A
burr develops when the material bulges or is raised, and can significantly increase the overall wire outer diameter.)
If a CO2 laser cannot be used for reasons of heat input control, the nanosecond laser should be considered next, specifi-
cally those with 532 and 355nm wavelengths. Nanosecond lasers
produce pulses of around 20ns, removing wire insulation mate-
rial with much less thermal interaction than that of the CO2 laser.
It can be used on smaller-diameter wires, or where the removal
edge must be well-defined with little or no burr. FIGURE 3 shows a
wire that has been stripped using a nanosecond laser with a wavelength of 355 nm.
The choice between 532 or 355nm is typically made based upon
the insulation material, with the 355nm being better absorbed by
more polymers. If the CO2 laser is likened to a large oxyacety-
lene blow torch, the nanosecond later would be analogous to a
smaller, more delicate torch that might be used for finishing off a
Note that the popular fiber laser operating at 1070nm is not well
absorbed by most of the typical wire insulation materials, and so
it is rarely used or considered.
FIGURE 2. Polyimide wire insulation
stripped by a CO2 laser.
FIGURE 3. Small-gage wire stripped by a
355nm UV laser.
TABLE. Selecting the right laser for wire stripping
LASER TYPE PROCESS ATTRIBUTES
Sealed CO2 Absorbed well by all polymers
Absorbed poorly by metals
Highly thermal removal process is suited to larger
532nm and 355nm
Absorbed well by most, but not all, polymers
Short pulses enable high control of removal
Ablation material removal minimizes heat input
Best quality removal and edge defnition
Cold processing with no heat input
Can potentially remove individual layers of