A report on the developmnt effort for laser channel drilling in ldpe using excimer lasers

TeoSys Engineering LLC
Capabilities & Review

Report on the Development Effort
For Laser Channel Drilling in LDPE
Using Excimer Lasers

Dana Lee Church
TeoSys Engineering, LLC
2138 Priest Bridge Ct. Ste. 10
Crofton, Maryland 21114
Tel: 410-451-8058
Fax: 410-451-8059
www.teosys.com

TeoSys Engineering LLC Confidential Page 1 Dana Lee Church

Overview of Contents of Report

•Part #1 120µm Thick LDPE M3 Requirements & Results
•Requirements of PO
•Part#1 120µm Thick LDPE Results
•Part #1 120µm Thick LDPE Implementation
•Implementation of Line Generator using Excimer Laser
•Part #2 & Part #3 480µm Thick LDPE M7 (50 Pass) & M15 (40 Pass) Requirements & Results
•Requirements of PO
•Part #2 480µm Thick LDPE Results
•Part #2 480µm Thick LDPE Isotropic Testing
•Part #2 480µm Thick LDPE Implementation
•Part #4 200µm Thick LDPE M3 Results
•Recommendations for Future Channel Drilling Applications Using Excimer Lasers


Purchase Order Requirements & Results for Part #1 120µm Thick LDPE M3
Part #1 120µm Thick LDPE Requirements Part #1 120µm Thick LDPE Results
•Drill channels through 120µm thick LDPE.
g µ •4CM by 4CM part was drilled using 193nm
wavelength in 12 hours
• Channel thickness should be as small as possible with goal of
less than 20µms. • Horizontal and vertical appeared all right but there
were some discontinuities with respect to the quality
•Part is 4CM by 4CM requiring 280 channels in the horizontal of the part when viewed from the top
and 280 channels in the vertical
vertical.
•It was determined after much development effort
• TeoSys requirement is that drilling time be less than 10 hours that the material is non-isotropic which leads to
for this part. We achieved a 12 hour runtime for the first part nonlinearities when drilling in certain directions
delivered.
• We did not align for the non isotropic nature of the
non-isotropic
material so the resulting top view shows the non-
linearity of the resulting squares.
•The nonlinearity was corrected in subsequent parts.

Part #1 Implementation
•4CM by 4CM part was drilled using 193nm
wavelength in 12 hours


Purchase Order Requirements for Part #1 120µm Thick LDPE
Part #1 Results
•Channels were drilled for
the 120µm thick part using
193nm wavelength.
•The vertical channel width
is approximately 16µms but
the horizontal channel width
is much larger at 29µms. We
found this to be true in all of
our experimentation.
•This turned out to be a
prime example of the non-
i l f h
isotropic nature of the
material with respect to
channel drilling. We did not
know the reason for this
behavior at the time we
drilled this part.
• We did not align for the
non-isotropic nature of the
p
material so the resulting top
view shows the non-linearity
of the resulting squares.

Channel Drilling Through 120µm Thick Part #1 M3
Because we had already proven that 193nm
wavelength could drill channels through the
material, the difficulty with this new purchase order •Depth study using
D th t d i
193nm through
was to find a way to economically drill the channels
120µms of LDPE
through varying thicknesses of the LDPE material.
We did successfully reconfigure our general excimer
system several times to achieve the requirements of
l i hi h i f
the purchase order, however we learned a lot about
the material and its interaction with not only 193nm
but also 248nm.
We d t
W determined that materials with thicknesses
i d th t t i l ith thi k
below 200µms could be drilled using 193nm •Actual 120µm
part being drilled
wavelength but anything thicker than that would using 193nm
require a reconfiguration of the excimer laser to
operate at 248nm. 193nm just did not have the
p j
energy in order to drill the channels through the
thicker materials in a reasonable amount of time.
We also determined that the material itself is non-
isotropic requiring channel drilling to occur along
certain directions in order for the vertical and
horizontal channels to be equal in width and depth.


Channel Drilling – Line Generator Aperture Configuration
To solve the problem of drilling the channels economically,
we decided to create a line generator as opposed to drilling
with a round spot.
The line generator uses an external aperture at the output of
the laser to block any beam that is not part of the vertical
line being generated.
The final width of the line aperture was 750µms wide by
2MM tall.


Channel Drilling – Line Generator Our final calibration at 193nm had a depth of focus of 300
microns which makes this an extremely favorable methodology
The line generator that we used created a line image at for production processing.
the work surface that was approximately 10 microns
wide by 350 microns long. D lt Z represents the change in focus as we fire a single shot
Delta t th h i f fi i l h t
on the work surface. For all of our calibration and setup, we
The line allows us to remove more material than a used a glass slide.
single round spot with the equivalent diameter of 10
microns.


Channel Drilling Through 120µm Thick Part #1 M3 - Implementation
We had to determine our actual drilling recipe speeds,
frequencies and number of passes using the material in
order t achieve th target depth of 120µms consistently.
d to hi the t t d th f 120 i t tl


Channel Drilling Through 120µm Thick Part #1 M3 - Results
The final run time for the 4CM x 4CM piece of M3 material which is 120µms thick LDPE was 12 hours.
After the development that occurred following the production of this sample, the run time can be reduced significantly
by i
b using a 248nm wavelength.
248 l th
However, 248nm is a more thermal process and care must be taken to ensure that the material does not melt instead of
ablate.

The final recipe was the following:
•Single pass solution
•550uJ +/- 30uJ as measured post line generator aperture.
•0.5 MM/sec moving speed
•300 Hertz laser repetition rate
•Fluence of approx. 17 J/cm^2
•12 Hour run time


Part #2 480µm Thick LDPE Part #2 & #3 (480µm Thick LDPE Results)
Requirements •3CM by 3CM part was drilled using 248nm wavelength in 7.5
y p g g
•Drill channels through 480µm thick hours significantly reducing the run time for all of the channel
LDPE as measured by our microscopes drilling
and as indicated by Joe. The PO was for a • It became extremely apparent, as will be shown, that the
480µm part and the material that was sent wavelength of 193nm would not achieve our run time requirements
g q
to us was 480µms although in subsequent of less than 12 hours. After optimization of the recipe for 193nm,
e-mails with the customer, the thickest our run time calculation was 45 hours of continuous drilling.
material is indicated at 400µms.
•We converted our excimer to 248nm wavelength and re-optimized
• Channel thickness should be as small as to get a final run time of 7.5 hours for the 50 pass Part #2 and even
possible with goal of less than 20µms.
ibl i h l fl h less for the 40 pass Part #3.
•Part is 3CM by 3CM, 210 lines each
direction. The requirement was 210 lines
in each direction but because our line
generator loses energy at the ends, we
actually ran for 230 lines in each direction
in order to provide the actual 3CM x
3CM.
• TeoSys requirement is that drilling time
be less than 12 hours for this part.


Part #2 & #3 (480µm Thick LDPE Results) –
Con’t
•Most of the orthogonality testing for the non-isotropic
nature of the material was performed at the 248nm
wavelength. The result of this effort was that the
material had to be rotated 45° in order for the lines in
both the horizontal and the vertical to drill at the same
dimensions given the same laser recipe.
• All of the subsequent parts were drilled at an angle of
45° in order to achieve the same dimensions in both
horizontal & vertical.
•Part #2 M7 was the first part drilled at an angle and
was drilled slightly off when rotated to drill the opposite
direction group of lines. In order to make up for this
slight offset, we drilled another part which was drilled
with the lines exactly orthogonal to each other.
•We consider this effort to have extremely successful as
given a much larger format excimer, we can reduce the
run times even more making the laser processing of
i ki h l i f
material areas of 10CM x 10CM realistic.


Part #2 480µm Thick Material - Implementation
•The depth and speed study for the 480µm thick part
indicated quickly that the deepest we could get using 193nm
and a single pass solution such as the first part was 330µms.
•This solution would not meet TeoSys requirements of a drill
time of less than 12 hours.
•Convert to 248nm.


•After the 248nm conversion the same alignment and speeds and
g p
feeds studies had to be performed in order to get an idea of what
was possible using this wavelength.
•248nm is a more thermal process and it became apparent that
the issue with directionality was worsened when we changed
y g
wavelengths. We had to solve the problem before we could
optimize our recipe.
•Because of the more thermal process, melting is always an
issue. We had to drill fast.
•We determined through testing that the material could only be
drilled in one direction. The material is unidirectional at 248nm.


•A cross test was drilled to see the performance of both
A
vertical and horizontal lines.
•The exact same program which means the exact same
recipe was run in both directions.
•The results were different. One direction had thinner
Th l diff O di i h d hi
channels and the other direction had thicker channels.
•This material would not be able to be drilled as expected
(and as delivered) but would have to be rotated. We then
had to determine h much rotation and subsequently, was
h dt d t i how h t ti d b tl
the rotation the same for all material thicknesses…?
•The results were that the material must be rotated 45° in
order for both sets of lines to exhibit the same behavior.
However,
However both sets are degraded in performance compared
to the best line generation seen on the material.
•This means that there is a best angle and direction in which
to drill channels on this material but in order to create a
criss-crossing pattern,
criss crossing pattern that angle and direction must be let go
in favor of one that allows the best overall performance.


Part #2 480µm Thick Material – Isotropic Testing
• Continuous cross tests were performed on the material to
determine at what angle both horizontal and vertical properties
began to be the same.
same
• A 45° angle from the way the material is fabricated is the best
angle


Part #2 480µm Thick Material – Implementation
• After the 45° angle was determined, we were back to recipe
generation.


•Determine number of passes.


•This recipe exceeded our expectations in drill vs. quality for
this project.
The fi l i
Th final recipe was the following:
th f ll i
• 40-50 pass solution
• 1.7mJ as measured post line generator aperture.
• 30MM/S moving speed
30MM/Sec i d
• 400 Hertz laser repetition rate
• Fluence of approx. 53 J/cm^2 / Power of 0.680 Watts
•7.5
•7 5 Hour run time


Part #4 200µm Thick LDPE Requirements Part #4 (200µm Thick LDPE Results)
•There was no requirement for TeoSys to drill this part •3CM by 3CM part was drilled using 248nm
3CM
but we thought it would be good to get a thinner wavelength in 4.5 hours significantly reducing the
example of 248nm channel drilling for testing run time for all of the channel drilling
• Channel thickness should be as small as possible with • All of the lessons learned were applied to this part
goal of less than 20µms. and it came out beautifully.
•Part is 3CM by 3CM, 210 lines each direction. The • All of the laser recipe is the same as Parts #2 & #3
requirement was 210 lines in each direction but because except for the number of passes which creates the
our line generator loses energy at the ends, we actually depth.
ran for 230 lines in each direction in order to provide
the actual 3CM x 3CM.


•ISO tests & depth optimization tests were all that was
p p
needed to be done for this part.


Part Fixturing
•Part fixturing was a developmental project of its own. A
description is outlined in the pictures.


Recommendations

1. Obviously speed of drilling is the key factor in the implementation of channel drilling through this material. The
thicker the material, the longer it will take to drill no matter what final solution or wavelength is chosen.
2. Investigation should be performed into why the material drills better at a 45° angle from its manufactured sides
because there is still some degradation in the quality of the channel drilling based on this rotation factor We chose
factor.
a happy medium but there is a better solution out there.
3. 248nm is the optimal wavelength for the speed of channel drilling. We would recommend this wavelength even for
the thinner materials. However, when using this wavelength, very, very fast and accurate stages must be used in
order to provide for the rapid motion in an opposite direction which is a problem for all motion systems.
4. The speed at which this application can be performed can be increased dramatically with a custom designed
system. There is more than enough laser power at 248nm in order to provide a split beam or some other creative
solution.
Click on
picture for
movie of
And as always, TeoSys is here to provide all drilling
operation.
custom system solutions whether they be with
our own excimer or we integrate a large format
excimer.
excimer We can almost guarantee a reduction
in processing times by a factor of 2-4 times.


A report on the developmnt effort for laser channel drilling in ldpe using excimer lasers

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