A GUIDEHow Novanta’s
picosecond laser
sub-systems achieve highquality micro-processing
Creating zero taper and smoothsurface finish via holes

The Challenge
Achieving precision in micromachining applications can be challenging, especially when working
with small spot sizes where any beam imperfection is amplified. If beam roundness is notsustained over a large depth of field, micromachined features will display a lack of symmetryespecially in high aspect ratio structures, such as via holes. This leads to defective material,
creates waste and may require additional post-cutting processes, all of which results in extra timeand cost for the end-user.

Background
Laser processing is commonly used in consumer electronics, e-mobility, medical andsemiconductor industries to machine small, precise features and cuts in materials. Within theindustrial environment, speed, accuracy, yield and cost are key parameters which drive thechoice of laser scanning system. Ultra short pulse lasers combined with beamsteering scanhead technology are employed to achieve a variety of processing features for a diverse range ofmaterials.
The challenge remains the same whether you are cutting PCBs or probe cards, glass or stainlesssteel, imprecise cuts will create product defects or waste especially with complex designs. To
overcome this, a high degree of control of the laser interaction with the material is required andkey to this is the roundness of the focused laser beam. A circular, symmetric beam combined withprecise, scan head movement delivers complete and reliable control of the processing, especiallywhen the circular symmetry is maintained over a large depth of field. As a result, high aspect ratio
holes with zero or controlled taper can be achieved for applications such as via hole drilling.
©2021 Novanta Corporation. All rights reserved.

Creating zero taper and smooth surface finish via holes

Examples of High Quality Processing With Dart
A variety of materials have been processed using Novanta’s Dart 8 picosecond laser combinedwith a hole drilling Novanta PRECESSION ELEPHANT scan head. Figure 1 shows a 200 µm
diameter via hole drilled through a steel plate. The closeup of the walls demonstrates both theprecision and smoothness.

Figure 1 – 200 µm via hole drilled in stainless steel showing a high level of wall smoothness. This wasachieved using a 1064 nm version of Dart.

Figure 2 shows a taper free via hole in glass with corresponding entrance and exit images. Thesedemonstrate both circular symmetry of the cut and zero taper. In addition, the brittle material isdamage free, with no signs of microcracks, a consequence of the low Heat Affected Zone (HAZ)
provided by using an 8 picosecond laser.

Figure 2 - 200 µm via hole drilled into a 0.7 mm glass substrate using a 532 nm laser. The diameter of theentrance and exit holes are both measured to be the same within 0.5 µm.

How does Dart achieve this?
The precision achieved in these examples is a consequence of Dart’s high level of beamroundness. Figure 3 shows the beam profile of >93% sustained over a large depth of field,
typically ±3 Rayleigh lengths. This facilitates the symmetric features with zero taper, smoothsurface finish and the potential for high aspect ratios.

©2021 Novanta Corporation. All rights reserved.

Creating zero taper and smooth surface finish via holes-3zR-1zRAt Focus+1zR+3zR

Figure 3 - Dart beam profile demonstrating the beam roundness of > 93% across ±3 Rayleigh lengths. Dueto the nature of the Dart design, this performance is repeatable from laser to laser.

Dart has been designed to be used with a wide range of scan heads. In each of the examples
above, the laser has been combined with a multi-axis drilling optic, the Novanta PRECESSIONELEPHANT. With this configuration the focal point of the laser can be moved in the X, Y andZ directions and tilted in two angles to the surface normal. Furthermore, usability tools likealignment cameras, a vision setup, an energy monitor and a polarization unit are integrated
in the optics. The high level of control and monitoring results in an ability to process the mostchallenging of geometries such as: cylindrical and tapered holes (exit side larger than theentrance); cuts with a wall angle of 90° to the surface; and undercuts. As a further degreeof freedom, the laser power on the workpiece can be dynamically varied with a fast opticalattenuator. This high level of manoeuvrability and control, coupled with Dart’s excellent beam
quality, results in high accuracy features.

Figure 4 - Novanta’s PRECESSION ELEPHANT scan head, paired with the Dart to deliver smooth, taper
free via holes.

Dart has been specifically engineered by Novanta for OEM users, and offers a straightforward
integration pathway with a single supplier for both laser and scanning sub-systems. As standard,
Dart features precision boresighting specifications that reduce the complexity of opticalalignment during installation. With a ruggedized, compact design, reliable pointing stability, andrepeatable beam characteristics from laser to laser, Dart delivers high quality picosecond laser
cutting and drilling even in tough industrial environments.

Novanta Advantage
Through our photonics technologies, we deliver finely tuned
laser sources and beam delivery systems that enable customers
to improve their process, increase productivity and achieve
breakthrough performance. We bring unprecedented value
to our customers through engineer-to-engineer collaboration,a wide range of application expertise, and state-of-the-art
application labs.

Contact us - photonics@novanta.com©2021 Novanta Corporation. All rights reserved.