Pyrolytic boron nitride (PBN) is an advanced ceramic material with high purity (up to 99.99%). It has a hexagonal crystal structure, with some similarities to graphite. It is synthesised under high-temperature, high-vacuum conditions through chemical vapour deposition (CVD) using ammonia and boron halides. The chemical vapor deposition (CVD) process used to create PBN produces a layered structure.
PBN offers benefits such as thermal performance, relatively low density, good chemical stability and high-frequency insulation. Due to its excellent high-temperature stability and thermal conductivity, PBN ceramic is ideal for various industries, including crucibles for the semiconductor and OLED industries, high-temperature electronic components and thermal management systems for the aerospace industry.
As already mentioned PBN is a layered material. This specific structure poses a challenge for conventional machining techniques as machining multilayer parts with hard tools can lead to delamination or unwanted material removal between layers. When working with hard or brittle materials choosing appropriate cutting tools and machining parameters to minimise wear and tear is essential, and an appropriate machining coolant is normally required.
Luxinar sealed CO2 laser technology addresses many of the challenges conventional tools face:
- Although the laser cutting process is relatively slow, the material can be cut without cracking, chipping or delamination, and the finished parts require only light post-process cleaning to remove surface dust.
- As a non-contact and frictionless process, there is no need to use a machining coolant or lubricant. Post-process cleaning is therefore reduced, resulting in overall shorter process times than conventional tools.
- No special tooling is needed, and there is no wear or tool lead time as CO2 laser cutting is a digital process.
The SR 15i laser source at a wavelength of 10.6μm has successfully cut PBN of varying thicknesses, including cone-shaped funnels with a wall thickness of 1mm and outer diameter of 56mm. The laser head is fixed, and the PBN sample is rotated for cutting, with a nozzle-to-surface distance of 1mm and the laser beam focused on the material surface. Oxygen assist gas is critical to the process, producing a smooth and clean-cut edge with no visible charring or discoloration.