Previous attempts to apply Nd: YAG lasers to marking processes were unsuccessful due to weak absorption at 1.064 μ m; Not enough energy is deposited on the surface layer to produce the desired effect. To this end, Synchron Laser Service (located in South Lyon, Michigan, USA) has developed surface treatment technology to enhance ceramic absorption of laser light in a shorter wavelength range. This process rapidly and slightly immerses the ceramic surface and enhances the deposition energy of near-infrared laser pulses at a sufficiently short distance to generate necessary melting and vaporization. Combining this patent pending surface treatment technology with SPI Lasers (located in Southampton, UK) fiber laser technology, the achieved process performance far exceeds that achieved by using CO2 laser marking machines.
The surface treatment greatly enhances the integration of the fiber laser beam into the top surface of the ceramic to begin the drilling process. The enhanced interaction between laser pulses and material surfaces, combined with a customized high-resolution beam transmission system that ensures consistent surface spot size, means that smaller morphologies can be achieved on ceramic substrates. Synchron has also considered some other existing laser technologies, hoping to process even finer lines; But the conclusion is that no technology can achieve the target speed in its unique way, and in some cases it is at least 10 times slower.
Compared with CO2 lasers, fiber lasers exhibit better consistency and reliability, allowing for finer morphology processing, including a more than three fold increase in edge quality after fracture. Figure 5 further illustrates the achievable edge quality, describing the original edge generated by cutting the arrow shape. Importantly, the new process can even achieve production speeds that cannot be achieved with CO2 lasers.
On a 0.0150 inch thick alumina substrate, the marking speed exceeds 1300 inches per minute, which is approximately twice that of a CO2 laser (both penetrate 30%); But the machining speed is at least the average, and in most cases the speed exceeds that of CO2 lasers. According to Synchron's situation, it is due to the use of a mobile control system rather than a laser that the output is limited.
This latest method can be used to process alumina and aluminum nitride ceramics. When using aluminum oxide, the process limit can reach a substrate thickness of up to approximately 0.060 inches, although thicker materials in more demanding applications require longer processing times. Thicker substrates can also provide more heat dissipation, such as in high brightness LED applications.
Aluminum nitride ceramics are generally more difficult to process than aluminum oxide because of their better thermal conductivity, thus requiring proportionally higher power for processing. On the other hand, finer morphology can be achieved because only the highest density part of the beam can produce the required process, and the high thermal conductivity of the material minimizes the HAZ on both sides of the beam energy distribution map. The preliminary results using this new method are excellent, and the process using this material can still be fine tuned.