The term “technical ceramics” encompasses a range of inorganic solid materials with a host of unique and desirable characteristics. Mechanically, they possess both compressive strength and high hardness, giving them excellent wear resistance and dimensional stability. They are electrically insulating, but also thermally conductive in some cases. They can function at very high temperatures without degradation, and they are chemically inert and resistant to corrosion. As such, technical ceramics are used to address particular engineering challenges in applications from aerospace to electronics.
For example, alumina (Al2O3) is commonplace in the electronics packaging industry, where it serves as a substrate for components including photovoltaics and high brightness LEDs. Alumina possesses high strength, excellent electrical insulation properties, and good thermal conductivity. Conversely, the challenges of working with technical ceramics are also well-known; the intrinsic properties that make them so useful pose distinct manufacturing challenges. This blog post will explore what makes technical ceramics challenging to cut and drill, and what other manufacturing options are available.
Technical ceramics are generally sintered from inorganic materials, yielding fired parts that usually require machining in some way – for example cutting, drilling, or scribing. The extreme hardness of the fired ceramics presents a problem for any kind of mechanical machining process. Although possible, traditional machining processes, such as cutting, drilling and milling, require diamond tools. These tools have a limited life cycle and have to be replaced on a regular basis. In some cases machining technical ceramics could induce mechanical stress. As ceramics are brittle materials, this could result in fracture. To preserve the mechanical integrity of the machined ceramic, a subsequent “heal fire” and stress-relieving sintering process may be needed. For thin ceramic components (a few millimetres thick), tooling and additional post-machining processes add significant cost and time to the manufacturing of the finished product. So, what is the solution?
Some of the non-conventional machining methods available for ceramic cutting include abrasive water jet (AWJ), electrical discharge machining (EDM) and laser-assisted milling (LAM). All of these have both advantages and disadvantages, a detailed discussion of which is beyond the scope of this article.
Laser processing of technical ceramics, whether cutting, scribing or drilling, is attractive because it is a precise and cost-effective method. The hardness of the material presents no problem, and the non-contact nature of the laser process means there is no tool wear, thus minimising downtime and eliminating the associated costs of tool replacement.
The carbon dioxide (CO2) laser is well-suited to processing ceramics, particularly the alumina wafers used in the electronics industry. Thin sheets can be divided by scribing, where the laser drills a series of closely spaced blind holes in the ceramic, penetrating roughly one third to a half of the thickness of the ceramic. The material is weakened along the scribed line, and can be mechanically broken to separate the components. Each hole is drilled using a single laser pulse, while the depth is controlled by the pulse duration; pulses up to 1ms are commonly used.
Thicker ceramic can be cut with very good edge quality, although this process is slow. High average powers do not necessarily lead to faster machining, due to plasma screening effects; in these applications, the laser pulse regime is critical. Pulse duration, peak power and pulse energy must be carefully controlled in order to minimise plasma absorption and maximise efficiency of material removal. Even with this high level of control, laser machining can cause heat build-up and mechanical stress in the ceramic material, and the process parameters must be chosen carefully in order to mitigate the risk of fracture.
At Luxinar, we have been manufacturing CO2 laser sources for 25 years. Our lasers are used globally for applications including electronics, medical devices and automotive components. They can be used to process a wide range of materials, including ceramics, plastics, textiles, paper, sheet metal and more. Our CO2 laser sources are designed for integration into industrial machines, where they can operate in harsh environments. Our SR series laser sources are particularly well suited to ceramic processing applications, including cutting, drilling, substrate dicing and scribing.
You can find further product details in our industrial range brochure, or contact us today for more information on ceramic cutting methods for technical ceramics or any other questions you may have.