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Ceramics are a type of inorganic non-metallic materials made from natural or synthetic compounds through forming and high-temperature sintering. It is a functional material with high melting point, high hardness, high wear resistance, and oxidation resistance, characterized by high hardness, high stiffness, high strength, non plasticity, high thermal stability, and high chemical stability. It is also a good insulator and is often used in fields such as military, aerospace, and high-end PCBs. However, ceramic materials are limited by process conditions during mechanical processing and cannot accurately reserve various holes, grooves, and edges for assembly. Therefore, drilling on engineering ceramic products is often required in production, and it is also an important technique in ceramic processing. The characteristics of high hardness, high brittleness, and easy fragmentation of ceramic materials require excellent processing techniques for precision drilling, especially for small and micro hole processing, forming processing, thread processing, etc., in order to expand the machinability range of materials and make them more widely used. At present, the main techniques for drilling ceramic materials include mechanical processing, ultrasonic processing, laser processing, and other methods.

1. Mechanical drilling method

Mechanical drilling is currently the most widely used method, which uses diamond hollow drills to grind and continuously penetrate ceramic materials until penetration. This method is particularly suitable for processing circular holes with diameters of several millimeters or more.

2. Ultrasonic drilling

Ultrasonic drilling is one of the appropriate and effective methods for ceramic materials with low tensile strength to use ultrasonic machining. Ultrasonic machining is a process in which an ultrasonic generator converts electrical energy into ultrasonic frequency oscillation and is fixed on an amplitude expanding tool to generate ultrasonic vibration, causing the liquid abrasive particles between the tool and the workpiece to continuously impact and grind the machined surface at a high speed and acceleration. Therefore, the machining efficiency and ultrasonic output power are affected The type of abrasive particles and processing speed are related.

3. Laser drilling

Laser drilling utilizes the high power and good spatial coherence of pulsed laser to melt and vaporize materials, forming holes. The process of laser drilling is a thermophysical process involving the interaction between laser and material. The interaction between laser and workpiece involves many different energy conversion processes, including reflection, absorption, vaporization, re radiation, and thermal diffusion. It is determined by the beam characteristics such as laser wavelength, pulse width, focusing state, and many physical properties of material. Due to the high power density and good directionality of lasers, laser drilling is commonly used for ceramic plates. Laser ceramic drilling generally uses pulse lasers or quasi continuous lasers (fiber lasers). The laser beam is focused on the workpiece placed perpendicular to the laser axis through an optical system, emitting a high energy density (10 * 5-10 * 9w/cm2) laser beam to melt and vaporize the material, A coaxial airflow with the beam is sprayed out by the laser cutting head, blowing out the melted material from the bottom of the incision to gradually form a through hole.

Alumina laser drilling substrate

Due to the small size and high density of electronic and semiconductor components, there are high requirements for the accuracy and speed of laser drilling processing. According to the different requirements of component applications, due to the small size and high density of electronic and semiconductor components, there are high requirements for the accuracy and speed of laser drilling processing. According to the different requirements of component applications, the range of micropore diameter is 0.05-0.2mm. Fiber lasers are commonly used for precision machining of ceramics, with a laser focal spot diameter of ≤ 0.05mm. Depending on the thickness and size of the ceramic plate, different through-hole drilling can be achieved by controlling the defocus amount. For through-holes with a diameter less than 0.15mm, drilling can be achieved by controlling the defocus amount. Obviously, traditional processing methods can no longer meet the high-precision machining requirements of ceramic substrates. With the continuous development of laser technology, laser processing has become one of the best methods for ceramic processing.

The advantages of laser drilling

① Fast speed, high efficiency, and good economic benefits. Due to the fact that laser drilling utilizes a high power density laser beam to instantaneously act on the material, the drilling speed is very fast. High efficiency drilling can be achieved by combining high-precision machine tools and control systems. On the same workpiece, laser drilling is 10-100 times more efficient than electric spark drilling or mechanical drilling.

② A large aspect ratio can be obtained. In micro hole machining, the depth to diameter ratio is an important indicator to measure the difficulty of small hole machining. Compared to other drilling methods, laser drilling is easier to optimize parameters, so it can obtain a much larger depth to diameter ratio than electric spark and mechanical drilling.

③ Can be carried out on various materials. Not limited by mechanical properties such as material hardness, stiffness, strength, and brittleness, this is very important for ceramic processing.

④ No tool wear and tear. Laser drilling is non-contact processing, avoiding the problem of easily breaking the drill bit during mechanical drilling of micro holes.

⑤ Suitable for processing large quantities and high-density holes. When the laser drilling machine is combined with an automatic control system and an industrial computer to achieve the integration of light, machine, and electricity, the repeatability of the laser drilling process is very strong.

⑥ Capable of machining small holes on inclined surfaces of difficult to machine materials. Mechanical drilling and electric spark drilling belong to contact drilling, and it is very difficult to drill on inclined surfaces.

⑦ Workpieces placed in vacuum or other conditions can be processed.