At present, to obtain aluminum nitride ceramic substrates with high surface quality, ultra-precision machining methods such as chemical mechanical polishing, magnetorheological polishing, ELID grinding, laser processing, plasma-assisted polishing, and composite polishing are mainly used.
Chemical mechanical polishing process of aluminum nitride ceramics
Chemical mechanical polishing (CMP) is the most widely used global flattening technology in the semiconductor industry. In chemical mechanical polishing, material removal is achieved through a combination of chemical and mechanical effects. Microcracks are prone to occur on the surface of processed aluminum nitride, resulting in subsurface damage. In addition, in the polishing process, the grinding fluid is easy to cause pollution and requires special process treatment, and the abrasive is easy to cause wear to the polishing pad, which needs to be corrected regularly. At present, the abrasives, polishing pad types, and polishing processes used for aluminum nitride are not as mature as those of silicon carbide, and further in-depth research is needed.
Magnetorheological polishing process of aluminum nitride ceramics
Magnetorheological polishing technology is a polishing method between contact polishing and non-contact polishing. Compared with traditional polishing methods, it has the advantages of high polishing accuracy, no tool wear and clogging, high removal rate, and no introduction of sub-surface damage. However, during the use of magnetorheological fluid, the magnetic conductive particles are worn due to mutual friction. The magnetorheological fluid needs to be sealed during use, resulting in a complex preparation process and high cost, which is not conducive to large-scale industrial use. Generally, this method is used in the last process of optical parts processing.
ELID grinding technology of aluminum nitride ceramics
ELID grinding technology is a composite mirror processing technology that combines traditional grinding, lapping, and polishing. It has the characteristics of high efficiency, simple process, and high grinding quality. The grinding fluid used is an aqueous solution of a weak electrolyte, which has no corrosive effect on machine tools and workpieces. The device is simple and suitable for promotion. However, during the grinding process, the change of the correction current can easily lead to discontinuity of the oxide layer, uneven surface of the workpiece, burns, residual stress, cracks, and other defects when grinding the workpiece.
Laser processing of aluminum nitride ceramics
Laser processing is an advanced processing technology with non-contact processing, no tool wear, high precision, and strong flexibility. It is a processing method suitable for brittle and hard ceramic materials. Its working principle is that light energy reaches extremely high energy density after being focused by a lens, causing the material to decompose at high temperatures. The laser processing method is low-cost and high-efficiency, but it is difficult to control the precision and surface quality of the product.
Plasma-assisted polishing process of aluminum nitride ceramics
Plasma-assisted polishing (PAP) is a dry polishing technology. Due to the influence of the grinding stone, the material removal rate of plasma-assisted polishing is lower than that of other processing technologies, and the processing equipment of PAP is expensive and not suitable for large-scale processing.
Aluminum nitride ceramic composite polishing process
For typical hard and brittle materials, non-contact processing methods, such as chemical etching and laser polishing, often have problems such as environmental pollution, high processing costs, and low processing efficiency. In contrast, contact abrasive processing methods include diamond grinding and free abrasive polishing. Although they have high processing efficiency and good workpiece shape accuracy, they will introduce serious surface and sub-surface damage and are only suitable for rough processing. They must be combined with etching or polishing processes to achieve damage layer removal and stress release.
From the above analysis, it can be seen that a single processing method cannot have various advantages at the same time. To improve the surface quality and processing efficiency of aluminum nitride ceramic substrates, some scholars have also used a variety of processing methods to study composite polishing technology. Common composite polishing processes include ultrasonic vibration-assisted grinding, ultrasonic abrasive water jet polishing, and ultrasonic-assisted bonded abrasive chemical mechanical polishing.
Edgetech offers aluminum nitride ceramic products with thermal conductivity ranging from 170-230W/mK. Please visit https://www.eticeramics.com for more information.
Aluminum nitride ceramics have high hardness and are difficult to machine. In various application fields of aluminum nitride ceramics, high requirements are placed on the surface machining quality and precision. Brittle and hard materials are prone to brittle fracture during machining, causing a series of surface defects such as broken layers, brittle cracks, residual stress, and plastic deformation zones on the machined surface. Ceramic substrates are mainly faced with working conditions in thermodynamic environments in LED devices, so the above defects will greatly affect the performance of the substrate and reduce the stability and life of the device. Therefore, it is very necessary to achieve near-damage-free machining of the surface of aluminum nitride ceramic substrates.
At present, to obtain aluminum nitride ceramic substrates with high surface quality, ultra-precision machining methods such as chemical mechanical polishing, magnetorheological polishing, ELID grinding, laser processing, plasma-assisted polishing, and composite polishing are mainly used.
Chemical mechanical polishing process of aluminum nitride ceramics
Chemical mechanical polishing (CMP) is the most widely used global flattening technology in the semiconductor industry. In chemical mechanical polishing, material removal is achieved through a combination of chemical and mechanical effects. Microcracks are prone to occur on the surface of processed aluminum nitride, resulting in subsurface damage. In addition, in the polishing process, the grinding fluid is easy to cause pollution and requires special process treatment, and the abrasive is easy to cause wear to the polishing pad, which needs to be corrected regularly. At present, the abrasives, polishing pad types, and polishing processes used for aluminum nitride are not as mature as those of silicon carbide, and further in-depth research is needed.
Magnetorheological polishing process of aluminum nitride ceramics
Magnetorheological polishing technology is a polishing method between contact polishing and non-contact polishing. Compared with traditional polishing methods, it has the advantages of high polishing accuracy, no tool wear and clogging, high removal rate, and no introduction of sub-surface damage. However, during the use of magnetorheological fluid, the magnetic conductive particles are worn due to mutual friction. The magnetorheological fluid needs to be sealed during use, resulting in a complex preparation process and high cost, which is not conducive to large-scale industrial use. Generally, this method is used in the last process of optical parts processing.
ELID grinding technology of aluminum nitride ceramics
ELID grinding technology is a composite mirror processing technology that combines traditional grinding, lapping, and polishing. It has the characteristics of high efficiency, simple process, and high grinding quality. The grinding fluid used is an aqueous solution of a weak electrolyte, which has no corrosive effect on machine tools and workpieces. The device is simple and suitable for promotion. However, during the grinding process, the change of the correction current can easily lead to discontinuity of the oxide layer, uneven surface of the workpiece, burns, residual stress, cracks, and other defects when grinding the workpiece.
Laser processing of aluminum nitride ceramics
Laser processing is an advanced processing technology with non-contact processing, no tool wear, high precision, and strong flexibility. It is a processing method suitable for brittle and hard ceramic materials. Its working principle is that light energy reaches extremely high energy density after being focused by a lens, causing the material to decompose at high temperatures. The laser processing method is low-cost and high-efficiency, but it is difficult to control the precision and surface quality of the product.
Plasma-assisted polishing process of aluminum nitride ceramics
Plasma-assisted polishing (PAP) is a dry polishing technology. Due to the influence of the grinding stone, the material removal rate of plasma-assisted polishing is lower than that of other processing technologies, and the processing equipment of PAP is expensive and not suitable for large-scale processing.
Aluminum nitride ceramic composite polishing process
For typical hard and brittle materials, non-contact processing methods, such as chemical etching and laser polishing, often have problems such as environmental pollution, high processing costs, and low processing efficiency. In contrast, contact abrasive processing methods include diamond grinding and free abrasive polishing. Although they have high processing efficiency and good workpiece shape accuracy, they will introduce serious surface and sub-surface damage and are only suitable for rough processing. They must be combined with etching or polishing processes to achieve damage layer removal and stress release.
From the above analysis, it can be seen that a single processing method cannot have various advantages at the same time. To improve the surface quality and processing efficiency of aluminum nitride ceramic substrates, some scholars have also used a variety of processing methods to study composite polishing technology. Common composite polishing processes include ultrasonic vibration-assisted grinding, ultrasonic abrasive water jet polishing, and ultrasonic-assisted bonded abrasive chemical mechanical polishing.
Edgetech offers aluminum nitride ceramic products with thermal conductivity ranging from 170-230W/mK. Please visit https://www.eticeramics.com for more information.
Ultra-precision machining of aluminum nitride ceramics