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The purpose of this paper is to provide a method and system to achieve automated measurement of micro drill bit wear.

A method and system of automated measurement of micro drill bit wear on the basis of machine vision are presented. Experiments are conducted to verify the developed method and system.

The worn area of the primary face is an appropriate index to reflect the wear condition of a micro drill bit. A machine vision based technique is an applicable tool for capturing and characterising images of worn micro drill bit. The developed system can accurately measure and characterise the wear performance of micro drill bits with different materials and different parameter designs.

The paper highlights the method and the system for achieving automated measurement of micro drill bit wear. The developed method and system can provide fast and precise evaluation of micro drill bit wear.

To provide a clear picture of the current status of mechanical drilling of printed circuit boards (PCBs).

A review paper detailing the developments of micro‐drill bit and PCB mechanical drilling techniques.

Mechanical drilling will still dominate the PCB hole processing methods. A design method on the basis of theoretical analysis, numerical simulation and experimental verifications is proved as an applicable way to improve the drill bit design efficiency. Newly developed tungsten carbide, novel coating techniques and high‐performance steel‐shank micro‐drill bits are expected. Solutions of micro‐drill bits for high‐density interconnection, IC substrate flexible PCBs, halogen and lead‐free assembly compatible PCBs, as well as 2 mm shank diameter drill bit are worthy of being concerned.

The paper highlights the state‐of‐the‐art techniques of micro‐drill bit manufacturing and novel developed micro‐drill bit. The development direction of micro‐drill bit in the future is concluded.

The purpose of this paper is to develop water vapour as a new cooling and lubricating technique in drilling Ti6Al4V. Water vapor is an economical and eco‐friendly coolant and lubricant. However, it is necessary to study the drilling chip deformation, forces and drilling temperature when drilling Ti6Al4V using this new green drilling technology, which meets the development trend of green machining technology.

Comparative experiments are carried out with HSS drill bits and YG6X (K10 type in ISO) cemented carbide drill bits in drilling Ti6Al4V under the conditions of oil water emulsion, water vapor as coolant and lubricant and dry drilling, respectively. The drilling forces, temperature and drill bit wear VBmax have been examined and analyzed. Further, a new type practical drilling quick‐stop device is developed for studying the chip deformation in drilling Ti6Al4V. The drilling forces distribution test in drilling Ti6Al4V is also developed.

When water vapor is used as coolant and lubricant, the torque is reduced by 15‐25%, 5‐10% in comparison with dry drilling and oil water emulsion, respectively; the thrust is reduced by 5‐10%, 4‐5%; the temperature is reduced by 15‐20%, 5‐8% and the wear VBmax of drill bit is reduced by 60‐80%, 10‐15%, correspondingly. Also, the contact length in chip‐tool interface decreases and the drilling deformation is reduced. The coolant and lubricant conditions and feed rate have little impact on the drilling force distribution in drill bit cutting edges.

A green machining technology, water vapor used as coolant and lubricant, is used in drilling Ti6Al4V; it can reduce drilling deformation, drilling forces, temperature and flank wear. A new drilling quick‐stop device is devised to obtain the drilling chip roots. Also, the drilling force distribution test was developed for obtaining the rate of drilling forces in cutting edges when drilling Ti6Al4V.

This paper aims to investigate and document the effects of copper-clad laminate (CCL) inorganic filler on the hole performance in printed circuit boards drilling process.

Drilling of brittle laminates can result in hole cracking, layer-to-layer delamination and drill-bit wear and tool breakage. Adding large amount of fillers not only shortens the life of the drilling tool but also affects the drilling properties significantly regarding hole quality. This paper introduces the influence of filler content, type, hardness, particle size and the compounding method in the manufacture of the CCL on the drilling performance.

The filler content, filler type, hardness of filler, particle size of filler and the compounding method used for the filler have a great influence on the drilling properties of CCL. The higher the filler content, the larger the particle size and the more the hardness of the filler, the worse the drilling properties. The combination of hard particles like silica with softer particles can improve the drilling performance of CCL.

The paper describes what affects the drilling performance of CCL and how this knowledge can be used to design CCL with good drilling performance.

The paper aims to present key points regarding the development of an ultra‐small micro drill bit for packaging substrate hole processing.

Key points for the development of ultra‐small drill bits are presented. These are based on a study of the influential mechanisms of micro drill bit material properties, key parameters and coating techniques on the behaviours of micro drill bit. Experiments were conducted to verify the drilling capability of the developed ultra‐small micro drill bits.

The material properties of micro drill bits are of great importance in ensuring the performance. Helix angle, primary face angle and point angle are three key parameters that significantly influence drill bit behaviour. Computer‐aided engineering analysis, temperature monitoring and video monitoring techniques in high‐speed drilling are useful tools for achieving the optimal design of ultra‐small drill bits. Using coating technology on ultra‐small drill bits can improve their hit limits by nearly four times.

The paper highlights key points to consider when developing ultra‐small micro drill bits. The presented points can provide an overall understanding of the challenges and solutions during ultra‐small micro drill bit design. Additionally, this paper presents a solution for packaging substrate ultra‐small hole processing by mechanical drilling.

In the manufacturing process for making printed circuit boards (PCB) it is necessary to drill holes in the base copper clad laminate. This is a crucial step in the case of multi‐layer boards where the holes must be plated with copper to complete the electrical connection between the layers. Drilling is an expensive process as it requires the use of extremely sophisticated equipment. Most often this resides with a handful of companies; namely board shops and drill bit manufacturers. In recent years, with the evolution of high performance resins such as high glass transition (T_g) and decomposition temperature (T_d) as well as low dielectric constant (D_k) and the continued embracement of the use of phenolic cured resins compared to dicyandiamide (DICY), issues around drillability have increased. As a part of our efforts we compared the mechanical and thermo‐mechanical properties of three resins. Actual drilling studies were performed on three‐high, copper clad stacks made from these three resins at Megatool in California, in order to confirm our fundamental property correlations. Resin toughness was found to play a crucial role in the final PCB drillability.

The purpose of this paper is to present a clear picture of the challenges of micro drill bit and the developments of novel micro‐drill bits for flexible circuit boards, environmental‐friendly printed circuit boards (PCBs), high aspect ratio drill bit and ultra‐small micro drill bit, as well as the developments of geometry design of micro drill bit.

The paper details the developments trend and challenges of micro drill and PCBs first. Then the current research status of novel micro drill bits for flexible circuit boards, environmental‐friendly PCBs, high aspect ratio drill bit, ultra‐small micro drill bit are described. Finally, the developments of geometry design and drilling process are reviewed.

To achieve excellent performance for drilling flexible PCB, a large helical angle, large flute/land ratio and small web thickness that guarantee the sharp evacuation capability, are adopted in drill bit design. A small helix angle and an appropriate primary face angle are employed for drill bit to process environmental‐friendly printed circuit boards. It is beneficial to implement big helix angle, small primary face angles and small point angles in the design of ultra‐small micro drill bit. An optimum web thickness and step feed should be taken into consideration in high aspect ratio drill bits design.

The paper reviews different solutions of micro drill bits for the state‐of‐the‐art PCB and the developments of geometry design of drill bit for printed circuit boards.

The flexible printed circuit (FPC) board with the characteristic of light and thin strengthened confronted the growing miniaturization requirements of the electronic product and the popularity of wearable devices. The reliability of circuit could be influenced by the hole quality of FPC, such as burrs, which is one of the major problem in FPC.

In this paper, micro-drill with a diameter of 0.1 mm was used to drill the double-sided flexible copper clad laminate. The thrust force, the burr and tool wear were investigated. The influencing factors of the height of the burrs were studied. The relationship between the thrust force and the height of the burrs was also explored. Finally, the formation mechanism of burrs was analyzed.

The entrance burrs were usually less than the exit burrs. The burr height increased with the feed per rotation. The height of the burr increased with the increase of the thrust force for the plastic deformation of the copper foil was dominant. The abrasion of the drill gave rise to increase the height of burr. In micro-hole drilling, the growth of burrs can be suppressed effectively by reducing the clearance between the FPC and the backup plate. The thrust force would be controlled in a certain range to reduce the burr with specific drilling parameters. There existed a certain relationship of Gaussian distribution between the height of the burrs and the thrust force of FPC.

The reliability of the integrated circuit was directly affected by the burrs of the FPC. This research on the formation mechanism of FPC burrs and forecast of burr height provided a firm foundation for further work in the area of improvement of the micro-hole quality.

To provide a solution for PCB drilling with strict requirements on hole wall quality.

The influential mechanism of key micro drill bit parameters on hole wall roughness is analyzed. A new type of micro drill bit is developed on the basis of theoretical analysis and experimental verifications.

The key factors in drill bit design which can enable superior hole wall quality are described. Experimental results show that very good hole wall quality is achieved by such newly developed drill bits. Meanwhile, the new drill bits show good performance in terms of wear‐resistance and hole registration accuracy. A solution for PCB drilling with strict requirements on hole wall quality is provided.

The paper highlights the influential mechanism of key parameters of micro drill bit design on the hole wall quality of PCBs. A new kind of micro drill bit which can achieve superior hole wall quality has been developed.

The purpose of this paper is to present key points relating to the development of micro drill bits with high aspect ratios and to provide a solution for high aspect ratio hole drilling.

Based on the analysis of challenges in high aspect ratio hole drilling, key points for the development of micro drills bit with high aspect ratio are discussed. A design example of a micro drill bit with 0.3 mm diameter and a 7.2 mm flute length is presented. Experiments are conducted to verify the performance of the developed micro drill bit.

Helix angle, web thickness and flute land ratio are three key parameters that significantly influence the behaviour of micro drill bits with high aspect ratios. Large helix angle, web thickness and flute land ratio are beneficial in terms of improving the performance of high aspect ratio micro drill bits. Step drilling is essential to prevent drill breakage and to ensure smooth debris evacuation. Meanwhile, proper steps and drilling parameters are of great importance to complete high aspect ratio hole drilling.

The paper highlights key points relating to the development of micro drill bits with high aspect ratios that can provide a satisfactory solution for high aspect ratio micro drill bit design.