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Large capacity current carrier printed circuit board (PCB) imposes strict control requirements on the hole wall roughness. The key factors are chip removal, drilling temperature and tool wear. This paper aims to find out a cryogenic drilling process to control the chip removal, chip morphology, tool wear and finally reduce the hole wall roughness.

The chip removal process, chip morphology, tool wear and hole wall roughness of glass fiber epoxy resin copper clad laminate (FR-4) drilling were observed and analyzed. The influence of cold air on the chip removal process, chip morphology, tool wear and hole wall roughness was also investigated. An optimization process of cold air auxiliary drilling was proposed to control the hole wall roughness of FR-4.

The results showed that the discharge time of copper foil chips with obvious characteristics can be used as the evaluation criterion for the smoothness of chip removal. The cold air can promote chip removal and reduce tool wear. In addition, the chip removal and cooling performance will be the best when using −4.7 °C cold air with the injection angle consisted with the angle of helical flute of the drill. The hole wall roughness of FR-4 could be controlled by drilling with −4.7°C cold air.

This paper was the first study of the effect of three kinds of cold air on PCB drilling. This provided a reference for the possibility that the cryogenic drilling methods apply to PCB drilling. A new cold air auxiliary drilling process was developed for large capacity current carrier FR-4 manufacturing.

In an integrated circuit (IC) substrate, more fillers, including talcum powder and aluminium hydroxide, are added, which leads to much higher rigidity and hardness compared with a traditional printed circuit board. However, the micro drilling of IC substrates is harder. This paper aims to test the drilling process of IC substrates to improve the drilling process and the micro hole quality.

Substrate drilling by a micro drill with 0.11-mm diameter was used under several drilling conditions. The influence of drilling conditions on the drilling process was observed. Drilling forces, drill wear and micro hole quality were also studied.

The deformation circle around holes, hole location accuracy, bugle hole and burrs were the major defects of micro holes that were observed during the drilling of the substrate. Reducing the drilling force and drill wear was the effective way to improve hole quality.

The technology and manufacturing of IC substrates has been little investigated. Research data on drilling IC substrates is lacking. The micro hole quality directly affects the reliability of IC substrates. Thus, improving the drilling technology of IC substrates is very important.

The purpose of this paper is to present a system for accurately measuring drilling force in the printed circuit board micro drilling process and to characterize the drilling force to provide a better understanding of the micro drilling process.

The drilling force measurement system was established first. Then the drilling force in printed circuit board micro drilling process was characterized experimentally. In particular, the drilling forces in drilling halogen‐free and lead‐free assembly compatible printed circuit boards and the drilling force characteristics in ultra small hole drilling were investigated.

A drilling force measurement system, with the key component of a KISTLER 9256C2 dynamometer, can accurately measure the drilling forces in the printed circuit board micro drilling process. The micro drilling process can be characterized by drilling force. Meanwhile, drilling force is very sensitive to drill breakage and drilling force can be utilized to detect drill breakage in the micro drilling process.

The paper presents a system for accurately measuring the drilling force. Drilling force provides fundamental information for the optimal design of micro drill bits. Drilling force can also characterize the micro drilling process, especially the ultra small hole micro drilling process.

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.

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 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.

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.

The purpose of this paper is to present a method and a system for measuring drill bit temperature on‐line in the micro drilling process and to characterize drilling processes via drill bit temperature.

The drill bit temperature measurement system was first established by the utilization of an infrared camera. Then the drill bit temperature in a drilling cycle was characterized. The temperatures of an ultra‐small micro drill bit and a coated drill bit were measured and compared.

The temperature of an ultra‐small drill bit can be measured on‐line via the proposed temperature measurement system. The drilling process can be characterized by the drill bit temperature. The drill bit temperature decreased when a coated drill bit was used.

The paper highlights key points for measuring the drill bit temperature on‐line by an infrared camera and characterizes PCB drilling processes by measuring the drill bit temperature.

This paper aims to present the main factors affecting the mechanical drilling of the printed circuit board (PCB for short) micro-holes and method of micro-ultrasonic powder molding (micro-UPM for short) by utilizing PCB micro-hole array.

To optimize the drilling process, the paper proposes the on-line monitoring methods for the drilling process including drilling force, drilling temperature, high-speed photography and vibration signals. Taking 0.10 and 0.15 mm micro-drilling as examples, the paper analyzes the drilling process of ultra-small micro-holes. Finally, by taking the PCBs with 0.10 and 0.15 mm micro-hole arrays as the micro-cavity inserts, utilizing ultra-high-molecule weight polyethylene powder with the average particle size of about 150 μm as raw material, two sizes of micro-cylinder array polymer parts are fabricated through micro-UPM process.

PCB micro-cavity inserts with micro-hole arrays fabricated by mechanical drilling has the advantages of low costs, high efficiency and good consistency. Taking 0.10 and 0.15 mm micro-drilling as examples, it is found that the both measured apertures are about 10.0 μm more than the diameter of the micro-drill bits on average. The average diameter of the micro-cylinders by micro-UPM process is smaller than that of the micro-hole with the same specification, while the value of the roughness of the cylinder surface is more than that of the hole-wall surface with the same specification.

This paper describes the challenges and the developments of mechanical drilling and by using PCB micro-cavity inserts with micro-hole arrays fabricated by mechanical drilling, two different micro-cylinder array polymer parts are successfully made and thus the application area of PCB micro-drilling is broadened.

The purpose of this paper is to verify the feasibility and reliability of mineral casting applied in high-precision printed circuit board (PCB) drilling machine. The mechanical properties of machine frame are quantified to provide a solution for machine tool industry to seek a perfect substance competing with classic materials such as cast iron and granite.

The optimal design of machine frame is performed via the CAD system combined with finite element analysis (FEA). The mechanical properties of the frame elements are evaluated by a series of mechanical experiments: static performance is quantified by flatness tests, dynamic behavior is estimated by experimental and numerical models, respectively. Meanwhile, the performance of the frame element with traditional materials is examined experimentally.

Mineral casting parts can be successfully applied to PCB drilling machine to meet high accuracy requirements. The characteristic of mineral casing gives the most possibilities in structural design. The frame parts show good static/dynamic behaviors by structural optimization processes. Especially, the machine frame with mineral casting gains a great weight reduction compared with traditional materials.

The application of mineral casting in PCB drilling machine offers greater design flexibility and innovative system solutions. The combination of FEA is convincing to achieve optimal structure and ideal weight to maximize the economic and technical benefits. Moreover, lightweight design of machine structural components achieves not only higher kinematic/dynamic precision but also considerable cost reduction.