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The purpose of this paper is to obtain the micro drill bit temperature field distribution in micro-drilling process and the temperature drop in retracting process with simulation software. Meanwhile, the key factors that affect the micro drill bit temperature will be obtained as well. The results can also be used to improve the accuracy in on-line drilling temperature measurement.

The purpose of this paper is to obtain the micro drill bit temperature field distribution in micro-drilling process and the temperature drop in retracting process with simulation software. Meanwhile, the key factors that affect the micro drill bit temperature will be obtained as well. The results can also be used to improve the accuracy in on-line drilling temperature measurement.

Micro drill bit high-temperature area mainly concentrates in the cutting edge and chisel edge. With the increase of spindle speed and feed speed, the micro drill bit highest temperature increased. The micro drill bit temperature drop rate reaches 20° in the micro-drilling retraction process with certain parameters. The micro drill bit highest temperature detected by an infrared camera is lower by 22° than that in real drilling. The simulation results can be used to guide the actual industrial production.

The simulation results can be applied to revise the temperature measurement by an infrared camera in the drilling process. Drilling experiments show that the simulation method is correct and has certain practical significance. The current temperature measurement method can satisfy most of the requirements of temperature measurements.

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.

Micro-holes are drilled and plated in flexible printed circuit boards (FPCs) for connecting circuits from different layers. More holes, with diameters smaller than 0.3 mm, are required to be drilled in smaller areas with flexible circuits’ miniaturization. The micro-hole quality of micro-drilling is one of the biggest issues of the flexible circuit manufacturers’ production. However, it is not easy to control the quality of micro-holes. The purpose of this study was to conduct research on the tool wear characteristics of FPC drilling process and its influence on micro-hole quality to improve the micro-hole quality of FPC.

The tool-wear characteristics of micro-drills after FPC drilling were observed. The influence of spindle speed, feed rate, number of drilled holes and entry board materials on tool-wear was analyzed. The hole qualities of FPC micro-drilling were measured and observed. The relationship between tool-wear and hole quality was analyzed.

The result showed that the tool-wear characteristics of FPC micro-drilling was similar to the tool-wear characteristics of rigid printed circuit board (RPC) micro-drilling. Abrasive wear occurred on both the main cutting edges and the chisel edges of micro-drills, even though there was no glass fiber reinforcing the cloth inside FPC. Resin adhesion was observed on the chisel edge. The influence of feed and number of drilled holes on tool-wear was significant. Tool-wear significantly influences the hole quality of FPC. Tool-wear will largely decrease the hole position accuracy of FPC micro-holes. Tool-wear will increase the thickness of PI nail heads and the height of exit burrs. Fracture was the main difference between tool wear of FPC and RPC micro-drilling. Resin adhesion of RPC was much more severe than FPC micro-drilling. Increasing the spindle speed properly may improve tool life and hole quality.

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

The purposes of this paper are to study the characterization of drill bit breakage in printed circuit board (PCB) drilling process based on high-speed video analysis and to provide an important reference for micro drill bit breakage prediction.

Based on PCB drilling experiment, the high-speed camera was used to observe the micro drill breakage process and the chip removal process. The variation of chip in the drilling process was studied and one of the key reasons for the drill bit breakage was analysed. Finally, the swing angles’ feature during the breakage process of the micro drill was analysed and researched with the image processing tools of MATLAB.

The micro drill was prone to breakage mainly because of the blocked chips. The breakage process of the micro drill can be divided into the stage of stable chips evacuation, the stage of blocked chips and the stage of drill bit breakage. The radians of swing angles were basically in the range of ±0.01 when the drilling possess is normal. But when the radians of swing angles considerably exceeded the range of ±0.01, the micro drill bit may be fractured.

This paper presented the method to study the characterization of drill bit breakage in the PCB drilling process by using high-speed video analysis technology. Meanwhile, an effective suggestion about monitoring the radians of swing angles to predict the breakage of micro drill bit was also provided.

The purpose of this study is to present the entry drilling process of flexible printed circuit board (FPCs) and its influence on hole quality, especially hole location accuracy. Compared with the traditional PCB drilling process, the technology of drilling FPCs is facing more problems, such as hole location accuracy, smear on the hole wall surface, burned hole wall surface, etc. Moreover, the materials of FPCs are quite different from the rigid printed circuit boards (RPCs). FPCs no longer contain glass fiber cloths to reinforce resin, resulting in flexibility. Micro-hole quality is the most important issue in FPC drilling. Suggestions were given to obtain higher hole qualities and higher FPC reliability.

The entry drilling process of FPC with different kind of entry boards was observed by a high-speed camera. The hole qualities of FPC micro-drilling, especially hole location accuracy and hole entrance quality, were measured. The relationship between entry boards and hole quality was analyzed.

Significant sliding occurred when drilling FPC with using no-entry board or pure aluminum plate entry board. On the contrary, no significant sliding occurred when using LC-110 or resin-coated aluminum foil (MVC) entry boards. The type, thickness and use-pattern of entry boards influenced hole location accuracy of FPCs seriously. In addition, entry board also influenced the micro-hole entrance quality and micro-hole diameter. The entrance quality of drilling FPC with LC-110 entry board was the best. The diameter variation of drilling FPC with MVC entry board was the smallest. The hole location accuracy decreased as the thickness of entry board increased. Thus, the best use-pattern of entry board was putting a LC-110 under MVC entry board, resulting in best entrance quality and hole location accuracy.

The technology and manufacturing of FPCs in China are obviously behind. Research of FPCs micro-drilling and research data are lacking so far. Thus, it is most necessary to improve the technology level of FPCs micro-drilling in China. Researches on hole quality, especially hole location accuracy of FPCs drilling, were performed in this paper. Suggestions were given to obtain higher hole quality of FPCs.

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.

The paper aims to investigate tool wear mechanism and tool geometry optimization of drilling PCB fixture hole.

An experimental study was carried out to investigate the chip formation and tool wear mechanism of drilling PCB fixture holes. Two types of drill with different types of chip-split groove were used in this study. The performances of these two types of drill bots were evaluated by tool wear and the shapes of chips.

The chips of drilling fixture holes contain aluminum chips from the cover board, copper chips from the copper foil, discontinuous glass fiber and resin from the CFRP. Feed rate and drilling speed have a great influence on the chip morphology. Abrasive wear of the drill lip is the main reason of the fixture drill bit in drilling PCB, and micro-chipping is observed on the tool nose and chisel edge. The influence of distance between the chip-split groove and drill point center on the axial force and torque is not obvious.

In this paper, hole wall roughness and drilling temperature were not analyzed in the optimization of drilling parameters. The future research work should consider them.

This paper investigated the mechanism of burr formation and tool wear in drilling of PCB fixture holes. Tool geometry was optimized by adding chip-split grooves.

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.

Compared with the traditional printed circuit board (PCB) drilling process, the technology of drilling IC substrate is facing more problems, such as much smaller hole diameter, more intensive hole space, thinner sheet and more complicated materials are drilled in process. Moreover, the base material of IC substrate is different from traditional PCB, more kinds of fillers added in IC substrate which make the drill worn seriously during drilling process. Micro-drills wear and micro holes quality are the most important questions when drilling IC substrate so far. Wear morphology of micro-drill, holes wall roughness and hole location accuracy are researched in this paper. The influence factors of micro-drills wear and micro holes quality are also studied in this drilling process. The paper aims to discuss these issues.

Two drills with same structure and different diameter are used to drill different stacks of IC substrate and drill different holes in this paper. There are four experiments made and the drilling parameters including spindle speed (n), feed rate (v_f) and retraction speed (v_r) are recommended by drill manufacturing company. Wear morphologies of drill are observed, holes wall roughness (R_max) and holes location accuracy (C_pk) are measured in this paper. Analyzing the main factors influence on drill wear, holes wall roughness and holes location accuracy through these experiments.

The micro-drills of IC substrate wear more severely compared with other material of PCB through the experimental results in this paper. Drill diameter has influence on micro-drill wear when drilling IC substrate, the smaller of drill is, the more severely of micro-drill wears. Drill diameter affect the holes wall roughness too, the holes wall roughness of larger holes is better than smaller one in a certain range. The drilled holes number also has influence on micro-drills wear, holes wall roughness and holes location accuracy. The more drilled holes, the seriously of micro-drills wear, and the worn drill would destroy the hole quality. Therefore, the more drilled holes lead the bad holes wall roughness and holes location accuracy in this paper. In addition, stacks of IC substrate affect much on the holes location accuracy, the more stacks, the worse holes location accuracy.

Chinese Mainland is obviously lagging behind in technology and manufacturer of IC substrate which is incompatible with the nation circumstances. There is few research of drilling IC substrate in China and research data are lacking so far. It is most necessary to improve the technology level of drilling IC substrate in China. In order to reduce the wear of micro-drills and improve the quality of micro-holes, many experimental tests about drilling IC substrate are researched in this paper.

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.