Lijuan Zheng

Experimental study on micro-drills wear during high speed of drilling IC substrate

Purpose – 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. Design/methodology/approach – 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 a...

Drilling Force and Chip Morphology in Drilling of PCB Supported Hole

Supported holes of Printed circuit board (PCB) are drilled with two different drill bits. Drilling force (thrust force and torque) and chip morphology are examined at different cutting parameters, and the effects of the two drills are discussed. The results indicate that the drilling force and chip morphology are affected by the feed rate, spindle speed and drill shape. Thrust force increases with the increasing feed rate, and decreases with the increasing spindle speed. Optimization of drill geometry can reduce the thrust force significantly, and is effective in chip breaking which can improve the chip evacuation during the drilling process.

A Review on Drilling Printed Circuit Boards

Drilling is a particularly complicated machining process, and it becomes much more complicated when the workpiece is printed circuit boards (PCBs). PCB is composite materials with anisotropy. Even a small defect in PCB may cause great losses. Both the drilling process and PCB structure design have been researched by many scholars. But the investigations into the drilling processes of PCB are not systematic. The present review article address the report about tool materials and geometrics, cutting force, cutting temperature, radial run-out and damages occurring in drilling processes. And as a conclusion, some of these critical issues are proposed to meet the challenges in analysis and optimization for PCB drilling.

Cutting Forces of PCB Supported Hole

A printed circuit board or PCB consists of conducting layers typically made of thin copper foil and insulating layers laminated together. Holes through a PCB are typically drilled with tiny drill bits made of solid tungsten carbide. This paper focuses on cutting forces of drilling PCB. The influences of cutting speeds, feed rate and drill diameter on thrust force are investigated. Finally the drilling force experimental formula’s mathematical model is derived.

The entry drilling process of flexible printed circuit board and its influence on hole quality

Purpose – 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. Design/methodology/approach – 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 an...

Milling Forces of Compacted Graphite Iron (CGI) and Gray Iron (GI)

Compacted graphite iron (CGI) has excellent comprehensive performance of strength, hardness, abrasion resistance, shock absorption and thermal conductivity as an ideal material for making engine parts. The material performance of CGI is compared with that of gray iron (GI) and spheroidal graphite Iron (SGI). Some research shows that the strong adhesion between the iron and the graphite forms semi-continuous chips when machining CGI which requires more energy than GI cutting, and theres no MnS layer on the cutting edge during CGI cutting. Thus, the cutting tool life of CGI is greatly reduced than GI. The experiment results indicate that the cutting forces of CGI milling are much higher than that of GI when the feed and the depth of cut increase.

Drilling characteristics of entry board and the influence on PCB micro drilling process

In this paper, the drilling characteristics of aluminum (Al) entry boards, resin coated Al entry boards, and phenolic resin entry boards were investigated. The chip removal, chip morphology, thrust force, and drilling temperature were measured and analyzed. The cutting characteristics among those materials were compared. In addition, the influence of alloy materials on thrust force of entry boards was analyzed. The results demonstrated four efficacy of entry boards, including chip removal, heat dissipation, buffering, and location. The function of location and buffering were mainly reflected in the beginning of drilling. Effect of chip removal and heat dissipation were related to material of entry board. The resin coated Al entry board performed better than aluminum entry board in buffer and chip removal. Moreover the influence of coating resin and its thickness on drilling process of entry board was obvious. Chips of aluminum entry board were easy to wrapping the drill bit than that of resin coated Al entry board. Thermal deformation of coating resin can increase the curl of aluminum chip, thus contributing to the chip removal. The effect of alloy material on thrust force was significant. The increase of coating resin thickness can enhance the buffer effect on thrust force in some degree. The heat dissipation of MVC resin coated Al entry board in PCB drilling was the best.

The tool-wear characteristics of flexible printed circuit board micro-drilling and its influence on micro-hole quality

Purpose n n n n nMicro-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. n n n n nDesign/methodology/approach n n n n nThe 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. n n n n nFindings n n n n nThe 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. n n n n nOriginality/value n n n n nThe 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.