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For the drilling of polyimide multilayers with acrylic adhesives, more care must be taken than for epoxy glass material. Due to the different mechanical properties in the multilayer ‘sandwich’ of the polyimide and the acrylic adhesive layers, the drilling parameters require a higher level of control. To avoid defects in the hole, such as nail heading of the polyimide or an uncontrolled ‘rip‐out’ of the acrylic adhesive, the relation between the cutting speed of the drill and the feed needs to be adjusted for each drill diameter. The following guidelines are valid: Wider drill diameters require a lower rotational speed and a lower feed to avoid deformation of the polyimide in the hole. Smaller drill diameters need high rotational speeds and a higher feed to minimise smear. In general, the drilling performance of wider drills is better than that of smaller drills. In all cases, it was impossible to prevent smear of the acrylic adhesive in the multilayer holes. The only reliable method for removing acrylic smear is by plasma etching. The minimum etch‐back required for acrylic adhesive was found to be ≥6 µm, which would be equivalent to an etch‐back of only 2 µm of the polyimide film. To achieve the etch‐back rate, the time in the plasma chamber should be between 20 and 30 minutes at 90–110°C. After the etch‐back, a high pressure water rinse is needed to remove some residues in the hole prior to through‐plating.

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 calibrate the surface emissivity of micro drill bit and to investigate the effect of different drilling parameters on the temperature of micro drill bit in printed circuit board (PCB) micro drilling process.

The surface emissivity of micro drill bit was obtained by experiments. Analysis of variance (ANOVA) was applied in this study to analysis the effect of different drilling parameters on the temperature of micro drill bit in PCB micro hole drilling. The most significant influencing factor on micro drill bit temperature was achieved by ANOVA.

First, the surface emissivity of cemented carbide rod decreased from 0.4 to 0.32 slowly with temperature in the range of 50-220°C. Second, the most significant influencing factor on the micro drill bit temperature was spindle speed among the drilling parameters including spindle speed, retract rate and infeed rate.

In this paper, the influence of roughness of black coating, carbide rod and micro drill bit on the surface emissivity calibration and the temperature measurement was not considered.

A new simple method has been presented to calibrate the surface emissivity of micro drill bit. Through calibrating the surface emissivity of micro drill bit, the temperature of micro drill bit can be measured accurately by infrared thermometry. Analyzing the influences of different drilling parameters on the temperature of micro drill bit, the mechanism of drilling parameters on drilling temperature is achieved. The basis for the selection of drilling parameters to improve the hole quality is enhanced.

An investigation of drilling temperature is essential in understanding the drilling mechanism of the material, thus improving the process efficiency. The aim of this study is to experimentally investigate influences of drilling conditions such as the drilling depth, feed rate and spindle speed on the twist drill bit temperature and thrust force in the dry drilling of AISI 1040 steel material using statistical techniques.

Drill bit temperatures were measured by inserting standard thermocouples through the oil hole of TiN/TiAlN‐coated carbide drills. The settings of drilling parameters were determined by using Taguchi experimental design method. An orthogonal array, the signal‐to‐noise (S/N) ratio, and the analysis of variance (ANOVA) were employed to analyze the effect of drilling parameters. The objective was to establish a model using multiple regression analysis between spindle speed, drilling depth and feed rate with the drill bit temperature and thrust force in an AISI 1040 steel material.

Statistical results show that drill bit temperature was significantly influenced (at 95 percent confidence level) by drilling depth and spindle speed values. The spindle speed has smaller influence (7.66 percent) on the thrust force value. The feed rate has no significant influence on the drill bit temperature.

In this paper, a new experimental approach was developed to measure drill bit temperature in dry drilling process.

ONE of the noticeable effects of the extensive application of drill jigs is a steady decline in the number of fully qualified hands. Too many operators are jig specialists and quite unable to handle anything else. This is hardly a matter for surprise. After all, the main function of a jig bushing is to control the movements of the drill, and to anyone accustomed only to this kind of work it is an extremely difficult matter to acquire, in a short time, the entirely different technique of jigless drilling. This awkwardness, however, is not incurable. Actually, it is a question of knowing how to prepare for drilling, as much as the drilling itself. It is because the opportunity of learning from others is not always present that the writer of these notes presents, for the first time, a selection of the methods favoured by himself. They will not miraculously transform an incompetent driller into a competent one, but they will help materially in the process.

Many small holes need to be drilled in printed circuit boards to achieve a high packing density of circuit components. Even with NC control, conventional mechanical techniques are relatively slow and holes smaller than 035 mm diameter are difficult to achieve in production. Laser drilling has been suggested as a potentially fast technique capable of drilling small holes, so trials have been conducted on thin, flexible kapton board, and on 08 mm and 16 mm thick epoxide woven glass fabric board with 12 and 36 micron thick copper cladding. Using a 600 W CO2 laser, the proposed technique was to pre‐etch holes in the copper which would then act as a mask to the beam, so drilling only where etched holes existed. This technique was feasible on the flexible board, but not on the thicker boards because of damage to the copper. Using a pulsed Nd‐YAG laser to drill through both copper and laminate gave good results, but more work is necessary to eliminate occasional delamination of the copper around the hole. Through‐hole plating of the drilled holes appeared to present no special problems.

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 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 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 purpose of this paper is to study and obtain the influence of resin and filler properties of printed circuit board (PCB) on the drilling force during micro drilling.

Experiments were carried out to study the influence of PCB on micro-hole drilling force under high spindle speed. A drilling force measurement system was applied, and then, the influence of resin and filler properties of PCBs on the force was analyzed. The proportion of resin and filler in the PCB was defined as four levels, and the influence of PCBs based on the drilling force measurement was summarized.

The drilling force decreased with the decrease in the feed rate, and lower filler (16-30 per cent) and average resin (31-50 per cent) would have a positive impact on the drilling force. At the same time, the size of uniform and fine fillers would help to reduce the drilling force.

The drilling force measurement system was applied, and the influence of PCBs on force was analyzed, which could provide a reference value on the optimization of the drilling force during micro drilling.