Glass Transition Temperatures of Polymers

In the present study, laser cutting of Kevlar laminate is considered, and the effect of assisting gas pressure and laser output power on the end product quality is examined. The end product quality is judged via measurement of out-of-flatness and kerf width ratios. Experimental tests are carried out using a CO2 laser beam with pulse repetition rate of 300 Hz. The cutting model introduced previously is accommodated to predict the kerf size for various laser output power and assisting gas pressures. The predictions are compared with the experimental results. It is found that the predictions of kerf size are in good agreement with the experimental results. The influence of assisting gas pressure is significant on the resulting cut quality, in which case, out-of-flatness and kerf width ratio improve considerably at high assisting gas pressures (500 kPa).

CO2 laser cutting of Kevlar laminate: influence of assisting gas pressure

Permittivity and dissipation factor (Dk and Df) are effects of polarization of different components of the dielectric substrate material when subjected to an electrical field. A database of these important design parameters for PWBs has been developed for Thermount RT. Effects of variations in the level of moisture (bone‐dry to completely saturated at various relative humidity levels), testing temperature (room temperature to 120uC) and testing frequencies (1MHz to 1.5GHz) on Dk and Df are reported. As the frequency of test is increased from 1MHz to 1.5GHz, the effect of moisture on the properties is reduced. Comparison with conventional glass/FR4 laminate properties shows the distinct advantage of Thermount. It is increasingly used in high frequency cellular telephone, satellite, and wireless applications which require HDI PWBs to achieve the highest packaging density at the lowest cost and weight.

Comparison of the dielectric constant and dissipation factors of non‐woven aramid/FR4 and glass/FR4 laminates

Kevlar laminates are difficult to machine using conventional machining methods because of their thermal and mechanical properties. Laser cutting offers advantages over conventional machining methods, such as precision of operation, non-frictional processing, and operational cost. This provides the motivation for the present study, which reports on laser cutting of Kevlar laminates of different thicknesses. The first and second law efficiencies of the cutting process are formulated and predicted in line with the experimental parameters. The laser cut surfaces are examined using optical and electron scanning microscopes. It is demonstrated that the first and second law efficiencies improve at high laser cutting speeds and low laser output power levels. For these conditions parallel sided kerfs with no sideways burning are produced.

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Laser cutting of Kevlar laminates: First and second law analysis †

The efficiency analysis of laser cutting of holes into Kevlar plates is carried out and the specific energy requirement for cutting is computed for different cutting speeds and laser output power levels. The maximum laser scanning speed required for cutting Kevlar plates of different thicknesses is determined. It is found that the minimum specific energy requirements decrease with increasing hole diameter. The energy and exergy efficiencies predicted are related to the resulting cut quality and it is concluded that cutting quality improves significantly at high energy and exergy efficiencies.

Efficiency analysis of laser hole cutting

Emerging ‘chip‐size’ packages, and bare flip‐chips, require new substrate properties if high lead count chips are to be reliably interconnected on printed wiring boards and multichip modules at low cost. Blind via holes have been shown to increase interconnect density significantly without adding layers which contribute to high cost. Until recently, the use of blind vias has been limited to high‐end applications since standard fabrication methods, either sequential lamination or controlled depth drilling, are too slow and expensive for most high volume commercial applications. To maintain a low layer count while interconnecting higher I/O packages, commercial and consumer electronics require a substrate technology which supports high speed, micro‐via hole formation. This paper describes a process for fabricating high speed micro‐vias in dimensionally stable non‐woven Aramid reinforced laminates using laser ablation technology. Laser equipment capable of producing over 100 blind micro‐via holes per second ...

High Speed Laser Ablation of Microbial Holes in Non‐woven Aramid Reinforced Printed Wiring Boards to Reduce Cost

This paper describes how PCB designers must adjust their approach to take into account the new requirements for the production of high technology printed circuit boards using the latest plated‐through hole and surface mounting techniques. It also describes how the correct use of dry film solder masks is contributing towards the achievement of zero‐defect soldering.

Designing for Zero‐defect Soldering

Printed (circuit) boards have been used in the electronics industry for the past 25 years and more. The technology used to design and manufacture PCBs is well known and accepted. Recently, however, designers of electronic equipment have shown that the use of newer materials and systems, such as flexible and moulded circuits, hybrid circuits, or a combination of these, can significantly improve the cost/performance ratio for electronic interconnects. This paper examines some of the many possibilities open to electronics designers and how these new opportunities can improve the economics and performance of electronic equipment.

Quo Vadis Printed (Circuit) Board

This paper deals with the design of PCBs, using the dielectric properties of solder mask as an insulation layer to protect boards and components; the elimination of selective solder filling of component holes; the protection of via holes during soldering, and the preparation of artwork, with particular attention to design tolerances using dry film solder mask. Future prospects in PCB design, employing dry film solder mask, are also discussed.

M. Weinhold

Papers

High Speed Laser Ablation of Microbial Holes in Non‐woven Aramid Reinforced Printed Wiring Boards to Reduce Cost

Designing for Zero‐defect Soldering

Quo Vadis Printed (Circuit) Board

Broader Functions and Improved Reliability of Printed Circuit Boards Using Dry Film Solder Mask Systems