ICT Annual Symposium - "PCB Technology in Market Sectors".
9th June 2004
Institute of Circuit Technology Chairman Andrew Hall welcomed delegates to the Stoneythorpe Hotel in Southam, Warwickshire, on 9th June 2004 for the 30th ICT Annual Symposium on the theme of “PCB Technology in Market Sectors”.
The symposium opened with a presentation from Chris Thomas, Technical Manager of Circast Electronics, entitled “Lean Manufacturing Techniques for High Reliability PCBs in Aerospace”. The paper described how Circast had undertaken training in the principles and techniques of Lean Manufacturing in partnership with a major aerospace customer, and had subsequently carried out a joint exercise to improve the efficiency of a heat-sink production department such that both sides could share the cost, quality and yield benefits. The presentation was illustrated with refreshingly honest “before” and “after” photographs, and demonstrated that by teamwork, the application of straightforward continuous-improvement procedures and direct involvement of the operators in data collection and analysis, and in the management of the programme, machine up-time had been increased by 47% and non-right-first-time product reduced by nearly 5%. The department had become tidier and better organised and a less-stressful working environment had been established. Perhaps the most encouraging result was psychological – an attitude change from suspicion to sense of achievement on the part of the operators, workers in adjacent departments wanting to become involved in equivalent exercises, and the general acceptance of a culture of continuous improvement throughout the company.
Simon Rowe, Business Development Manager at Printech Circuit Laboratories, then gave a very comprehensive and informative introduction and overview of “Microwave Materials and their Applications”. He described the fundamental characteristics of PTFE-based materials: inherently low dielectric constant, stable over a wide frequency range, very low water absorption, high temperature capability and non-flammability, and went on to demonstrate how materials are manufactured, and how the ratios of PTFE to glass reinforcement and filler materials are controlled in order to produce materials with different dielectric constants and dissipation factors for a range of applications. Dielectric constant could range from 2.17 for a pure PTFE material to 10 for a ceramic-filled grade. The higher the dielectric constant, which determines signal propagation velocity, the smaller the circuit features could be made, generally at the additional expense of achieving tighter etching tolerances. Taking as his example a mobile telecom base station, Simon explained how different PTFE material grades are chosen for specific high-frequency functions within the overall assembly, whilst standard FR4 materials are used in the control electronics where high-frequency characteristics are not a critical issue. Designers of such systems were faced with a whole series of cost/performance decisions in choosing and specifying their high-frequency materials. For certain critical components, performance was the only issue, regardless of cost. In less demanding functions, “the cheapest material which would do the job” was appropriate. The definitive materials list represented the most cost-effective compromise within the system-loss budget. Simon concluded his presentation with an outline of the fabrication process for PTFE circuits. Materials had become progressively more user-friendly such that, with the addition of an off-line plasma-etch or sodium-etch stage, a standard FR4 line could be used for PTFE processing. Multilayer bonding required higher temperatures than FR4; general-purpose presses could achieve the typical 220 deg C required if bond-films were used, but PTFE fusion bonding required a press with 350 deg C capability.
Chris Gould, Graphic’s Environmental Manager gave a paper entitled “Advances in Effluent Treatment for PCB Processes at Graphic”. He reviewed the evolution of chemical processes in circuit manufacture, from the simple ferric chloride etchants of the 1970s to the enormous range of metal-finishing and surface treatment chemistries associated with present-day PCB fabrication technology, and how environmental legislation had evolved in parallel over the same period. Against this background, he described how Graphic’s effluent treatment procedures had progressed since the early 1990’s when consent limits on metals, pH and chemical oxygen demand had first been introduced. Graphic had always acknowledged their environmental responsibilities and their pro-active approach had resulted in them being the first UK PCB manufacturer to achieve ISO 14001 accreditation. In the pioneering days of the 1970s, there were no trade effluent consents; rinse waters went direct to sewer and spent solutions were tankered away to landfill. When consent limits began to be enforced, compliance was achieved by separation of high-copper-concentration rinses for batch treatment, low-copper rinses being discharged to sewer in combination with rinses from other processes which effectively diluted copper content to acceptable levels. Spent solutions were treated by neutralisation and precipitation, the resultant sludge being sent to landfill. The use of BEWT cells to remove copper electrolytically from microetches and neutralisers had dramatically reduced sludge volumes and corresponding disposal costs, but a significant development had been the investment in a filter press to de-water sludge and produce a filter cake with sufficiently high metal content to make it attractive to a reclamation company with whom Graphic had formed a working partnership. In 1999, Graphic shipped their first 18 tonnes to Germany. Remarkably, and perhaps ironically, in 2000 Graphic received an award under the Devon Environmental Business Initiative effectively for exporting their waste (in the form of high-metals-content filter cake) to Europe! By this time, almost all of Graphic’s metal-bearing solutions could be neutralised and filter-pressed. The BEWT cells became redundant and were de-commissioned. A de-ionisation system was introduced which, together with recycling of rinse waters and other improvements in water management had led to annual savings of 40% in water volume and £20,000 in costs.
The final paper of the symposium was given by Tony Ridler, Senior Global Process Engineer with Rohm and Haas Electronic Materials, entitled “Embedded Passives Technology – The Future is Buried?”. Tony explained the function and purpose of passive components in electronic assemblies, the potential benefits of embedding passives within the structure of the PCB, both technical and economic, and reviewed the proprietary technologies available for fabricating embedded capacitors and resistors. On a typical printed circuit assembly, discrete passive components comprise 91% of components, 29% of solder joints and occupy 41% of board surface area. Approximately 800 Billion passive components are consumed annually at a ratio of 9 capacitors to each resistor, growing at a rate of 50% of integrated circuit consumption.
Discrete components had continued to become smaller – 0201 (0.020” x 0.010”) and 01005 (0.010” x 0.005”) formats, and their associated placement equipment, were now a reality and their introduction had delayed many designers’ decisions to consider embedded. But size reduction was not the only consideration – cost reduction, performance enhancement and reliability improvement all needed to be taken into account, together with the impact on the value chain, with value potentially migrating from the CEM to the component supplier and from the PCB fabricator to the material supplier. Tony showed a simple model of cost versus resistor density (whilst emphasising that, in real examples, the model could be very complex) which indicated that once density exceeded 2-3 components per square centimetre, the embedded option became a viable consideration. But he was frank in stating that the uptake of embedded component technology had been slower than forecast. There were still design and reliability issues to be addressed, but electrical performance requirements would probably be the long-term driver, particularly in the mobile telecom sector, and the market for embedded components could be worth $500 million by 2006.
All of the presentations were received with interest by an attentive audience, and generated some lively interactive question-and-answer dialogue.
Following the technical session, delegates were invited to visit Circast Electronics PCB fabrication plant and Cirtron PCB Services sub-contract services facility, in Leamington Spa.
Pete Starkey
ICT Council