The Institute of Circuit Technology Autumn Seminar

Estimated reading time: 10 minutes

Apart from the obvious advantages of bridging the supply-demand gap and reducing Europe’s dependence on global PGM supply chains, the PLATIRUS Project offered potential benefits in reducing energy costs and environmental impacts as well as providing solutions requiring lower capital investment than centralised refineries and maximising the exploitation of local waste sources. The work of the PLATIRUS Project was due to be completed and the final report published in October 2020.

Frank Ferdinandi, director of Azurion Technology described an environmentally friendly surface finish for PCBs, which was effectively an ultra-thin fluorochemical conformal nano-coating deposited and polymerised in-situ by a plasma process. Where the coating was deposited on copper, it offered long-term protection against oxidation, but the copper remained solderable by standard techniques. Elsewhere on the PCB, it provided a durable waterproof finish. Ferdinandi showed samples of boards coated more than 10 years previously, using an early version of the finish. The copper remained bright and tarnish-free, but still easily solderable. There had been a programme of continuous development, and the current finish represented the third iteration.

Ferdinandi explained that the new technology outperformed existing surface finishes in key areas and provided major advantages for PCB protection and post-processing. Its functional benefits included excellent long-term protection against oxidation together with a solder-through capability compatible with current reflow processes for lead-free and leaded solders. After soldering, its non-wetting properties across the complete surface gave circuits increased resistance to aggressive environments, resulting in longer product life with no rework issues. A major environmental benefit was that since no water was used, the effluent associated with traditional surface coating processes was eliminated and health and safety issues were significantly reduced. Plasma deposition was carried out in a single chamber, and in-situ cleaning was possible. The system could be semi-automated for high throughput.

Solderability, solder joint reliability, and electrical properties had been extensively studied and compared favourably with immersion silver, HASL, OSP, ENIG, electroplated nickel-gold, and immersion tin. Although previous commercialisation programmes had shown only limited success, there was currently renewed interest—particularly from China—where the opportunity to reduce water consumption was especially attractive.

The team behind Rainbow Technology Systems introduced a specialised surface-cleaning technology to the printed circuit manufacturing industry over 30 years ago. Their system of contact sheet-cleaning and web-cleaning solutions, based on rubber pick-up rollers lifting minute particles from surfaces and transferring them to an adhesive roll, became the industry standard. David Westwood, Rainbow’s sales and marketing manager, explained how this proven technology maintained its relevance and impact in the advancement and development of ultra-fine-line circuitry.

Aided by a series of animations, and frequently wielding a small hand-held pick-up roller and a pad of adhesive sheets for dramatic effect, Westwood demonstrated the potential effect of dust-related imaging defects on manufacturing yield. His illustration of typical dust and debris on a design of the 1980s with 300-micron track and gap included particles varying in size, including 75–100 microns, 50 microns, 25–30 microns, and down to 15 microns. At this level of design rule, even if the efficiency of cleaning was only 98%, any issues associated with the remaining 2% could be touched in by a skilled operator with a steady hand. It’s not so for current designs with track and gap trending towards 15–20 microns!

The KSM Superclean division of Rainbow Technology Systems had stayed ahead of the technology and was confident that contact cleaning remained the most effective method of removing debris from surfaces. Roller and adhesive technologies had been developed that enabled greater efficiency of cleaning to 99.9% at finer particle sizes down to the 0.5–3-micron critical levels. Harder rollers were available with precision surface finishes, silicone-free, and static-dissipating. And the adhesive rolls were based on clean-room film materials. Westwood believed that contact cleaning would continue to be the most effective means for the permanent removal of surface debris as design technology progressed from fine-line to ultra-fine line.

Cobley brought the seminar proceedings to a close, thanking the audience for their attention and the presenters for generously sharing their knowledge. A special thanks went to Bill Wilkie for another superbly organised learning and networking event.

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