Day 1: Cutting Edge Insights at the EIPC Summer Conference

Estimated reading time: 15 minutes

The European Institute for the PCB Community (EIPC) Summer Conference took place this year in Edinburgh, Scotland, June 3-4. This is the second of three articles on the conference. The other two cover the keynote speeches and Day 2 of the technical conference. Below is a recap of the first day’s sessions.

Sustainability and Recycling

The technical program began with a session on sustainability and recycling, moderated by EIPC treasurer Emma Hudson, who introduced Chris Klok of MacDermid Alpha Electronic Solutions in the Netherlands described the CIRC-UITS project, a three-year initiative funded by the European Union with a consortium of 20 partners, designed to enhance sustainability and circularity in the European electronic components industry, particularly within the automotive and mass electronics sectors.

Klok reviewed the projects’ objectives: to provide new design and manufacturing practices, improve the electronics circularity level, and reduce the dependency of European electronics-related sectors on extra-EU supplies. The project aims to increase resource efficiency and independence, reduce the negative environmental footprint of electronics manufacturing processes, adopt the circular-economy paradigm in the automotive sector, improve the sharing, exchange, and standardization of information and data between industry leaders in similar value chains, and demonstrate the practical benefits of reusing and re-manufacturing semiconductors and electronic components through four pilot projects.

The first pilot supports the development of an environmentally friendly electronic control unit; the second supports the development of new-generation tire sensors; the third supports the development of embedded circuits; and the fourth improves the classification and storage of obsolete printed circuit boards from various electrical and electronic circuits.

Klok discussed the details of these pilots and reviewed their progress. One partner is assessing the possibility of disassembling and repairing electronic stability program equipment, while another has designed two new tire pressure monitoring systems following eco-design logic. Two partners are assessing the eco-design and repairability of in-mold electronic prototypes, while another two partners are assessing new sorting procedures for automatic obsolete PCB selection. In addition, one partner is supporting all four pilots by designing, implementing, and testing new AI-based PCB disassembly procedures, enabling the reuse of specific semiconductors de-soldered from samples supplied by each pilot leader.

Klok focused on the added value of materials, with particular reference to replacing SAC305 solder with low-temperature solder and replacing electroless copper with carbon-based direct metallization. Test vehicles are being built for assessing silver, dielectric, and carbon inks as materials for in-mold electronics.

Recyclable Liquid Metal

Xiaochuan Fang, research associate at the University of Glasgow, opened his presentation on sustainable, fully recyclable liquid metal PCBs for wireless applications by asking: “Are PCBs sustainable?” He stated that PCB assemblies contain critical raw materials, and their manufacture consumes valuable resources. He indicated that PCB assemblies contain critical raw materials and that valuable resources are consumed in their manufacture. Manufacture of active components results in high carbon emissions. He cited a 90nm integrated circuit, with a CO2 equivalent of 7kg (15.4 lbs), as an example; barely any waste electrical and electronic equipment (WEEE) gets recycled. Furthermore, most existing “green” PCB circuits made of sustainable materials are not suitable for wireless applications, and there are no reports of recycling in such applications.

He described how to implement sustainable PCBs and discuss antenna and circuit fabrication techniques. In his example of the fabrication of a functional circuit assembly, the substrate is formed by 3D printing of polylactic acid, and the tracks are filled and interconnects made using Galinstan, a eutectic alloy of gallium, indium, and tin, which is liquid at room temperature.

At end-of-life, the recycling process involves soaking the assembly in 10% sodium hydroxide at room temperature, which degrades the polylactic acid, enabling the recovery of the components and the liquid metal.

Fang showed examples of various fabricated PCB assemblies, including power amplifiers, voltage control oscillators, and broadband monopole antennas, and demonstrated the capability to recover their materials with less than 2% total waste at a cost of less than £1.10 ($1.49) per circuit. The repeatability of recycled antennas has been quantified, with less than 0.15 dB/cm attenuation of transmission lines after more than nine cycles.

Next-gen Electronic Assemblies

Kunal Shah’s presentation was titled: “Sustainability and Circularity are Key Parameters for Chemistry Choices for Next-generation Electronic Assemblies.” Shah described LiloTree’s cyanide-free, nickel-free alternative gold finish for PCBs. The chemistry he is promoting produces a 50- nanometer layer of gold on a nano-engineered barrier-layer treatment on the copper surface. The process is cheaper to run than ENIG and provides more reliable results, in addition to its environmental benefits.

Because the brittle nickel layer is eliminated, solder joints are made directly to copper, via a tin-copper rather than a tin-nickel intermetallic, and are stronger, with a higher force-to-failure on a solder-ball shear test. An additional benefit is the freedom from possible nickel-bridging on ultra-fine-line work.

Shah highlighted concerns around E-waste, which amounts to 70 million tons globally per year. Of this, only 20% is recycled; the remainder is either burned or sent to landfill. Landfill disposal is already prohibited in some U.S. states. Gold mining is a potentially highly toxic process, and one ton (2,000 pounds) of ore typically yields one gram of gold, whereas one ton of E-waste could yield 300 grams (10.6 ounces) of gold— an incentive to develop efficient recovery techniques. Wwhat about spent gold deposition processes and gold-bearing rinse waters? LiloTree has developed efficient electrolytic recovery systems, which further contribute to the principles of sustainability and circularity.

From Microvias to Medical Implants

Martyn Gaudion, CEO of Polar Instruments, moderated the session, “From Microvias to Medical Implants: Materials and Processes Enabling Tomorrow’s Technologies.” The first presenter was Vasco Duarte da Costa, R&D engineer at Dyconex in Switzerland, with a paper on Advances in Biocompatible Substrate Technology for Neurological Implants.

Traditionally, electrodes are prepared by labor-intensive manual methods, attaching cables to electrodes, pulling the cables through a tube, and attaching them to a connector. The question is how to transition from wires to substrates, to minimize invasiveness, make devices smaller, improve the precision and resolution of measurement, reduce the production cost with fewer manual steps, and improve the quality.

In 2016, Dyconex and Duke University made the first fully biocompatible electrode— a liquid crystal polymer (LCP) grid array with 256 electrodes of 75 micron diameter at 750 micron pitch and a pure gold surface. This proved to be a reliable implant for up to 12 months, and Duke University published the results in 2018. 

Why was LCP chosen as the alternative to traditional polyimide film? Da Costa listed the benefits, the main one being that LCP is thermoplastic and can be thermoformed and laminated, or fusion bonded without adhesives. It has low water absorption and permeability, together with superior barrier properties for gases. These attributes make it a suitable biocompatible insulator.

A downside is its limited adhesion properties to sputtered metals, requiring special treatment and design considerations. Otherwise, LCP can be processed in the same production line with the same equipment as polyimide film.

Conductors in contact with the human body need to be made in noble metal, typically electroplated gold on a palladium seed layer. Inner layer conductors can be copper. A gold surface is acceptable for short-term exposure, but a platinum coating is preferred for extended exposure. Silver/silver chloride can be used for reference electrodes.

Da Costa demonstrated the  level of routing complexity that could be achieved: sequential construction with blind vias, up to six independent conductor layers, 50-micron vias, and feature sizes less than 50 microns. He showed examples of cylindrical forming, flex-to-flex bonding, and LCP encapsulation. His final illustration showed a complete, fully flexible, biocompatible LCP electrode.

Enhanced Copper Plating Performance

Copper plating has come a long way since the buckets, rubber aprons, and Wellington boots of my youth.

Gustavo Ramos, senior director of global sales and service at Greensource Engineering, explained how to enhance copper plating performance with a novel high-efficiency plating system. Reviewing the benefits and limitations of existing technologies, he shared that vertical plating is the traditional methodology, enabling the batch processing of multiple panel sizes with a large plating window and flexibility for multiple batch types. Soluble anodes are used, and process times are characteristically long. Vertical continuous plating improves uniformity over standard methods, with continuous panel movement through plating baths with insoluble anodes. Various configurations are available, offering touch-free handling of ultra-thin panels and high-density designs.

What is the justification for a new plating tool? Standard vertical plating suffers from high variability in copper thickness due to the large window. It has limited ability to handle ultra-thin panels; it is labor-intensive, and maintenance-heavy. Vertical continuous plating equipment has constraints in panel size and product mix and occupies a large footprint.

Ramos’ proposed solution is modular in concept, with precise plating control at the single-panel level. It has fully automated, touch-free handling and offers advanced horizontal fluid delivery in a vertical mode. It takes a holistic approach to vertical wet processing by integrating rinsing as a critical process step, combining positive and negative-pressure rinsing for superior solution exchange in complex features. Roto-molded tanks with integrated sumps prevent leaks and contamination, improve fluid dynamics and sump control, and bring efficient horizontal fluid delivery into a vertical system design. Altogether, it offers a flexible and controlled plating process.

Ramos described the details and main characteristics of the plating cell design, which features high current density capability, together with vertical and lateral variable-frequency-drive-controlled panel agitation for improved distribution, mixed-metal-oxide coated titanium anodes, and remote copper oxide replenishment.

He described details of the fluid delivery system and the panel-holding and agitation system. Similarly, the cleaner and pre-dip processing cells and the rinsing technology are all designed with customers’ wastewater systems in mind.

Ramos’ microsection photographs of high-aspect-ratio blind microvias illustrated the superior performance of the integrated process.

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