EIPC Technical Snapshot: Updates, Methods, and Interconnections

Estimated reading time: 8 minutes

On the medical side, various PCBs with novel ALD coatings were in pre-clinical and clinical trials and ALD had already been established as a means of producing pinhole-free coatings for electro-active implants such as cardiac pacemakers.

Pudas explained that atomic layer deposition was an advanced thin-film coating method used to produce ultra-thin, highly uniform and conformal material layers for a variety of applications, using sequential, self-limiting and surface-controlled gas phase chemical reactions to achieve film thicknesses in nanometre and sub-nanometre dimensions. The film formation mechanism occurred only at surfaces, to yield a dense and defect-free film built up by consecutive atomic layers. Its thickness, structural and chemical characteristics could be precisely and repeatably controlled on an atomic scale at relatively low temperatures, allowing coating of sensitive substrates such as plastics and polymers.

A wide range of materials could be deposited, including oxides, nitrides, fluorides, carbides, and sulphides as well as metals, hybrid materials, and polymers. ALD metal-oxide coatings were being developed with ESA as replacements for organic solder masks in space applications, and to achieve effective encapsulation of low-clearance BGA and flip-chip components, as well as mitigating tin whiskers. Further applications were being explored in the medical sector. Pudas reviewed several examples and case histories, together with Picosun’s equipment and development roadmap.

Jan Pedersen: UHDI
The final presentation came from Jan Pedersen, senior technical advisor at Elmatica in Norway and recent recipient of the Dieter Bergman IPC Fellowship Award for his commitment and significant contribution to global standards development. 

Pedersen heralded a new era of complexity in the PCB industry—the concept of Ultra High-Density Interconnections (UHDI)—products with lines and spaces below 50 microns, dielectric thicknesses below 50 microns, microvia diameters below 75 microns and product attributes beyond the existing IPC 2226 Producibility Level C for HDI boards.

IPC D-33AP Task Group had been formed as a result of adding organic IC packaging substrates to IPC 1791 – Trusted Electronic Designer, Fabricator and Assembler Requirements – with the desire for a product quality standard to be listed in the quality requirements section of IPC 1791, and was initially focused on creating industry standards for IC packaging substrates.

Existing Ultra HDI structures were organic IC component packaging substrates, substrate-like PCBs (SLP) and larger-format boards with Ultra HDI layers or patches. A listing based on IPC 2226 Table 5-1 compared feature sizes from Level C through SLP, to wafer-level fan-out. Achieving the manufacturing transition from 40 micron to 20 micron line and space would require changing the technology from subtractive, through modified semi-additive (mSAP) to semi-additive (SAP) processing. Producibility levels associated with the hierarchy of existing IPC 2220-series design specifications suggested that 25% of those manufacturers currently involved in HDI manufacture to IPC 2226 should be able to develop the capability beyond Level C.

Pedersen showed cross-sections of typical IPC-2226 HDI constructions, and indicated how the feature dimensions would be reduced in Ultra HDI constructions, commenting that plated-through-holes would be eliminated because of surface-plating thickness considerations. He discussed the new UHDI feature specifications being considered by his task group: conductor thickness, thinner foil or no foil, plating thickness, laminate defect allowances, cleanliness, cosmetics and tolerances, as well as qualification and performance tests. A further challenge was decide how to allow for non-HDI structures, HDI structures and Ultra HDI structures to be used in the same product, or whether new standards should be assigned.

As may be imagined, these webinar presentations prompted an energetic Q&A session, expertly mediated by Alun Morgan and demonstrating the effectiveness of EIPC as a platform for the exchange of business and technology information in the European electronics industry. 

Acknowledging the splendid efforts of executive director Kirsten Smit-Westenberg and technical director Tarja Rapala-Virtanen in organising a very successful event Morgan announced that the next in the series would take place on October 14, and that it was hoped that a traditional EIPC conference could be organised early in 2022.

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