2020 EIPC Winter Conference, Day 2
Editor’s note: Read Pete’s recap of the 2020 EIPC Winter Conference, Day 1, here.
Rested and refreshed, delegates returned to the conference room for the second day of the 2020 EIPC Winter Conference in Blijdorp, Rotterdam, South Holland. The first session on new technologies and design was moderated by EIPC board member Martyn Gaudion from Polar Instruments. He was delighted to welcome back Dr. Despina Moschou, assistant professor at the University of Bath in the U.K., for her update on recent developments in the design and manufacturing of lab-on-PCB devices.
Dr. Moschou gave a brief introduction to the University of Bath—a centre for biosensors, bioelectronics, and biodevices, developing technologies to improve biomedical diagnosis, environmental monitoring, industrial bio-processes, and the understanding of biological functions. “Lab-on-chip technology is no longer science fiction; it’s actually happening!” She drew a parallel with the progress of the development from the old fashioned computer to present-day “system-on-a-chip” integrated circuits.
The lab-on-chip micro-total-analysis-system (μTAS) offered unique advantages in miniaturization, low reagent volumes, rapid analysis time for early detection, together with automation and portability. But economic manufacture of integrated smart microsystems on silicon relied on economies of scale, and there was no established commercial manufacturing technology. The lab-on-PCB approach had emerged as a very strong candidate, owing to its inherent upscaling potential: the PCB industry being well-established world-wide, with standardised fabrication facilities and processes.
Many material and process options were currently available commercially, and prototypes compatible with lab-on-chip dimensions and requirements had been demonstrated for various applications. Dr. Moschou showed many examples of lab-on-PCB devices and reviewed some of the challenges that had been encountered and overcome. The concept was truly cost-effective in mass production, and work was continuing on standardization and engagement.
Jean-Paul Birraux, sales and marketing manager for First EIE in Switzerland, discussed direct imaging, versatile automation, and data format management, remarking that First EIE had more than one thousand installations of imaging equipment worldwide. He referred to the acquisition of the company in 2015 by Inspec in Japan, commenting that the strong synergy and complementary product portfolio extended their range from imaging to include automatic optical and visual inspection, automation, and roll-to-roll technology.
Birraux went on to describe First EIE’s latest CFX-compliant direct imaging system, which could be configured in several configurations from a single stand-alone machine to a fully automatic line. They continued to use their proven mercury UV light source, which gave a full spectrum from 350–465-nanometre wavelength. The system was capable of accepting all data formats and resolving 20-micron features. A new glass-mask-imaging system had been developed, capable of resolving 15-micron features on large-format chrome masks for applications including LCD, TFT, OLED, and touch panel manufacturing.
Hans Fritz, owner of SAT Electronic in Germany, described a new innovation for PCB registration improvement developed by InPeKo and launched at productronica 2020: a multilayer ultrasonic welder. With videos, he demonstrated how two cameras detected layers and prevented incorrect layer build-up. Accuracy was better than 10 microns. There were four welding heads, and the actual welding process took less than one second for stack heights up to 9.5 mm. The very small weld area saved space on the outer border of the layer, which could be as narrow as 6 mm. The major benefit of the ultrasonic welding process was that heating was very localised, generated only in the prepreg. Therefore, there was no thermal distortion of the material beyond the welding point. An added capability was “aufslippen,” meaning that prepreg could be welded to the external surfaces of the stack if necessary.
The concept of the machine was flexible and modular, with options from semi-automatic to fully-automatic, and it could be adapted to provide customer-specific solutions. In its standard format, it could handle panel sizes from 500 x 330 mm to 700 x 800 mm with real-time control of temperature, time, and energy.
The final session, on manufacturing technologies and new processes, was moderated by EIPC board member Oldrich Simek, owner of Pragoboard in the Czech Republic, and his first presenter was Joan Tourné, CEO of NextGIn technology in the Netherlands.
Tourné explained the concept of “vertical conductive structures” (VeCS) as a means of increasing the efficiency of high-density interconnect in terms of increasing the connection density, simplifying the laminating process, and reducing signal distortion. He clearly demonstrated the principles using X-ray and microsection photographs of actual VeCS interconnections.
There were two classifications: VeCS 1 used all through-slots, and VeCS 2 used multiple depths of blind slot. In either case, the slots were formed by routing or peck-drilling, then metallised and plated, then drilled over-size at intervals to leave a series of vertical conductors on the walls of the original slots. Tourné stressed that any board shop with the capability to produce high-end circuits could manufacture VeCS with no additional investment in equipment or process.
Tourné showed many examples of VeCS designs, discussed how detail process improvements had been made, and reviewed the results of reliability testing. He explained how VeCS 2 could be used to produce separate circuits on top and bottom of the panel to increase density and make better utilisation of routing space without vias penetration through the board with no sequential lamination being required. Connections could be created for power-hungry power and ground applications, and stubless connections made to internal layers without back-drilling. He acknowledged the development and evaluation work carried out in China by WUS PCB on real-life products.
Horizontal plating lines have been in operation for many years, but traditional transport systems are not ideal for the thinner panels and delicate fine-line photoresist patterns associated with modified semi-additive processing (mSAP) and advanced modified semi-additive processing (amSAP) technologies. Atotech had recognised the need to develop a non-contact transport system to handle these challenges, and Global Product Manager Mustafa Özkök described the features of their latest horizontal copper plating equipment.
In their new system, mechanical damage to fine pattern features was avoided by using fluid streams instead of wheels to guide the panel and to support it between the anodes, so that the pattern area of the panel had no contact with any mechanical components. Özkök showed a video to demonstrate the system in operation. The clamping mechanism for providing cathode connection had been redesigned to avoid panel bending and optimise transportation. Further, the latest pulse plating technology has been incorporated, and the software and control system was ready for Industry 4.0 integration. The patented anode design gave very uniform plating distribution.
The equipment could be configured for panel plating, mSAP or amSAP processing, and Atotech had developed appropriate specialist chemistry and a new copper electrolyte. Özkök explained the principal process differences between mSAP and amSAP. The sequence for mSAP was to use a substrate with very thin copper cladding, less than 5 microns, electroless copper approximately 0.4 microns, followed by 1–3 microns strike copper plate, photoimaging, pattern plating with blind-microvia filling, then resist stripping and differential etching to achieve line and space of better than 30 microns. amSAP followed a similar sequence but with thinner substrate copper, typically 3 microns, and relied on heavier electroless copper, up to 1 micron, so that strike plating could be eliminated. Better than 20 microns line and space could be achieved with amSAP, and it gave better capture-pad cleanliness. Özkök showed microsections of blind microvias produced in the new equipment with the new copper electrolyte. The first installation of the new system had been completed, and qualification was ongoing at a customer in Europe.
Excessive heat is increasingly a major cause of failure in electronic assemblies, especially those with high power electronic devices, and system reliability can be critically dependent on efficient thermal management. Mike Tucker, field applications engineering manager for Kinwong Electronic, gave a comprehensive review of thermal management solutions using PCBs. He first discussed options based on FR-4 PCBs: thermal vias, copper coins, and metal cores, then explored those based on insulated metal substrate (IMS) PCBs: metal-clad PCBs (MCPCB), copper-base pedestals, and flexible IMS PCBs.
Tucker demonstrated the effect of hole-wall copper thickness on the efficiency of thermal vias, and explained how selective plating methods could be used to increase the hole-wall thickness and hence improve heat dissipation. Copper coins of various shapes could be embedded inside FR-4 boards to act as efficient local heat sinks. Alternatively, a metal core could be incorporated between the inner layers of an FR-4 board and used not only for lateral heat spreading but optionally as a bus-bar for high-current applications.
Insulated metal substrates were widely used for heat dissipation, the simplest construction being a single-layer circuit etched on a copper-clad, aluminium-based IMS. Tucker showed examples of more complex multilayer interconnects on IMS, and some typical design rules. When the metal base of the IMS was copper rather than aluminium, copper-base-pedestal techniques could be used for heavy-duty LED lighting and power-train systems, enabling the heat-generating component to be soldered directly to the copper base to give a shorter heat dissipation path with less thermal resistance. Flexible (probably better termed “bendable”) IMS substrates with good thermal characteristics could be formed into three-dimensional shapes after assembly.
Heiko Lang, sales director of the electronics business unit in the Schmid Group, introduced the company’s “Green Fab Concept” on behalf of his colleague Laurent Nicolet, who was stranded Hong Kong as a consequence of coronavirus. He remarked that global development was revealing new challenges for the PCB and substrate industry. 5G, embedding, high-frequency and high-power applications, and new materials were pushing the industry in the direction of the integration of new processes and production solutions.
Schmid’s objective was to work toward increasing technical capabilities but with a green approach and an optimized cost structure. They had recognised technical challenges in general process technology, particularly in metallisation, subtractive mSAP, SAP, and embedded traces in production concepts, such as automation and greener production, design requirements, and new materials. The company’s development was all driven by intensive cost analysis because only by efficient process technology could they offer added value to their customers. They had carried out in-depth research on chemical consumption and utility data in cooperation with customers and chemical suppliers.
For example, Lang discussed in detail was their modular in-line plasma system for touch-free, simultaneous single-sided or double-sided vertical processing of high-end PCBs and IC substrates. The system could be configured flexibly by combining etch and sputtering process modules. The first installation was running successfully in Switzerland. Compared with traditional permanganate wet-processing, it had been demonstrated that the system could make savings of nearly 80% in electricity consumption, 70% in water consumption, 46% in chemical consumption, and reduce CO2 emissions by 35%.
Their wet process lines for mSAP technology offered higher flexibility, higher yield, and substantial improvements in the total cost of ownership. Their high-end vertical process line had the capability to run thinnest flex-material down to 25 mµ touch-free. And all of Schmid’s equipment was Industry 4.0 ready and capable of being integrated and automated.
At the conclusion of the conference programme, Alun Morgan made his closing remarks, once again acknowledging the support of the sponsors, thanking all of the speakers for so generously sharing their knowledge and experience, the moderators for keeping good time and good order, and the delegates for their interest and attention.
Particular thanks from all present went to EIPC Executive Director Kirsten Smit-Westenberg and Project Manager Carol Pelzers for their flawless organisation and administration of another immaculate event.
The 2020 EIPC Summer Conference will be June 16–17, 2020, in Sweden.
As ever, I am extremely grateful to Alun Morgan for allowing me to use his photographs.