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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.