EIPC Winter Conference 2023: Day 1 Review

Estimated reading time: 18 minutes

Surface Finish Conductivity
Morgan next introduced Dr Kunal Shah, president of LiloTree, who offered recommendations on achieving optimum signal integrity at 5G millimetre-wave frequencies using a novel nickel-free surface finish for PCBs. The process he described was cyanide-free, halogen-free and compliant with RoHS and REACH directives. 

Shah reviewed the causes of insertion loss on high-frequency PCBs and indicated a correlation between conductor loss and the selection of surface finish. Electroless nickel immersion gold is a commonly used finish, characterised by long shelf life and low surface roughness, but the low conductivity of nickel has an adverse effect on insertion loss. Moreover, electroless nickel is associated with hyper-corrosion issues and brittle solder-joint failures. 

Of the alternative finishes available, immersion silver has limited shelf life and poor corrosion resistance, and direct immersion gold, electroless palladium immersion gold, and electroless palladium autocatalytic gold show concerns in terms of higher insertion loss and brittle solder joints; they are not cost-effective at higher precious metal thicknesses. 

Shah introduced a novel nickel-free surface finish: 50 nanometres of cyanide-free gold on copper treated with a nano-engineered barrier layer. This enables robust solder joints with thin and distinct intermetallics. The finish is cost effective because of its significantly lower thickness of gold than the alternative nickel-free finishes mentioned. 

The nano-engineered barrier layer on the copper surface prevents diffusion of copper into the gold, leaving the surface corrosion-free even after six reflow cycles, and the finish shows insertion loss equivalent to bare copper. It has been exhaustively tested and confirmed as a high-reliability finish for high-frequency applications.

Dry Phase Patterning
“And now for something completely different,” Morgan said as he introduced Dr. Roland Bejjani from DP Patterning in Sweden, who has a novel process for volume production of simple flexible circuits without chemical etching. Dry Phase Patterning is a mechanical reel-to-reel process and the self-contained unit is designed to be used in-house and integrated with final assembly, as an alternative to relying on sub-contract suppliers. It has particular appeal to manufacturers in the automotive, LED lighting, and RFID sectors, simplifying the production process, reducing lead times and transport logistics. Because there is no chemistry involved, waste management is simplified. 

The basic imaging tool, known as a cliché, is made in the form of a metal roller on standard equipment well-known in the printing industry. A web of flexible material—Bejjani’s example was single-sided 18 micron copper on 50 micron polyimide travelling at 10 metres per minute—is passed between the cliché and a milling wheel that mechanically removed the protruding pattern from the copper layer, leaving the required conductor pattern at a resolution of 100 microns, while the dielectric layer remains untouched. 

Dry phase patterning technology can also be used for the texturing of metallic films by alteration of micro-topography, as well as for various non-electronic and non-conductive applications. 

Smart Technology
The session on new process technology and Smart manufacturing was moderated by Emma Hudson from EHTC in the UK. Her first presenter was Philip Johnston, CEO of Trackwise Designs, also in the UK, who added a further dimension to the technology of flexible circuit fabrication with his paper on “Length-agnostic FPC manufacturing.”

What was meant by length-agnostic? Trackwise has established the unique capability to produce multilayer flexible printed circuit boards of any length, the ultimate length being governed only by the availability of suitable material. Their proprietary technique is based on roll-to-roll processing and digital imaging. Developments in software have given them the capability to produce non-repeated and non-separated images.

Trackwise’s key markets are the automotive, aerospace, medical,  scientific, and industrial sectors. In automotive applications, flexible PCBs are suited to electric vehicles in battery modules, battery packs, and battery management systems. Examples with copper weights of six ounces are capable of carrying high-voltage power. In aerospace, large-scale flex (LSF) offer a 70–90% weight reduction in data cables and 10–20% weight reduction in power cables. They can be used for fuselage-length or full-wing-width interconnects and are qualified for high temperature operation in harsh environments. At the other end of the scale, long, ultra-flexible and finely etched printed circuits have become key enablers for catheter-based distal electronics, with tracks and gaps as small as 50 microns.

Trackwise has established the capability to carry out roll-to-roll assembly, giving the potential for active interconnect, Smart harnesses, and flexible hybrid electronics. 

CAM and AI
Hudson next introduced Claudio Bellistri, European business manager for KLA-Orbotech in Belgium, who discussed CAM-based analytics using machine learning and artificial intelligence in the context of the Smart PCB factory. Building on their background of experience in front-end manufacturing processes and CAM reference technology, KLA’s software gives easy access to visual analytics that enable quality issues to be addressed proactively and rapid corrective action to be taken. 

The system is capable of merging cross-departmental data and CAM-based analytics, and can be connected seamlessly to multiple machines and vendors, across numerous sites and hundreds of connected machines.

It offers a one-stop solution for electrical testing and AOI, with the facility to view comparative data to identify potential root causes. Defects are shown on the selected CAM feature to make analysis easier and an interactive defect gallery offer a large reference album of images and videos. The distribution of repeated defects and the number of repetitions are available to view on multiple panels, and data can be shared and exchanged with third-party software.

Automation
The final presentation in the session on new process technology and Smart manufacturing was given by automation specialist Frank Tinnefeld of ASS Luippold in Germany. His talk, “Smart Factory Solutions,” described an impressive range of automated tasks in printed circuit manufacture, from simple economic solutions to complex and customised automation.

Tinnefeld’s portfolio includes base material logistic and work-in-process storage solutions using automatic guided vehicles and autonomous mobile robots, wet processes, exposure and AOI processes, inner-layer production solutions, multilayer flash cutting and edge bevelling, panel stacking, and pinning, as well as outer-layer production solutions, horizontal and vertical galvanic processes, solder mask, and final clean. 

He commented that there are still many companies relying on manual handling to transfer product from one process to the next, and this could result in many disadvantages in addition to potential handling damage. These include order confusion and searching for specific orders, downtime due to operator unavailability, and low to no traceability. 

New production philosophies will enable the realisation of targets like 100% product and process traceability, lead-time reductions by inline production wherever it is useful, automation wherever it is useful, intelligent work-in-process storage solutions with fully automatic interconnection between different process clusters, Smart production planning solutions with the elimination of manual data input and paper travellers, product tracking at all processes, and interface integration for the connection to Smart MES or ERP platforms.

Tinnefeld showed a series of examples of actual projects that have been realised, for example, direct connection of a material-logistic system with the pre-clean process, a loading station for sequential build up technology panels with integrated paper recognition, copper and panel thickness control, and DMC laser printing. 

Other realised projects include an inner-layer production setup with 100% order tracking and an example of process connection possibilities by the integration of work-in-process storage solutions and automatic guided vehicles. 

Inkjet Techniques
The afternoon session, moderated by John Fix, manager and director, marketing and sales at Taiyo America, focused on additive manufacturing and new materials. The first speaker was Bas Le Grand, process development engineer with SUSS MicroTec in the Netherlands, who explained that control on solder mask thickness can be made easy using inkjet techniques. 

Having briefly reviewed the main characteristics of inkjet technology in solder mask imaging, he detailed the process sequence, commencing with front-end data input. 

Once the PCB design data is loaded, the user has the opportunity to input board properties, ink properties, and pre-treatment properties, then to select the fiducials and their detection method, followed by the layer properties for the respective copper layer, solder mask layer, and drill layer—and finally to compensate for droplet size and flow out before calculating the required print layers. 

The encrypted production files are then ready to export to the inkjet printer. They are compatible with multiple printers, and data for a particular PCB is selected by barcode.

The versatility of the system enables the thickness of the solder mask deposit to be varied locally as required by the particular design: none, thin, medium, or thick, wherever it is needed.Page 3 of 4

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