EIPC Technical Snapshot: Automotive Technology

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In his example, the LED package had a coefficient of thermal expansion (CTE) of 10 ppm/°C, whereas that of the aluminium base was 23 ppm/°C. The CTE mismatch was reduced by using a low-CTE aluminium alloy (19 ppm/°C), and the dielectric was re-formulated to lower its elastic modulus so that it effectively became a compliant inter-layer. An additional benefit of the re-formulation was to increase its maximum operating temperature to 155°C. The outcome was that the modified IMS material enabled the LED headlight to exceed 3,000 thermal cycles without failure.

The final presentation, entitled “Today’s Multilayer PCB Requirements for the Automobile Industry,” came from Multiline International Europa Managing Director and EIPC Board Member Paul Waldner. He also used a see-through motor car illustration to demonstrate the extent to which numerous electronic systems had become fundamental to the operation of the vehicle.

This time the focus was on how the automobile sensed its environment and how it would need to become increasingly networked: vehicle-to-vehicle, vehicle-to-cloud, vehicle-to-infrastructure, vehicle-to-pedestrian, vehicle-to-road-sign, and vehicle-to-drone. He remarked that tomorrow’s automobiles would incorporate many elements of industrial development.

1Paul_Waldner.jpgInputs, processing, and outputs would be controlled with a high-performance server, and high-frequency PCBs would be an essential requirement for vehicle radar and lidar and for supporting ultra-fast communications. There was a convergence of technologies in multilayer PCB requirements for the communications, military, and automobile industries because of the signal-speed requirements of 5G communication networks and distance-to-hazard sensing in the development of autonomous vehicles. PCBs for future automobiles would require high circuit density and high layer counts with different materials—some of which would demand very high lamination temperatures. High reliability was fundamental.

Waldner considered that there were three necessities for managing the technology convergence: better pressing technology, better layer to layer registration of multilayers, and better signal integrity for high-speed circuits. He discussed the principles and details of a proprietary lamination press, with induction heating offering uniformity of temperature throughout the stack and the benefits of accurate control of parameters and low power consumption. Although the four-slot tooling system had been established for many years, he believed that it still offered many advantages, particularly when laminating mixed materials with different expansion coefficients.

And regarding signal integrity, the track geometry of fine-line designs could be controlled to precise limits with a proprietary modified semi-additive process using an ultra-thin palladium catalyst layer to initiate electroless copper deposition. His example showed 20-micron traces on a 50-micron pitch with a square cross-section.

A question-and-answer session followed the presentations and raised points for discussion on the subjects of stacked microvia reliability, SAC alloys for automotive applications, and high-frequency challenges, to which the experts responded readily. Emma Hudson did a skillful job of moderating the session and keeping the whole proceedings within the scheduled one-hour time slot. Thanking the speakers for their contribution and the audience for their attention, she announced that further technical snapshot webinars are planned for November 18 and December 19.


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