Verification of roll-to-roll printing quality for printed wiring backplanes with automated roll-to-roll electrical test equipment

Roll-to-roll (R2R) printing process enables large-scale manufacturing of conductive wirings for system integration of printed and hybrid electronics. As the number of roll-to-roll printed units in a run is typically high, a systematic approach is required to verify the outcome of the manufacturing process extensively. This study presents an automated roll-to-roll testing equipment capable of comprehensive electrical testing of printed and flexible electronics, and discusses the main findings provided by the test system in a use case of R2R printed 7*20 RGB LED matrix with 150 meters roll length.

The main parts of presented automated roll-to-roll test equipment are conveyor system, bed-of-nails fixture and electrical measurement equipment. The conveyor system is dedicated to move the web containing printed electronic structures and includes machine vision features for automatic alignment of the web and bed-of-nails. The bed-of-nails fixture is a layout-specific board assembled with wired pogo-pins to provide physical contacts from the test equipment to the printed electronics. The actual measurement operations are performed with automated test equipment including general-purpose test and measurement equipment such as LCR meter, power supplies and electronic load.

The verification of printed wiring functionality is of high importance to pinpoint the possible manufacturing defects before the component assembly and system integration. In this study, the functional tester is utilized to evaluate the outcome of R2R printing process for a large area backplane wiring of 7*20 RGB LED matrix. The study presents the needed test cases for the full test coverage of printed wiring with the area of approximately 200 mm * 400 mm in each backplane unit. As the roll length is over 150 meters, the testing process produces systematically over 100000 resistance measurement results to evaluate manufacturing process yield and process variations from electrical perspective. The paper concludes the main test results and discusses the usability of the developed testing system and protocol in the use case application.