In this paper, an energy efficient streetlight for pedestrian roads is introduced. Energy efficiency is achieved via up-to-date light-emitting diode (LED) technology and added intelligence utilising integrated sensors and wireless control. Thermal and electrical design of the luminaire contributed to good technical functionality. The performance of the luminaire was validated with testing. The luminaire was compared with commercial lamp and LED-based street lighting technology by technical values and user acceptance. Energy savings of 19-44% through improved luminous efficacy was demonstrated without added intelligence. With smart control further power saving potential of 40-60% was shown depending on the lighting environment and pedestrian presence. User feedback of a pilot installation comparing commercial luminaires with the newly developed streetlight revealed that on average the users preferred the developed streetlight over the commercial luminaires.

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To improve thermal performance of high-power chipon-board multichip LED module, a copper-core metal core printed circuit board (MCPCB) substrate with copper filled microvias is introduced. As a reference, the performance is compared with alumina module with the same layout by means of thermal simulations and measurements. Up to 55% reduction in the thermal resistance from the LED source to the bottom of the substrate is demonstrated. The excellent performance of the Cu MCPCB module is due to copper-filled microvias under the blue LED chips that occupy the majority of the multichip module. The conclusion was verified by measuring increased thermal resistances of red chips without thermal vias on the Cu MCPCB module. However, as the blue LEDs dominate the thermal power of the module, they also dominate the module thermal resistance. The thermal resistance was demonstrated to correspond with the number of vias as lower thermal resistance was measured on modules with larger number of vias. The Cu MCPCB was processed in standard PCB manufacturing and low cost material, FR4, was utilized for the electrical insulation. Thus, the solution is potentially cost-effective despite the higher cost of copper in comparison with aluminum that is the most commonly used MCPCB core material.

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Evolution of lumens per watt efficacy has enabled exponential growth in light-emitting diode (LED) lighting applications. However, heat management is a major challenge for an LED module design due to the necessity to conduct heat away from the LED chip. Elevated chip temperatures cause adverse effects on LED performance, lifetime, and color. This paper compares the thermal performance of high-power LED modules made with two types of circuit boards: novel substrates based on insulated aluminum material systems (IAMSs) technology that inherently allows using thermal vias under the LEDs and traditional metal core printed circuit boards (MCPCBs) commonly used with high-power LED applications. IAMS is a thick-film insulation system developed for aluminum that cannot handle temperature higher than 660°C. The coefficient of thermal expansion of IAMS pastes is designed to match with aluminum, which minimizes any bowing. The thermal via underneath the LED enables excellent thermal performance. More than 7°C reduction in LED junction temperature at 700-mA drive current and 27% reduction in the total thermal resistance from the LED junction to the bottom of the substrate were demonstrated for the IAMS technology when compared with MCPCB. When considering only the thermal resistance of the substrate, reductions of around 70% and 50% were obtained. This versatile and low-cost material system has the potential to make LEDs even more attractive in lighting applications.

The roll-to-roll (R2R) printing process enables large-scale manufacturing of conductive wirings for the system integration of printed and hybrid electronics. As the number of R2R printed units in a run is typically high, a systematic approach is required to verify the outcome of manufacturing process extensively. This study presents a piece of automated R2R testing equipment, which is capable of the comprehensive electrical testing of printed and flexible electronics, and discusses the main findings provided by the test system in a use case of an R2R printed wiring backplane for a large-area display element. The automated R2R tester utilizes a bed-of-nails test method incorporated into the reeling equipment as a stop and go process. In this scheme, a bed-of-nails is a layout-specific test fixture providing physical contacts on the web. The actual measurement operations are performed by general-purpose electrical test equipment through standard industrial buses. Overall, the movement of the web containing printed electronics and the test operations for these are controlled by a test automation software. In this study, the R2R functional tester is utilized to evaluate the outcome of a rotary screen printing process for a large area backplane wiring of s 7×20 RGB LED matrix. The study presents the needed test cases for the full test coverage of printed wiring at an area of approximately 190 mm×405 mm in each backplane unit. As the roll length is over 150 meters, the testing process systematically produces over 100 000 resistance measurement results to evaluate the manufacturing process yield and process variations from an electrical perspective. The paper concludes the main test results, and discusses the usability of the developed testing system and the protocol in this use case application.

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