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C O N N ECT T H E D OTS AUGUST 2025 I DESIGN007 MAGAZINE 47 • Pay attention to pinouts when using alternate vendor parts. Even if pin size and through- hole size are a confirmed match and solder joints appear sound, a part can still not work as expected. Similar parts with the same foot- print might look like they should act identi- cally, but they won't always have the same pinout. Each transistor has a gate, drain, and source, but manufacturers can differ in what goes where. Be aware of this as you select parts for your design. • Be aware of mechanical fit. It's not just the footprint and through-holes that are impor- tant. The physical size of a component can keep parts from fitting into designated spaces. MMC body size should be the rule, so pay attention to the tolerance range. To learn more about how to address each of these common causes for board failure, read my book The Printed Circuit Board Designer's Guide to…™ Designing for Reality or if you're in the car, check out the On the Line With… podcast for a deep dive into design and manufacturing. Don't be surprised to see a future article called "How to Avoid Five More Common Causes of Board Failure." DESIGN007 Matt Stevenson is vice president and general manager of ASC Sunstone Circuits. To read past columns, click here. Download Matt's book, The Printed Circuit Designer's Guide to… Designing for Reality and listen to the podcast here. Multi-wavelength light sources are required for op- tical transceivers to increase data. However, scal- ing the laser array size increases thermal crosstalk, which may affect laser efficiency and reliability. In a new study published in IEEE Journal of Se- lected Topics in Quantum Electronics, Dr. David Coenen and his team developed an experimental- ly validated thermo-optic laser model. The model is demonstrated for a case study where a transceiver with 64 laser output channels is required. To identify the configuration which is energy efficient, reliable and occupies a small area, the following input pa- rameters were studied: how many lasers can fit in one die, laser die size, output power per laser gain, ambient temperature, thermal management strate- gy and finally integrated vs. external laser. We found several interesting conclusions: there exists a clear trade-off between laser array area and overall thermal resistance. A smaller array area will drastically increase the thermal crosstalk and temperature. Furthermore, increasing the laser length allows the generation of more light per gain section and decreases laser thermal resistance. Finally, external lasers, which need to overcome fiber coupling losses, suffer at high ambient tem- peratures and have more difficulty reaching the re- quired output power. However, an advantage of an external laser is that it can be thermally decoupled from any high-power electronic chips, e.g. a network switch with co-packaged optics. These results will help designers to understand the trade-offs in la- ser array design, providing tools to evaluate the im- pact of design choices and key performance met- rics. More model validation results will be published at the CLEO conference. (Source: PR News Wire) IEEE Study Shows Thermal Scaling Analysis of Large Hybrid Laser Arrays for Co-packaged Optics