ZHCU623 January   2019

 

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4.3 PCB Layout Recommendations

The layout for the flex PCB patch was done on a two-layer board, with the intention of maximizing overall board flexibility. Higher numbers of layers will likely limit the bending radius of the board and affect wearer comfort. Since the primary goal of this design is temperature measurement, the tech note Layout considerations for wearable temperature sensing (SNOAA03) provides a concise summary and explanation of many of the techniques employed. For general recommendations for flex PCBs, designers should consult with the desired manufacturer of their flex board. These boards are extremely thin, therefore they can be sensitive to heat applied during the process of soldering or reflow. It is important that this aspect be considered to minimize potential damage to the board traces. If reliability is a concern, consider applying a semi-rigid design form factor by applying a stiffener to the back of the active portion of the board.