Issue link: https://iconnect007.uberflip.com/i/1512857
DECEMBER 2023 I DESIGN007 MAGAZINE 29 erence, with a distance of 10.2 mils. e trace width required to obtain a 100-ohm imped- ance matched pair is 6.41 mils. If everything works fine, the environment will be consid- ered controlled. Because of a lack of planning, mechani- cal changes are required to make the product smaller and sleeker. e PCB stackup width must be cut in half—down to 32 mils. ese are the sort of changes that keep PCB design- ers up at night. A relatively simple change causes considerable problems in the design, especially in how these differential pairs work. Not making any changes in the PCB in terms of material, with the new thickness on the PCB, means that the trace width cannot exceed 4.226 mils. is change may also affect the required distance between the two traces to allow the correct coupling of the energy wave of each trace to allow them to work correctly and cancel any noise. In conclusion, meticulous considerations are vital when altering the PCB's physical aspects and impacting its physics. Validate material changes for their electrical properties, ensur- ing compatibility with signal propagation and impedance requirements. Evaluate the impact of shape modifications on electromagnetic interference (EMI) and signal integrity, con- ducting simulations or analyses to anticipate disruptions. Assess thermal properties to pre- vent overheating or impedance variations due to alterations. Follow industry standards and guidelines to maintain desired characteristics. Collaborate with electrical engineers and uti- lize simulation tools to predict and mitigate potential changes in impedance, signal loss, or EMI. Test prototypes rigorously to validate alterations before final implementation. Do not decide to change the shape of the PCB without considering how those changes will impact your overall PCB design, the pros and cons, and whether you are opening the proverbial can of worms. DESIGN007 John Watson is a professor at Palomar College, San Marcos, California. To read previous columns, click here. Figure 1: Details of a 62-mil PCB stackup that had to be reduced to 32 mils, potentially causing a variety of snafus.