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48 DESIGN007 MAGAZINE I JUNE 2023 costs with little added benefit. If your com- pany intends to build hundreds of thousands of assemblies, then the potential cost saving can be quite significant. Analyzing the PDN ensures the best performance at the most cost- effective price. Many competent PCB designers will retire within the next few years leaving a void in the knowledge base. is creates a shortage of skilled and experienced PCB designers, increases the demand for new and young PCB designers, and allows for more opportunities for collaboration and innovation among PCB designers. However, the lack of manufactur- ing knowledge of the upcoming designers can cause design errors and failures, increase the design time and cost, and reduce the manufac- turability and yield of the product. Experience is the best teacher of all. PCB designers need to have more knowledge and skills to design PCBs that have high signal integrity, power integrity, thermal perfor- mance, and electromagnetic compatibility. PCB designers must understand the principles, methods, and tools for analyzing and optimiz- ing all aspects of PCB design. Key Points • PCB designers must deal with various issues in finding the right balance between the form factor, functionality, and power requirements of their boards. • BGA pitches of 0.5 mm and lower are becoming more popular. • 0.3-mm ultra-fine pitch BGAs and increased functionality within the same package are the next generation. • Currently there are no formal IPC design guidelines or layout rules specifically tai- lored to supporting 0.3-mm pitch devices. • Blind microvias and vias-in-pad are normally required for the breakout of 0.5 mm pitch or less. • Accommodating the high number of individual power supplies to the BGA is also an issue. • e increased data rates also require more complex modulation schemes for data encoding, such as non-return-to-zero (NRZ) to pulse amplitude modulation 4-level (PAM4) encoding. • e impedance should be simulated by a field solver to obtain accurate values of impedance for each signal layer of the substrate. • Flight time delay and skew are the key pillars in high-speed PCB design signal integrity. • e integrity of the PCB stackup and the PDN are the basis for a stable product. • e lower core voltages of today's proces- sors require higher currents and faster edge rates. • e effective impedance of the PDN should be kept below the target impedance up to the maximum required bandwidth. • If the impedance is too far below the target, then this implies that the PDN has been overdesigned which unnecessarily increases costs with little added benefit. DESIGN007 Resources • Beyond Design by Barry Olney: "Fly-over Tech- nology: When It All Gets Too Fast," "Signal Integrity (Parts 1 & 3)," "The Target Impedance Approach to PDN Design." • AM57xx BGA PCB Design, Texas Instruments. • "Metric Pitch BGA and Micro BGA Routing Solu- tions" by Tom Hausherr. Barry Olney is managing direc- tor of In-Circuit Design Pty Ltd (iCD), Australia, a PCB design service bureau that specializes in board-level simulation. The company developed the iCD Design Integrity software incor- porating the iCD Stackup, PDN, and CPW Planner. The software can be downloaded at www.icd.com. au. To read past columns, click here.