Issue link: https://iconnect007.uberflip.com/i/1530269
DECEMBER 2024 I DESIGN007 MAGAZINE 47 When designing a PCB stackup, several important considerations must be made to ensure proper functionality, signal integrity, and manufacturability 1 . 1. Consider factors such as signal density, power distribution, and noise isolation. 2. Allocate power and ground planes to pro- vide a stable, low-impedance power distri- bution network. 3. Maximize ground plane size to reduce noise, improve signal quality, and facilitate thermal dissipation. 4. Place decoupling capacitors near power and ground plane pairs to suppress high-frequency noise and provide clean power to components. 5. Plan the arrangement of signal layers to minimize signal degradation and maintain good signal integrity. 6. Proper layer ordering, impedance control, and controlled dielectric constants are cru- cial for managing signal integrity issues such as crosstalk, signal reflections, and impedance mismatches. 7. Minimize EMI through careful placement of signal and power planes, using shielding layers if necessary, and use proper ground- ing techniques. 8. Determine the order of signal layers to min- imize crosstalk and ensure efficient routing. 9. Grouping high-speed signal layers and separating them from low-speed layers can help manage signal integrity. 10. Design the stackup with controlled imped- ance for critical high-speed signals. 11. is involves calculating and controlling the trace widths, dielectric thickness, and layer separation to achieve the desired impedance values. 12. Use thermal vias and distribute thermal planes to manage heat dissipation. 13. Place components with high heat produc- tion away from more sensitive components. 14. Note the capabilities and limitations of your PCB manufacturer (minimum track width and spacing, minimum drill size, and mate- rial availability). 15. Select laminate materials based on electrical performance, thermal properties, and cost. Different materials have different dielectric constants, loss tangent values, and thermal conductivities that can affect the overall performance of the PCB. Note: PCB stackup methods and design guidelines will vary somewhat from one sup- plier to another, depending on the project's specific requirements, such as the frequency of operation. e board fabricator selected or qualified by your company may recommend a stackup sequence different from those shown here, one that the matches their unique pro- cess procedures, environmental conditions, and industry standards. Before investing a lot of time in the design phase of the product, make an effort to con- sult with the potential circuit board fabricator to review the construction options most suit- able for the application. For example, when the external surfaces of the board require a greater level of conductor routing density for the high I/O very fine-pitch semiconductor interconnect, the supplier may recommend implementing the sequential build-up (SBU) process. is process enables up to three addi- tional conductor layers to be incorporated on the external surfaces of the board but the sequential build-up process will have its own unique set of design rules. DESIGN007 References 1. PCB Stackup Design Guidelines, 2. Cadence Design Systems. Vern Solberg is an indepen- dent technical consultant, specializing in SMT and microelectronics design and manufacturing technology. To read past columns, click here.