Creating a layout for boards that use FR4 is definitely one of the more strategic types of board design and some thought is also required on how a signal behaves.(FR4 is some weird good, bad, an ugly) FR4 is the go-to material for a broad array of electronic applications due to its cost, performance and mechanical robustness balance. Performance and durability improvements are not the only benefits, optimizing PCB designs for FR4 can also incur cost savings in your final product. These strategies allow design to fit the strengths of FR4.
Good Practices in Layout to Reduce Signal Loss
Control Impedance: Separated impedance can cause severe signal integrity problems in high-speed circuits. One way you can keep impedance under control in an FR4 PCB is by correctly determining trace width + spacing. A typical 50-ohm single-ended trace width might range from 0.006 to 0.010 inches, depending on the stack-up of the PCB and the specific dielectric constant of the FR4 material used, which typically has a value of 4.5.
Differential Pairs for High-Speed Signals Differential signaling reduces crosstalk and EMI efficiently. By running differential pairs side by side in close physical proximity, thus allowing the signal and its inverse to experience an identical set of interference influences, you get common-mode noise-the equally balanced noise affecting both signals that subsequently gets removed. With FR4, you can have a gap of 0.007 - 0.012 inches for the differential pairs depending on the trace geometry and the board layout.
Thermal Management Requirements
Heat dissipation FR4 has a relatively low thermal conductivity of around 0.25 W/mK Strategically place thermal vias near heat-generating components to reduce hot spots and to transfer heat to the top or bottom of the board or into an attached heat sink. A VIA GRID heat dissipation system can have a much higher thermal performance.
Use of the layers for more durability
Stack-up Layout: The advice for the multilayer FR4 boards shorten the inner layer, you desire to not let the board warped and unfastened its structural as nicely, preserve it symmetrical. As an example, a 4 layer board might have a stack-up of signal-ground-power-signal, which would provide symmetric copper distribution so internal stress and warping would be minimized.
High up Manufacturing Yield & Lower Cost
Designing with FR4 Follow DFM Guidelines: Following the Design for Manufacturability (DFM) is a MUST when designing with FR4 to achieve high yields and lower costs. This consists of such considerations as adequate annular rings, no acute angles in traces, and appropriate pad sizes for soldering without causing tombstoning and other assembly problems.
Design for trace and space: Sufficiently wide and clear the trace and the space should be accommodated in routing so that no etching issues occur during the process of manufacturing your board. The majority of FR4 can confidently accommodate trace and space widths down to at least 0.005 inches, but as always, check with your manufacturer as capabilities can vary.
However, there are environmental and compliance things to consider.
Choose the Right FR4 Type: There are a number of FR4 levels offered, some of which are created for more performance or better flame resistance. The selection of a high-performance or a halogen-free FR4 variant might be required to meet specific performance or environmental or regulatory requirements in stringent environments.
FR4 PCB design optimization involves a mix of the understanding of the materialistic limitation and implementation of Best design practices. These are the areas designers need to get right to take full advantage of what FR4 has to offer, while also minimizing the problems that could undo some of that performance and longevity on a PCB. Efficient design optimization leads to better functionality and performance of the PCB, along with reducing the lifecycle of the products.