PCB Fabrication: This is the multi-step process of converting the electronic schematic and PCB layout into a physical board. It involves a series of complex procedures such as photolithography, chemical etching, and electroplating.
Line Trace and Spacing:
Trace Width: Affects the current-carrying capacity and impedance of the trace. Calculated based on the current requirements and temperature rise.
Trace Spacing: Important for minimizing cross-talk and ensuring signal integrity. For high-frequency signals, the "20H rule" often applies, where the space between traces should be at least 20 times the height of the trace above the ground plane.
FR-4 is the most commonly used material, known for its good dielectric properties and decent thermal performance. Alternative materials like Polyimide are used for flex circuits.
Dielectric Constant (ϵr): Affects the speed of signal propagation.
Thermal Conductivity (k): Important for heat dissipation.
Comprises layers for copper traces, solder mask, and silkscreen.
Should include drill files and board outline files.
HASL (Hot Air Solder Leveling), ENIG (Electroless Nickel Immersion Gold), and OSP (Organic Solderability Preservatives) each have specific pros and cons in terms of cost, shelf life, and signal integrity.
Layer Count: More layers generally mean higher costs.
Materials: Specialty materials can significantly increase the cost.
Turnaround Time: Rush orders will be more expensive.
Via Choice: Consider the use of laser-drilled microvias for high-density layouts. Mechanical vias are generally more cost-effective for standard designs, but laser drilling can offer higher precision and smaller sizes, which might be crucial for high-frequency or compact designs.
Test Points: Ensure that the design includes accessible test points for crucial signals and power rails.
Programer and Debug header: Implementing test access ports for complex boards to facilitate testing.
Understanding the Fabrication Steps: A deep understanding of each step can help designers make more informed decisions during the design phase to ensure manufacturability.
Quality Control is Crucial: A multi-layered quality assurance process involving both automated and manual inspection is key to high-reliability PCBs.