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PCB GROUND - Coggle Diagram

- - - - factors
        
        spacing between the microstrip line and the top ground
        plane G
        
        pcb layer substrate’s height h
        
        relative dielectric constant of the substrate itself
        
        microstrip line width is also important when the
        width becomes narrow
      - thin substrate
        
        variation of Z0 between 100 MHz and 2 GHz is
        negligible
        
        largest variation in Z0 occurs when the gap, G,
        becomes significantly smaller than the line’s width
        
        G variation negligible
      - thick substrate
        
        Z0 is more affected by f
        
        G variation is important
        
        bad return loss
      - G = 1.5h + h/W + 20/er
        
        G >= 1.5h
      - conclusion
        
        the Z0 of a microstrip line becomes sensitive to changes in G when thicker substrates are used or when W is narrower
      - stray capacitance
        
        good because it helps forming a characteristic impedance when desired
        
        bad because it causes capacitance when a characteristic impedance is not desired
- - - - prevent the solder from flowing up into the via and over the others side where it can short components
    - - prevent the solder paste from
        wicking into the via and creating a poor solder joint
  - - - HASL
        
        immersing circuit in a molten pot of tin/lead alloy and then removing the excess solder by using "air knives", which blow hot air
        
        main benefit
        
        identify any delamination issues beforoe mounting expensive components
- - - - excite cables and wires
      - affect other sensitive areas