Resistor Power P = I^2*R = V^2/R = I*V
Thick Film Chip Resistor Power Dissipation
PCB Layout Considerations
Dimenions described below are in mils (1 mil = 0.001 inch)
Smallest via depends on finished material thickness. PCB Manufacturer would like to see the hole aspect ratio at less than 5:1
a. Meaning on a .062 thick board with a .062 via would be a 1:1 ratio
b. a .031 hole would be 2:1 ratio and so forth
c. Ideally they do not like to drill smaller than .013 on a .062 with a pad size of at least .026
Minimum trace width will vary depending starting base copper weight.
a. On a 1.0 oz base copper they can do 8/8 .
b. On a 0.5 oz base copper they can do 5/5 .
c. that is trace/trace pad/trace pad/pad
Try to minimize number of drills, although many board houses have no penalty for number of drill sizes.
Mistakes are endless. The single biggest mistake really is just not calling out or identifying what you would really like i.e copper weights, color of mask, stackup on multi layers, panel requirements etc...