pcb design

used units

 the PCB editor is preferably set to mil = 1/1000 inch, 
 while the boardhouse calculates with micrometers and millimeters.

 1000 mil = 25.4 mm
   50 mil =  1.28mm

   40 mil approx 1.00 mm
   10 mil approx 0.25 mm
    4 mil approx 0.10 mm

    35 um approx 1.4 mil

    35 um is said to be 1 ounce copper per square foot
    70 um is said to be 2 ounce copper per square foot

a few constraints

A standard pcb is 35 um (1 ounce/sqrfoot) copper. The following values are valid for that. Other available thicknesses are 18 um, 70 um, 105 um, 200 um and 300 um.
A standard FR4 pcb is 1.6 mm. Other available thicknesses are 1.0 mm, 0.8 mm, 0.6 mm, 0.4 mm ...

One board house (preciprint) gave me the following numbers : Another one (zbinden) operates with : Another one (db : oneshot) operates with : This means check these numbers first. I found that smaller numbers lead to a higher price as they have to be more careful, spend more drills and so on.

high current considerations

Be the pcb a 35 um copper pcb. The resistance of copper is 17 mOhm for a wire of 1m length and 1 mm^2 crossection. This means a track of 100mil width has approx Another aspect is the heat dissipation in a track.
See : Utracad with dozends of articles.
Utracad's paper on current and temperature

high voltage considerations

To be continued

Impedance considerations

Recommended is Appcad, a tool downloadable from Agilent. It is located somewhere on their pages, the internal search machine is able to locate it. Last time I looked, it was under educatorscorner , Teacher's tools, References, RF corner, RF cool links a site somehow connected to Agilent/HP.

To be continued ...


last updated: 12.june.03, or perhaps later

Copyright (2003) Ing.Büro R.Tschaggelar