- Fri Oct 04, 2013 7:25 am
#164158
Width is generally decided by the current that the signal carries, Saturn PCB Design's PCB toolkit is a free program that will calculate the track width for you given conditions entered and this uses current standards, not outdated 50 year old tables. I suggest you look it up.
For a minimum width I would consider about 8 thou an average, yes you can thin it down but if you do not need to then dont. The same goes for the track to track/pad gap - the bigger you can make it the better. Generally the fatter the track the lower the impedance to signal travel.
When you start to get your tracks down to thin widths you risk higher failure rate in manufacture among many other electrical issues.
Although thin widths and close spacing can be and are made often, this comes with higher board costs, higher likelihood of crosstalk etc so its best not done unless necessary.
As for running tracks through pads, there are IPC standards that say the opposite is god and through pads is bad - however IMO these are way outdated and no longer good practice.
ISTR reading that having lots of little spurred off connections is bad for EMC but running through the pad does not.
On the other hand I have read that running through a PTH pad can if the pad is lifted, break the entire connection and the whole net causing failures. There are arguments on both sides as to whether that is good or bad (it depends on the circuit).
PCB layout practice is a difficult subject to talk about because there are so many that have differing views because some make small runs, some make hundreds of thousands, some do low speed, some do high speed, some pass EMC, some dont. So many different circuits, methods, techniques rules, regulations, standards to meet etc.
For everything I have said there will be at least 2 people that disagree completely - and probably (hopefully) 2 more that agree.