Homebrew PCBs

On Fri, 10 Jun 2005 05:04:42 +0200, David McNab <david@...>  
wrote:

> Even though I'm using a good drill press, the drilling played havoc with
> the fine pads, and left me with having to either:


If that is the case you definitely have too small pads.
Remember the pads are not only for electrical connection, but also for  
mechanical mounting, and nothing is more annoying than a PCB with the pads  
lifting off.
You surely understand they must be MUCH bigger in non-PTH boards as the  
plating acts like a rivet that holds things together - and still i have  
managed to pull PTH padstacks out with improper soldering, so they were  
too small too. Most PCB software is set to tiny pads meant for PTH boards.

Make bigger pads, make oblong pads if the spacing doesn't allow more, for  
example, for a 100mil pitch DIL IC you can make 4mm long pads which still  
look good.

I tend to make bigger pads for components that are either mechanically  
large, are connectors, or have many pins. This helps those components that  
have the highest stress (e.g. electrolytic caps are often pulled/pushed by  
handling of the board because they are higher), And helps the parts that  
are hard to desolder.

If you make oblong pads, it is best never to go with the trace into the  
pad in the center at right angles to the orientation of the pad. I have  
had the fault that drilling did cut the trace free from the rest of the  
pad, but it was not visible easily. So always go into one of the ends of  
the pads.

ST