OSH’s DRU minimums are 6 mil trace width / 6 mil spacing / 13 mil drill size / 7 mil annular ring. In routing a 100 pin BGA part I have found that to meet these rules on a 2 layer board I have to make my pads 12 mils. The default for this part is 16 mils. So this gives me pause and I ran it by the guy who supports DipTrace over at their forum and he thinks it is not a good idea either. The fact is, with these minimums, there doesn’t seem to be any way to route the innermost pins on a 2 layer board without getting the pads down to 12 mils.
Are there PCB manufacturers that have smaller DRUs than the ones I stated above that OSH Park uses? This was the fanout I was able to get with OSH’s minimums plus making the pads 12 mils. It is the best I can do and the autorouter does worse.