Homebrew PCBs

> Hi Chris,
> 
> Most of the low priced board services I've seen limit line width and 
> gaps to 7 to 10 mils and the minimum drill size to a 12 to 15 mil range 
> with a 7 to 10 mil minimum annular ring which sets the minimum via size 
> to the 26 to 35 mil range. A 10 mil hole with a 5 mil annular ring limit 
> allows you to use a 20 mil via which allows for higher density routing.
> 
> HASL, Hot Air Leveled Solder, finish is quite common and works fine for 
> through hole parts but produces an uneven surface. For SMT parts, you 
> want a flat surface that can have solder paste printed onto it. One of 
> the more common finishes used to passivate the copper and maintain a 
> flat surface is Electroless Nickel Immersion Gold or ENIG. It's a non 
> electroplated process the deposits a few, typically 3 to 10, micro 
> inches of gold over a nickel base.
> 
> If you are forced to use a HASL finish, you can always remove the excess 
> solder with solder wick and flux but it's a hassle and, if your iron 
> gets too hot, you run the risk of lifting pads.


Thanks for the response Bruce.  I was mostly concerned with the HASL finish spec - thanks for explaining that.  I will be hand soldering the board so that should pose a problem for me.  I do have one small, 100 pin QFP chip that it could cause a bit more effort but seeing as I have un-soldered and re-soldered that size chip on DIY boards, I should be able to handle it.

Thanks again for your help !

Chris