Homebrew PCBs

Chris wrote:
>> 10 mil holes with 5 mil rings. Nice. The only issue I see is you can 
>> only get HASL finish not ENIG
>> which makes working with small SMT parts tough.
>>
>> Bruce
>>     
>
> Bruce,
>
> I do not know what those specs mean, can you explain? I have a number of surface mount parts going on this board.  I have had good success soldering surface mount components on DIY boards and this will be my first purchased board.
>
> Chris
>   
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.