Homebrew PCBs

dbrock178 wrote:
> Hello all,
> I am looking to create my first homemade pcb using the photolithlgraphy method. I've read some tutorials on both methods and did some browsing on the board here, but I still have some questions.
> 
> 1. Does negative dry film resist share the same characteristic of longer development times for aged film that pre-coated boards have?
> 
> 2. Does negative dry film resist provide greater detail than positive pre-coated boards?
> 
> 3. What are some advantages/disadvantages of negative dry film vs positive pre-coated boards besides the following?
> 
> -Negative dry film: Lower cost
> -Negative dry film: Needs clean board/more steps required
> 

I've never used pre-coated positive photoresist boards so I cannot 
comment. Does anyone know how this resists is applied, since I don't 
think dry film positive resists exist. All the positive resists I've 
come across are in liquid solvent.

I've use the old spray on Electrolube PRP photoresist , and all I can 
say is its a pita to use compared to negative dry film. Even when you do 
manage to get a uniform, contaminate free, well adhering coating, the 
stuff is lot less forgiving in the developer and exposure time compared 
to negative dry film.

Professional PCB manufactures exclusively use negative dry film 
photoresist. It must be economical overall, weather that's because it is 
easier to process with simple equipment or lower bulk material cost.