Homebrew PCBs

twb8899 wrote:

> Some thoughts about rinsing,  in our first system (using electroless 
> copper)we had a 25 gallon flowing tank for each rinse cycle. Our 
> small shop used over 7000 gallons of water per day with this rinse 
> setup. This entire flow had to be waste treated which was a GIGANTIC 
> headache. 
> 
> When I built the palladium based system we used a spray wand to rinse 
> for about one minute into a trough that collected the spray water. 
> Then the panels were dipped into a 25 gallon rinse tank that flowed 
> about 2 gallons per hour after which the panels went on to the next 
> process tank. The idea was to use a small amount of water as a spray 
> to do 99% of the rinsing and then a quick dip into a slow flowing 
> rinse tank caught anything else. Very efficient rinsing with very 
> little water.
> 
> All of this rinse water was collected into a common holding tank that 
> was fed into an evaporator system that boiled off the water at a rate 
> of about 30 gallons per hour. We ran the evaporator tank several 
> hours per day and had a ZERO DISCHARGE system with no connection to 
> the sewer drain. Our only discharge was clean water vapor and we were 
> able to reduce our water consumption to about 75 gallons per day. The 
> savings were tremendous and it satisfied the environmental 
> authorities as well.
> 
> 
> Tom
> 

7000 gallons (26500 liters) down to 75 gallons (280 liters) is a 
massive saving !!
Had you thought about using "counter flow" rinse systems or 
sometimes called cascaded rinse. This system is suppose to be 
most efficient, and the more tanks you have chained together the 
more efficient.  The price is longer rinse times because of the 
multiple dip & drip cycles. For example 4 cascaded rinse tanks 
with a fixed ratio of water flow volume to drag in volume of 10:1 
will theoretically dilute the concentration by more than 10000 
times. In other words the concentration ratios of solution 
wetting the PCB before and after rinsing is 1/10000 and you only 
need to use 100 ml of rinse water for a typical 12"x12" PCB 
wetted with 10 ml of liquid.

http://www.finishing.com/135/03.html

Adam