Our rinse water is cycled through a DI system and recirculated into the plating area. We add enough
new water to the system to replenish the water in approximately two days. The water is particle filtered,
carbon filtered and softened prior to adding it to the rinse system, so it is in effect DI water and does
not have the chemicals that the city adds to prevent bacterial growth.
My questions are: 1. Will slime in a rinse tank contribute to poor adhesion of Au plating on the nickel that was rinsed in this tank?
2. How can this slime be reduced or eliminated?
3. How often should a plating area clean and/or replenish its rinse tanks.
4. What is everybody else doing to reduce/eliminate bacterial growth in the rinse water? The environmental engineer
has been investigating an ultraviolet system but would like additional information on how other pwa manufacturers
effectively handle bacterial growth in rinse water systems.

Bob Dewlin
Modular Components

Modular Components National, Inc.
2302 Industry Court
Forest Hill, MD 2150
PH (410) 879-6553
Fax (410) 838-7629
Remco Engineering (remco.com/home.htm)
Industrial Water and Wastewater Treatment Systems
San Luis Obispo, California USA

During the IPC conference in San Jose, a paper entitled "BACTERIAL CONTAMINATION
OF CHEMISTRY USED IN PWB MANUFACTURING" will be presented. Jill Steeper of Shipley
will give this paper on 3/11/97 at 1:30p. Included in this paper are types of bacteria,
process areas most commonly affected, problem resolution, and monitoring mechanisms.

The Shipley Company
John S. Grosso
Director
PWB Research, Development, & Engineering
(508)229-7441

Hi,

Welcome to the world of recycled water. You have THE problem, this is THE cure.

1. Shut down the system.
2. Peroxide treat all of the recirculation water and the tank, use about 3% peroxide.
This will kill the bugs. Keep the DI system out of the loop.

3.Check with your di systems resin manufacturer for the sterilization procedure for the resin.
Do it.

4. Add a UV sterlizer on the exit from the DI system and another (that's 2)on the exit from the
DI water storage tank.

5. Use black tanks to store water. Peroxide treat once per month.

6. Dump all the water in the system monthly and recharge with fresh.

7. Your makeup water should go through the di before it hits the system. I couldn't tell where you
were adding the make up water.

Other stuff:

8. You can put individual uv lamps on the problem rinses. They will put a little ozone in the water to
keep the bugs in check

9. You can use a small RO for makeup water after the softener. This will keep the DI just working on your
plating chemistry and increase the time between regenerations (by a lot)

10. You can regenerate more often. Most people on a recirculation system let the TDS rise pretty high
before they regenerate. If you've got a DI system, make DI water. Regerate when the tds out gets to 3-5 ppm.
Starve them bugs!

11. Increase the flows in your rinse tanks to keep the tds low.

12. A bob special. I have here a lamp that is from 9/4/79. It is a GE germicidal lamp, that goes in a
florescent fixture and has a GE part number G25T8. I originally bought this when I worked a Gyrex years
ago and it came from WW Graingers but they do not carry them anymore. If GE still makes them, it is possibly
a cheap way to continuously sterilize a tank. I'm not selling this one (I've been hauling it around for
17 years and it's MINE), but you could buy them from you're local GE lighting distributor with a fixture
and hang it where ever you want. But, they generate ozone and are harmfull to the eyes so they have to be
somewhat enclosed. (if you buy some of these, let me know, tks)

That's about it, good luck, your're on the leading edge, have fun!

Bob Mesick

Regarding item # 10 below, I believe it is the organics that may be present in water that will "feed"
the bacteria. These are best removed by carbon filtration, especially right after a peroxide treatment
when the organics have been broken down into smaller bits. Remember that organics are not pulled out by
ion exchange resins and will only be pulled out by RO if they are large enough (as they have no charge).

Patty