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Water Conservation

Source newsletter summer 1996

Water Recycling in Printed Circuit Manufacturing

Advanced Flex Incorporated (AFI), located in Chaska, Minnesota, manufactures flexible printed circuits for use in a variety of products. It has approximately 90 employees.

Manufacturing printed circuits is a complex process with many steps involved in producing a final product. The process uses electroplating and etching solutions, as well as acids, bases and other waterbased solutions. These solutions must be rinsed off with water between each process step, which requires large amounts of water. The primary contaminant in the rinse waters is copper.

Significant water volumes also cool the presses used to laminate layers of printed circuits. Cooling water is generally discharged to the sewer, but is clean enough to be reused for cooling or rinsing.

In August 1995, AFI installed a water recycling system that treats for reuse approximately 60 percent of the water used in its manufacturing processes. Recycling this water saves AFI the costs of purchasing 14 million gallons of water annually.

Incentive for Change
AFI invested in a water recycling system because of concerns from the City of Chaska about AFI's water use and discharge quantities. Without a recycling system, increased production would have increased AFI's water use to an estimate 26 million gallons in 1996. As a result of the increased water use, sewer accessibility charges (SAC) would have increased to $318,210.

With a new water recycling system, AFI's initial goal was to recycle and reuse 50 percent of its plating rinse and all of its cooling water. To achieve this goal, AFI hired a vendor, U.S. Filter Recovery Services, Inc., to design and install a water recycling system for its process operations. Installation of the system began in August 1995 and was running at full capacity by October 1995.

Recycled water is now used for all plating rinses, the electroless deposition line and the fume scrubber. Cooling water is also recycled through the new system and reused as rinse water.

System and Quality Concerns
AFI's primary concerns with its recycling system were: 1) removing contaminants; 2) achieving and maintaining water quality; and 3) maintaining an acceptable pH in the recycled water before it is reused. AFI initially focused on its copper rinses, which are segregated from other rinses and routed through the recycling system.

AFI worked with process and equipment vendors to obtain water quality requirements for their products, which helped establish quality standards for the recycled water. A team of engineers from AFI and U.S. Filter then worked to design the process flow of the recycling system. Tin/lead rinses were originally segregated from the other rinses to prevent contamination of the water. The long-term solution was to use an alternative coating in place of the tin/lead. Currently, the alternative coating has replaced 90 percent of the former tin/lead needs.

Incoming city water is softened and run through carbon filters to remove chlorine and organic contaminants before it is fed into the recycling system. After the recycling system stabilized, AFI was able to reduce its softening salt use by 70 tons per year.

Another unexpected benefit of the recycling system is that the recycled water has significantly fewer contaminants than incoming city water. The recycling system is producing water between 25,000 to 40,000 ohms, which is 15 to 20 times cleaner than the city water.

Employee Involvement
AFI quickly realized that its 50 percent water reuse goal would not be reached without employee training and participation.

AFI encouraged participation by increasing employee awareness of SAC costs and how that affected overall company profitability. It posted a goal of reducing water discharge by 36,000 gallons per day, in addition to a weekly
performance chart in the employee lunch room.

Training consisted of showing employees basic operating changes, such as turning off equipment when not in use. This process was simplified by installing one or two red on/off switches or manual shut-off valves in easily accessible locations. To enforce this training, reminder sheets were
posted near the on/off switches.

Within three to four weeks, employees became used to turning off equipment when not in use. Posting the weekly water discharge reduction goal helps to motivate employees and remind them of the importance of their diligence and participation.

Operating Costs
The new recycling system increased water treatment costs by about $91,800 annually. Major costs were for filters, filter disposal, special resins, carbons, electricity and labor. However, the recycling system saved $88,700 in reduced raw material costs, which almost entirely offset the increased operating costs. Savings resulted from reductions in: water purchases, copper ion exchange resin regeneration, softener salt use, and deionized water costs. Although annual treatment costs slightly increased, it is expected that improved product quality, as a result of rinsing with cleaner water, will more than make up the difference. In addition, there was a one-time SAC savings of $82,100, which was based on future water use increases coinciding with AFI's facility expansion.

Future Changes
AFI plans to purchase a chiller for about $5,000 to stabilize the temperature of the recycled water, particularly during the summer when water is used for press cooling.

More Information
For more information about reducing water use, call MnTAP at 612.624.1300 or 800.247.0015.

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