Source Recovery of Isopropyl Alcohol at an Electronic Equipment Manufacturer
Zytec Corporation manufactures and services computer power units. The production process includes the building, soldering and testing of electronic circuit boards; assembling of units; packaging; and shipping. As a part of the soldering process, solder fluxes are used to chemically clean and deoxidize the copper circuit surface in preparation for soldering.
In 1989, Zytec successfully implemented a low-solids foam soldering flux (LSF) process. The flux solution contains about 93 percent isopropyl alcohol (IPA), which acts as a thinner and a solvent for the flux. Circuit boards are wetted with this solution prior to soldering. After a predetermined number of production runs, the spent solution is removed and disposed of as hazardous waste.
In addition to the high IPA content in the LSF, virgin IPA is used extensively throughout the Zytec facility. Hand- soldering, testing and inspection areas rely heavily on IPA for removing residual fluxes from circuit boards and for general cleaning. IPA is applied to returned parts and boards to prepare them for re-work. IPA is also used to clean computer chassis before final assembly of the power units.
Incentive for Change
Zytec hoped to save money by reducing the volume of IPA waste by setting up an IPA recovery system. During a six-month period, about 700 gallons of flux solution was shipped off-site as hazardous waste and 440 gallons of fresh IPA was purchased for cleaning purposes. The total annual cost for purchase and disposal of IPA was $5,100.
The purpose of the intern project was to study the recovery of IPA from the flux-thinner waste and reuse it in Zytec’s general cleaning areas. During the project, the intern:
- inventoried fresh IPA consumption and spent IPA-flux disposal;
- distilled and assessed samples of spent flux by comparing them with fresh IPA and noting employee’s comments; and
- acquired information on distillation equipment size and selection, fire code issues, safety operating procedures and economic feasibility.
For most cleaning purposes, distilled IPA performed as well as virgin IPA.
For Zytec’s current usage, a distillation unit with a 7.5-gallon capacity was deemed adequate since it recovered 90 percent of the IPA. Through discussions with the local fire department, city inspector and insurance agency, it was determined that the distillation equipment must be explosion-proof and located in an area with adequate ventilation (up to six air changes per hour).
The cost for the distillation equipment would be $5,600. Costs for equipment operation and maintenance, and disposal of still bottoms costs total $2,100 per year. Annual savings due to reduced amounts of IPA purchased and decreased disposal costs are estimated at $4,800, with a payback period of 14 months. Zytec expects to purchase and install the recovery equipment during 1994.