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76 SMT Magazine • March 2017 cause they find it to be more effective, flexible, and less expensive. Here's the essence of vapor degreasing: It is a closed-loop system with few moving parts that inherently recycles the solvent. This keeps costs down and through-put up. In particular, vapor degreasing offers excellent performance when cleaning miniature components. In the simplest configuration, a vapor degreaser consists of a top-loading cleaning machine composed of two chambers. The first chamber is called the boil sump and the second chamber is the rinse sump. Both chambers are filled with a special nonflammable cleaning flu- id that boils near room temperature. In the boil sump, the solvent is heated and immersed parts are cleaned in the roiling fluid. The heat also generates vapor (e.g., steam from the solvent). The vapors rise inside the machine until they are captured by refrigerated coils that encircle the perimeter of the system. The refrig- eration condenses the vapors back to the liquid state. This pure, clean distillate liquid is chan- neled into the rinse chamber which eventually overflows back into the boil sump. Without any air knives, blowers or dryers, the parts come out clean, dry, spot-free and im- mediately ready for further processing. Depend- ing on the process requirements, vapor degreas- ing can handle the largest parts, the highest vol- umes and the most challenging shapes. A few simple additional features can make this simple system even more flexible. An automated hoist can move the dirty parts through the cleaning system. Ultrasonics can enhance cleaning and ensure residue-free re- sults. The sumps can be fitted with filtration systems to remove insoluble contamination MINIATURE COMPONENTS ON PCBS REQUIRES FLEXIBLE CLEANING METHODS Figure 1: Vapor degreasing.

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