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PCB-Oct2017

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62 The PCB Magazine • October 2017 THE CRITICAL IMPORTANCE OF RINSING, PART 2 Use of Air Agitation Air agitation improves rinsing in two ways: by keeping the rinse water mixed so that con- centrated pockets do not occur, and by contin- uously moving fresh water to the board surface. Air agitation should not be used in rinses imme- diately after cleaners with a tendency to foam. There are many low foaming cleaners available today. The process engineer should evaluate carefully prior to implementing such a product in production. Spray Rinsing Spray rinsing is an effective method to rinse contaminants and process solutions from circuit boards. However, if not controlled properly, there will be a huge amount of wa - ter consumed. This can be a very effective way to rinse. It is easy today to control the amount of water used in spray systems with on-off switches. Meaning that the spray is activat- ed when the boards enter the rinse station. And the rinse is then switched off after the panels exit the chamber . This is not an easy thing to accomplish if one is using a manual operation. Another concern with spray rinsing is that smaller diameter vias (and thicker boards) do not clean up as well when compared to immer- sion rinsing or countercurrent rinsing. Summary Improved rinsing techniques often do not re- quire additional water use. Many techniques are both inexpensive and easily implemented, once understood. Some of these techniques include air agitation, sprays (continuous, time or pulsed), counterflows, tempering, longer drip times and new rack designs. Use the tools available and one will not only conserve precious water, but will also ensure a high quality final product. To ensure the highest quality printed circuit board, do not short change the critical impor- tance of rinsing. PCB References 1. T. Mooney, "The Art and Science of Wa- ter Rinsing," Metal Finishing Handbook, 1996, p. 135. 2. J.P. Gong, K.Q. Luo, and Yinlun Huang, "Dynamic modeling and simulation for envi- ronmentally benign cleaning and rinsing," In- dustrial and Engineering Chemical Research (1997), pp 63–70. Michael Carano is VP of technology and business develop- ment for RBP Chemical Technology. To reach Carano, or read past columns, click here. How we use and generate electricity has changed dramatically over the past century yet the basic components that control its flow remain remarkably similar. Researchers at KAUST have now developed a novel type of component that could improve the performance of electrical circuits. Electronic circuitry is tra- ditionally constructed from three primary elements: a resistor, a capacitor and an inductor. A sinusoidal elec- trical signal passing through these devices will change in signal strength, or am- plitude, and the relative timing of the crest of the wave, known as its phase. A resistor will change amplitude only while a capacitor and an inductor can also change phase, but only by exactly one- quarter of the length of the wave, or 90°. Compo- nents that could alter the phase of the electrical sig- nal by a different amount would enable electrical circuits with more varied functionality. Bringing Signals into Phase

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