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Board-by-Board Optimization
Temat: Nauka i technologia
Do some Exercises: Słuchaj i zapisuj Tworzenie zdań Ukryte słowa
Just as each board type enjoys its own thermal profile in your surface mount oven, each board type also enjoys its own board-wave parameters in your wave machine. The optimal dwell time for that board was found to be 3.6 seconds, in contrast to 2.8 seconds for the first board. As you can see, the "dwell time profiles" of the two boards are different. This process resulted in dramatically lower defect rates for the second board studied (which had also been previously run at 1.0 seconds), although never quite as low as the new baseline which was attained for the first board. This strongly indicates the presence of sources of defects unrelated to dwell time, for example non-optimal immersion depth or design problems. Immersion Depth: Changing your immersion depth changes your contact length and dwell time. This makes the direct and accurate measurement of immersion depth critical. Your pump speed produces a wave height (although this can diminish as your solder pot empties of solder), but the actual immersion depth of your boards depends on several factors, including solder pot height, how they sit in the fingers, if your fingers are bent, broken or crooked, the angle of your conveyor and whether or not pallets are used. Yet controlling your immersion depth - measuring it and keeping it consistent - is only one piece of the puzzle. Another is: At which immersion depth is your board quality optimized? So, different board types benefit most from different immersion depths. Quantifying Cost Benefits: Prior to this study, yield loss was tracked on a monthly basis as a measure of the cost of production failures. Production volume for the board studied was 11,000 per month. 1.) With the implementation of optimal dwell time procedures using the described device, yield loss went from 3.0% (330 boards) to 1.6% (176 boards) in the first month of daily use. 2.) This meant a reduction in yield loss of 154 boards per month. For a 30 day month, this means 5.13 boards per day. 3.) At 0 for the cost of each board, cost reduction based on improved yield loss alone was ,200 per month, which annualizes to 4,400. 4.) That means that the return on investment on the device used in the study was less than five days. Conclusion: A seemingly small daily improvement in wave solder quality meant fast, very large, measurable monthly and annual cost savings. These figures do not even account for the valuable savings from benefits like reduced rework and field failures, less downtime and increased throughput, each of which in its own right can be more valuable than the rapid savings on yield loss. Source: http://www.articlecircle.com/ - Free Articles Directory About the Author The article is written on the information the author got from www.swpc.co.il. The information the author got from here regarding the wave soldering was good and true enough on each and every aspect of the technology discussed above. As the author has been dealing in the manufacturing of PCB's on large scale.
