How wide is the window for the good pasteprint:| 26 October, 2000
I would like to read your opinion of the following matter:
How wide is the window for good pasteprint quality if the quantity of paste is its indicator? Usually the amount of paste on landings varies quite a lot from set to set and there are significant areal differencies on every pcb. If the average (and target) is 100% were starts the gray area between the good and poor pasteprint and when printing is already black?
Re: How wide is the window for the good pasteprint:| 26 October, 2000
Of all of the process steps, paste printing is the most critical with respect to minimizing defects. Therefore, paste printing must be tightly controlled, particularly in the case of fine pitch (peripherally leaded) devices and BGAs. I believe that paste volume should be controllable +/- 10% and that variations greater than this value will prouduce an unnecessary number of defects.