What is a typical SMT placement defect rate?

Hi,

If you can not rely on your programmer and the tools he uses then "double checking" can save you only materials but in time you really do not save often extend meaning. There are things you can identify before the stove, but if you use tools like AOI or visual inspection then you should be covered with solder problems. Let's say the issue depends on the product (density components, types of components, etc.) and tools that you have. I suggest that would decompose the matter to topics and see how you can save. For example can you troubleshoot your programmer level, whether manual tools provide you or need automated tools, and the like.

Best Regards, Alexei

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As has been pointed out by other well experienced individuals, this is a complex question. But the simple answer is "It is your decision". Choose any goal less than 100% and strive to reach it. There are hundreds of questions to ask before an objective conclusion can be reached: value of the PCB, type of machine, age, and budget. For instance if you have 20 year old poorly maintained equipment you should inspect every board. If you have decent equipment with qualified personnel, easily over 95%

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Our company has a process standard that requires a double person check at the beginning of every run (size of run is irrelevent, whether 20 panels or 500 panels). Every changeover that occurs a first piece inspection is made before reflow. If all is well there, we use AOI to determine later in the run if defects are occuring, and can attack the problem then before more defects are made. Usually issues arise from dirty laser alignment lenses or low vacuum from toolbits, something simple and quick to fix but can cause bad placements. Also, we check solder print first piece as well to verify solder is centered on the pads. I would have to say, and this is from my experience, the program itself is usually pretty stable, the machine wear and tear that affects placement is over a long period of time, and if you have a good setup, fiducials, and CAD data, there shouldn't be a real necessity for checking every panel.

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In my office we strive for no retouch prior to reflow, it can be done, you just need your operator to be competent enough to know how to set up your machine correctly. I would say 99% of parts that are misaligned are user error, they are either not correctly programmed, or poorly aligned or tolerances are to far out all of which can be adjusted for. I still inspect every board visually but with just a small amount of time and understanding put into programming I only have to adjust 1-2 parts per 1000 placed, and so can you.

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