AOI ( automated optical inspection) benchmark

I am not a fan of "Gold Board" type of inspection. There are many new sophisticated ways of inspection one being neural networking. This is a method where learning occurs by exposure to a truthed set of inputs and outputs data where the algorythim interactively adjust the acceptance synapses. Simply, a learning tree (or a family tree)where certain criteria or conditions are met for acceptance. This is just my preference cause it is fast, powerful, and flexible. hope this helps

Cal

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When evaluating AOI you must first define what type of inspections you want the system to perform, pre-solder or post-solder. What separates many mfgs. of these systems is how effective they are at finding post solder defects. This is where camera resolution comes into play, in addition to other factors. Remember that what you see in the monitor of the AOI system is not what the ?system? sees. Human eye sight can only differentiate a small number of color shades whereas a machine can resolve millions in some applications. Certainly check the specifications of each system and beware of mfg?s. ?specmanship?. This is where mfgs. tend to express their specifications in the ?best case? scenarios. You need to bring them down to ?real world? applications. If you are looking at AOI for post-solder defects you must realize that an AOI cannot see all the defects, such as insufficient heel fillets on gull-winged devices and many J lead devices and all BGA. X-ray is best for finding just about all solder defects. X-ray systems come in 2D or 3D, 3D being the fastest and most effective. Current AOI systems that I know of can only see the obvious. Some are better at flagging the insufficient fillets. That?s what I?ve found to be what separates most mfgs. Bridges are the easiest. AOI is best for finding component assembly defects such as missing, incorrect, reversed, skewed, lifted (billboard & tomb stoned). If you decide on AOI then you MUST go and source inspect at the mfg?s nearest demo facility or at a local customer. When doing such an evaluation get a group of your boards and induce defects. For insufficient fillets induce a group of them on a graduating level from minor to major on the finest pitch component you have. In these same boards you should induce component defects as well and to substitute components with different mfgs. that have a different look to them, like shade, color and markings. Some AOI mfgs. may request that you send all the materials and PCB info ahead of time. Do not do this. You must SEE everything they are doing to program the board. You don?t want any surprises when you get a system into your factory. Give yourself enough time to evaluate the system before ordering one. Ease of programming is one of the important criteria when looking at systems. After all the programming is done and proved out by processing bare boards ( some mfgs. require this) and a group of known good assembled boards, then process your boards with the induced defects and component substitutions. You will see how effective the system is at finding the defects and how flexible it is when it comes to component substitutions. It is mandatory to use this same set of boards at each mfg. you source inspect to maintain an ?apples-to-apples? comparison. Too many people in our industry do not scrutinize equipment mfg. claims on programming, performance and operation and do these kinds of source inspections. ?Oh, the salesman said this, or the mfg. said that, etc?? Here is a general list of criteria when looking at AOI for post-solder: 1. Performance- how good is it at finding the defects 2. How easy is it to program- does each board have to be programmed from scratch or can the system build a library so each new board only needs programming for features that ?it has not seen before? 3. Cost of ownership- maintenance and programming time (labor cost), replacement parts cost- get a list of the recommended spare parts kit with prices. 4. Flexibility- How flexible is the system for inspecting boards and component features and how about other applications such as thru-hole inspections and thru-hole solder joints. Final thought: An AOI (and X-ray for that mater) machine is a ?tool? to provide real-time feedback for assembly or solderability problems in your mfg. processes. This ?tool? should enable you to find your process problems sooner so you can find the route causes and fix them. In time, if you follow this methodology, the amount of defects and AOI or X-ray will find should be nil. Your goal is to make such a system obsolete for manufacturing processes and relegate it to the QA department to perform QA audits and in-process inspections on a random basis.

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David,

I can say this we have 2 vision systems Orbotech and Omron.

Both working OK but there is a problem with both....They find a solderballs in board and there is no solderballs!

Otherwise can not tell what is a best system.

Regards, MadReindeer

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