We currently use a YesTech M1 system and we are looking to buy another. Two important areas to look at when pursuing AOI equipment: 1) Camera resolution 2) Light sources Depending on your needs, camera resolution can be important depending on the size of the parts you are inspecting. The M1 system is standard with 20u/pix and expandable down to 12.5. The lower resolution is fine down to 0201 parts. Many systems offer high resolution cameras, so finding one is not a problem. Lighting plays an equally important role in that it can determine your inspection coverage. For instance, if you have a system that uses only white/red lignting, there are only 3 possible combination of light sources available to you, white, red and white/red. However the M1 uses a patented fusion lighting system that has multi-color LEDs in the camera head. The more colors, the more possible combination light sources you can achieve. Why is this important? Because some component markings show up better under different light sources. As an example, some LEDs don't have a marking, but you can see the dye under the plastic. I use blue/green lighting for this which you could not see using white/red. I have been happy with their product and would recommend it to anyone. I don't have any experience with other AOI mfg., but YesTech's tech support has been outstanding.
When you do demo a unit, "break" a board. Meaning, put defects into the pcb to test whether the AOI will catch it or not (i.e. solder bridge, lifted lead, missing part, reversed part etc.). When I did this, I did not tell the demo guy what was wrong with the board. That way, he doesn't have the opportunity to tweak the program to make it pass. Also, watch the demo guy and make sure he is not setting the pass scores too low on the recipe. Some will do this so they don't have to explain why they keep getting false-fails and makes the system look more impressive than it really is.
P.S. One item of interest: Of the three mfg we demoed, Christopher, Mirtec and YesTech, YesTech was the only system that was able to test the markless LEDs consistantly and they were the only mfg who let us "play" with the system when they left.
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