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14 SMT Magazine • June 2017 independent processes. The big- gest challenge we face today is the use of all the data from the inspection: we have 3D imag- es, we have data, we have mea- surements. The challenge is to use that huge amount of infor- mation to improve the process," he said. "The past year, we in- vested to develop a solution that combines data from the SPI and the AOI. In fact, this combina- tion gives more valuable and ac- tionable information to the user than just a picture at the AOI re- view station." That solution is called feed forward—a direct communication between SPI and AOI. Today, there are already systems that enable direct communication between the printer, to the pick and place machine, and oth- ers. What Vi TECHNOLOGY did, according to Peallat, was to focus on making SPI and AOI work together hand in hand to improve SMT line quality. In fact, the combination of these data, at the end of the line, offers more infor- mation about SPI parameters that really impact the quality. Peallat noted that one of the benefits of this system is that users don't have to wait for the post reflow inspection to improve their process. Adjustments can be made at the printer level or at the SPI level to improve the process. Then you gain quality and also reduce your costs of rework. "I cannot disclose too much of this as we are currently working on an article, but we have done this with an EMS company on their automotive application," he said. McMeen added that one of the challenges that they are also facing is the ability of getting the wetting angle. But he noted that the 3D AOI systems now are allowing them to ensure that on their passives, they are getting a 75% solder fillet going up the side of the part, 75% of the height, and then a nice wetting angle off of it. "If you're looking for a high degree of reliability and repeatability in your process, you're look- ing for getting the wetting on these caps and re- sistor faces up to 75% of its effacement and get- ting a nice fillet off of that." At this point, McMeen asked Peallat about how 3D AOI al- lows them to get that measure- ment and why it's an improve- ment over 2D AOI. "The 2D was not able to measure the profile of the fil- let because even with a set of lightings, your 2-D image is a flat image," explained Peallat. "The only solution to measure 75% of the side of the compo- nent is to use 3D measurement. The challenge of 3D is what we call specularity, which is main- ly when you have a very shin- ny joint, and the difficulty is to avoid the specular effect—meaning that you sometimes have a bright spot due to the angle of the light coming from the projector and go- ing up directly to the cameras. Of course, 3D is a better way to measure this angle and the height of the joint. The challenge is, again, back to the size and the miniaturization of the component. Today, most of the systems have the ability to give you a profile of your joint, but the difficul- ty that I think most of the vendors have is to be clearly compliant to the IPC standards." McMeen said STI Electronics now uses 2D and 3D inspection systems. "We have 2Ds throughout our plant and we're starting to add 3D into our final inspection. Then we want to migrate the 3Ds back through our in-process AOIs. We have clients that have requirements beyond IPC for aerospace applications, where we've got to be 100% up the face of the com- ponent. That has always been done by visual inspection by human inspectors, but the 3D AOIs are on the verge of being able to do that at speed and give you the repeatability that you need to be able to use that tool set so that you don't have to put as much burden on the hu- man inspector." According to McMeen, 3D, for the first time, gave them the ability to do co-planari- ty. "As you do these bottom terminations, you can now see if you're afloat or askew or a-lift, because in all honesty, a part should be fairly co-planar and flat, which means that you prob - ably dispersed and wetted underneath those 3D: TOWARDS BETTER INSPECTION CAPABILITY Mark McMeen

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