Issue link: https://iconnect007.uberflip.com/i/622045
58 SMT Magazine • January 2016 process control." In meta-process control your assembly system will not only identify those areas that are of process control concern, but actually will self-correct automatically whatever the issue is. We use printing solder paste as an example. When you get a bare board that has tiny pads on it for 01005 (English) components, you can't even tell they're components because they're so small. If, when you print paste on the board, the paste is offset from the pads, the system will rec- ognize that offset and will actually change the placement programming. The pick and place machine that's placing those components, in- stead of placing the component on the pads, will actually offset the component placement and put it fully in the paste. What we do in the paper is look at the difference in placing the component on the pads with the paste offset, or placing the component also offset with the offset paste to see which situation yields the best result. Goldman: in the meantime, if you're still off the pad though, isn't that a problem? Borkes: You're still off the pad, but when the solder melts... Goldman: it's enough to make it connect? Borkes: Yep, the results are striking in terms of the amount of defects you have when you have an offset of the solder paste and put the compo- nent on the pad where it was programmed to go, versus when you have an offset in the sol- der paste and a matching offset the component placement. As the paste melts, wets and pulls on to the pad, it brings the component along with it – right onto the pad. Goldman: how interesting! Borkes: We can't afford for a human to moni- tor the printed paste and either reject, wipe the board and start over, or manually offset the component placement coordinates to match the paste shift. What meta-process control sug- gests is that the automation has the intelligence to be able to recognize the variation in paste printing and automatically make the adjust- ment to the pick and place component place- ment program to put the component entirely in the paste, rather than on the pad. That's an in- frastructural type of thing. In other words, you have to have that as part of your manufacturing FEATurE inTErViEw THE JEFFErSOn PrOJECT figure 2: 75% paste offset with on-pad compo- nent (left), and 75% paste offset with matching 75% placement offset (right).