Issue link: https://iconnect007.uberflip.com/i/622045
January 2016 • SMT Magazine 59 FEATurE inTErViEw THE JEFFErSOn PrOJECT equipment infrastructure. That's not something you could just decide you want to do. Again, the point is in order to exploit the automation you need more than just investing hundreds of thousands of dollars in leading- edge automation equipment. You have to have an infrastructure that allows you to make these kinds of process adjustments automatically, and you need to design the products for the automa- tion so that you have a chance at these 99.5% plus yields. The other thing I should mention is why it is so important—what goes along with low yields, is the fact that you're going to have a lot of products that have to be troubleshot and then reworked and retested again with this ex- pensive labor. But, here is the bonus. You're fa- miliar with the in-circuit test, which is an elec- trical test that's done on the circuit board after it has been assembled. ICT checks to make sure the correct components are where they should be, that they are oriented correctly, that there are no opens or shorts, etc. – in other words, the board was assembled without assembly defects and the component values are generally within electrical tolerance. However, components are rarely out of tolerance these days. The problem is that if you are going to do a functional test your customer doesn't care that you do an in- circuit test. Unfortunately what in-circuit tests have become, as AOI is becoming, is a way to separate the good boards we assemble from the bad boards, and that's a bad use of that tool. So, ICT in many cases compensate for poor process – and, we keep doing the test rather than try to identity and correct the root cause process issue. Goldman: You should be taking that information and using it right? Borkes: People rarely do that because they have the next job they have to move on to. What you want to do is obviate the need to do process issue troubleshooting by eliminating process defects. Then, you can go one step further. If you achieve 99.5% yields and above, and you're going to do a functional test on the board or the product anyway—which is a test that says the board or the product is producing the de- sired output—there is no value-added to an in- circuit test. If you only have one out of the 200 boards that have an assembly defect, it doesn't pay back to ICT all 200 boards. You're going to do a functional test on the 200 anyway and will identify the one defective board. And the func- figure 3: post-reflow of on-pad component placement. figure 4: post-reflow of on-paste component placement.