Have anyone deal with X-Out boards? These defects are declared if one cavity or more from multi cavity boards are defective.
There have been a request to use these boards in order to reduce the multi cavity board spoilage at supplier.
How to manage these boards in production lines? My opinion : 1. X-Out Board Identification 2. Special Program to skip mount non-usage cavity 3. Special AOI Program to save the inspection time & false error.
I would assume every EMS company runs into this issue on a daily basis. Before we get to how a machine handles it, I would recomend setting up an acceptance criteria with your board supplier... if you plan on accepting them at all. (ex. No more than 1 x-out per panel, No more than 10% of the total Panels have x-outs, etc...) As far as machines go, all equipment (Part Placement, Inspection, etc..) should have a "Bad Sense", "Circuit Bypass", or "Image Skip" funtion you can turn on. If you do not have any of these options, you can start modifying programs and hope you always build with the correct one.
Allowing fabricators to X-Out boards is a bad idea. * X-Outs are randomly placed * Machines can't read X-Outs * X-Outs are on the second side as often as they're on the first side
If you're going to allow X-Outs, you need to make your fabricators: * Mark [remove, tape over] the fiducials on both sides of the defective boards in the panel * Sort panels by front side or back side defects * Sort panels according to location of the defect on the panel side
When assessing the costs of X-Out panels, it's easy to start counting at the placement machine. Don't forget to consider wasted solder paste when assessing the cost of X-out panels.
Most PNP machines and AOI machines shuld have a X out feature.
For us we use to use whiteout pens to mark the badsense spot. Now atm we use white lables, becuase there is no dry time.
The lables have there own issues, They cause overpasteing issues on naboring circuts so we probably will not be sticking with them. Likely we will move to white paintmarker.
We loose about 15 seconds of production per a panel in PNP checking for xouts, Our mirtec AOI machine is the worst offender here, Loosing about 1/3 of max volume on a simple layout, and about 1/8 on a complex layout, just to check for Xouts.(assuming panel fids, 2 pictures a circuit, + 1 more for xout) (assuming 5 pictures a circuit + 2 per module fids, add a xout)
You also have other costs, about 1/4 of the X out circuts get populated on 1 side or the other by 1 or more PNP machines, for various reasons. The AOI machine will sometimes scan a Xout resulting in hundreds to thousands of false positives.
Also there are a lot of counting issues with X out panels. It sounds so simple to just count how many circuits are done and subtract the Xouts, but it probably doubles or triples the time to count a run, and you cant always trust the PNP machine's count due to missed X Outs.
There a headache but i cant see us ever not having them.
When I enter in the program data for a particular PCB on our Juki, I choose a board fiducial and enter its X Y location as the "bad mark position". (Although I'm not sure if your model refers to this as a "bad mark" as well.) Place a sticker over that fiducial on any board that is an X-out. It will not place any components on it. I'll use the remainder 2 board fids (across corners from each other), or the fids on the breakaways as boc marks to locate the boards.