Pat, Are X-outs causing you a problem or are you just looking to minimize the number shipped?. The simple approach is to not allow X-outs. Unfortunately depending on the technology level of your boards, that will cost you $. On simple low tech boards the difference is typically little but on high tech fine line boards, be prepared to pay. In real life, shop yields probably run from 80 to 98% depending on the degree of difficulty. Your best price per board will be as single boards. Specifying an array will usually cost more because of wasted panel space (depending on the shop's production panel sizes). Specifying an array with no X-outs will cost even more because you are asking you shop to scrap the good boards on a panel with X-outs. The lower the shop's yield, the higher the 'no X-out' price. In situations where you must go with a 'no X-out' policy, you need to insure that the board you are buying fits the daily niche of that supplier. This will keep your 'no X-out' price increase at a minimum. If your insertion equipment is smart enough to avoid stuffing X-outs, it would be my opinion that your best policy would be to allow them (possibly add a max. percentage on the number shipped in a lot). X-outs can be very useful as an educational tool. If you should have a supplier quality concern, reviewing the X-outs included in the shipment can be very enlightening. It can lead to a better understanding of your supplier's manufacturing problems as well as improvements in your board designs. Norm Dill ---------- From: [log in to unmask] To: [log in to unmask] Cc: [log in to unmask] Subject: Re: X-outs On Multiple Board Arrays Date: Monday, December 16, 1996 12:37AM Hello, There are a couple of ways to look at x-outs. I have seen one application where the impact on yield is calculated by using the binomial probability distribution. You know the single-image yield and the number of boards in the array. From statistics, you can then calculate the overall yield as a function of maximum x-outs allowed. I think this way considerably overstates the yield impact. For example, allowing a few x-outs max on a 20-image array where the single-image yield is 90% would drop the overall yield to a very low number using binomial probability distribution. It is unlikely that would really happen. At the other extreme, the 20-image array could be treated as one large board. How many board fabricators figure in the size of the board when determining yields for pricing? These are the two extremes; reality is somewhere in between. What's reasonable depends on the difficulty and volume of the board. For an array of 20 images, 5% is only one image, which may be a bit restrictive for the fabricator. I personally think the greater of 20% or 1 image is reasonable unless there are circumstances that require more restrictive specifications. As an additional spec, we sometimes specify the max percent of the arrays in a shipment that can have any x-outs. For example, on an array with five images, we might allow one x-out on 20% of the arrays in a shipment (the remainder would have to be 100% good). This is usually the spec we give our fabricators and I have not seen price increases because of it. Regards, Denis Mori, Materials Engineer Hewlett-Packard Company Roseville, CA [log in to unmask] ______________________________ Reply Separator _________________________________ Subject: X-outs On Multiple Board Arrays Author: Non-HP-patb (rosemail.rose.hp.com!relay.hp.com!simon.ipc.org!uunet.uu.net!zytec!owl!patb ) at HP-Roseville,mimegw3 Date: 12/13/96 1:04 PM I was wondering what policies others have regarding accepting x-outs on multiple board arrays. We currently allow 50%, with the intent being we would use a two up array with one x-out, but don't want to see 10 x-outs on a 20 up array. We are contemplating going to something different, say 5% or 1, whichever is greater. Or possibly no x-outs, but I'm concerned about the cost ramifications of this (cost is a function of yield, right?). I would appreciate any input from both fabricators and assemblers. Regards, Pat Bailey Zytec Corporation *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************