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Component attrition

Paul Black

#22833

Component attrition | 23 December, 2002

Does anyone have a tried-and-true method to account for machine losses of SMT parts? I remember reading an article once that stated that 5% - 10% of components of certain sizes are known to be lost during placement, and I know some CM's overplan by 5% for small parts, but does anyone know if there is actual data that exists? Something that shows normal attrition for 0603's vs. 1208's vs. SOIC08's, etc.?

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Jon Fox

#22836

Component attrition | 23 December, 2002

If you are using a well maintained chip shooter, you should not see more than 1%-2%, and that is on the high side. Most pick and place machines (depending on what they utilize) with laser, vision, mechanical centering will most likely reject a different number of parts. Laser being the least (not always a laser, can also be a light source) and of course mechanical centering rejecting the most. We plan for about 5% loss but this also includes the fact that some of our components come in with little or no leader for the feeder, so we have to strip back the tape to form one suitable for our feeders. If you are losing more than say 15%-20% you have something wrong in your process. Whether it is due to machine rejects or operators stripping down reels is for you to investigate. What kind of machine are you using? If it is a turret shooter, chances are that when you have a problem, all 10+ heads will dump their components at one time.

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#22842

Component attrition | 23 December, 2002

Tried and True is counting your components if there is any indication of loss... this is a great TOPIC... unfortunately there are many ways to lose components. Feeder setup,problems with a feeder while in the machine(IE mylar problems or wrong step). The placement machine can(typically) tell you if they missed a pick or if the there was a rejection because of vision or if it did not place the part(vacuum sensor).. does this data mean you lost the part? In my experience it doesnt. It is a great indicator, however its not anything you can depend on fully to tell you how many parts you have lost. In our process we use all indicators to flag a component to be counted(after the run). Operators and setup people flag components to be counted. When the job is finished the flagged components are counted. There is nothing worse than finding you are short after setting up a job.. Our best defense for losing components? Depending on the operators to check for loss at various stages of the run.. they use the machine software which in real time tells them if the machine is having trouble with any part.. also checking the reject bin and feeder tape bin for lost components at various stages of the run Flagging parts to buy extra 1%,2% etc...can pose many problems(in my opinion) because there will be many exceptions to the rule. I would love to hear from anyone who doesnt have to do any counting in their process... ANYONE????

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#22843

Component attrition | 23 December, 2002

Hi,

You can't void of loose parts. But can reduce.

You can ask your Lead operator or the the person in charge for that individual line to keep track on the hourly monitor. If they tracking the number of PCB went thru the machine (getting the count at the machine) also look into the Production Information (for Panaserts) or Production Analysis (fuji??) This infor should tell you Pick up rate and so is Placement. Then they can also track down individual feeder for Pick up miss or recognition problems. You can take the %%% on the machine rejects (Plus new part teach need to be saved by empty out the bin each time being teach so the part like CAP or RES won't get mixes up. Remember its may not show up on the monitor # of parts teach. Operators also need to report or call for a Tech or someone with more experience if the same feeder got problem twice on the first run so the problem will be fixes the first time or will bet out of hand and will be too late and end up with more handplaces or the work order will be seating in the corner waiting for the shortage that may take days or weeks. For the new set up.. (seem to help) Give the Operators extra Electro static bags so the can keep the loose parts and write down the part numbers that if they have to strip the tape for feeders set up. They may need at the end of run. Still, This can not tell you the accurate of loose parts but I believe its will reduce.

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#22844

Component attrition | 23 December, 2002

Search the fine SMTnet Archives for background descussion.

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