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Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Silly Attrition Levels

#24317

Silly Attrition Levels | 28 April, 2003

This may be a really silly question but does anyone pick up and hand place the reject parts from the scrap bins of the machine?

My attrition rates are out of control and i think this would not only highlight the problem but also save oodles of money. What does anyone think? Too much operator/labour time to save anything? to risky with regards to incorrect part being placed?

Chrissie

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terrapinstation

#24325

Silly Attrition Levels | 28 April, 2003

Chrissie,

There is no "silly" question.

It seems to me that, not with standing the issues highlighted in your posting, notably - risks, time, etc..

Your time would be much better spent determining the reason for the reject. If your placement equipment tracks "machine data" relevant to rejects by feeder, this can be reviewed by product to determine the reason for the rejects. Ultimatly, the time spent doing this will result in lowering your attrition rate - now and in the future.

As an example, you may have a QFP which is rejected due to coplanarity issues. You would hate to manually place the component having the product end up in rework.

Best of luck

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#24330

Silly Attrition Levels | 28 April, 2003

We have retaped the components ourselves or had a tape house do it for us and we have on the more expensive components hand placed them in a couple of instances, this is not a common solution and only should be done as a damage control procedure.

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Brian W.

#24336

Silly Attrition Levels | 28 April, 2003

We typically do not try to pick up and hand placve chip resisstors and capacitors. The risk and cost is too high for components that are a penny or less. We take into consideration that on many of our components, someone will have to test them to verify the correct values. Of course, there are components whose cost or availability makes hand placing a requirement. Many of the pick and place machines keep track of placements, drops, and misses. Depending on the machine, you can usually take the type of error and point to a feeder or nozzle (if mechanical), or the part (program related). In a previous incarnation, we used to have the operators monitor the placement error rate. If it was more than 2%, the line was stopped and a technician had to check the problem out. I believe some of the newer software with some of the equipment can actually alarm now if programmed limits are violated. I would strongly recommend that you monitor your placement rates and then delve deeper and resolve your maintenance or programming problem before accepting the situation and handplacing components.

If I can be of any further help, please let me know.

Brian W.

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#24337

Silly Attrition Levels | 29 April, 2003

Thanks for your replies guys, i definately will look into the retapeding option as on further inspection of the line yesterday i found that some of the reels have a crappy plastic on top of them that our feeder literally just pulls off, exposing lots of components and bunching up the tape at the back (i hope that make sense to some of you!). Apparently procurement will not act unless this it is specified that a certain type of tape and reel is required, and they can't do that until they have a report signed by a bunch of managers. So i'm now writing the report and hopefully the situation will be fixed - that part of it anyways. Do you have any recommendations of retaping companies - i'm in the UK but as long as they have a quick turn around it doesn't mater where they are - the exsiting tapes need to be fixed if my attrition rate are to go down!!

Chrissie

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#24346

Silly Attrition Levels | 29 April, 2003

Chrissie,

what type of equipment do you have? Is your tape PSA (pressure sensitive) or HSA (heat sensitive)?

Jason

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#24354

Silly Attrition Levels | 30 April, 2003

Jason, From what i can gather it's a bit of both. The feeders are the siemens sliplace feeders. What it seems to me is that we have gone for the cheapest option of parts and they aren't good enough. Nobody appears to have written this down though!! Chrissie

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#24364

Silly Attrition Levels | 30 April, 2003

Sounds like PSA cover tape. Contact Siemens about this. There may be an adjustment or modification to the feeder to stop it from delaminating the tape. This is generally a problem in feeders that have continuos tension on the take up mechanism (such as the SiPlace feeders broken cover tape detector) versus slip clutch type. Also check out 3M website (manufacturer of pressure sensitive cover tape). They have written a document on the subject. This may be your biggest component in the "silly attrition levels". I think the website is http://www.mmm.com.

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Rocky

#26286

Silly Attrition Levels | 6 November, 2003

I would just like to add that here at 3M we have worked with various equipment manufacturers in resolving issues of psa cover tape delamination due to higher tension feeders or adhesive build-up in collection bin type feeders. If anyone is interested I can provide technical bulletins concerning these developments.

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#26289

Silly Attrition Levels | 7 November, 2003

Rocky, i would be interested, do you want to email me them direct?

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Loz

#26290

Silly Attrition Levels | 7 November, 2003

Tape and reeling services as follows:- Specific Components Ltd. Tel. 01257 279944

Others available are Action Circuits, in Luton. Intosert in Northampton. Sorry no contact details for above.

Loz

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