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Scrap criteria

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OEM Manufacturer

#36698

Scrap criteria | 19 September, 2005

Does anybody know of any standards that are available that cover how many times a part or complete unit can be reworked before it is considered to be scrapped?

I am currently writing a process to review this with a supplier.

For example, a bga device can only be replaced twice before the unit is scrapped and rebuilt etc.

Thanks,

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#36701

Scrap criteria | 19 September, 2005

There is not "one size fits all" answer. One criteria I've heard used is scrap it after so many hours of troubleshooting if it's not fixed. End use of the board would be a factor as well. I would want someone giving up salvaging a board for a defibrillator long before they would give up on a VCR controller.

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RDR

#36708

Scrap criteria | 19 September, 2005

It all comes down to cost and reliability. Which order is up to you. You don't want to spend $100 fixing a $1 board.

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#36719

Scrap criteria | 20 September, 2005

I would say it depends on the process requirements for the board and the reliability requirements as has already been mentioned. If you do two-sided reflow you might allow for fewer rework attempts, for example. If it's a medical device you might only allow one attempt to rework a single site on a single sided assembly.

Obviously the abilities of your rework people are critical too. One repair cycle with a heavy hand on a 10 mil pad with an iron that's too hot is one cycle too many.

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OEM Manufacturer

#36726

Scrap criteria | 20 September, 2005

Ok sounds like it is very mush devised by the type of technology and also cost. The boards are double sided telecoms boards with immersion tin finish and very complex (Multi-Layer, 0.4mm QFP, pressfit, double sided BGA's, >$1500 each

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intermin

#36727

Scrap criteria | 20 September, 2005

Well, at that value point, I'd go with the hourly ( unburdoned ) high-skill rework/repair rate up to 50%-60% of the board value. If this is part of an integrated system ( in-house assembly ) repair to value ratio could go even higher.

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#36729

Scrap criteria | 20 September, 2005

Wow! How would it be possible to spend $700-$800 in labor to repair a single board? What are labor burdens these days? $30-$40 per hour at most?

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Slaine

#36749

Scrap criteria | 21 September, 2005

i set this up for one of nokias manufacturing plants and based it on the value of the board, caluclated the average rework times, worked out the costs of rework and costs of the board then for each type manufactured put a figure on the number of times it could be reworked. for smaller boards was 2 or 3 times, for larger boards up to about �3500 each worked out how many hours should be spent on them but they werent much of a problem as you normally fixed them before you got near the scrap price. i worked on 60 to 80% of the board cost. and used the phrase beyond economic repair (BER)

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#36765

Scrap criteria | 21 September, 2005

I was going to ask the same question. As was mentioned, it depends on the classification of product. If it's IPC Class 3, with a requirement for high reliability, I'd want the OEM manufacturer to have a defined statement on this issue for more that 2 placements - backed up by testing ie: pry and dye or SEM cross section. I've discussed this with 2 other companies and one scraps the PWB after the second placement, the other has to have Technical Review Board's sign off for a third placement. If there is an excessive number of BGAs to be removed and the boards are a high cost, possibly the process and the board design should be reviewed. Is there a standard out there that defines this issue?

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OEM Manufacturer

#36921

Scrap criteria | 30 September, 2005

> Does anybody know of any standards that are > available that cover how many times a part or > complete unit can be reworked before it is > considered to be scrapped? > > I am currently > writing a process to review this with a > supplier. > > For example, a bga device can only > be replaced twice before the unit is scrapped and > rebuilt etc. > > Thanks,

I currently work on the BER (Beyond Economical Repair) assumptions and also the 3 strikes rule (i.e. on the 3rd attempt of repairing the same fault the part is scrapped and high value items scrapped. Suppliers are renouned for reworking boards until they work and the only way to tie this down is to specify in contractual terms.

I have even seen pad replacement in some instances. Thanks for the threads - I guess this just confirms that there is no real reference to point to.....

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