Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Stencil life

Views: 2336

#80275

Stencil life | 19 April, 2018

Hello experts,

what would you recommend as a standard practice for stencil replacement? I am having here a stencil from 2004 that is worn out enough and has a small dent on the image, but still have to prove why I want to change it.

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dwl

#80276

Stencil life | 19 April, 2018

When your stencil foil looks like cooked bacon it's time to replace it.

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#80284

Stencil life | 20 April, 2018

We usually replace stencil when we start to get problems with the solder paste printing i.e. uneven solder paste deposit etc. Until then it doesn't matter how many years ago it's manufactured, but how many prints it passes and if the operators didn't do something silly with it.

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#80286

Stencil life | 20 April, 2018

Show that it is cheaper to replace than to make bad boards that need rework. Surely you can get QC to complain about the boards pasted with that stencil.

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#80513

Stencil life | 7 June, 2018

Hello, the colleagues are all right. What I did in addition to show customers and quality that we either need or dont need a stencil: 1. Made a procedure - in there i defined 50 000 cycles and then the stencil has to be checked by me. In the checks if you have dents on the image, rust, signs of delamination from frame (if you use frames). I also got a special tool to measure the tension of the stencil to see if it is ok. 2. Made a special check list in where i check all that, input the tension results from the 4 corners and the middle 3. Get information from SPI (cpk, trends, defects). If spi is giving bad panels because of stencil - immediate change. 4. If everything is okay - 50000 more cycles or until SPI signals way too many defects. Keep all check lists :) Oh yeah i forgot - we had traceability system to count cycles and automatically stop production at 50k. Then only i can release it back to production. If you have any more questions feel free to contact me.

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x-ray inspection