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

Printed Circuit Board Assembly & PCB Design Forum

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Stencil Cleaning



Stencil Cleaning | 13 April, 2001

I�ve just had an argument with my Boss on the frequency of Stencil cleaning. He told me to remove the procedures that asking the operator to send the Stencil for cleaning ( using Automatic machine ) after every 8 hours. I said big NO!! NO!!. He said the cleaning doesn�t serve any purpose as the printer is running 24 hours. I know he got his point but, wouldn�t it be bad or not healthy to the printing quality if we keep using the stencil with proper machine cleaning. ? Everybody knows that the automatic under screen cleaning is not effective, esplly running 0402 and 20 mil pitch. Pls help is this the right things to do.


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Dave G


Stencil Cleaning | 13 April, 2001

We actually switch stencils at the end of each 8 hour shift. We have two for each job #. Operators get one clean one from the rack and put the used one in the Washer for the next shift. Since we started doing this our DPMO for solder defects (Bridging,Insuff,Skips,etc.) has went down significantly. Mainly due to the fact that you are starting with fresh paste & a totally clean stencil at the beginning of each shift. When we switch products during the day the operators still put in a clean stencil before 2cnd shift comes in. We went to the two stencil procedure because operations used to groan about the downtime. This costs a bit more (Especially if you have lots of job #'s) but, the savings in rework more than cover the cost.

Hope this Helps.

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Stencil Cleaning | 13 April, 2001

dgrenier is on the right track. We are a volume shop and with a up back stencil you can keep CFM line going with no down time. DMPO also at our shop have inproved. We also use AOI equipemnt as a process indicator to monitor when stenicls need to be changed / cleaned.

Two stencils easly pays for its shelf !!!!

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Stencil Cleaning | 13 April, 2001

Proper setup and cleaning of stencil helps ensure repeatable printing performance. Cleaning processes need to be compatible with materials used in the manufacturing of stencils and solder paste. IPC 7525 should also help you out. We here would Inspect the first board of the day as it comes out of the printer. Every hour from that point we would inspect a board until the end of the shift. Keep a running log (pictures, inspection capture) of each board and note how (if) each board get progressively worst as the day goes on.

Maintenance be it stencil, machine, materials or what ever should never be excused but encouraged. Your bosses theory "As long as the car is running you should never have to change the oil" is incorrect.

I love Schedulers that would never build maintenance time into production runs. Does that mean you never take you Component placement machine off line for maintenance?

I actually like your bosses thinking- cause it promotes job security for me and the company I work for.


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mike weekes


Stencil Cleaning | 25 April, 2001

Can you recommend a good material to put in the cleaner for both water soluble AND no clean residues?


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