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Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Solder paste stencil modification

Bernie

#12940

Solder paste stencil modification | 14 January, 1999

Due to an foul up on my part, a circuit board ECO snuck up on me and I have a solder paste stencil that doesn't quite match the board. Two pads are off by about half a pad each. Can the solder paste stencil be modified? If so, what is the technique and how long would a patch hold up?

I need a temporary fix only until I can get a new stencil.

Thanks for any advice you have.

Bernie

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Mike McM

#12941

Re: Solder paste stencil modification | 15 January, 1999

Bernie, If the pads are for a chip component and only about a half a pad off without anything else in the misregistered area, go ahead and use the stencil as is. Surface tension of the solder at liquidus should cause it to wick back to the pad, even if it is printed off the pad. Otherwise, put a couple of small pieces of kapton tape on the bottom of the stencil to cover the misregistered portion of the aperture and live with a little less volume in the solder joint.

| Due to an foul up on my part, a circuit board ECO snuck up on me and I have a solder paste stencil that doesn't quite match the board. Two pads are off by about half a pad each. | | Can the solder paste stencil be modified? If so, what is the technique and how long would a patch hold up? | | I need a temporary fix only until I can get a new stencil. | | Thanks for any advice you have. | | Bernie |

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Steve Gregory

#12942

Re: Solder paste stencil modification | 15 January, 1999

| Due to an foul up on my part, a circuit board ECO snuck up on me and I have a solder paste stencil that doesn't quite match the board. Two pads are off by about half a pad each. | | Can the solder paste stencil be modified? If so, what is the technique and how long would a patch hold up? | | I need a temporary fix only until I can get a new stencil. | | Thanks for any advice you have.

Bernie,

I've had to modify stencils in the past before, so don't feel like the lone stranger. Be advised though, this is just a temporary fix, and you may wind-up having to touch-up the location though, but then you may get lucky and accomplish the modification where it'll work just fine, but at least you're not D.I.W. (dead in the water..ol' navy term,hehehe). By the way, I've only tried something like this with passive pads, and only down to 0805's...if it's anything else, forget it.

I've always used a Dremel Tool, got me a nice sharp bit whose diameter is close to the pad size or just a little smaller, and done it that way. The key is having a very sharp bit, and having patience. You don't want to force the bit at all you want to let it cut itself through the foil, otherwise you'll deform the metal and have a bump that will protrude out and hold the stencil up off the board. I'll use calipers to determine where I'm going to drill by measuring the board and then transfering my measurements to the stencil using an existing aperture and pad on the board as a reference to base the measurement off of.

In your case it sounds like it'll be fairly easy just to enlarge the holes that you have and then use some very small peices of kapton tape to mask off the part of the opening that is not over the pads...it's a little trying to get the tape placed where you want it, but if you have a clean surface when you place the tape it'll hold up enough to where you can use the stencil. You may have to replace the tape a time or two while using the stencil.

I know this just some bubble-gum and baling wire, but I've done this to get me out of a jam a few times...

-Steve Gregory- | | Bernie |

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Steve Moore

#12943

Re: Solder paste stencil modification | 19 January, 1999

Bernie, Steve Gregory approach is the simplest solution. But,If you ever get yourself into a real bind and need an array of holes added and the cost of a new stencil is astronomical. Approach Hamlet at BeamOn. I have seen him add and enlarge holes on existing stencils with the precision of a newly cut one.

Steve

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Mike Vina

#12944

Re: Solder paste stencil modification | 19 January, 1999

| Bernie, Steve Gregory approach is the simplest solution. But,If you ever get yourself into a real bind and need an array of holes added and the cost of a new stencil is astronomical. Approach Hamlet at BeamOn. I have seen him add and enlarge holes on existing stencils with the precision of a newly cut one. | | Steve | | | |

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Mike Vina

#12945

Re: Solder paste stencil modification | 19 January, 1999

| Bernie, Steve Gregory approach is the simplest solution. But,If you ever get yourself into a real bind and need an array of holes added and the cost of a new stencil is astronomical. Approach Hamlet at BeamOn. I have seen him add and enlarge holes on existing stencils with the precision of a newly cut one. | | Steve | | Gee Steve, I direct your attention back to this site and you plug somebody else's service. Thank you!?

Mike | |

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Tony A

#12946

Re: Solder paste stencil modification | 20 January, 1999

| | Bernie, Steve Gregory approach is the simplest solution. But,If you ever get yourself into a real bind and need an array of holes added and the cost of a new stencil is astronomical. Approach Hamlet at BeamOn. I have seen him add and enlarge holes on existing stencils with the precision of a newly cut one. | | | | Steve | | | | | | | | | | Hi there, I am currently appliying through hole technology through the SMT process, that is pending that the through hole components can be reflowed. We have been very successful and yes we make several modifications to our stencils. In order to make modifications it helps that your stencil is laser cut from start, than you can modify appertures as required. I-Source is another stencil house that have laser cut machines.

Thanks

Tony A

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Bernie

#12947

Re: Solder paste stencil modification | 20 January, 1999

Thanks for the info. I modified the stencil, ran the boards, and just got a new stencil. Life is good again. Bernie

| Due to an foul up on my part, a circuit board ECO snuck up on me and I have a solder paste stencil that doesn't quite match the board. Two pads are off by about half a pad each. | | Can the solder paste stencil be modified? If so, what is the technique and how long would a patch hold up? | | I need a temporary fix only until I can get a new stencil. | | Thanks for any advice you have. | | Bernie |

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