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Printing off contact

Views: 3408

mk

#47262

Printing off contact | 7 February, 2007

We have been processing a family of boards for 3 years. No issues. New PCB Vendor and the boards suddenly will not print very well. Sloppy printing definition. Closer inspection reveals that the soldermask is built up .0012-.0019 over the vias, preventing the stencil from gasketing. Vendor claims they are built to print.. Opinions? Pictures at ; http://www.sipad.com/ssiqa/3942vias.pdf

mk

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JAX

#47274

Printing off contact | 7 February, 2007

mk, Should I read into the fact that you posted this on a sipad website?

You could always add an etch process to you stencil design to gasket around the raised mask locations. It is currently done when additive etch's/trace's are used. The extra $20 on the stencil will work... and it doesn't matter if the board is double sided or not.

Sipad has its advantages, being the answer to fake questions isn't one of them.

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#47276

Printing off contact | 7 February, 2007

Jax: Matt works for Sipad. In the past, he has posted questions, often with pix, seeking help resolving production issues, often involving issues with bare boards. He's not pimping his product.

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mk

#47291

Printing off contact | 7 February, 2007

Wow JAX. Way off buddy, I promise!!!!

This is real as have all my posts.

As an officer of the SMTA Atlanta Chapter for the second term, I am familiar with the Forum Etiquette..

Thanks for defending our site's honor JAX. I don't like people who abuse the forum either.

Now, do you have an actual opinion about this mask situation or are you just wasting your time cruising the Forums looking for bad guys???

mk

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#47302

Printing off contact | 7 February, 2007

Board vendors are always right. Unless you build yourself in their facility, at their price. Ways around this are half etch your stencil over the vias, open the resist (mask) on the vias, or use your own product (Sipad).

The resist (mask) does appear to be rather on the thick side in your picture. Just my opinion.

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#47334

Printing off contact | 7 February, 2007

> We have been processing a family of boards for 3 > years. No issues. New PCB Vendor and the boards > suddenly will not print very well. Sloppy > printing definition. Closer inspection reveals > that the soldermask is built up .0012-.0019 over > the vias, preventing the stencil from gasketing. > Vendor claims they are built to print.. Opinions?

Change the print they built to. Put a limit to the thickness. If they say they can't, ask how the previous vendor did it, and look for a new one.

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JAX

#47431

Printing off contact | 9 February, 2007

If the attack was unwarranted I apologize. I still stick to my answer. Unless the board shop can get rid of it you have to find a way to deal with it. Etching trace paths into the stencils is inexpensive and works just fine. If you do not have the time to design a stencil... try to make the board house design one... or at least create a common gerber layer, containing pads and affected traces, to create a stencil from.

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MAC

#47457

Printing off contact | 9 February, 2007

Not an expert on PCB manufacture, but it looks like mask from other side of PCB flowed through vias before this side was masked. Is it possible previous vendor masked this side first, or used film-type mask which would not flow through?

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cevans MPM printer specialist

#47620

Printing off contact | 13 February, 2007

Off contact is generaly less favourable than on contact printing. print height becomes a issue towards the edge or foil clamps. If you Had little or no issues with your previous board vendor re-check your specs you supplied to your current vendor. If he is maintaining the spec across a random sampling of the boards you may want to investigate your spec tolerances. If you go down the path of etched stencil appertures that will require a new stencil for this product and possibly numerous others if other boards are supplied from your new supplier.

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realchunks

#47621

Printing off contact | 13 February, 2007

If you're using vaccuum to hold the board, too much vacuum can cause bad print. This generally occurs during snap off. You can either decrease snap-off time of reduce vacuum.

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mk

#47841

Printing off contact | 20 February, 2007

Thanks to all for the info. The ideas to correct the situation are all excellent and if we see any more boards from this source with this condition we will know what to do now.

In the end however, the real questions we are trying to answer are,

1.If you were processing boards with a flat soldermask finish and your normal stencil cut, then switched to boards with soldermask built up on the vias .0012-.0019 in height, same stencil, would that result in a heavier print volume and poor print definition?

2. Do you see this condition in your shop? We've never seen this much mask on a board in 5 years.?? Is this comon?

Thanks in advance for your opinions/help. mk

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Steve

#47843

Printing off contact | 20 February, 2007

One question about the build to print statement; is there some note saying that the vias are to be plugged with mask?

If so, I'm wondering when the circle of mask was done over the vias. If it was done as a secondary operation after flood coating, then I can see why there's a raised bump over the vias. It should be done prior to flood coating.

There will be a raised profile of the bump initially, but when the rest of the mask is applied during flood coating, it should become flush with the finish of the LPI.

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Wave Master Larry

#47846

Printing off contact | 20 February, 2007

LISTEN i know its been awhile but i'm back.just got back from consulting in China. i tell ya them Chinese realy have there acts together. anyway ive recently been consulting for SMTA as well. you see here i am posting from thier address.i'm pretty tight with the top brass there so if needed i'll have these false advertisers reported to the proper arthourities

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