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Solder paste height

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#58228

Solder paste height | 2 March, 2009

Hi to everyone, I'm new with the Solder Paste Inspection machines, and I'm doing my first measures and I noticed that I'm getting a solder paste heigth of 7 & 8 mils using a 5.0 mils stencil, with metal squeegees and 0.0 Snap off. are this results normal?

Thanx!

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#58229

Solder paste height | 2 March, 2009

Check stencil is their a lot of paste still on the stencil if so that is the extra thickness maybe add more pressure. check to see if board is coming up far enough to touch the bottom of the stencil.

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CL

#58258

Solder paste height | 4 March, 2009

Hi Jorge,

Take a bare board and measure over the same pad. We have had similar issues with a higher deposition than the stencil thickness. In some cases, we have found that the top of the pad was higher than the solder mask. Our inspector uses the board level as the baseline so whatever the hight difference is needs to be subtracted from the height measurement. Some systems allow you to set an offset if you know that the pad height is different.

Just something to look at.

Good Luck.

Chris

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#58268

Solder paste height | 5 March, 2009

When you measure "solder paste heigth of 7 & 8 mils using a 5.0 mils stencil," are you measuring the top of a flat brick? Sometimes if you snap-off the stencil too fast, the paste touching the stencil walls form peaks along the edge of the brick that are higher than the majority of the paste deposit.

Bottom-line: if the volume of paste is correct, move on.

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#58273

Solder paste height | 5 March, 2009

We've realized that the bricks are not that flat, most of our bricks have higher points at the edge, we are working with slow snap off parameters. fortunately we are not experiencing solder bridges.

thanx to all

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PR

#58274

Solder paste height | 5 March, 2009

Are you using HASL PCB's? Try measuring a bare board and compare.

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#58277

Solder paste height | 5 March, 2009

Most likely, placing components will smush the higher points on the edges of your paste deposit

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#58292

Solder paste height | 6 March, 2009

Is this a manual measurement machine? As already stated, knowing the height of the pad underneath the paste brick is critical to knowing the true height an/or volume of paste. Any decent automated inspection system will have a way to factor out the pad thickness, you might want to go back to your vendor and see what they recommend.

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