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Solder Paste Printed Volume

ianchan

#18252

Solder Paste Printed Volume | 25 November, 2001

Hi All,

We juz purchased a 2nd hand CyberOptics 3D paste inspection machine (what a mouthful...) and am seeking info :

1) what formulae is applicable, to calculate the deposited solder paste volume onto the pre-defined PCB pads?

1.a) from our observations, paste is seldom "brick" printed, and more like a "mountain hill" shaped.

2) want to pre-calculate the required volume (cubic-cm) measurements, so will know what USL/LSL to program the CyberOptics machine, and trigger the "process-error" alarm...

3) for those guys with experience in similar 3D volume paste inspection machines, any suggestions as to whether we are in the right direction in application of this machine? as really need this machine to measure the paste volume and reflect into SPC charts, thus cutting down time wastage for my operators (who measure paste Z-height manually)

Suggestions and directions appreciated, guys, thanks!

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Michael Parker

#18257

Solder Paste Printed Volume | 26 November, 2001

1. The formula for cubic area (LxWxH) applies to get the expected volume target value.

Caution- do not assume the pad surface square are is correct for the part. Do consider the footprint of the device beign placed and its solder requirements to create a mechanical and electrical bond. The designer may have created a multi-purpose pad to accomodate several different parts. You can end up with too little or too much paste without considering the actual need. 2. Paste print "bricks vs. mountains" - Process variations cause this - consider squeegee type, speed, angle. Also stencil seperation rate from the PCB can lift the paste to a mountain shape. Poor alignment of stencil aperture to pads can cause non-brick shapes. Aperture geometry in the stencil will also misform "bricks". Paste viscosity (too cold, too hot), not enough or too much flux also affect "brick" shapes.

3. You are starting to follow the right direction. Just remember - Paste Height or volume is just an attribute - many variations affect it. You need to establish a target value, determine acceptable range for process variations such as those I just listed, then you can create a simple chart with Upper and Lower limits that will be meaningful.

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ianchan

#18268

Solder Paste Printed Volume | 26 November, 2001

M.Parker,

thanks a million!

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Jamstart

#18312

Solder Paste Printed Volume | 30 November, 2001

It will be a 'risk' to rely the volume using cyberoptic as it does not tell you the true volume. With no disrespect to them, they are only using 'mathematical' calculation (LxBxH)to get the volume. As we know that the paste will never be a flat surface, so getting a single height is not sufficient to know the entire volume. Hope my comment is right.

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ianchan

#18320

Solder Paste Printed Volume | 3 December, 2001

Hi,

actually this point was raised a cuppa times, from the past discussion forums... thats why I posed this questions once again *yawn* to find out any new delvelopments in relation to paste Volume giving accuracy???

Obviously it doesn't seem to have improved eh? Anyway in my humble opinion, volume (math-calculated or true cubic cm measurements) is definately going to be better than only rely on simplistic paste height readings?

Mebbe some egg-brain blokes at the machine manufacturer's side, can help R&D a solution out for the SMT industry?

thanks guys for the sharing :)

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Damian Holzmann

#18396

Solder Paste Printed Volume | 11 December, 2001

Regarding your comment "technology doesn't seem to have improved". Actually, technology has improved significanty. Cyber Optics uses a line measurement, a new unit from Germany uses sine wave differential measurement. The Gridmeter unit captures a video image and performs 300,000 measurements in less than a second. One measurement is taken for each pixel displayed, mapping the entire field of view of the camera. To acheive extremely accurate measurements of solder paste deposits, the operator sets 3 points of reference over copper, and draws a window over the paste deposit to be measured. The window can be drawn oversized because the unit automatically identifies exactly where the paste is and displays cubic volume. Accuracy is +/- 1 micron for height and min/max can be preset with different colors diplayed for Min/OK/Max, Red/Green/Yellow.

Significantly more accurate than line measurement.

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ianchan

#18407

Solder Paste Printed Volume | 11 December, 2001

Damian, Hi,

thanks for the technological update... considering current cyberoptics marketing strategy of its pricing terms for its machines, little wonder when I personnally may have the chance to encounter this new little baby... Thanks.

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Jamstart

#18430

Solder Paste Printed Volume | 12 December, 2001

Hey, I wonder where can I get this machine? I believe others are interested as well. Thanks in advance.

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Cyber Legacy Division

#18492

Solder Paste Printed Volume | 20 December, 2001

Also check out the ASC International machine called VisionMaster. This true 3D inspection system has been around for at least 3 years. It provides the highest level of paste measurement in its class. The software is also very easy to operate.

The web site is http://www.ascinternational.com

Good Luck.

Steve

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