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Labeling before paste printing

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SMTA-64386201

#87697

Labeling before paste printing | 7 March, 2022

We previously labelled PCBs after assembly but before AOI. Now we need to trace panels during assembly as well, so have the need to apply labels before the assembly process starts. Our stencils are thus not stepped to accommodate labels.

I suppose the answer is "it depends..." but are there general guidelines regarding proximity of labels to apertures to ensure that the label will not negatively impact the print?

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#87698

Labeling before paste printing | 7 March, 2022

I wish traceability was not part of our job. If I have to pick, I will laser etch barcodes rather than use labels. Small footprint and fine pitch parts will always hate the label when you print paste. Pick thinner labels, keep away from problematic locations when possible.

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#87705

Labeling before paste printing | 10 March, 2022

How far from apertures is the label supposed to go? I'd say 1 inch is plenty. 3/4 inch might be plenty also.

Do you have the ability to measure paste height? I'd say place the label on one board and print two. Is there an appreciable difference in paste height?

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SMTA-64388039

#87743

Labeling before paste printing | 23 March, 2022

In my experience a distance of 30 mils per 1 mil in height above PCA nominal is sufficient for the squeegee blade to bend (in the direction of squeegee travel) so that you don't have excessive solder issues near the label. Labels are about 5 mils tall, so any components 150 mils away should be fine. However, the squeegee blade doesn't bend well along its length. You will see excessive solder for about an inch to either side of the label in that direction.

I see four options: 1. Laser mark labels. 2. Use panel labels for component traceability, then add board labels before AOI. 3. Order a new stencil that is stepped in the label area (with plenty of margin for 'misplacement' of the label). 4. Just live with excessive solder. If affected components aren't too small, you are probably fine.

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SMTA-64386201

#87926

Labeling before paste printing | 3 May, 2022

Yes, I fully agree on the pain of traceability and on laser etching. We are aiming to go the laser route in the long run

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SMTA-64386201

#87927

Labeling before paste printing | 3 May, 2022

Thank you, this was exactly the type of guidance that I was hoping for!

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SMTA-64386201

#87928

Labeling before paste printing | 3 May, 2022

We do have a CyberOptics SQ3000 that is currently only used for AOI, but I hope to start doing sample 3D SPI with it soon.

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