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Pasteprinter | unffilled Pads

Pasteprinter | unffilled Pads

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Hello, we have increased problems with a product with the p... - Feb 14, 2023 by Yannick Herzog

The slower the squeegee speed the more tendency for "dr... - Feb 14, 2023 by Sr. Tech

the viscosity of the paste is too high, printing parameter i... - Feb 15, 2023 by Wippsen

If these pads are on the edge of the board try increasing th... - Feb 15, 2023 by dima

These guys said most of what I was going to say. I'll add ... - Feb 15, 2023 by ProcEng1

Hello, thank you for your responses. Some time has passed s... - Oct 13, 2023 by Yannick Herzog

Did the paste make it there and did not stick, or the paste ... - Oct 13, 2023 by Evtimov

I would say that the paste never made it in this corner. Enc... - Oct 16, 2023 by Yannick Herzog

Is there only 1 pcba affected or more? Can try splitting th... - Oct 16, 2023 by MagyarT

Have you tried making two passes with the blades? ... - Oct 16, 2023 by ProcEng1

@MagyarT the error occurred across multiple PCBs throughout ... - Oct 16, 2023 by Yannick Herzog

Based on these pictures, please check Board/Stencil co-plana... - Oct 16, 2023 by Evtimov

It looks to me that you might have a poorly etched/polished ... - Oct 16, 2023 by AlexV

Just for fun can we see pictures of the blades? ... - Oct 18, 2023 by Stephen

Mass confusion here. Let me drop some knowledge.. #1. Unl... - Oct 19, 2023 by Sr. Tech

I agree, and also, assuming you have SPI (if the solder past... - Oct 20, 2023 by MagyarT

I agree with Sr. Tech. What does the reflowed joint look lik... - Oct 20, 2023 by DWL

Yes, we use an SPI to inspect the solder paste print. We do ... - Oct 21, 2023 by Yannick Herzog

Time flies. 25 years ago we would have asked the durometer o... - Oct 23, 2023 by Stephen

Yannick Herzog

#88960

Pasteprinter | unffilled Pads | 14 February, 2023

Hello,

we have increased problems with a product with the paste pressure. Here we can see pads that are not completely printed.

We suspected that the squeegee speed was too fast and the amount of paste on the stencil was insufficient. Unfortunately, changing both parameters did not bring any improvement.

Does anyone have any other ideas as to what this could be?

Greetings

Yannick

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Sr. Tech

#88962

Pasteprinter | unffilled Pads | 14 February, 2023

The slower the squeegee speed the more tendency for "drag out" Raise the print speed and pressure. Rule of thumb 1.5 to 2 LBS squeegee pressure per inch of blade to start. OR try 2 passes with the squeegee.

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Wippsen

#88964

Pasteprinter | unffilled Pads | 15 February, 2023

the viscosity of the paste is too high, printing parameter is not the problem. did you use old solder?

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dima

#88965

Pasteprinter | unffilled Pads | 15 February, 2023

If these pads are on the edge of the board try increasing the stroke.

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ProcEng1

#88966

Pasteprinter | unffilled Pads | 15 February, 2023

These guys said most of what I was going to say. I'll add this. Do you notice a difference when the print is front to back, vs back to front? Are the voids still there, just on opposite sides? Do you notice that this happens more for the first couple prints but then it evens out as the paste gets "massaged" on the foil? Is this happening more with apertures towards the edge? Do you have good board support under these spots?

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Yannick Herzog

#90075

Pasteprinter | unffilled Pads | 13 October, 2023

Hello,

thank you for your responses. Some time has passed since then. Unfortunately, we have been facing the issue of incomplete filling in the production when it comes to large openings in the template.

This phenomenon occurs in both directions. The circuit boards are generally well supported. The error doesn't only occur on the initial circuit boards. Additionally, this issue doesn't always happen solely in the outer areas of the circuit boards but everywhere on the PCB.

Could it be that the openings are too large to be filled completely? What design rules should be considered in this case?

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Evtimov

#90077

Pasteprinter | unffilled Pads | 13 October, 2023

Did the paste make it there and did not stick, or the paste never made it in this corner? is the question to answer.

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Yannick Herzog

#90080

Pasteprinter | unffilled Pads | 16 October, 2023

I would say that the paste never made it in this corner. Enclosed, you can see some different pads with this failure.

Attachments:

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MagyarT

#90081

Pasteprinter | unffilled Pads | 16 October, 2023

Is there only 1 pcba affected or more?

Can try splitting the large apertures in 4. Check squeegee blades and paste quantity on stencil?

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ProcEng1

#90082

Pasteprinter | unffilled Pads | 16 October, 2023

Have you tried making two passes with the blades?

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Yannick Herzog

#90083

Pasteprinter | unffilled Pads | 16 October, 2023

@MagyarT the error occurred across multiple PCBs throughout the entire job. So, for example, the issue isn't limited to just the first printed one but spans the entire duration.

At what dimensions would you recommend a division? The apertures on the image to the far right, for instance, are 2.3 mm x 2.3 mm. The squeegee blades are inspected daily. The solder paste roll is measured using a laser and has been set to a minimum of 15 mm.

@ProcEng1 Yes, we have already tried two squeegee strokes, but this sometimes results in higher cycle times.

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Evtimov

#90084

Pasteprinter | unffilled Pads | 16 October, 2023

Based on these pictures, please check Board/Stencil co-planarity. Sometimes there might be a distance/gap between them helping this phenomenon(solder mask might be too thick). Also decreasing print speed, might help to mitigate it. You might be too fast.

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AlexV

#90086

Pasteprinter | unffilled Pads | 16 October, 2023

It looks to me that you might have a poorly etched/polished stencil. Also, I would check separation speed and distance.

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Stephen

#90100

Pasteprinter | unffilled Pads | 18 October, 2023

Just for fun can we see pictures of the blades?

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Sr. Tech

#90102

Pasteprinter | unffilled Pads | 19 October, 2023

Mass confusion here.

Let me drop some knowledge..

#1. Unless there is some special requirement, that small amount of scavenging is completely meaningless.

#2. Large apertures are always going to be prone to this condition. If it bothers you, then utilize more panes in the stencil aperture like mentioned above.

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MagyarT

#90105

Pasteprinter | unffilled Pads | 20 October, 2023

I agree, and also, assuming you have SPI (if the solder paste roll is measured by laser) the SPI should not fail a board for such amount of missing paste.

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DWL

#90106

Pasteprinter | unffilled Pads | 20 October, 2023

I agree with Sr. Tech. What does the reflowed joint look like? Is there an actual defect in the solder joints? If its good, I wouldn't worry about the print not being text book perfect.

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Yannick Herzog

#90107

Pasteprinter | unffilled Pads | 21 October, 2023

Yes, we use an SPI to inspect the solder paste print. We do not classify this as a defect. Since we can measure the solder paste deposits, and the volume on these pads is always fine, we do not rework these errors.

The goal was only to identify a cause of the issue in order to potentially address it through an adjustment of the stencil or similar measures.

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Stephen

#90119

Pasteprinter | unffilled Pads | 23 October, 2023

Time flies. 25 years ago we would have asked the durometer of the squeegee blades. But I have only seen metal ones in the last couple of decades.

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