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PCB finish - Printhead vs Squeegee

fcouture

#17636

PCB finish - Printhead vs Squeegee | 18 September, 2001

Hello Jeff,

I found some good information from what I read until now...so thank you! I have two questions:

1) What finish did you use on the PCB for 0201 ? I think with an aperture so small (12x15mils) tin plated is impossible, what do you think?

2) Did you use squeege or print head for printing 0201? Is the printhead better for print definition or release?

thank you! Francois

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Jeff Schake

#17647

PCB finish - Printhead vs Squeegee | 19 September, 2001

Pad Metallurgy Used: Copper OSP pads were used for all of the results that I have been reporting. The same design test boards with Nickel/Gold pads are available and awaiting further assembly tests. I will consult with a board technology and metallurgical expert concerning your question about tin plating and post a response later on. Is your question about this targeting the current industry capability of using tin plating technology on such small pad dimensions?

Printhead: The 0201 assembly defect trend data shared was generated using 60-degree metal squeegee blades. In parallel with this, printing tests have also been performed using enclosed pressurized printhead technology. Both systems produce equivalent results for printing 0201 boards.

Some reasons one may consider using the enclosed printhead system over squeegees include:

1. Apertures that are designed with more challenging area ratios (i.e. smaller openings and/or thicker stencil) may see improvements in transfer efficiency from the enclosed printhead system, as this provides more direct pressure on the material to fill the apertures completely.

2. More efficient utilization of the solder paste material on the stencil with less waste generated.

3. Solder paste material is expected to have longer stencil life, since it is protected from exposure to the ambient in a sealed chamber.

Further enhancements to the present day standard enclosed printhead system are expected to show better print definition and volume scatter control compared to squeegees, which I look forward to sharing soon.

-Jeff

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fcouture

#17650

PCB finish - Printhead vs Squeegee | 19 September, 2001

>Pad Metallurgy Used: >Is your question about this targeting the current industry capability of using tin plating technology on such small >pad dimensions?

Actually I should have asked for tin/lead plating (HASL) and yes it's to have an idea on capability of such a small pad. On a test board we did for 0201, we order tin/lead plating (HASL) and the palting was so bumpy we weren't able to print. So the second board is now immersion gold and we have pretty good result, probably because surface is more flat...

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Jeff Schake

#17675

PCB finish - Printhead vs Squeegee | 21 September, 2001

I asked several people their opinion of HASL 0201 pads and there was no positive feedback whatsoever. The most common concern was the domed/convex shape of the pad finish that would result in aperture gasketing problems, which you may already have experienced. You should have better success with the immersion gold pads.

-Jeff

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