I am ordering the stencils and I do not know if I shuld order .12 o .1 ones. There are some TQFP64 ISs and 0603 passive elements. I'd like to avoid bridges.
Thank you Peter
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\$\begingroup\$ Ask your board assembler. \$\endgroup\$– Leon HellerApr 20, 2018 at 12:56
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\$\begingroup\$ It is for my own use. Manual printing. \$\endgroup\$– 0___________Apr 20, 2018 at 13:10
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\$\begingroup\$ You can still query PCB assemblers. Send an email their way and ask for advice \$\endgroup\$– CuriousApr 20, 2018 at 13:18
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2 Answers
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I normally use 0.12mm stainless steel in a 370 x 470 frame, with a good manual stencil printer. No problem down to 0402.
The stencil thickness is not the biggest variable, squeegee technique and solder paste consistency and positioning are more critical.
If your stencil is some other material or very large you may want to use something else.
answered Apr 20, 2018 at 13:38
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\$\begingroup\$ Thank you very much. My ones are steel framed ones. I will follow your advice. \$\endgroup\$ Apr 20, 2018 at 13:50
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A laser-cut, stainless steel 0.125 mm stencil with electropolished trapezoidal walls is recommended. Electropolishing "smooths" aperture walls, resulting in reduced surface friction, good paste release and void reduction. Using a trapezoidal section aperture (TSA) promotes paste release and also forms "brick-like" paste deposits that assist in firm component placement.
Solder mask variations are also important with unmasked apertures may need to be adjusted for less than or equal to 0.5mm pitch to reduce risk of bridging .e.g 0.05 smaller
