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How should paste layer be for SMT? I asked JLC and they said to make it a bit smaller than the pad
HasanTheSyrian_ , 12-04-2025, 12:21 PM
I made a rule for paste to be 20% smaller
QDrives , 12-04-2025, 10:27 PM
First question: who's task is it to 'shape' the paste layer?That question (in part) comes down to who does the assembly?If you order a stencil and do the assembly yourself, then you are.Second question: what is the board finish (ENIG, HASL, OCP, etc.)?ENIG and HASL have a general -10% reduction while OCP is 0%.For the thermal pad you want to reduce the solder / bare copper to about 50...60%."Window paint" it, so no openings bigger than about 1.0...1.5mm.Then there are the (inverse) home plate, etc. ...https://smtnet.com/library/files/upload/Stencil-Design-Guidelines.pdf
Robert Feranec , 12-08-2025, 12:58 PM
the biggest problem may be the exposed pad - the big pad. if there is too much solder the component will float on it and pads will not connect correctly. so as @QDrives mentioned, the solder on the big pad is usually made from small squares. about other pads, usually solder is the size of pad, but maybe jlc has some recommendations: https://jlcpcb.com/help/article/opening-process-standard-of-stencil
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