Solder Stencil Apertures using NO-Clean Paste and 402's| 22 October, 1999
Working DFM SMT issues with respect to a client's artwork together with a heavily modified solder stencil, I was able to reduce 0402 tombstoning from 80% across the board to 3%. I winged the aperture reductions, but are there any "rules" or guidelines available when using no-clean solder paste with 3mm pitch devices, 402's, large RF components and filters (i.e. Lorch filters)?
Re: Solder Stencil Apertures using NO-Clean Paste and 402's| 22 October, 1999
Tombstoning is usually oven profiling, see October 14 thread below. Aperture rules are misleading. Component mix, stencil thickness, paste factors, all contribute. Also, are you making the stencil from a paste or pad layer or from a soldermask layer? The actual pad sizes compared to the customer file can be very different to start with. Do some tests and develop an aperture size that works with the componets you are having trouble with, than give that as a standing spec to your stencil vendor. Good luck...dan.