SiM3C1xx
6.5.1. QFN-40 Solder Mask Design
All metal pads are to be non-solder mask defined (NSMD). Clearance between the solder mask and the metal pad
is to be 60 µm minimum, all the way around the pad.
6.5.2. QFN-40 Stencil Design
1. A stainless steel, laser-cut and electro-polished stencil with trapezoidal walls should be used to assure
good solder paste release.
2. The stencil thickness should be 0.125 mm (5 mils).
3. The ratio of stencil aperture to land pad size should be 1:1 for all pads.
4. A 3x3 array of 1.1 mm square openings on a 1.6 mm pitch should be used for the center ground pad.
6.5.3. QFN-40 Card Assembly
1. A No-Clean, Type-3 solder paste is recommended.
2. The recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification for Small Body
Components.
86
Preliminary Rev. 0.8
SILICON [ SILICON ]
