EFM8SB2 Datasheet, PDF (37/49 Pages) Silicon Laboratories – The EFM8SB2 highlighted features are listed below

7.2 QFN32 PCB Land Pattern
EFM8SB2 Data Sheet
QFN32 Package Specifications
Figure 7.2. QFN32 PCB Land Pattern Drawing
Table 7.2. QFN32 PCB Land Pattern Dimensions
Dimension
Min
Max
C1
4.80
4.90
C2
4.80
4.90
E
0.50 BSC
X1
0.20
0.30
X2
3.20
3.40
Y1
0.75
0.85
Y2
3.20
3.40
Note:
1. All dimensions shown are in millimeters (mm) unless otherwise noted.
2. This Land Pattern Design is based on the IPC-7351 guidelines.
3. 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.
4. A stainless steel, laser-cut and electro-polished stencil with trapezoidal walls should be used to assure good solder paste release.
5. The stencil thickness should be 0.125 mm (5 mils).
6. The ratio of stencil aperture to land pad size should be 1:1 for all perimeter pads.
7. A 3 x 3 array of 1.0 mm x 1.0 mm openings on a 1.2 mm pitch should be used for the center pad.
8. A No-Clean, Type-3 solder paste is recommended.
9. The recommended card reflow profile is per the JEDEC/IPC J-STD-020C specification for Small Body Components.
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