Silicon Laboratories C8051F347 - Manual (Page 40)

C8051F340/1/2/3/4/5/6/7/8/9/A/B/C/D
40 Rev. 1.3
Figure 4.9. QFN-32 Recommended PCB Land Pattern
Table 4.7. QFN-32 PCB Land Pattern Dimesions
Dimension Min Max Dimension Min Max
C1 4.80 4.90 X2 3.20 3.40
C2 4.80 4.90 Y1 0.75 0.85
E 0.50 BSC Y2 3.20 3.40
X1 0.20 0.30
Notes:
General:
1. All dimensions shown are in millimeters (mm) unless otherwise noted.
2. This Land Pattern Design is based on the IPC-7351 guidelines.
Solder Mask Design:
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
m minimum, all the way around the pad.
Stencil Design:
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 pins.
7. A 3x3 array of 1.0 mm openings on a 1.2mm pitch should be used for the center pad to assure
the proper paste volume.
Card Assembly:
8. A No-Clean, Type-3 solder paste is recommended.
9. The recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification for Small
Body Components.