C8051F320/1
38 Rev. 1.4
Figure 4.6. QFN-28 Recommended PCB Land Pattern
Table 4.5. QFN-28 PCB Land Pattern Dimesions
Dimension Min Max Dimension Min Max
C1 4.80 X2 3.20 3.30
C2 4.80 Y1 0.85 0.95
E 0.50 Y2 3.20 3.30
X1 0.20 0.30
Notes:
General
1. Al
l dimensions shown are in millimeters (mm) unless otherwise noted.
2. D
imensioning and Tolerancing is per the ANSI Y14.5M-1994 specification.
3. T
his Land Pattern Design is based on the IPC-7351 guidelines.
Solder Mask Design
4. Al
l metal pads are to be non-solder mask defined (NSMD). Clearance between the solder
mask and the metal pad is to be 60m minimum, all the way around the pad.
Stencil Design
5. A st
ainless steel, laser-cut and electro-polished stencil with trapezoidal walls should be used
to assure good solder paste release.
6. The stencil thic
kness should be 0.125mm (5 mils).
7. T
he ratio of stencil aperture to land pad size should be 1:1 for all perimeter pins.
8. A 3x3 array of 0.9
0mm openings on a 1.1mm pitch should be used for the center pad to
assure the proper paste volume (67% Paste Coverage).
Card Assembly
9. A No-Cl
ean, Type-3 solder paste is recommended.
10. T
he recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification for Small
Body Components.
