Stencil Design Guidelines
A properly designed solder screen or stencil is required
to ensure optimum amount of solder paste is deposited
onto the PCB pads. The recommended stencil layout is
shown in Figure 26. The stencil has a solder paste deposi-
tion opening approximately 70% to 90% of the PCB pad.
Reducing stencil opening can potentially generate more
voids underneath. On the other hand, stencil openings
larger than 100% will lead to excessive solder paste smear
or bridging across the I/O pads. Considering the fact that
solder paste thickness will directly affect the quality of
the solder joint, a good choice is to use a laser cut stencil
composed of 0.127 mm (5 mils) thick stainless steel which
is capable of producing the required fine stencil outline.
The combined PCB and stencil layout is shown in Figure
27.
Figure 25. Suggested PCB Land Pattern and Stencil Layout
Figure 26. Stencil Outline Drawing (mm)
Figure 27. Combined PCB and Stencil Layout
AVAGO [ AVAGO TECHNOLOGIES LIMITED ]
