S2083 MA-COM [M/A-COM Technology Solutions, Inc.], S2083 Datasheet - Page 5

• Manufacturer Part Number: S2083
• Description: Surface Mount Instructions for QFN / DFN Packages
• Manufacturer: MA-COM [M/A-COM Technology Solutions, Inc.]

5
Surface Mount Instructions for QFN / DFN Packages
ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions
is considering for development. Performance is based on target specifications, simulated results,
and/or prototype measurements. Commitment to develop is not guaranteed.
PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology
Solutions has under development. Performance is based on engineering tests. Specifications are
typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available.
Commitment to produce in volume is not guaranteed.
Application Note
S2083
Solder Mask Considerations
The solder mask, a permanent part of most PCB’s
applied after etching the metal pads, helps protect
the spaces between the metal pads from solder
paste and unintended adhesion of solder.
metalized pad areas on a printed circuit board can
be classified as either solder mask defined (SMD)
or non-solder mask defined (NSMD), depending on
the size of the opening in the solder mask relative
to the size of the metal pad.
An SMD metal pad has its periphery partly covered
by the solder mask.
within a larger opening in the solder mask.
The copper etching process used to define metal
pads provides tighter control than the solder mask
process, so M/A-COM recommends using NSMD
pads whenever possible.
solder mask opening for all lead pads should be
140 microns larger than the pad size, which results
in 70 microns clearance between the copper pad
and solder mask. For example, the 4 x 4 mm 20-
lead package has an indicated width of the PCB
lead pad (X) of 0.28 mm (Table 1) and the width of
the solder mask opening (Wm) would be 0.42 mm
(Table 2). In the other direction, the length of the
solder mask opening (Lm) should be 180 microns
extended outward from the edge of the package
and 70 microns inward from the PCB pads, which
results in a total length of 900 microns (see
Table 2).
An NSMD metal pad sits
The recommended
Figure 2-1 Solder Mask Designs
All
M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make
changes to the product(s) or information contained herein without notice.
To avoid any solder bridging between the thermal
pad and lead pads, we recommend making the
thermal pad an SMD pad so that the solder mask
defines the thermal land. The mask opening (Tm)
should
recommended thermal land size, which would be
2.1 mm for the 4 mm PQFN package. See Table 2
for additional recommended thermal land solder
mask opening dimensions.
To prevent solder wicking inside the via during
reflow, we recommend solder mask pads over all
thermal via areas.
should be 100 microns larger than the via diameter.
Based on our experience with suppliers, we have
found fewer voids under the die paddle using
solder mask printing on the top surface of the PCB,
as compared with solder mask printing on the
bottom. Filled vias also work well as an alternative
to solder mask to further enhance thermal
conduction for high power amplifier products (see
figure 1-3).
include 1 oz. copper plating in vias which are
subsequently filled with a conductive via fill material
and then over-plated. It is recommended that there
be 2 oz. final copper thickness on the thermal pad
for optimal heat transfer.
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be
100
These printed boards should also
microns
The solder mask diameter
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smaller
than
Rev. V10
the