Solder
Mask versus Performance
Bree
Engineering offers our standard surface mount packages in two styles,
with or without solder mask. There are advantages to both options
and care should be taken when specifying which.
Advantages:
With
solder mask applied to the bottom of the filter, applications requiring
reflow mounting will have tighter controlled positioning. This is
due primarily to the effect of the surface tensions of the solder
during the reflow operation.
The
filter package without solder mask will have better electrical isolation
characteristics. This is due to two factors. First the lack of continuous
ground plane on the bottom of the package. This goes along with
the age old adage "when it comes to grounding more is better".
Secondly, the solder mask itself will lift the package up off the
mounting surface slightly. This lifting will cause extremely small
inductance strays at the grounding points.
Recommendations:
Application
is everything. Typically both styles of surface mount packages will
be limited to 50 dBc of isolation, especially above the 1500 MHz
range. In cases where a reflow operation will be utilized in placement
and the isolation requirements are less then 50dBc then a solder
mask is recommended.
If
higher isolation is needed or the filter will be hand soldered in
place then a package without solder mask is recommended.
If
both a reflow environment and higher levels of isolation are needed
then we recommend trying both package styles in a short pre-production
run.
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