MLO
TM
SMT Crossover
AUTOMATED SMT ASSEMBLY
The following section describes the guidelines for automated
SMT assembly of MLO
TM
RF devices which are typically
Land Grid Array (LGA) packages or side termination
SMT packages.
Control of solder and solder paste volume is critical for
surface mount assembly of MLO
TM
RF devices onto the PCB.
Stencil thickness and aperture openings should be adjusted
according to the optimal solder volume. The following are
general recommendations for SMT mounting of MLO
TM
devices onto the PCB.
SMT REFLOW PROFILE
Common IR or convection reflow SMT processes shall be
used for the assembly. Standard SMT reflow profiles, for
eutectic and Pb free solders, can be used to surface mount
the MLO
TM
devices onto the PCB. In all cases, a temperature
gradient of 3°C/sec, or less, should be maintained to prevent
warpage of the package and to ensure that all joints reflow
properly. Additional soak time and slower preheating time
may be required to improve the out-gassing of solder paste.
In addition, the reflow profile depends on the PCB density
and the type of solder paste used. Standard no-clean solder
paste is generally recommended. If another type of flux is
used, complete removal of flux residual may be necessary.
Example of a typical lead free reflow profile is shown below:
Profile Parameter Pb free, Convection, IR/Convection
Ramp-up rate (Tsmax to Tp) 3ºC/second max.
Preheat temperature (Ts min to Ts max) 150ºC to 200ºC
Preheat time (ts) 60 – 180 seconds
Time above T
L
, 217ºC (t
L
) 60 – 120 seconds
Peak temperature (Tp) 260°C
Time within 5ºC of peak temperature (tp) 10 – 20 seconds
Ramp-down rate 4ºC/second max.
Time 25ºC to peak temperature 6 minutes max.
Critical Zone
T
L
to Tp
Ramp-down
Ramp-up
Ts max
25
t 25ºC to Peak
Ts min
ts
Preheat
Tp
tp
T
L
t
L
Time
Temperature
6
150
