Page 7
SMD TRANSMITTER AUTOMATED ASSEMBLY GUIDELINES
For high-volume assembly, most users will want to auto-place the modules. SMD
versions of the modules have been designed to maintain compatibility with most
pick-and-place equipment, however, due to the module's hybrid nature certain
aspects of the automated assembly process are far more critical than for other
component types.
Following are brief discussions of the three primary areas where caution must be
observed.
Reflow Temperature Profile
The single most critical stage in the automated assembly process is the reflow
process. The reflow profile below should not be exceeded since excessive
temperatures or transport times during reflow will irreparably damage the
modules. Assembly personnel will need to pay careful attention to the oven's
profile to ensure that it meets the requirements necessary to successfully reflow
all components while remaining within the limits mandated by the modules
themselves.
Shock During Reflow Transport
Since some internal module components may reflow along with the components
placed on the board being assembled, it is imperative that the module not be
subjected to shock or vibration during the time solder is liquidus.
Washability
The modules are wash-resistant, but are not hermetically sealed. Linx
recommends wash-free manufacturing techniques, however, the modules can
be subjected to a wash cycle provided that a drying time is allowed prior to
applying electrical power to the parts. The drying time should be sufficient to
allow any moisture which may have migrated into the module to evaporate, thus
eliminating the potential for shorting damage during power-up or testing. If the
wash cycle contains contaminants, transmitter performance may be adversely
affected, even after drying.
Figure 13: Maximum Reflow Profile
125
°
C
60
0
0
50
100
150
200
250
300
°
C
120
180
240
300
30
90
150
210
270
330
360
180
°
C
210
°
C
220
°
C
Temperature
Time (Seconds)
Ideal Curve
Limit Curve
Forced Air Reflow Profile
1-1.5 Minutes
2-2.3 Minutes
Ramp-up
Preheat Zone
Cooling
Soak Zone
Reflow Zone
20-40 Sec.
2 Minutes Max.
