Specifications

L70 Hardware Design
L70_HD_V1.0 - 33 -
7. Manufacturing
7.1. Assembly and soldering
L70 is intended for SMT assembly and soldering in a Pb-free reflow process on the top side of the
PCB. It is suggested that the minimum height of solder paste stencil is 130um to ensure sufficient
solder volume. Pad openings of paste mask can be increased to ensure proper soldering and solder
wetting over pads. It is suggested that peak reflow temperature is 235~245ºC (for SnAg3.0Cu0.5
alloy). Absolute max reflow temperature is 260ºC. To avoid damage to the module when it is
repeatedly heated, it is suggested that the module should be mounted after the first panel has been
reflowed. The following picture is the actual diagram which we have operated.
Time(s)
50
100
150 200 250 300
50
100
150
200
250
160℃
200℃
217
0
70s~120s
40s~60s
Between 1~3℃/S
Preheat Heating Cooling
℃
s
Liquids Temperature
Figure 22: Ramp-soak-spike-reflow of furnace temperature
7.2. Moisture sensitivity
L70 is sensitivity to moisture absorption. To prevent L70 from permanent damage during reflow
soldering, baking before reflow is required in following cases:
 Humidity indicator card: At least one circular indicator is no longer blue
 The seal is opened and the module is exposed to excessive humidity.
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