
Revision 1.0
39
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15.0 Soldering
(Continued)
15.0 Soldering
The LMX9820A bumps are designed to melt as part of the
Surface Mount Assembly (SMA) process. The LMX9820A
is assembled with a high-temperature solder alloy to
ensure there are no re-reflow conditions imposed upon the
module when reflowed to a PCB with these typical low tem-
perature 60/40 (S = 183°C, L = 188°C), 62/36/2 (E =
179°C), or 63/37 (E = 183°C) solder alloys.
Where:
S: Solidus
– Denotes the points in a phase diagram representing
the temperature at which the solder composition be-
gins to melt during heating, or complete freezing dur-
ing cooling.
L: Liquidus
– Denotes the points in a phase diagram representing
the temperature at which the solder has molten com-
ponents. The temperature that melting starts at.
E: Eutectic
– Denotes solid to liquid without a plastic phase.
The low-temperature solder alloy will reflow with the solder
bump and provide the maximum allowable solder-joint reli-
ability.
Reflow at a peak of 215 --> 220°C (approximately 30 sec-
onds at peak). Do not to exceed 220°C, measured in close
proximity of the modules. to avoid any potential re-reflow
conditions.
Table 41 and Figure 27 on page 40 provide the soldering
details required to properly solder the LMX9820A to stan-
dard PCBs. The illustration serves only as a guide and
National is not liable if a selected profile does not work.
Table 41. Soldering Details
Parameter
Value
PCB Land Pad Diameter
24 mil
PCB Solder Mask Opening
30 mil
PCB Finish (HASL details)
63/37 (difference in thickness < 28 micron)
Stencil Aperture
28 mil
Stencil Thickness
5 mil
Solder Paste Used
Low temperature 60/40 (S = 183°C, L = 188°C),
62/36/2 (E = 179°C),
or 63/37 (E = 183°C) solder alloys
1
Flux Cleaning Process
No Clean Flux System
1
Reflow Profiles
See Figure 27 on page 40
1.
Typically defined by customer.