SARA-R5 series - System integration manual
UBX-19041356 - R04 Handling and soldering Page 99 of 118
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3.3 Soldering
3.3.1 Soldering paste
"No Clean" soldering paste is strongly recommended for SARA-R5 series modules, as it does not
require cleaning after the soldering process has taken place. The paste listed in the example below
meets these criteria.
Soldering paste: OM338 SAC405 / Nr.143714 (Cookson Electronics)
Alloy specification: 95.5% Sn / 3.9% Ag / 0.6% Cu (95.5% tin / 3.9% silver / 0.6% copper)
95.5% Sn / 4.0% Ag / 0.5% Cu (95.5% tin / 4.0% silver / 0.5% copper)
Melting temperature: 217 °C
Stencil thickness: 150 m for base boards
The final choice of the soldering paste depends on the approved manufacturing procedures.
The paste-mask geometry for applying soldering paste should meet the recommendations in
section 2.11.
☞ The quality of the solder joints should meet the appropriate IPC specification.
3.3.2 Reflow soldering
A convection type-soldering oven is strongly recommended for SARA-R5 series modules over the
infrared type radiation oven. Convection heated ovens allow precise control of the temperature and all
parts will be heated up evenly, regardless of material properties, thickness of components and surface
color.
Consider the “IPC-7530A Guidelines for temperature profiling for mass soldering (reflow and wave)
processes”. Reflow profiles are to be selected according to the following recommendations.
⚠ Failure to observe these recommendations can result in severe damage to the device!
Preheat phase
Initial heating of component leads and balls. Residual humidity will be dried out. Note that this preheat
phase will not replace prior baking procedures.
• Temperature rise rate: max 3 °C/s If the temperature rise is too rapid in the preheat phase it
may cause excessive slumping.
• Time: 60 ÷ 120 s If the preheat is insufficient, rather large solder balls tend to
be generated. Conversely, if performed excessively, fine
balls and large balls will be generated in clusters.
• End temperature: +150 ÷ +200 °C If the temperature is too low, non-melting tends to be
caused in areas containing large heat capacity.
Heating/ reflow phase
The temperature rises above the liquidus temperature of +217 °C. Avoid a sudden rise in temperature
as the slump of the paste could become worse.
• Limit time above +217 °C liquidus temperature: 40 ÷ 60 s
• Peak reflow temperature: +245 °C
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