User's Manual

4
REFLOW PROFILE GUIDELINE
The reflow profile is dependent on many factors including flux selection, solder
composition and the capability of user's reflow equipment.
USI does not request a specific reflow profile but provides the following
general guidelines
The solder composition typically sets the peak temperatures of the profile.
Recommend lead free solder pastes SAC305: Type 4, water soluble or no clean
are acceptable.
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■ Reflow equipment needed at least nine heater zones. Recommend forced air
type reflow oven with Nitrogen.
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■ It is recommended that the peak temperature at the solder joint be within 245°C
and the maximum component temperature should not exceed 245°C.
■ It is recommended that time above 217°C for the solder joints is between 40-90s,
and with a minimum of 40s.
■ Optimal cooling rate is <1℃ /sec. from peak to 217 ℃
■ To develop the reflow profile, it is recommended that the user place
thermocouples at various locations on the assembly to confirm that all locations meet
the profile requirements. The critical locations are the solder joints of SiP Module.
When developing the reflow profile, it is recommended that the actual fully loaded
assembly be used to make sure that the total thermal mass is accounted for.