reflow profiles consist of four stages.
¡E Cool down
is critical to have the rate of temperature change, maximum
temperature, and time duration within each stage controlled
to create solder joints that have flowed properly. Solder
reflow Charts are available for our connectors and components.
Below is the profile for RJ Connectors.
Average Ramp-Up Rate
Rate during Preheat
1-2, max 4 ¢X/sec
125¢XC of solder temp.
within +0 -5¢XC of actual Peak
preheat stage is used to bring the entire assembly up to
about +125¢XC (¡Ó25¢XC). Typical temperature increase rates
used on convection systems are about 2-3¢XC per second.
A temperature rise rate lower than 5¢XC per second should
be used because higher rates may cause the solder paste
to bubble and ¡§explode¡¨, potentially causing solder balls
to form. It is also
possible to damage some of the components being mounted
on the board if the temperature rise rate is not held to
below this level.
pre-flow stage starts at the end of the preheat stage and
allows the temperature across the surface of the board to
achieve equilibrium at a level near the melting point of
solder. The rate of temperature rise in the pre-flow stage
is reduced to less than 1¢XC per second, and is typically
around 0.5¢XC per second. If the temperature is allowed
to get too hot in the pre-flow zone, the solder paste will
oxidize and solder balls will form. A pre-flow period of
less than 120 seconds is recommended, during which the temperature
can rise up to (but should not exceed) +180¢XC.
reflow stage is the time period where the solder changes
from a solid to a liquid, and will flow in the areas where
solder paste has been applied and solder mask is not present.
The rate of temperature change increases rapidly to a specified
level, then the PCB has a dwell time at the
specified temperature where the flux action occurs and good
wetting is obtained. After remaining at the specified temperature
for the required dwell time the heat is removed and the
cool-down stage is started.
We recommend using a maximum of 235¢XC to 250¢XC for low
temperature parts and 260¢XC for high temperature parts.
We recomments the time at any temperature above 215¢XC be
less than 30 to 60 seconds. The total time above +183¢XC
should be less than 180 seconds.
is the final stage, and refers to the period after reflow
where the temperature is decreasing and is below the solder
liquidus (+183¢XC) once again. The solder grain size and
fatigue resistance of the joint is controlled by the rate
the temperature drops, and generally you would like to cool
the PCB down as quickly as possible. Cool down rate should
be approximately 2- 4¢XC/second and should not exceed 5¢XC/second.