User Manual

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AV02-4191EN - November 8, 2013
The reow prole is a straight-line representation of
a nominal temperature prole for a convective reow
solder process. The temperature prole is divided into
four process zones, each with dierent ∆T/∆time tem-
perature change rates or duration. The ∆T/∆time rates or
duration are detailed in the above table. The temperatures
are measured at the component to printed circuit board
connections.
In process zone P1, the PC board and component pins
are heated to a temperature of 150 °C to activate the ux
in the solder paste. The temperature ramp up rate, R1, is
limited to 3 °C per second to allow for even heating of
both the PC board and component pins.
Process zone P2 should be of sucient time duration (100
to 180 seconds) to dry the solder paste. The temperature is
raised to a level just below the liquidus point of the solder.
Process zone P3 is the solder reow zone. In zone P3, the
temperature is quickly raised above the liquidus point of
Recommended Reow Prole
Process Zone Symbol ∆T
Maximum ∆T/∆time
or Duration
Heat Up P1, R1
25 °C to 150 °C 3 °C/s
Solder Paste Dry P2, R2
150 °C to 200 °C
100 s to 180 s
Solder Reow
P3, R3
P3, R4
200 °C to 260 °C
260 °C to 200 °C
3 °C/s
-6 °C/s
Cool Down P4, R5
200 °C to 25 °C -6 °C/s
Time maintained above liquidus point , 217 °C > 217 °C
60 s to 120 s
Peak Temperature
260 °C
–
Time within 5 °C of actual Peak Temperature > 255 °C
20 s to 40 s
Time 25 °C to Peak Temperature 25 °C to 260 °C
8 mins
solder to 260 °C (500 °F) for optimum results. The dwell
time above the liquidus point of solder should be between
60 and 120 seconds. This is to assure proper coalescing
of the solder paste into liquid solder and the formation
of good solder connections. Beyond the recommended
dwell time the intermetallic growth within the solder con-
nections becomes excessive, resulting in the formation of
weak and unreliable connections. The temperature is then
rapidly reduced to a point below the solidus temperature
of the solder to allow the solder within the connections to
freeze solid.
Process zone P4 is the cool down after solder freeze. The
cool down rate, R5, from the liquidus point of the solder to
25 °C (77 °F) should not exceed 6 °C per second maximum.
This limitation is necessary to allow the PC board and
component pins to change dimensions evenly, putting
minimal stresses on the component.
It is recommended to perform reow soldering no more
than twice.
50
100 150 200 250 300
t-TIME
(SECONDS)
25
80
120
150
180
200
230
255
0
TEMPERATURE (°C)
R1
R2
R3 R4
R5
217
MAX 260° C
P1
HEAT UP
P2
SOLDER PASTE DRY
P3
SOLDER
REFLOW
P4
COOL
DOWN
60 sec to 120 sec
Above 217° C