9
Recommended Reflow Profile
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 100s to 180s
Solder Reflow 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 60s to 120s
Peak Temperature 260°C -
Time within 5°C of actual Peak Temperature > 255°C 20s to 40s
Time 25°C to Peak Temperature 25°C to 260°C 8mins
The reflow profile is a straight-line representation of
a nominal temperature profile for a convective reflow
solder process. The temperature profile is divided into
four process zones, each with different 'T/'time tem-
perature change rates or duration. The 'T/'time rates or
duration are detailed in the above table. The tempera-
tures 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 flux 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 sufficient 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 reflow zone. In zone P3, the
temperature is quickly raised above the liquidus point
of 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 rec-
ommended dwell time the intermetallic growth within
the solder connections 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 reflow soldering no more
than twice.
50
100 150 200 250 300
t-TIME
(SECONDS)
25
80
120
150
180
200
230
255
0
T - TEMPERATURE (°C)
R1
R2
R3
R4
R5
217
MAX 260°C
60 sec to 120 sec
Above 217°C
P1
HEAT
UP
P2
SOLDER PASTE DRY
P3
SOLDER
REFLOW
P4
COOL DOWN
