8
Recommended Reflow Profile
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 DT/Dtime temperature
change rates. The DT/Dtime rates 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 APDS-9003
castellation pins are heated to a temperature of 160°C to
activate the flux in the solder paste. The temperature
ramp up rate, R1, is limited to 4°C per second to allow for
even heating of both the PC board and APDS-9003
castellations.
Process zone P2 should be of sufficient time duration
(60 to 120 seconds) to dry the solder paste. The
temperature is raised to a level just below the liquidus
point of the solder, usually 200°C (392°F).
Process zone P3 is the solder reflow zone. In zone P3, the
temperature is quickly raised above the liquidus point of
solder to 255°C (491°F) for optimum results. The dwell
time above the liquidus point of solder should be between
20 and 60 seconds. It usually takes about 20 seconds to
assure proper coalescing of the solder balls into liquid
solder and the formation of good solder connections.
Beyond a dwell time of 60 seconds, 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,
usually 200°C (392°F), 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 APDS-9003 castellations to change dimensions
evenly, putting minimal stresses on the APDS-9003.
50 100 150 200 250 300
t-TIME
(SECONDS)
25
80
120
160
180
200
230
255
0
T - TEMPERATURE (C)
R1
R2
R3 R4
R5
220
MAX 260C
60 sec
MAX
Above 220 C
P1
HEAT
UP
P2
SOLDER PASTE DRY P3
SOLDER
REFLOW P4
COOL DOWN
Process Zone Symbol ∆TMaximum ∆T/ time
Heat Up P1, R1 25°C to 160°C 4°C/s
Solder Paste Dry P2, R2 160°C to 200°C 0.5°C/s
Solder Reflow P3, R3
P3, R4 200°C to 255°C (260°C at 10 seconds max)
255°C to 200°C 4°C/s
-6°C/s
Cool Down P4, R5 200°C to 25°C -6°C/s