Reflow Profile
The reflow profile is a straight-
line representation of a nominal
temperature profile for a convec-
tive reflow solder process. The
temperature profile is divided
into four process zones, each
with different
∆T/∆time
tempera-
ture change rates. The
∆T/∆time
rates are detailed in the following
table. The temperatures are mea-
sured at the component to
printed circuit board connections.
In
process zone P1,
the PC
board and HSDL-3603
castellation I/O pins are heated
to a temperature of 125°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
HSDL-3603 castellation I/O pins.
Process zone P2
should be of
sufficient time duration (> 60
seconds) to dry the solder paste.
The temperature is raised to a
level just below the liquidus point
of the solder, usually 170°C
(338°F).
Process zone P3
is the solder
reflow zone. In zone P3, the
temperature is quickly raised
above the liquidus point of solder
to 230°C (446°F) for optimum
results. The dwell time above the
liquidus point of solder should be
between 15 and 90 seconds. It
usually takes about 15 seconds to
assure proper coalescing of the
solder balls into liquid solder and
the formation of good solder
T – TEMPERATURE – (°C)
230
200
183
170
150
125
100
R1
MAX. 245°C
R3
R4
R2
90 sec.
MAX.
ABOVE
183°C
R5
50
25
0
P1
HEAT
UP
50
100
150
200
P3
SOLDER
REFLOW
250
P4
COOL
DOWN
300
t-TIME (SECONDS)
P2
SOLDER PASTE DRY
Figure 15. Reflow graph.
Process Zone
Heat Up
Solder Paste Dry
Solder Reflow
Cool Down
Symbol
P1, R1
P2, R2
P3, R3
P3, R4
P4, R5
∆T
25˚C to 125˚C
125˚C to 170˚C
170˚C to 230˚C (245˚C max.)
230˚C to 170˚C
170˚C to 25˚C
Maximum
∆T/∆time
4˚C/s
0.5˚C/s
4˚C/s
–4˚C/s
–3˚C/s
connections. Beyond a dwell time
of 90 seconds, the intermetallic
growth within the solder connec-
tions 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 170°C (338°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
-3°C per second maximum. This
limitation is necessary to allow
the PC board and HSDL-3603
castellation I/O pins to change
dimensions evenly, putting
minimal stresses on the
HSDL-3603 transceiver.
12
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