12
Recommended Reflow Profile
Figure 16. Reflow graph.
0
t-TIME (SECONDS)
T – TEMPERATURE – (°C)
230
200
160
120
80
50 150100 200 250 300
180
220
255
P1
HEAT
UP
P2
SOLDER PASTE DRY
P3
SOLDER
REFLOW
P4
COOL
DOWN
25
R1
R2
R3 R4
R5
60 sec.
MAX.
ABOVE
220°C
MAX. 260°C
The reflow profile is a straight-
line representation of a nominal
temperature profile for a con-
vective 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 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 I/O 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
HSDL-3003 I/O pins.
Process Symbol ∆T Maximum ∆T/∆time
Heat Up P1, R1 25°C to 160°C4°C/s
Solder Paste Dry P2, R2 160°C to 200°C 0.5°C/s
Solder Reflow P3, R3 200°C to 255°C (260°C at 10 seconds max.) 4°C/s
P3, R4 255°C to 200°C–6°C/s
Cool Down P4, R5 200°C to 25°C–6°C/s
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 coalescence 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 transceiver’s castellation I/O
pins to change dimensions evenly,
putting minimal stresses on the
HSDL-3003.