Reflow Profile
255
230
220
200
180
160
120
80
25
0
P1
HEAT
UP
50
100
150
200
250
P4
COOL
DOWN
300
R1
MAX. 260°C
R3
R4
T – TEMPERATURE – (°C)
R2
60 sec.
MAX.
ABOVE
220°C
R5
t-TIME (SECONDS)
P2
P3
SOLDER PASTE DRY
SOLDER
REFLOW
Figure 13. 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 160˚C
160˚C to 200˚C
200˚C to 255˚C (260˚C at 10 seconds max.)
255˚C to 200˚C
200˚C to 25˚C
Maximum
∆T/∆time
4˚C/s
0.5˚C/s
4˚C/s
–6˚C/s
–6˚C/s
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 above
table. The temperatures are
measured at the component to
printed circuit board connections.
In
process zone P1,
the PC board
and HSDL-3203 castellation 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-3203 castellation I/O pins.
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 tem-
perature 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 inter-
metallic 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 nec-
essary to allow the PC board and
HSDL-3203 castellation I/O pins
to change dimensions evenly,
putting minimal stresses on the
HSDL-3203 transceiver.
10
AGILENT [ AGILENT TECHNOLOGIES, LTD. ]
