9
Lead-Free Reow Prole Recommendation (IPC/JEDEC J-STD-020C)
Reow Parameter Lead-Free Assembly
Average ramp-up rate (Liquidus Temperature (TS(max) to Peak) 3°C/ second max
Preheat Temperature Min (TS(min)) 150°C
Temperature Max (TS(max)) 200°C
Time (min to max) (tS) 60-180 seconds
Ts(max) to TL Ramp-up Rate 3°C/second max
Time maintained above: Temperature (TL) 217°C
Time (tL) 60-150 seconds
Peak Temperature (TP) 260 +0/-5°C
Time within 5 °C of actual Peak temperature (tP) 20-40 seconds
Ramp-down Rate 6°C/second max
Time 25 °C to Peak Temperature 8 minutes max
Note 1: All temperatures refer to topside of the package, measured on the package body surface
25
Time
Temperature
Tp
T
L
tp
t
L
t 25°C to Peak
Ramp-up
ts
Ts
min
Ramp-down
Preheat
Critical Zone
T
L
to Tp
Ts
max
Figure 26. Surface Mount Assembly Prole.
SMT Assembly
Reliable assembly of surface mount components is a
complex process that involves many material, process,
and equipment factors, including: method of heating
(e.g., IR or vapor phase reow, wave soldering, etc.) cir-
cuit board material, conductor thickness and pattern,
type of solder alloy, and the thermal conductivity and
thermal mass of components. Components with a low
mass, such as the SOT package, will reach solder reow
temperatures faster than those with a greater mass.
Avago Technologies’ diodes have been qualied to the
time-temperature prole shown in Figure 26. This prole
is representative of an IR reow type of surface mount
assembly process.
After ramping up from room temperature, the circuit
board with components attached to it (held in place
with solder paste) passes through one or more preheat
zones. The preheat zones increase the temperature of
the board and components to prevent thermal shock
and begin evaporating solvents from the solder paste.
The reow zone briey elevates the temperature su-
ciently to produce a reow of the solder.
The rates of change of temperature for the ramp-up and
cool-down zones are chosen to be low enough to not
cause deformation of the board or damage to compo-
nents due to thermal shock. The maximum temperature
in the reow zone (TMAX) should not exceed 260°C.
These parameters are typical for a surface mount assem-
bly process for Avago Technologies diodes. As a general
guideline, the circuit board and components should be
exposed only to the minimum temperatures and times
necessary to achieve a uniform reow of solder.