7
Lead-Free Reow Prole Recommendation (IPC/JEDEC J-STD-020C)
Reow Parameter Lead-Free Assembly
Average ramp-up rate (Liquidus Temperature (T
S(max)
to Peak) 3°C/ second max
Preheat Temperature Min (T
S(min)
) 150°C
Temperature Max (T
S(max)
) 200°C
Time (min to max) (t
S
) 60-180 seconds
Ts(max) to TL Ramp-up Rate 3°C/second max
Time maintained above: Temperature (T
L
) 217°C
Time (t
L
) 60-150 seconds
Peak Temperature (T
P
) 260 +0/-5°C
Time within 5 °C of actual Peak temperature (t
P
) 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
Figure 18. Surface Mount Assembly Prole.
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
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.) circuit 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’s diodes have been qualied to the time-temper-
ature prole shown in Figure 18. This prole is represen-
tative 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 evapo-
rating solvents from the solder paste. The reow zone
briey elevates the temperature suciently 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 components due
to thermal shock. The maximum temperature in the reow
zone (T
MAX
) should not exceed 260°C.
These parameters are typical for a surface mount assembly
process for Avago 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.
