7

Lead-Free Reflow Profile Recommendation (IPC/JEDEC J-STD-020C)

Reflow Parameter

Lead-Free Assembly

Average ramp-up rate (Liquidus Temperature (T

3°C/ second max

Preheat

Temperature Min (T

150°C

Temperature Max (T

200°C

Time (min to max) (t

60-180 seconds

Ts(max) to TL Ramp-up Rate

3°C/second max

Time maintained above:

Temperature (T

217°C

Time (t

60-150 seconds

Peak Temperature (T

260 +0/-5°C

Time within 5 °C of actual Peak temperature (t

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 Profile.

25

Time

Tp

tp

t 25

Ramp-up

ts

Ramp-down

Preheat

Critical Zone

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 reflow, 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 reflow temperatures faster than

those with a greater mass.

Avago’s diodes have been qualified to the time-temper-

ature profile shown in Figure 18. This profile is represen-

tative of an IR reflow 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 reflow zone

briefly elevates the temperature sufficiently to produce a

reflow 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 reflow

zone (T

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 reflow of solder.