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AN2036 - APPLICATION NOTE

When the measured wetting force is zero, the two forces are balanced. This point is called the “zero cross

greater than zero).

Note: No aging is applied, before the wetting balance test, during process control of production. Aging is

applied for data collection purpose only.

Criteria: the test is considered as passed if:

–

The wetting force reaches 0.1mN/mm within 5 seconds of immersion

–

The zero cross time (t0) is less than 3 seconds.

Note: these criteria are applied for small-signal devices. Power devices can require different criteria to take

into account the thermal mass of their connections.

Table 3. Tests Conditions

Note:

–

The wetting force, as measured by the balance, is divided by the total perimeter of the connections at

initial immersion.

–

In the case of leads that are connected to a thermal mass, such as to a dissipater, the test must be

redefined to include preheating.

CONCLUSIONS

Through two standard tests (“Dip and Look” and “Wetting Balance”), ST Lead-free devices are warranted

to pass solderability tests using Sn-Pb solder or Sn-Ag-Cu solder, and so to meet all the requirements for

electronics soldering. In fact the solderability tests provide customers with an additional warranty that the

components can be soldered without affecting the common reliability performance.

Solder

Sn-Ag-Cu melted at 245°C (±5°C)

Flux dipping

5 to 10 seconds

Solder dipping

10 seconds

Sn-Pb melted at 235°C (±5°C)

Flux dipping

5 to 10 seconds

Solder dipping

10 seconds