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AN2036 - APPLICATION NOTE

WETTING BALANCE TEST

Connections are dipped inside a non-activated flux. Then the package is loaded on the wetting balance

arm, and the connections are dipped into a molten solder. The force exerted on the balance arm is plotted

as a function of time.

This test cannot be applied for all the packages. It can, though, be adjusted to fit special cases.

Typical forces versus time curves are shown in Figure 2.

Figure 2. Wetting Force Plotted against Time, for Three Cases

The shape of the curves can be explained as follows:

–

At the beginning, the buoyancy forces (due to the interfacial tension) are predominant, and so the

wetting force is negative.

–

Gradually, the solder begins to wet the terminals, and the wetting force increases with time,

overcoming the buoyancy force.

–

Eventually, it reaches a flat (plateau) zone.

No Forced Ageing

Ageing:

16 hours, 150°C

Ageing:

8 hours, 85°C and

85% Humidity

Immersion: 10 seconds