E-32
ElektroPhysik
8.6 Diffusion layers
Some metals tend to penetrate into the surface of the
next layer. For that reason, the instrument may switch-
off after de-plating the pure metal layer e.g. Sn.
If you examine the measuring area, you cannot see the
next metal layer but the metal of the first layer which
has penetrated into the layer underneath. In such case,
we recommend to decrease sensitivity i.e. to set a higher
voltage value.
On the other hand, when measuring extremely distinc-
tive diffusion layers (e.g. Zn), the voltage jump may not
be sufficiently strong enough to switch off measurement.
In such cases, the voltage curve may return to normal
until a new voltage jump occurs after a short while. This
voltage jump however may not be quick enough to
switch-off measurement. In such case we recommend
to increase sensitivity i.e. to set a lower voltage value.
For setting optimum sensitivity, make sure the instrument
does not switch off before the second voltage jump (see
also section 10 „Sensitivity“).
The print-out of voltage curve on MiniPrint 4100 shows
both, thickness of the pure metal as well as the thickness
of the diffusion layer. Please refer also to section 10
“Sensitivity”.
8.7 Currentless nickel
When measuring currentless nickel (chemical nickel),
the phosphor content will cause a slowing down of the
de-plating process. The delay time as related to the
phosphor content can be taken from the following table:
For accurate measurement, the calibration factor has to
be determined according to section 9.2 „Calibrating by
means of a factor“ and then divided by the appropriate
correction value as specified in the table above.
Note:
The correction values as specified in the above table
only apply if calibration has been carried out by means
of a nickel standard without phosphor content.
Phosphor
content
4%
5%
6%
7%
8%
9%
10%
11%
Correction
value
1,11
1,14
1,16
1,19
1,22
1,24
1,26
1,28