Specifications

Accordingly, the residual parameters have greater effects on higher frequency measurements and
become a primary factor of measurement errors. The accuracy of measurement results after com-
pensation depends on how precisely the open/short measurements have been performed.
Figure 4-16. Relationship of residual parameter values to the typical impedance measurement range of the RF I-V
method
To perform optimum compensation, observe the precautions for open/short measurements
described in Section 4.3.2. In the high frequency region, the method of open/short compensation
dominates the measurement correlation. To obtain measurement results with a good correlation and
repeatability, the compensation must be performed with the same conditions. A difference in the
compensation method will result in a difference in measured values, leading to correlation problems
on measurement results. Short measurement is more critical in terms of increasing the need for low
inductance measurements.
4.7.5 Consideration for short compensation
To make the short measurement at the contact terminals of a test fixture or of a component handler,
a short bar (chip) is usually employed. When measuring very low impedance (inductance), the
following problems arise from the short bar:
• Different residual impedance is dependent on size and shape
• Method of defining the residual impedance
If a different size or shape of the short bar is used, it is difficult to obtain a good correlation of the
measurement results. The residual impedance of the short bar is different if the size differs. Hence,
the same size of short bar must be used when making the short measurement.
If the definition of the short bar’s impedance is different, it causes a difference in measured values.
To have a good correlation, it is desirable to determine the short bar’s residuals. However, it cannot
be determined only from the inherent impedance of the short bar itself. The actual impedance
depends on surrounding conditions such as contact terminals, thickness of the closely located
conductors, permittivity of insulators, ground conditions, etc.
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