Application Note                                                                                              Zaptron Systems, Inc.

Improve the Performance of a VPTC Ceramic Semiconductor

Goal: 
Find a way to increase the performance of a VPTC (vaporized positive temperature coefficient) ceramic semiconductor (containing TbO, LaO, ...) used in eletronic packaging.

Method:

The performance of the VPTC ceramic semiconductor is determined by P0/Pmin,  the ratio of its resistance at temperature 0 and that at minimum temperature. The resistance-temperature curve is nonlinear with peaks and valleys.

Data from previous experiments were used   and it was found that all data points were distributed in a linear fashion in a projected subspace (one of the rear cases where linearity existed).

Data mining techniques were used to build a model from past experiment data, and the model was used to extropolate the data space for new VPTC design. The innovation was the ability to separate good data from bad data, so that useful features were selected and a reliable mathematical model could be built.

Result:
The model so obtained from data was used to guide the material design process. After one extropolation, the P0/Pmin ratio was increased from 20 to 25, and by a second extropolation, the P0/Pmin ratio was increased from 25 to 27. This was a significant improvement of the VPTC performance.

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