Presentation Details
| Challenges and solutions for determining the end contact resistance of interconnects based on electrically conductive adhesives with statistical significance Maria Ignacia Devoto Acevedo1, Raphael Shanmugam 1, Daniel Tune1, Tobias Nitsche2, Daniel Buckland2, Giuseppe Galbiati2, Tobias Meßmer1. 1ISC Konstanz, Konstanz, Germany.2Henkel, Düsseldorf, Germany |
Abstract
Accurate determination of contact resistivity in electrically conductive adhesive (ECA) interconnects is essential for assessing their suitability for photovoltaic applications. Existing analytical approaches based on transmission line model (TLM) test structures rely on extracting the end contact resistance as an input parameter. However, for emerging low-flexibility and advanced R&D ECA formulations, determination of end contact resistances can become negative due to unavoidable resistive contributions from the metal fingers in test geometries, rendering the extraction of contact resistivity unreliable. In this study, a slight modification for our currently used TLM-based test structure is proposed to enable a direct measurement of the end contact resistance without requiring subtraction of additional resistive components. The new structure preserves compatibility with our established analytical method while altering the ECA dispensing layout and measurement configuration. Two ECAs are investigated: a commercial formulation previously characterized using our conventional test structure and a low-flexibility R&D formulation that exhibited negative end contact resistance values with the original design. Identical curing conditions are applied to ensure comparability. A comprehensive set of current–voltage measurements is performed to observe bulk and end contact resistances, with repeatability, linearity, and consistency evaluated across multiple contact spacings and current injection ranges. Preliminary results for the R&D ECA demonstrate highly repeatable measurements with standard deviations below 5% over wide current ranges. While bulk resistance measurements exhibit a highly ohmic behavior at moderate-to-high current injections, end contact resistance measurements require significantly higher current levels to approach quasi-ohmic behavior. These findings show that it is possible to use our current test structure with a slight modification, however, caution must be taken to select suitable measurements under suitable current ranges. The next step in this study is to bring these preliminary findings to a statistically significant scenario and the use the raw date to feed the analytical method.
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