Internal sensor compensation for increased Ca test sensitivity

Abstract

The development of state-of-the-art barrier films and encapsulation schema for displays and photovoltaics requires precise measurement of water vapor permeation as quickly as possible. We have demonstrated improvements to our electrical, Ca-trace-based water vapor transmission rate measurement technique without introducing any additional cost or sample handling concerns. Most importantly, the contacting scheme was changed so that the effective length of the sensor traces can be more precisely determined making the contact resistance between the Ca and Au/Ti films far less likely to affect the results. A 4-pt contacting pattern was also applied to the internal (non-data) witness trace. This expanded the potential utility of the witness trace from just an indicator for the integrity of the sample assembly, to also being used to compensate for measurement error. Lastly, we increased the relative precision of our resistance measurements by implementing a Ca sensor trace with significantly higher resistance. Principally, these changes produce significant measurement improvements for permeation rates less than 10(-4) g/m(2)/day, by lowering the noise floor, reducing required measurement time, and increasing the reproducibility of this test method.

Highly Oriented Gold/Nanoclay–Polymer Nanocomposites for Flexible Gas Barrier Films

“…To overcome this weakness of the MOCON system, many researchers have been using the electrical Ca-test. [1][2][3][4][5][6][7] In addition, many previous studies have verified the credibility of the electrical Ca-test. [2][3][4][5] Moreover, as shown in Figure S4, a comparable nanocomposite barrier film sample shows almost the same WVTR values (electrical Catest: 0.15 g m -2 day -1 , MOCON system: 0.17 g m -2 day -1 ) at a value over 0.05 g m -2 day -1 when comparing the MOCON and electrical Ca-test results.…”

“…It is well known that the electrical Ca-test is capable of measuring WVTR values in the range of 100-10 -6 g m -2 day -1 . [3][4][5] On the other hand, the MOCON system, which is the most popular commercial permeability measurement system, has a critical weakness associated with the range of WVTR values that it can measure. The MOCON system is unable to measure WVTR values under 0.05 g m -2 day -1 .…”

A Review on Emerging Barrier Materials and Encapsulation Strategies for Flexible Perovskite and Organic Photovoltaics

“…This degradation can be monitored and then related to the WVTR. [ 220–225,229–235 ] WVTR results as low as 3 × 10 −7 have been reported using the Ca test, [ 18 ] providing an acceptable measure of moisture permeation for ultrahigh barrier applications.…”

Note: Inhibiting bottleneck corrosion in electrical calcium tests for ultra-barrier measurements

“…The effect is also observed for samples with Al contacts deposited after the Ca sensor and for Ag contacts, as we display in Figure S2. 17 The importance of the Ca-electrode interface has been shown before by Dameron et al 8 However, they observe an electrode delamination, which is fundamentally different from this cause of failure and should not be mixed up. Here, the preferred corrosion of Ca in the proximity of the electrodes is likely caused by the difference in electrochemical potential E 0 between the two touching metals Ca (sensor, E 0,Ca = −2.868 V) 19 and Al (electrode, E 0,Al = −1.662 V).…”

“…1-3 Existing commercial systems show very good sensitivities and can accurately characterize barriers; however, they are not suited for quick material screening during research and development due to high invest costs and lacking system parallelizability. Where vacuum evaporation equipment is already present, electrical calcium corrosion tests (Ca-Tests) can be a low-cost alternative for barrier measurements [4][5][6][7][8] if a sufficient sensitivity is reached, since doing many tests in parallel does not significantly increase time or money spent on the system. We show a measurement failure cause inherent to the Ca-Test and the means to prevent it-enabling to detect WVTRs in the 10 −5 g(H 2 O)/m 2 /d regime.…”