Permeation of Water and Oxygen

Principle

Permeation measurement depends on the high reactivity of elemental calcium. In the atmosphere a metal-like shiny calcium layer reacts rapidly with moisture and oxygen forming transparent calcium hydroxide and calcium oxide. In the experiment test cells containing a thin calcium layer are encapsulated with the material to be characterized under inert atmosphere. The rate of calcium degradation under the chosen conditions is a measure of the barrier action of the tested materials. This method is especially suitable for transparent polymer films (adhesives, resins, binders, laminating resins, barrier substrates). For the characterization of barrier properties of polymers films with or without coatings we have to distinguish between volume and defect dominated permeation. The latter can be assessed via the degradation of calcium using a digital camera and image processing software. The method was established successfully for the characterization of adhesives and barrier layers. The diffusion of oxygen could be separated in proportion to temperature and moisture.

Applications

• encapsulation of sensitive electronic components (OLEDs)
• flexible substrates
• water and oxygen permeation of adhesives and polymer substrates as a function of temperature and moisture
• evaluation and reliability of encapsulation structures
• defect analysis of substrates

Specifications

• developed by Fraunhofer IZM Teltow
• encapsulation under inert atmosphere
• thermal curing under pressure up to >100ºC, without pressure up to 300ºC,
• UV curing up to 100ºC under pressure,
• measuring of optical transmission at 630 nm,
• mirror area 21x30 mm², typical thickness 100 nm,
• detectable oxygen / water amount 35-90 µg,
• detectable range of  transmission rates depending on sample geometry and measuring time 10³-10^-4 g/m² d,
• microscopic defect analysis,
• sample area 3.5x5 mm², resolution 5 µm

References and Cooperations

The work was funded by the BMBF and the Fraunhofer-Gesellschaft (Förderkennzeichen: 01BI158, MAVO Polymerelektronik) and executed in close cooperation with the the Fraunhofer Institutes ISC and IZM Berlin.