X Link®: Cross-linking control in the blink of an eye

In solar modules, the ethylene vinyl acetate (EVA) or polyolefin encapsulation protects the sensitive solar cells from the environment. In consequence the degree of intermolecular cross-linking of EVA or polyolefin is decisive for the long-term stability and performance of a module. Cross-linking is achieved by thermally curing the polymers during the lamination process.
The X Link® system enables fast, automated, non-destructive and accurate evaluation of the level of EVA or polyolefin cross-linking immediately after lamination. It can be integrated into any solar module production line, offering 100% coverage for process and quality control.

X Link® in-line version

For in-line applications, the measurement heads can be integrated into the cooling press of the laminator or further down the production line. The employment of multiple measurement heads  enables the determination of center-to-edge uniformity. This way, X Link® facilitates closed loop feedback process control and quality assurance.

X Link® off-line version

The off-line version is designed for lab applications, manually handled production lines, R&D labs and pilot lines, ready to test full-size production-type modules with or without frames. R&D labs can even test plain sheets of EVA or polyolefin without glass or backsheets. High-resolution spatial mappings of the cross-linking degree and statistical evaluation can be performed.
Furthermore, the manual off-line version allows multiple-point measurements on laminates and out-of-production modules, and modules from the field. This setup is a highly useful quality control tool for module manufacturers, investors, certifiers and consultants.
Using X Link® off-line could not be simpler for engineers and operators. The user easily positions the module under the measurement head, supported by laser beam targetting. The device is equipped with a touch panel, which controls the measurement process with user-friendly software.

X Link® SAM: semi automated mapping system

PV module lamination control: Mapping of curing state of encapsulant across the whole moduleX Link® SAM is a semi-automated X Link mapping system which  creates maps of the curing state of full-size modules. After loading a module into the device, the tool measures the degree of cross-linking at predefined positions on the module with a typical measurement time of less than one minute per point. The whole measurement procedure is non-destructive and does not affect the functionality of the tested modules. Presentation of the measured data as color maps give immediate information on the uniformity of the curing state of the encapsulant across the whole module.

The X Link® SAM has been developed with focus on regular spot tests in production lines and delivery control. Used in a production line, it gives fast feed-back on homogeneity in the lamination process, allowing quick reaction on production issues. In delivery control it allows to check the quality of the encapsulation, spotting quality issues at a glance.

Benefits

With X Link’s direct feedback, the lamination process can be quickly optimized for better cross-linking quality by adjusting the heating zones and the duration of lamination. The result is a perfect lamination process, which is the key to high-quality modules.

X Link® in mass production

X Link® offers a lot of benefits for mass production of PV modules. Hanwha Q CELLS GmbH (Germany) published recently the results of their X Link® evaluation. Their tests have shown that the tool provides extremely accurate measurements, faster and more exact process control, quality control, recipe evaluation as well as laminator characterization. All this enables an early failure detection and saves costs! Find more in our summary of Hanwha’s technical paper  …more>

Integration

X Link® can be integrated into every solar module production line. Meyer Burger, a global technology group specializing in systems, product equipment and services along the PV value chain, directly integrates X Link in the cooling press of laminators. This allows for closed loop process control and 100% quality assurance of EVA lamination and fully replaces slow, error-prone and costly off-line analysis methods. Find more in white paper of Meyer Burger (Page 8)

Calibration

High accuracy of X Link® systems is indispensable for process control and quality management in solar module production. It is recommended to calibrate X Link® after its delivery or moving as well as once a year to fulfill the requirements of quality auditors. To guarantee X Link's high precision, LayTec offers X Cal - a set of high precision equipment for on-site calibration of X Link® systems.
Please download X Cal Data Sheet for more information.

Background

LayTec and Fraunhofer USA joined forces to successfully develop this novel method of measuring the cross-linking degree of encapsulants. The method is based on the measurement of physical properties associated with the level of cross-linking. The high precision measurements are performed through the backsheet, thus determining the degree of encapsulant's cross-linking non-destructively. They take only a few seconds, do not influence the performance of the tested module and have a precision of ±1.5%. The method is successfully applied to EVA and polyolefins. Further investigations are conducted to adapt X Link® to other new encapsulation materials.