STR will come to your site, or simply provide the guidance, to help you get the most out of your laminators. STR can provide "starter" cycles that have been proven effective, but because lamination equipment varies depending on manufacturer, age, or materials used, the only way to get the most out of your process is to go through an optimization exercise. This is an iterative process requiring a time and materials commitment, but the productivity gains in the end usually far outweigh the initial costs.

Step one is to map out your current process. We're looking to see how long it takes to reach a full vacuum or what temperature the EVA is at during various stages. When optimizing a cycle it is important to capture the temperature between the encapsulant sheets and behind the cells.

Testing for Gel Content

STR strongly recommends the use of gel content testing in order to establish that sufficient cure levels have been reached. We suggest a target of 75%. This testing is important not only in the initial development of a lamination cycle, but for continued monitoring as well to ensure that the process does not drift. An insufficiently cured module may experience cell movement, delamination, or current leakage during wet hi-potential testing.

STR suggests using a four minute evacuation and eight minute press at 150°C as a starting point. This cycle has consistently resulted in gel content values close to or exceeding 80%. From here higher temperatures or reduced evacuation times can result in cycles approaching eight minutes total.

STR recognizes that the long testing time and hazardous solvents involved in gel content testing can be problematic. We have now developed a way of using differential scanning calorimetry (DSC) testing to determine gel content levels.

The DSC method shows excellent correlation to the well established solvent soak method and yields results in 30 minutes instead of 24 hours. STR continues to recommend that the solvent soak method be used to establish the initial lamination process and correlation to the DSC method. We are happy to provide this as a service to our customers, eliminating the need to construct a wet laboratory or go through the time and expense of sending gel content samples to an outside lab. Once a customer has purchased their own DSC STR can also provide any methods and training needed.

How STR Can Help

This case study shows actual data and cycle times generated by STR at one of our customer’s sites. They use a large belt fed laminator from a prominent European manufacturer and their standard process was developed around using a competitor’s encapsulant. As the graph to the right demonstrates, the encapsulant temperature does not always match the platen settings, and some laminators operate more efficiently at higher temperatures. Knowing that shrinkage would not be a problem with our encapsulant, we began building a cycle around the 154° set point.

The end result is that STR was able to achieve defect free modules with gel content values comfortably above 75% all while reducing our customer’s cycle time from 18 minutes to 10. Contact us to find out how we can help you too.