The dam & fill process with two materials is mainly used in cases where a component needs to be protected with either an optically-transparent or opaque encapsulant or if a conventional glob-top material is too viscous to flow around and underneath fine wires. Optically transparent encapsulants usually have a low viscosity. A dam is therefore applied around the component first to prevent the potting material from flowing over the substrate.
Epo-Tek OG116-31 is a UV-curable epoxy. Due to its thixotropic nature it is often used as a dam. It can be cured with UV-light in a very short time. Afterwards the encapsulant – either a UV-cure or a thermoset material – can be applied. Whilst OG142-87 is typically used for a UV fill, both products have a high glass transition temperature.
As most UV-cure epoxies, both OG116-31 and OG142-87 are cationic products. Ionic polymerisation is initiated by photo-generated ions. The cure process continues until all polymers are consumed. Generally, cationic products have the benefits of less shrinkage and higher adhesion over free radical cured systems and are not adversely impacted by an oxygen rich curing environment.
Rob Church, sales manager at JP Kummer, said: “The dam & fill process is often a tricky operation. However, these two new UV-curable epoxies make it more straight-forward, with more consistent applications.”
