Peters’ thick-film coating for rapid UV LED curing

Peters has developed Elpeguard thick-film coating twin-cure DSL 1602 FLZ/400, in particular for UV LED curing at a wavelength of 395 nm. Within seconds, the coating can be cured with an energy of 1500 mJ/cm2 and a capacity of 1500 mW/cm2. After UV curing, it is tack-free and thus inline-capable. Curing in shadow areas under room temperature – e. g. under components – is reliably executed by reaction with moisture.

Minimized process times make twin-cure DSL 1602 FLZ/400 particularly economic: Function tests and packaging can be done right after the UV LED curing. At the same time, the additional chemical cross-linking in shadow areas with atmospheric humidity will lead to an optimization of the properties.

In the meantime, this Elpeguard thick-film coating (basis materials FR-4 and CEM-1) has been approved by UL – best non-combustibility class. In addition to the UL approval, any solvent / VOC emissions can be avoided when using this system with its 100 % solids content. Thus, an optimal VOC balance can be guaranteed which considerably improves the environmental balance of this conformal coating.

Elpeguard thick-film coating twin-cure DSL 1602 FLZ/400 unites the final properties of a polyurethane system (UR) with the fast UV LED curing of unsaturated polyacrylates (AR) in one 1-pack copolymer. This polymer is very efficient under mechanical, chemical, and climatic stress and also most resistant to extreme thermal shocks.

It also offers advantages in handling: the coating can be easily checked for completeness under black light due to the fluorescent agent; in case of repair, it can be removed mechanically. Elpeguard twin-cure DSL 1602 FLZ/400 thus is a coating for the safe operation of assemblies in critical climatic surroundings, e. g. during longer dewing periods.

In the last years, the use of conventional UV technology has increased steadily, and thus Peters has arranged for extensive investigations in this respect. The Peters UV LED curing coating has to be cured tack-free with classical UV curing devices – which was the challenge. Peters Research was able to promptly give proof of the general possibility not only visually but also via the haptic of the cured test boards.

 Also relevant is the question whether the positive final properties of the conformal coatings, which actually are to be cured by means of UV LEDs, can also be achieved with other radiators. Or might deviations of the final properties under climatic stress appear? A detailed test set up including its realization are described in a test report. The results of this comparison lead to the conclusion that the kind of curing lamp (UV LED, undoped or gallium doped mercury radiator) has an impact on the final properties on the thick-film coating Elpeguard twin-cure DSL 1602 FLZ/400. This impact, however, is not too relevant so that the mechanical, electrical and climatic characteristics of the coating systems within the tolerances may be considered as identical.

To sum up, the test report shows that next to the recommended UV LED lamps, Elpeguard thick-film coating twin-cure DSL 1602 FLZ/400 can be cured by means of common UV lamps. To put it into other words: The properties remain almost unchanged.