Selecting the best silicone for an electronic application goes beyond the product’s numerous functional attributes. Two other questions should be addressed to identify the ideal product: how it will be applied, and what type of UV cure is best for your process. The viscosity and flowability of the coating must align with the process technology being used – how it will be dispensed, and what type of equipment is being used in the manufacturing process. Novagard is able to supply the exact coating needed to meet specifications by understanding where and how the silicone needs to be placed.

Dispensing and Curing Your Silicone

With silicones, tuning the material to its required performance metrics is only step one in the process toward a well-protected product. Just as critical is assuring the silicone is getting to where it needs to go using the dispensing equipment on your line. This is where proper viscosity and flowability selection is critical.

Higher viscosity provides greater control of speed and distance of flow to prevent spreading into safe areas, while enabling thicker coating layers to be laid down in one pass. Lower viscosity aids high-speed production techniques such spraying or jetting, and allows your coating to flow through vias or under chips.

Silicone viscosity ranges shown on chip

To that end, Novagard offers designers the following range of electronics grade silicone products:

  • Sprayable formulations, from 500 cPs to 1,500 cPs
  • Flowable formulations, from 1,500 cPs to 40,000 cPs
  • Semi-flowable and self-leveling formulations from 40,000 cPs to 100,000 cPs for potting and encapsulation
  • Thixotropic pastes ideal for instant formed-in-place gasketing that dispense like a liquid, yet hold shape like a paste.

Then, to choose the optimum cure profile for the applied silicone, it’s important to establish exactly what comes next for the component. Does the PCB get installed later that day? Will the part be packaged immediately? Is this a fully automated mass production process, or perhaps just a short-run batch? Whatever your volume or line setup, UV-cured silicones deliver the goods, hardening and completely curing within seconds.

Standard UV Cure

For boards with deep sections (up to 1″ thick), when the component needs to be immediately processed for the next step in your production cycle, and for those applications where the component is directly inserted into packaging, a simple UV cure is usually sufficient. Novagard’s patented, ultraviolet-energy chemistry provides UV cure silicones with a speed and depth of cure far exceeding most other UV silicone-based cure systems. This unique chemistry allows deep sections to cure almost instantly. The protective silicone hardens throughout within seconds, completely cured and ready for the next phase of the process.

Advanced UV/Dual Cure

When superior adhesion is required, or boards have shadow areas, UV/dual cure technology is the best option for curing. This approach combines a UV cure that dries tack free in seconds with a secondary alkoxy chemistry moisture cure that eliminates unreacted coating in shadow areas. Broader viscosity ranges offer better coverage, and even components with deeper shadow areas can essentially finish curing by temperature or humidity as they move on to the next stage of manufacturing.

Ultimately, choosing the right silicone requires care, but the process doesn’t have to be daunting. Novagard is ready to walk you through the steps.