Silione conformal coatings are an excellent choice for customers who have a high temperature or moisture environment. Download the Silicone Resin 101 Guide today to learn more about this popular coating!
Receive your instant download of the Silicone Resin 101 Guide now by filling out this simple form.
How Silicone Protects Surfaces
Corrosion can occur when a continuous layer of water condenses on the electronic circuitry. The water needs only a few dissolved ions to become conductive and allow electrochemical reactions to start, resulting in corrosion of metals on the circuit or the creation of electrical leakage between conductors, especially with bias voltages that are present in the circuitry. Protecting the circuit with silicone, however, has been found to be one of the most effective ways to extend the life of the electronics in harsh use environments. This has been documented over decades of use in the industry in many different applications and use situations.
Why Use Silicone Conformal Coating
One of the keys for providing protection to underlying circuitry and other metallic surfaces is attaining good wetting and adhesion of the cured silicone to all surfaces of the electronic device or module. Liquid water is easily excluded at the cured surface of silicone coatings, but water vapor, present as humidity in the air, can permeate to the interface. However, without a place to collect below the coating, it causes no ill effects. Good adhesion eliminates gaps where liquid water could condense.
Besides humidity, conformal coatings provide protection from vibration and a wide variety of contaminants such as vapors, some solvents, and salt spray. Silicone conformal coatings are most widely used in high temperature environments due to their innate ability to withstand prolonged exposure to higher temperatures than most other conformal coating chemistries. This attribute has made them the primary choice for under the hood automotive applications. They are also capable of being applied in thicker films making them useful as a vibration dampening / isolation tool if the coated assembly is to be placed in a high vibration environment.
Silicone-based conformal coatings can be either tough, abrasion resistant, or soft, stress-relieving materials, depending on the formulation. They are most recognized for their stability over a wide temperature range and during temperature cycling. These conformal coatings provide good moisture and corrosion resistance and are available as both solvent-based and 100% solids formulations. The 100% solids materials can be cured with heat, moisture, or UV. Removability is typically not an issue as chemical strippers are available that enable this process. As with epoxies and urethanes, there are some handling issues with silicone coatings.
Repair is not uncommon. Silicone is very hydrophobic, with high moisture permeability; it may not prevent excess moisture-retention within PCBs, conditions that can stimulate the component’s corrosion and metallization.
Silicone Thickness & Repair
As a conformal coating, silicone cures rapidly; its generally thicker film application also generates superior vibration dampening and thermal protection. When applied in a thick enough coat, it can actually serve as a shock absorber for the coated item, helping to protect it against heavy impact. These factors assure good adhesion to those PCB materials that do not require thinner film covering to ensure operation; UV and corrosion resistance are superior to most competing conformal coatings. Featuring high dielectric strength, silicone surfaces are easily reworked if repair is necessary.