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.
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 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.
We are committed to serving the industry with rapid turn times for parylene, (normally 10 business days) with expedited service in as little as 2-5 business days depending upon the complexity and quantity. For liquid coatings, our normal turn time is five business days. Expedited service is avaiable in as little as 2-3 business days.
Diamond MT’s quality manual ensures every employee is focused on continuous improvement and service excellence. Our ESD safe facilities stretch over 12,000 square feet dedicated to your conformal coating requirements. We are continually researching and updating our equipment to make sure we are providing the best ESD protection available.
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