Polyurethane coatings are amongst one of the most popular choices for conformal coating applications, they are available as single component, two component, UV curable, and water borne systems. Download the Urethane Resin 101 Guide today to learn more about this popular coating!
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How Urethane Protects Surfaces
Polyurethane coatings are amongst one of the most popular choices for conformal coating applications, they are available as single component, two component, UV curable, and water borne systems.
Why Use Urethane Conformal Coating
As a group, all provide excellent humidity and chemical resistance plus outstanding dielectric properties for extended periods; which make them one of the more popular coatings when it comes to protection of the critical operation of your printed circuit boards (PCBs). Conformal coating circuit boards reduces conductor spacing’s on PCBs and it will offer superior protection in an aggressive environment as well as protecting the PCB against environmental particulates.
A main reason conformal coatings are used are to extend the warranties on consumer electronics in the following fields automotive, control drives, fire alarms as well as military/aerospace safety features and long term reliability. The selection of conformal coating material is a crucial factor that needs to be considered carefully and in relation to the application method. The wrong selection can not only affect the long term reliability of the circuit board but can cause massive difficulties with both processing and costs.
The most common standards for conformal coating are IPC A-610 and IPC-CC-830. These standards list indications of good and bad coverage and describe various failure mechanisms such as de-wetting and orange peel.
Conformal coating inspection is a critical factor in determining successful coating application and long term reliability of PCBs. Using the IPC standards allows the coating operator to monitor the coating application performance. This can be done manually by the operator in an inspection booth by examining the PCB under white and UVA light or it can be done automatically by a conformal coating inspection system.
Urethane gets applied much like other liquid coatings. It can be applied via dip or by being brushed on. Other methods include spraying it onto the substrate using either human or robotic labor. Once applied, urethane requires an extended period of time to cure. While it can be dry to the touch within a few minutes, a full cure is usually measured in hours or, with some types of urethane, in as long as 30 days.
There are many benefits with using Conformal Coating. Using printed circuit boards as an example, conformal coatings lower the necessity to hermetically seal a board and the board is more reliable to function properly in humid environments. Urethane in particular also offers these additional benefits.
One of urethane's other strengths is also a potential weakness. It is a strong coating, creating a hard shell around the item that it covers. However, this characteristic can also make it brittle. In environments where it will be subjected to high levels of vibration, its structure can break down, eventually causing it to fail. While parylene is hard enough to provide a degree of physical protection, it also has more flexibility. This makes it much less likely to fail under vibration. On the other hand, urethane's hardness make it an excellent choice for settings where it will be exposed to abrasion. While both coatings resist abrasive forces, urethane offers an extra degree of protection.