Enhanced protection for enhanced PCB performance
Conformal coatings are designed to protect printed circuit boards and related equipment from their environment. Typically applied at 25-75μm, these coatings ‘conform’ to the contours of the board allowing for excellent protection and coverage, ultimately extending the working life of the PCB.More info > Download product selector chart > Download product brochure >
The use of conformal coatings is particularly important in automotive, military, aerospace, marine, lighting, industrial and green energy applications. Due to the rapid expansion of the electronics industry, conformal coatings are also finding their way into the domestic and mobile electronics industries, providing the necessary combination of high performance and reliability within a vast array of electronic devices.
Conformal coatings can be used in a wide range of environments to protect printed circuit boards from moisture, salt spray, chemicals and temperature extremes in order to prevent corrosion, mould growth and electrical failures, for example. The protection provided by conformal coatings allows for higher power and closer track spacing, in turn enabling designers to meet the demands of miniaturisation and reliability.
Electrolube is among the world’s foremost experts in the formulation and application of conformal coatings designed to meet international approvals (including European and American military specifications). The range of products currently available comprises acrylics, silicones, polyurethanes, hybrid chemistries and environmentally friendly options.
Electrolube can offer both transparent and pigmented coatings to improve or camouflage the appearance of printed circuit boards. The range also includes a number of ancillary products to complement the use of our conformal coatings, including thinners and removers, peelable coating masks and thixotropic materials for dam and fill applications.
Electrolubes Conformal Coatings Technical Director Phil Kinner recently wrote a micro e-book on conformal coatings for harsh environments. It’s a great little insight into the selection, implementation and testing of protective coating process.
Solvent based conformal coatings cure by evaporation of solvents, this process can be accelerated in most cases by using heat, however this can affect the properties of the coating and cause coating defects if not performed correctly. In the Case of Electrolube’s Silicone based DCA for example, if you heat cure you get additional chemical resistance and greatly improved properties. Without heat cure, it offers good humidity protection.
AFA, a non cross-linking solvent-based acrylic on the other hand, will reach the same protective capability regardless of the curing conditions, the use of heat just accelerates the process.
UV curing uses intense ultraviolet light to set off a chemical reaction within the coating in order to cure almost immediately in areas exposed to the UV radiation. Due to the 3-D nature of most assemblies there will nearly always be areas that remain unexposed to the UV radiation (e.g. beneath components) and therefore a secondary cure mechanism is required. Moisture is the most common secondary initiation process since it does not require an additional process step, however formulations are available that use heat, although the cure times are relatively long (30 mins or more), and the temperatures are quite high (>120°C) which places additional thermal fatigue on the assembly.
UV curing materials are popular in high throughput environments, since in most cases the parts can continue through the process within seconds of the curing process, thus speeding up manufacturing velocity and reducing Work In Progress (WIP).
Moisture cure coatings require moisture from the atmosphere to cure. The humidity in the atmosphere can affect the speed of cure; increasing the humidity will often speed up the process. Humidifiers can be added to conventional and IR ovens to provide greater humidity and accelerate this process. It is important that these products are handled with care. If containers are left open for long periods of time then moisture will be absorbed and the coating will begin to cure.