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Ellsworth Adhesives - Home>Resources>News

Dowsil Silicone Conformal Coating Selection Guide

 

Source:Dow.com / Editor:Ellsworth Adhesive

 

Dow Performance Silicones has been a global leader in siliconebased technology for more than 70 years. The versatility of silicone chemistry expands design freedoms, increases processing options, broadens performance parameters, and introduces unique options for sustainability. Compared specifically to organic-based coatings, silicone solutions offer these valuable benefits:

● Greater thermal stability: Silicones perform reliably at sustained temperatures as low as -45°C and as high as 150°C – a far broader range than organic coatings, which degrade at such extreme temperatures. Many silicones can even withstand brief exposure to temperatures up to 250°C.

● Stress relief: Silicone conformal coatings offer an extraordinarily broad range of durometers, as well as extremely low modulus options.

● That means they deliver better stress relief on delicate board components during thermal cycling.

● Solventless fast cure: Silicones – including UV-cure grades – are nearly all solventless, making them the material of choice where emerging regulations impose complex and costly special handling and processing requirements.

 

Viscosity

 

Low viscosity for high-speed production Our low-viscosity silicone coatings support high-speed production methods, including manual or automated spraying, flow, or jetting techniques. These faster flowing materials are also suitable options when you want your coating to flow through vias or under chips.

 

Higher viscosity for greater control Offering incrementally higher viscosities, this category of silicone coatings provides increasing control over the speed and distance of flow, to prevent their spread into “no go” areas. Higher viscosity silicones also enable thicker coating layers in one pass, and some grades even offer a stable coat on tall vertical surfaces.

 

Cure Profile

 

Fast, moisture cure

These coatings cure quickly at room temperature to provide a “dispense and forget” solution that is tack-free, and ready to move down the production line in less than ten minutes, making them the ideal option for high-volume assembly operations.

 

Extended-working-time moisture cure

Silicone coatings in this category also cure at room temperature, but permit more time for the material to flow further over large or complex boards.

 

Heat cure

Sometimes labeled “command cure” for the control they allow over the rate of cure, coatings in this category are the material of choice when your processing operation demands full cure in under five minutes.

 

Hardness

 

Highest stress relief (<15 Shore A)

Our softest silicone coatings maximize stress relief on very fine wires, or dense components that can be most susceptible to thermal cycling.

 

Stress relief (15 Shore A to 40 Shore A)

The ideal alternative to brittle organic coatings, silicones in this category offer an optimal combination of stress relief and protection against harsher environmental elements, such as moisture, dust, vibration, and impact.

 

Abrasion resistant (40 Shore A to 25 Shore D)

Silicones in this class cure to form hard, tough coatings comparable to acrylics – except silicones offer greater flexibility, and perform reliably at much higher and lower temperatures.


References: https://www.dow.com/en-us/document-viewer.html?ramdomVar=2877994042807859458&docPath=/content/dam/dcc/documents/en-us/catalog-selguide/11/11-36/11-3666-01-innovative-silicone-conformal-coatings.pdf