When applying conformal coatings to PCBs with connectors, the coating compound may seep into critical contact areas and affect the performance of the connector. This is known as ‘wicking’, and the phenomenon is as common as water moving from one container to another along a material path due to capillary action.
Much like water, conformal coatings behave according to the same forces of adhesion, cohesion, and surface tension. With each component material having its own surface properties, and each coating product having a specific viscosity, controlling wicking is important to avoid contamination.
Samtec offers some quick tips for a proper conformal coating process when using their connector products. Masking is the most common and effective method for preventing wicking, and using a water soluble flux during soldering is also recommended.
SAMTEC [ Processing Tips – Conformal Coating Connectors ] Topics covered include masking methods and application methods.
Masking Methods
Rubber Masking Boots
Peelable Mask
UV Curing Peelable
Mask Masking Tape
In addition to those methods, be sure to note the use of thixotropic gels as a blocking agent. Loctite 3705 is one example, and because it is UV curable, it can be used simultaneously with a UV curable mask.
Application Methods:
Dip
Brush
Dispense
Spray
Selective Spray
Vacuum Deposited
A great way to continue research on conformal coating chemistry and application methods is through the HumiSeal blog site (Topics List) [ HumiSeal Blog ].
Samtec products are sell represented on the Digi-key site: [ Samtec Product Line ], or simply search for the key word ‘Samtec’ from our home page: [ Digi-key Home Page ].
A few HumiSeal products are currently available as well through Ellsworth Adhesives: [ HumiSeal Products ].
Check out this article on the Digi-key Tech Forum for information on conformal coating defects: [ How to Identify and Resolve Conformal Coating Defects ].
For convenience, full URLs are posted below:
{Link Update Pending]
Samtec Processing Tips – Conformal Coating Connectors
HumiSeal Blog
https://blog.humiseal.com/
Samtec Product Line
https://www.digikey.com/en/products/result?s=N4IgTCBcDaIM4EMC2AXApgYxAXQL5A
HumiSeal Products
https://www.digikey.com/en/products/filter/coating-grease-repair/642?s=N4IgTCBcDaIBYFcC2BLAzgUwIYBsQF0BfIA
Digi-key Home Page
https://www.digikey.com/
How to Identify and Resolve Conformal Coating Defects
How to Identify and Resolve Conformal Coating Defects