With reliable moisture barrier properties, parylene (XY) conformal coatings generally have a hydrophobic surface when deposited onto substrates, causing liquids to form separate droplets on film surfaces. While this outcome is useful for many XY applications, greater hydrophilic response, wherein XY molecules form ionic or hydrogen bonds with water molecules, can also be desired. This can be achieved by applying glue or epoxy on top the deposited parylene; surfaces acquire enhanced hydrophilic properties, becoming more wettable.
Read MoreParylene Coating Blog by Diamond-MT
Tags: parylene properties, parylene process, parylene rework
Tags: parylene properties, parylene coating process, parylene rework
Parylene’s CVD method of application generates exceptionally lightweight yet durable conformal coatings, with superior barrier properties. Compared to liquid processes, the effects of gravity and surface tension are negligible, so there is no bridging, thin-out, pinholes, puddling, run-off or sagging.
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Despite conformal coatings’ ability to dependably protect substrate surfaces of printed circuit boards (PCBs) and related electrical components, problems can sometimes occur which compel their removal. Chemical removal, which does the least damage to PCBs, is fine for wet coating substances like acrylic, epoxy, silicon and urethane. Chemical removal methods are far less successful for parylene, despite the use of a chemical vapor deposition (CVD) process for its film application.
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In addition to cracking, a range of associated issues may interfere with successful coating of parylene films. Because it is applied via CVD, parylene generates a structurally continuous film covering a PCB or similar assembly. In CVD, the interaction of vapor-phase chemical reactants formulate a non-volatile solid film on a substrate, useful for a variety of applications like corrosion resistance, erosion defense, and high temperature protection.
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Removal of Conformal Coatings
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When it comes to reworking, parylene's strengths are also its biggest drawbacks. In addition to its ability to comprehensively coat substrates, it is also, by design, very challenging to remove. However, "very challenging" and impossible are two different things. Furthermore, good planning strategy before coating can also help to reduce the need for parylene rework.
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Parylene's benefits as a conformal coating are well known. It resists heat, cold, moisture, and pressure; salt spray, electricity, and solvents can't permeate it. And while these attributes of parylene contribute to the conformal coating's appeal, they also present distinct challenges, particularly in regards to parylene removal, rework, and repair.
Parylene's benefits as a conformal coating are well known. It resists heat, cold, moisture, and pressure; salt spray, electricity, and solvents can't permeate it. And while these attributes of parylene contribute to the conformal coating's appeal, they also present distinct challenges, particularly in regards to parylene removal, rework, and repair.
Tags: parylene, parylene removal, parylene rework