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Home > News > Industry News > Plasma treatment improves sili.....

Plasma treatment improves silicone coating adhesion

  • Author:Ella Cai
  • Release on:2017-06-06
The bonding of difficult materials can be improved by plasma treatment, according to PVA TePla, a company with sites in Germany and the USA – silicone and PTFE are amongst the firm’s specialities.

It offers both plasma surface modification to increase surface energy, and plasma-enhanced chemical vapour deposition (PECVD).

PECVD, for example, can be used to deposit a thin film of silicon dioxide to a substrate as an intermediate layer to improve the adhesion between the surface and a functional linker coating or directly to a coating.

One application of plasma to improve adhesion is keeping silicone stuck to PCBs, where otherwise it can de-laminate at the edges of the PCB board, and allow air pockets to form on or around components, opening a route to moisture ingress.

“Silicone over-moulding is often used to protect electronic boards from outdoor weather conditions, often preferred due to its low water absorption, wide temperature range of use, thermal stability, electrical resistance, and stability to ultraviolet light exposure”, said the firm. “Unfortunately, the topography of a PCB means the silicone must bond to many types of materials, including polymers, metals, alloys, ceramics and the FR-4 board itself, all of which have unique surface energy and chemistry.”

Rather than find a way to separately increase the affinity of each surface to silicone, use PECVD to coat everything with a layer that silicone likes, is the answer, according to company spokesman Michael Barden: “In terms of surface energy, the best strategy is to deposit a thin film coating over everything so the silicone only has to bond to one surface energy,” he said. “A process using plasma can basically harmonise all of the many surfaces and turn it into one.”

To accomplish this, PVA TePla has a specific process starting with a cleaning and surface-activation treatment followed by the deposition of an inert chemical primer that serves as the uniform layer for the silicone.

The adhesion properties of PTFE can be improved using PECVD techniques, creating a coating with polar functional groups on the surface that act as excellent anchors to either hydrogen bond or covalently attach hydrophilic coatings.

“The ability to selectively functionalise the surface with primary amines, hydroxyls, and carboxylic acids means that engineers can now broaden the use of this material in medical technology,” said the firm.

Biological molecules (proteins, antibodies, cells or carbohydrate, for example, can be attahed to difficult surfaces for medical use.