Printed circuit boards (PCBs) electrically connect and power all but the simplest electronic products. To function as designed, PCBs and their components – capacitors, resistors, etc. – require protection against operating problems caused by corrosive liquids, dust, physical shock, temperature extremes and, in the case of medical implants, bodily fluids. Conformal coatings are applied over PCBs to safeguard mechanisms and maintain functionality.Read More
Parylene Coating Blog by Diamond-MT
Contributing to good performance for internal medical appliances, lubricity is a conformal coating’s ability to lower operational friction that might retard its function and endanger patient health. Lubricious coatings offer essential protection for appliances like cardiac-assist devices (CADs), catheters, elastomers, guidewires, and stents. Compared to an uncoated device, lubricious films can reduce frictional forces by more than 90%, dramatically decreasing potential harm caused by excessive insertion-force or internal puncture damage. This relative ease of use is important for implants and similar devices that require navigation throughout the patient’s vascular system or other internal structure; otherwise, patients can suffer from abrasion generated between the device surface and blood vessel walls.
Coefficient of Surface Friction
The degree of physical resistance a device demonstrates is numerically expressed by a coating’s coefficient of friction (µ), which quantifies:
- the magnitude of resistance a surface exerts on substances moving across it, or
- the minimum force necessary for an object to slide on a surface, divided by the forces pressing them together.
Static friction (µs) occurs when an object moves across a stationary surface; kinetic friction (µk) results for two objects simultaneously in motion, moving across each other. Conformal coatings are used in both circumstances, especially for medical implants with moving MEMS/nano-tech components.
Where higher-level surface lubricity is sought, lower µ-values are the objective; they signify lessened frictional resistance, minimizing non-release, dry-sticking challenges that interfere with devices’ performance. For instance, a µ-value of 1 indicates an equal quantity of force is needed to either lift an object, or slide it across a level surface; these calculations compare an object’s weight to the total force required to make it move. Most everyday objects and materials have a coefficient between 0 and 1; values closer to 1 are not feasible for medical purposes. For medical devices, a µ-value:
- ranging from 0.01 to 0.1 is ideal,
- but remains difficult to achieve
- for application to the expansive degree of metallic and polymeric substrates used for medical appliances,
- which require highly-specified levels of abrasion resistance and non-thrombogenic properties,
- in addition to biocompatibility and lubricity.
Appropriate safety standards also need to be met.
Much depends on the materials comprising the touching surfaces. Conformal coatings like Teflon (PTFE) and parylene, which provide high-level lubricity, maintain that level for a prolonged operational duration, making them very useful for specialized medical applications.
Properties of Reliable Coating Lubricity
Lubricated surfaces have lower levels of friction. Wet hydrophilic coatings amass water as a source of lubricity, applied by liquid methods such as dipping or spraying the film substance onto substrates. Applied to catheters or guidewires, they temporarily minimize development of thrombosis. However, their lubricious function decreases with time, dissociating or dissolving from the matrix surface, leaving particulates in tissue or the bloodstream, endangering patient health. Thus, they are less reliable long-term than hydrophobic coatingsRead More
The Need for Cleanliness TestingRead More
As the name suggests, spray coating is a method of application where the conformal coating is sprayed directly onto the printed circuit board (PCB). It is typically applied manually in a spray booth or by aerosol, although it can be automated/robotic, for selective coating assignments.Read More
Conformal coatings insulate printed circuit boards (PCBs) and similar electronics; their protection increases devices’ tolerance to harsh environments. The result is undisturbed function through a range of frequently harsh operating environments and performance conditions. Conformal coatings provide these services for aerospace/defense, automotive, consumer, and medical devices. They are adaptable for LED uses, as well as MEMS/nanotechnology, and other uses.Read More
The conformal coating process requires watchful administration to ensure successful implementation. Recognizing the unique properties of various coating-types is critical to selecting the kind most applicable to the project and its purposes, while meeting clients’ material and operational specifications. Regardless of the coating material and the substrate, these five fundamental procedures are essential to good conformal films.Read More
Managing the conformal coating process begins with a precise definition of coverage required. Pre-process negotiations between the client, the coating provider, and end-user, clarify coating requirements. They include agreement about whether:Read More
Liquid application resins acrylic, epoxy, silicone and urethane are applied to electronic circuitry in a liquid format by brush, dip or spray techniques, either manually or through robotic processes; they require curing before they can be used.Read More
For various reasons, even people familiar with the variety of existing conformal coatings, their strengths, weaknesses and respective use often assume that the chemical vapor deposition (CVD) process used for parylene films incorporates a solvent, as an integral component of the procedure. This is false, for the reasons detailed below.Read More
The value of polymeric conformal coatings for protecting printed circuit boards (PCBs) from functional retardants like dust, corrosion, moisture, and temperature fluctuations has been well-documented. Conforming to the physical configurations of the exposed face of the PCB, conformal coating:Read More