This Small Business Innovation Research (SBIR) Phase II project seeks to further develop and commercialize a new class of durable, water-resistant nanocomposite coatings identified and explored during the Phase I project. The unique processing conditions used to make these nanocomposite coatings produce a virtually invisible, conformal, nanometer-scale film that is comprised of surface bound nanoparticles and offers superior water barrier properties while still permitting through-film electrical connections. The newly developed coating has the potential for great commercial impact and can be thought of as a "game changer" for certain consumer electronic markets. The innovation and research plan for Phase II centers on two critical issues for commercial integration: 1) the overall processing efficiency of the material and 2) issues of long-term reliability and chemical interaction with existing platforms.
The broader impact/commercial potential of this project will be felt in a number of consumer, military, and medical products. It is estimated that about 1.2 billion mobile handsets are produced annually and that 8% of all the damages that occur to handsets are from liquid ingress. If fully adopted by the industry, this coating could reduce the liquid ingress damage to nearly zero, resulting in significant savings to consumers. Additionally, medical hearing aids would benefit from the oleophobic protection provided by this material, and its use would result in a decrease in the number of units returned annually for corrosion, water damage and ear wax contamination (this number currently stands at 11 million). Finally, the integration of our protective coating into other existing electronics products will add significant value to these products and will make them more durable and attractive to consumers globally.
(Grant: IIP-102657) - Project Outcomes PI: Jeffrey Chinn, Ph.D. (jeff@insurftech.com) Overview: Integrated Surface Technologies (IST) and in conjunction with its partner at Auburn University, the Dept. of Chemical Engineering (AU), developed a super-hydrophobic nano-particle based composite film using a hybrid vapor deposition technique that includes ALD-like alumina and CVD-like silica processes. In Phase-I, many electronic products tested exhibited excellent water resilience when their PCB assemblies were conformally coated with this super-hydrophobic film. In Phase-II/IIB, minimal viable material characterizations were performed in order to qualify this new material for several select applications. Additionally, continuing studies on the films properties, how to improve its performance and how to ensure manufacturability were executed. At the close of this SBIR grant, the nano-composite film has been incorporated into several commercial products (eg. hearing aids). Summary of Research Performed: The nano-composite film is based on a technique called VPD (Vapor Particle Deposition) which uses a sub-atmospheric pressure gas-phase flow-through reactor. This coating scheme is highly suited for large batch chambers and can be easily scaled. The unique nano-composite structure is created using a cross between atomic layer deposition (ALD) surface limited reactions and chemical vapor deposition (CVD) condensation process conditions in which super-saturated vapor conditions are created directly over the targeted coating surface. During the process, a metal organic precursor is oxidized in such a way that the required film roughness and aerial coverage for a super-hydrophobic property is achieved. Subsequently, the nano-particles are immobilized into a silica-based matrix to improve the film’s durability. It was observed that the use of thinner alternating deposition/immobilization steps similar to conventional ALD resulted in films with better uniformity and durability compared with non-layered deposited films. The final step in the process sequence is a surface modification treatment with a perfluoronated agent to create a low surface energy layer over the entire film. In order to achieve a super-hydrophobic property, the film requires a critical value of surface roughness, surface energy and a new parameter which the SBIR team found important of aerial coverage. These critical parameters were achieved by a layered deposition approach as shown in the image and how it effects the water contact angle. The film roughness increases to a maximum of ~450nm rms. The SBIR team observed that surfaces with similar RMS roughness values could also have drastically different contact angles and thus concluded that the RMS roughness alone was insufficient for characterizing the transition to super hydrophobic behavior. A new parameter of surface coverage was required to further define a super-hydrophobic surface. There is a critical aerial density or coverage required (typically greater than 20%). The super-hydrophobic nano-composited was certified for Underwriter’s Laboratory (UL) compliance under UL-94, the Standard for Safety of Flammability of Plastic Materials for Parts in Device Applications. The nano-composite was deemed compliant to Standards for Safety: Printed Wiring Boards, UL746E. A flammability rating of V-0 was obtained which the best (lowest) of the 12 flame classifications. The Repellix film is authorized to bear the UL recognized component mark and is a standard that most printed circuit board manufacturers require to use of the material on their circuit boards. Electro-Chemical Migration (Corrosion Suppression) The super-hydrophobic nano-composite film has been shown to reduce corrosion, commonly referred to as Electro-Chemical Migration (ECM) induced corrosion when electronics are exposed to any electrolyte or moisture. Corrosion effects are commonly observed as dendrites which form between electrical traces resulting in shorts and surface leakages. Under bias, the dendritic grow is often in-line with the electrical field between the trace leads. Typically a conformal coating of urethane, epoxy or silicone is applied to form a mechanical barrier over the solder and electrical leads. When the super-hydrophobic nano-composite film is applied over a printed circuit board, it creates a boundary layer of air which retards the onset of ECM since the solder surfaces are not wetted by the electrolyte. Shown in the image are typical ECM corrosion phenomena that can be observed of unprotected and coated solder traces and a resistor network. On a resistor network, the nano-composite coated structure did not exhibit any visible signs of corrosion for extended periods of time. The super-hydrophobic nano coating reduces the leakage current by more than 200x compared with uncoated components for typical battery operating voltages. Commercialization Activities: The SBIR team believes that the super-hydrophobic nano-composite coating develop has a unique niche for electronic application in which coated PCB’s are protected by an enclosure preventing mechanical wear. IST has been issued three (3) US. Patents to-date covering the developed technology. US Patent 7,968,187,(June 28, 2011) "Surface Coating" US Patent 8,221,828, (July 17, 2012) "Surface Coating Process" US Patent 8,071,160, (Dec. 6, 2011) "Surface Coating Process"
