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www.us-tech.com Protecting Liquid-Sensitive Devices Continued from page 66
applied inline by straightforward processes at the manufacturer. They also eliminate the need for costly capital investments and mitigate the bottlenecking batch process of vacu- um-based manufacturing or masking operations. Aculon’s NanoProof series of coating chemistries provides IPX8-
imposed by high-volume manufac- turing lines. It can be readily applied by
high-speed jetting or dispensing equipment, such as those manufac- tured by Nordson ASYMTEK or PVA. The material can be dispensed onto all sensitive component areas, with no need for masking or damming and filling. The coating
out impeding their performance. While this treatment does not pro- vide oleophobic properties, its ability to coat circuitry with consideration for connectors, test points, etc., is valuable.
Experimental Setup For testing PCBs, NanoProof
coatings were compared with two traditional, notable, conformal coat- ings: acrylic-based Humiseal® 1B315 and polyurethane-based Conathane® CE-1164. Several IPC-B-25A multi- purpose test boards were treated with two coatings from the NanoProof series: NanoProof 7.0 and NanoProof 8.4 using rod and dip coating. IPC-B-25A multipurpose test boards were selected per IPC guidelines for testing solder masks (IPC-SM-804C) and for testing con- formal coatings (IPC-CC-830B). Populated devices, LED strips,
Aculon’s coating chemistry, NanoProof 7, achieves
IPX7 protection and beyond, as well as providing a water- and oil-repellent surface to circuitry.
level protection to devices by manip- ulating molecular self-assembly. The company’s new class of
coating chemistry, NanoProof 7, achieves IPX7 protection and beyond, as well as providing a water- and oil-repellent surface to circuitry, even within the tight constraints
chemistry also contains no volatile organic compounds, making it desir- able for applications in industries with strict atmospheric regulations. Aculon’s NanoProof 8 series is a
hydrophobic coating that provides IPX8 protection and can also be applied to push-pin connectors, with-
were also tested to illustrate the issues with using the industry-standard con- formal coating test procedures to approximate water ingress testing. IPX7 and IPX8 qualification of devices coated with the NanoProof 7 and 8.4 series using rod and dip coating were evaluated, as well as testing for mois- ture and insulation resistance (IPC- TM-650 2.6.3.4 Rev A). Aculon NanoProof 7.0 and 8.4
were applied to general multipurpose test boards manufactured in compli- ance with the IPC — Association Connecting Electronics Industries. The coated boards were then sub- merged underwater following a mod- ified stress test of the IPX7 testing standard which essentially mimics removal of the enclosure and immer-
sion in a conductive aqueous media, making it an IPX8 level test. The boards were immersed in “instant ocean,” an aquarium product that mimics seawater, while being for- ward-biased for an extended period and while measuring the leakage current between the conductive paths of the comb pattern on the multipurpose test board. The test boards’ leakage current
was plotted to demonstrate the over- all insulation of NanoProof 7.0 and 8.4, while being stress-tested in salt water. Fluctuations in current were attributed to either the development of minor conductive paths, due to polarization of molecules in the NanoProof 7.0 and 8.4 coating or due to extraneous effects on the circuit, such as line noise, floating ground, etc., since the test setup was not placed inside a Faraday cage nor was the ground circuit isolated. In a separate test, NanoProof
7.0 and 8.4 were subject to moisture and insulation resistance testing in accordance to IPC-TM-650 2.6.3.4 Rev A, where the coatings were sub- jected to a variety of temperatures and humidity levels over a period of 178 hours, as well as large biasing loads, while monitoring current and insulation resistance. Similar to the modified IPX7 testing, fluctuations in current were attributed to the development of conductive paths under or through the coating, which is typically due to mobilization of flux residues left from soldering on the contact wires. In a final test, NanoProof 7.0 and 8.4 were subjected to the same
Continued on next page
February, 2019
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