Symposium Conference Proceedings


IPC-CC-830B Vs The real world: A quantitative comparison of the ability of CC-830B to predict the ability of a conformal coating to successfully protect a test assembly during thermal shock and salt-mist testing

Author: Phil Kinner
Company: Electrolube
Date Published: 11/18/2014   Conference: Symposium


Abstract: PowerPoint Presentation Only

Conformal Coatings are often used to increase the reliability of electronic assemblies operating in harsh or corrosive environments where the product would otherwise fail prematurely.

Conformal coatings are often qualified to international standards, but always on a flat test coupon, which is not representative of real world use conditions. In order to better correlate international standards with real world-use conditions, three-dimensional Surface Insulation Resistance (SIR) test boards have been manufactured with dummy components representative of those commonly used on printed circuit assemblies. A variety of commercially available conformal coatings have been applied to these coupons by a variety of common methodologies including dip, spray and selective-spray, at a variety of thicknesses. The applied conformal coatings were cured in accordance with the manufacturer’s recommendations. The conformal coating thickness and coverage over critical areas was assessed by non-invasive optical methods.

The coated samples were then subjected to 1000 thermal shock cycles (-40°C to + 125°C) and salt-mist cycles to represent typical end use qualification testing. Voltage was applied to the SIR boards during the salt-spray test regime to better correlate to real use conditions. The corrosion evident on assemblies was visually assessed by optical microscopy under 10-40X magnification and compared with the measured SIR to assess corrosion resistance of the various process combinations.

Lead-free solder was used exclusively for this test, and water-washable, cleanable ‘no-clean’ and no-clean flux samples were included, to investigate the effect of cleaning on the overall reliability of the coated system. Conformal coating thickness and coverage were assessed for the various coating techniques.

The results of the thermal shock and powered salt-spray test results were correlated back to the application method, coating thickness, flux, cleaning and coating chemistry to determine the best overall process and material combinations for high reliability applications.



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