Circuits Assembly - July 2008 - (Page 57)

Conformal Coatings A Novel Non-VOC Conformal Coating Jade Bridges The polyurethane pre-polymer, 100% solids material performed well in SIR and thermal shock testing. cause problems in spraying and dipping applications. They can be applied only in thick films and therefore can take a long time to cure. In most cases, however, the viscosity is so high that successful coating of a delicate PCB cannot be achieved. A novel non-VOC conformal coating uses a polyurethane pre-polymer as the base oisture-cure and 100%-solids resin, a 100%-solids material in the form of chemistries have been used for a high viscosity liquid. The pre-polymer is years in a range of applications; pre-reacted polyurethane and isocyanate however, previous attempts to develop where some of the functional groups are moisture-cure conformal coatings have blocked. Upon exposure to moisture, the been unsuccessful. Moisture-cure coatings reaction continues to completion, forming tend to be fast-reacting and could block a coating. machines, particularly spray equipment The non-VOC coating is created by where a fine needle dispenser is used to adapting polyurethane pre-polymer with apply the coating. These 100%-solids matea blend of carefully chosen diluents to rials are high-viscosity materials that can ensure all materials are reacted within the system. The !%,1(!:#%;( (?(@ABC( diluents chosen offer a massive reduction in viscosity, creating a 100%-solids material at a sprayable viscosity, similar to that of solventbased materials, without VOC emissions (sidebar). The cure profile starts with the polyurethane pre-polymer reacting with moisture in the air. This is then followed by a further reaction with the diluent blend, releasing only Figure 1. Salt spray environment results of novel coating immediately CO 2 from the reaction. This after testing and after a recovery period. Standard acrylic coating is cross-linking is designed to M '#!" '!!" !"#$%&'()*+",% (/'+0+1%*&'(2343567( &!" %!" $!" #!" !" !" '!" #!" (!" $!" )!" %!" *!" &!" 809'(290*"1'+7( +,,-"./-0/12341/"541/6"7819:;8" +,,-"./-0/12341/"541/6" 5" ?/23"541/6"@&!5"A,1"#B1CD" 5" shown for reference. circuitsassembly.com Circuits Assembly JULY 2008 57 http://circuitsassembly.com

Table of Contents Feed for the Digital Edition of Circuits Assembly - July 2008

Circuits Assembly - July 2008 Contents Caveat Lector Industry News Market Watch Talking Heads Focus on Business Global Sourcing On the Forefront Screen Printing Tech Tips Will Electronics Follow the Sun? ‘Warm’ Manufacturing Heats Up Reputation Trumps Recession, China ‘Web Circuits’ A Novel Non-VOC Conformal Coating Krypton: Benchmarking Customer Satisfaction 2008-09 CIRCUITS ASSEMBLY Buyers Guide Wave Soldering Pb-Free Lessons Learned Process Doctor Materials World SMTA Int'l Product Preview Ad Index Assembly Insider Technical Abstracts

Circuits Assembly - July 2008

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.