SUMMARY OF NEW ENGLAND LEAD FREE CONSORTIUM IMPLEMENTATION PLAN OF HIGH VOLUME ASSEMBLY OF PRINTED WIRING BOARDS
Authors: Sammy Shina, Greg Morose, Liz Harriman, Richard An Date Published: 1/17/2006
Pan Pacific Symposium
Abstract: The New England Lead-free Electronics Consortium is a collaborative effort of New England companies spanning the electronics supply chain, sponsored by the Toxics Use Reduction Institute, the U.S. EPA, and the University of Massachusetts Lowell. The consortium has completed and published the results of two phases of manufacturing and testing of lead-free Printed Wiring Boards (PWBs) with the goal of achieving zero-defect lead-free soldering processes with comparable reliability to that of leaded solder processes. Phase I examined various solder alloy combinations and reflow profiles, while Phase II focused more broadly on processing parameters, utilizing a mix of component types and finishes in combination with five different PWB finishes, two reflow atmospheres (air and nitrogen) and three solder paste compositions based on the same Sn3.8Ag0.7Cu alloy. Phase III efforts began in August 2004 and will be completed by November 2005. The objective for Phase III testing is to focus on implementation issues by simulating an actual production board for parameters such as board layers, board size, and component density. The Phase III PWB is a twenty layer board with components on both sides, and populated with 1,750 components. Thirty-six PWBs were built and inspected to IPC 610 D standards by Benchmark Electronics in April 2005. The PWBs underwent thermal cycling at Raytheon Reliability Labs test facilities and Highly Accelerated Life Testing (HALT) at Teradyne test facilities. Pull testing was conducted at the University of Massachusetts Lowell. In this paper, the authors will present the results of Phase III efforts, including the PWB interconnect stress test, test coupon failure mode analysis, visual inspection, thermal cycling, HALT, and pull tests.