technology today 2005 issue 4 - Raytheon

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Meeting the Challenges of RoHS The worldwide movement towards reduction of hazardous substances As the Cheshire cat explained in Alice in Wonderland, maintaining your position requires continuous exertion. Nowhere is this advice more pertinent than with Raytheon’s need to maintain its high level of Mission Assurance despite the challenges posed by the worldwide movement toward the reduction of hazardous substances (RoHS). European RoHS legislation, together with other regulations and market forces, are leading a revolution in the materials used to manufacture all electronics. Because the suppliers of the electronic components and assemblies that Raytheon purchases also serve the wider electronics industry, they will respond to the needs of the majority of their customers. As it happens, military electronics represents a very small fraction of the entire electronics market. This presents a special challenge for Raytheon. Automotive 5% Industrial 7% Consumer Electronics 14% Telecom 20% Military 1% Computers 53% Figure 1. Military electronics represents a tiny fraction of the overall electronics market. Raytheon’s electronic assemblies are often called upon to perform in harsh environments for extended periods of time — and with unquestioned reliability. This is in contrast to the vast majority of electronic products which are subject to fairly benign environments for much shorter periods of time, and where the consequences of failure are often trivial. (For example, today’s cell phone has an average life expectancy of 18 months.) Therefore, the new materials and processes that are being implemented by the larger electronics industry may or may not be suitable for Raytheon usage. 18 2005 ISSUE 4 RAYTHEON TECHNOLOGY TODAY Transition to Lead-Free Manufacturing Chief among these changes, in terms of impact on our industry, is the elimination of lead (Pb), one of the principal constituents of solder. The worldwide transition to leadfree solder is having a major impact on all electronics manufacturers. It’s affecting not only the solder compositions, but also the construction of electronic components and printed circuit boards, and the modification of all the processes associated with their manufacture and assembly. Even though there is no current mandate for Raytheon to implement lead-free manufacturing in the vast majority of our products, changes are already being made. In fact, many of the components Raytheon purchases are suitable for lead-free assembly. Over the long-term, it’s likely that Raytheon will need to use an increasing number of fully lead-free assemblies. It might start when we purchase commercial off-the-shelf products that, starting in July 2006, must be RoHS-compliant to be sold commercially in Europe — a trend which may accelerate. Finally, if lead-free manufacturing becomes the de facto standard of the electronics industry, it may become impractical to cling to the legacy tin-lead processes. A similar situation exists with many of the other materials affected by RoHS, including hexavalent chromium (which Raytheon uses extensively for corrosion prevention on aluminum), cadmium, mercury and certain brominated flame retardants. Each of these materials will post their own unique set of challenges, and the transition will need careful management if Mission Assurance is to be maintained. Raytheon Takes Proactive Measures Fortunately, Raytheon did not wait for these issues to arrive at our doorstep before acting; instead we began to exert ourselves several years ago in anticipation of these challenges. The first challenge to maintaining unquestioned reliability that arose was the issue of tin whiskers, a phenomenon that has caused failures in electronics since the 1940s (Figure 2). The time-honored solution to the problem involves alloying tin plating with lead. Many of our commercial component suppliers have begun to eliminate the use of lead in their tin platings for compliance with RoHS requirements. Figure 2. A tin whisker bridges the layers of an internal via within a bus bar assembly.
Unfortunately, this has led to the revival of the risk posed by tin whiskers. Recognizing the situation, the commercial industry has been working to develop a new set of standards. However, commercial suppliers are unwilling to assume any liability for safetycritical with military products that incorporate tin. The draft standard therefore simply indicates that the use of tin is not suitable for such applications. A large number of component suppliers that elected to use pure tin have therefore effectively abandoned our industry. What was required was a parallel response tailored to the needs of our industry. Raytheon has assumed a leading role on the issue, forming an industry-wide working group in 2003. The group, which includes our government customers, has served as a focal point for discussions. From these discussions a variety of notices and significant results pertaining to tin whisker risks and their mitigation has been published. To wit, Raytheon pioneered standardized procedures for risk assessment and mitigation implementation, which have since been adopted into new aerospace industry standards. Raytheon also partnered with the U.S. Navy and the University of Maryland CALCE Center in proposing and executing a program funded by the Office of Naval Research to qualify a robotic process that can replace tin plating with tin-lead. Because of Raytheon’s numerous timely efforts, high levels of Mission Assurance are being maintained in spite of the disruption created by the introduction of tin. Joining Forces to Maintain Mission Assurance The next challenge that we are grappling with is the use of lead-free array attach components such as ball grid arrays (BGAs) and chip scale packages (CSPs) when used in combination with a tin-lead solder process. Raytheon is working with the Joint Group on Pollution Prevention (JG-PP), an industry-wide consortium, on issues relating to the use of lead-free solder and components. In addition, Raytheon is performing independent process development and reliability studies (see Figure 3). Although the results of the studies are not yet known, one thing is clear: Raytheon is proactively taking steps to ensure that Mission Assurance is maintained when confronted with these new lead-free package styles. Raytheon is also preparing for the inevitability of fielding fully lead-free assemblies in the future. To better leverage our efforts, the company is partnering with a number of consortia and working groups within the industry. We are actively participating with the Lead-free Electronics in Aerospace Project-Working Group (LEAP- WG), the Massachusetts Toxic Use Reduction Initiative (TURI) Lead-Free Project, the University of Maryland CALCE consortium and the JG-PP. We are also engaged in internal research targeted at our specific needs and internal processes. Our goal in these efforts, as always, is to ensure that reliability and mission success will not be compromised despite the disruptions. Although the technical challenges are significant, preserving Mission Assurance in the face of these RoHS-driven disruptions involves much more than pure technical challenges. New and modified procedures must be adopted by many functions, including Operations, Supply Chain Management, Environmental Health and Safety, Subcontracts and Legal. Understanding the need for widespread internal cooperation, Raytheon has assembled a high-level cross-functional team to coordinate activities in this area. The team will ensure that all of our processes function together smoothly within the new environment. Raytheon’s response to the challenges posed by RoHS is proactive, cross-functional, integrated internally across our businesses and coordinated with our customers and partners. We believe that all of this exertion will allow the company to continue providing unquestioned reliability in the face of external challenges. Dave Pinsky david_a_pinsky@raytheon.com Figure 3. A cross-section of a lead-free solder ball that has been attached using tin-lead solder is revealed. RAYTHEON TECHNOLOGY TODAY 2005 ISSUE 4 19
Page 1 and 2: technology today HIGHLIGHTING RAYTH
Page 3 and 4: TECHNOLOGY TODAY technology today i
Page 5 and 6: often, these products are fielded b
Page 7 and 8: Information Assurance & Survivable
Page 9 and 10: Solution sets enhance capability an
Page 11 and 12: Future Opportunities for Raytheon i
Page 13 and 14: HAWKER 4000 aerodynamic performance
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Page 21 and 22: The Information Fusion Engine (IFE)
Page 23 and 24: A New Spin on Radar Receivers: The
Page 25 and 26: PEOPLE: Raytheon’s Greatest Asset
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Page 35 and 36: International Patents Issued to Ray

technology today 2005 issue 4 - Raytheon

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