International Conference on challenges in IT, Engineering and Technology (ICCIET’2014) July 17-18, 2014 Phuket (Thailand)

A Lead-Free Transition Plan for Safety and Reliability Critical Products

Elviz George, and Michael Pecht

 of lead-free legislation [1], [2]. These high silver SAC alloys Abstract—In some industries, such as oil & gas, chemical, and are close to eutectic and have near-eutectic microstructures. metals & mining, there are a variety of harsh operating conditions The move away from the near-eutectic SAC alloys towards a that the products are subject to over life times ranging over 10 years. lower silver content alloy was motivated by the cost savings In addition, the risks of failure are extremely high. For example, the from reducing the amount of silver and to avoid intellectual Emerson DVC6215 remote mount sensor, has operating requirements from -52oC to 120oC (which may get extended to -60oC in the future), property issues with Iowa State University [2], [3], who very high rates of temperature change during manufacture, require developed the Sn-4.7Ag-1.7Cu alloy. In addition, the Battelle 3G or 3X environments in testing, along with combined formation of large Ag3Sn platelets in the near-eutectic SAC vibration testing up to 50G‟s and temperature extremes. Since alloys was believed to degrade their thermal fatigue resistance. industrial products are designed for use in specific industries (with Therefore, the Japanese Electronics and Information their specialized operating conditions), there is no standardized set of Technology Association (JEITA) and the IPC recommended operating conditions for industrial grade products. As a result, such products have been exempt from the restriction of hazardous the hypoeutectic Sn-3.0Ag-0.5Cu (SAC305) alloy. The substances (RoHS) lead-free requirements. However, this regulation SAC305 alloy has excellent thermal cycling reliability due to is soon to change. This paper discusses the changes, the risks and the presence of silver, and has become the de facto industry candidate plans for a transition to lead-free in safety and reliability standard. The SAC alloys have a melting point in the range of critical products. 216°C~217°C. George et al. [4] recommended the use of SAC305 solders Keywords—Critical products, harsh environment, lead-free, in applications that operate below 185oC, thus eliminating the RoHS recast. need for specialized solders. SAC305 soldered onto 256 I/O and 144 I/O BGAs were subjected to temperature cycling from I. INTRODUCTION o o -40 C to 185 C. The authors concluded that specialized HE original version of restriction of hazardous substances solders used in high temperature applications can be replaced T (RoHS) directive, passed in January 2003, exempted four with SAC305 solder on polyimide boards in applications with categories of electrical equipment – fixed installations, large- temperatures up to 185oC and life requirements of 400 thermal scale stationary tools, monitoring and control instruments cycles. Crandall [5] tested 2512 chip resistors soldered with including those used in industrial installations, and spare parts commercially available Sn3.5Ag and SAC305, and for equipment already in use. The exemption for measuring experimental SAC+Mn and SnAg+Cu nano alloys on ENIG and monitoring equipment was put in place to allow sufficient finished copper under three conditions. Isothermal aging at time for suppliers to demonstrate long-term reliability of the 185°C for up to 1000 hours and at 200°C for up to 500 hours RoHS compliant products. There is a recast version of RoHS was performed to measure the interfacial intermetallic that will take effect in 2017. In this version, monitoring and thickness, assess intermetallic compounds, and view the control instruments are no longer exempt. microstructure. A durability assessment was performed The adoption of lead-free legislation has resulted in the featuring thermal cycling ranges of -40 to 185°C and -40 to proliferation of alternatives to eutectic tin-lead solder. Near- 200°C intermixed with 50G vibration cycling, and was eutectic Sn-Ag-Cu (SAC) alloys were initially recommended followed by shear testing to determine the most durable solder by the National Center for Manufacturing Sciences (NCMS) alloy. However, there is limited testing that included and the International Electronics Manufacturing Initiative temperatures as low as -60oC. (iNEMI) as the primary solder replacements after the adoption High silver Sn-Ag-Cu alloys exhibit significantly poorer performance than eutectic SnPb under high strain rate Elviz George is a PhD candidate at the University of Maryland, College conditions such as drop testing. With fine BGA interconnect Park, MD, 20742, USA. He is also a research assistant at the Center for geometries such as pitches of 0.5 mm or less, SAC405 or Advanced Life Cycle Engineering (e-mail: [email protected], [email protected]). SAC305 alloys showed performance orders-of-magnitude Michael Pecht is a Chair Professor of Mechanical Engineering and the poorer than eutectic SnPb in drop testing [6]. The impact of founder and Director of the Center for Advanced Life Cycle Engineering the Ag content on the SnAgCu solder interconnects has been (CALCE) at the University of Maryland, College Park, MD, 20742, USA reported in the literature [7]. Increasing the Ag content could (corresponding author‟s phone: +1(301)405-5323; e-mail: [email protected]). form a platelet-like Ag3Sn intermetallic compound (IMC)

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International Conference on challenges in IT, Engineering and Technology (ICCIET’2014) July 17-18, 2014 Phuket (Thailand) under certain thermal regimes that is not compatible with the reliability lead-free alloy, 90iSC, to be used in high- interfacial microstructures geometrically, thus causing the temperature applications [10]. The 90iSC solder is a multi- interconnect joint to be brittle. This could be a concern in component alloy based on a traditional SAC with improved some industrial applications. temperature resistance and reliability characteristics. The alloy To improve the drop/shock reliability, SAC alloys with has a temperature cycling range from -40oC to 155oC, lower silver content are generally used for mobile electronic optimized creep resistance at high temperature, vibration and applications due to their better drop/shock reliability. drop test performance comparable to SAC and other lead-free However, there have been no studies on the thermal cycling alloys, and printing and reflow behavior consistent with durability of low silver SAC alloys above 150oC. alternative lead-free materials. Microalloy additions, also known as solder dopants, are Indium Corporation claims to have a high temperature lead- elements (typically 0.1% or lower) other than the main free solder paste, BiAgXTM, as a drop-in replacement for high- constituents of the alloy that have been shown to improve lead solder pastes. BiAgXTM has a solidus temperature of solder performance. The benefits of microalloy additions are 260oC and requires minimal process optimization. This solder being explored, and several microalloy additions are already is designed to work in high-temperature environments at being used commercially. Among the quaternary versions of temperatures in excess of 150oC with no degradation of the SAC alloys, Sn-Ag-Cu-Ni, Sn-Ag-Cu-Bi, Sn-Ag-Cu-Mn, and mechanical structure or other properties [11]. Sn-Ag-Cu-Sb are the most studied [8]. However, no studies Although several high melting point solder alloys exist, have tested the temperature cycling durability of these very few have been successful in creating an impact or have quaternary solders beyond 150oC or as low as -60oC. even been studied by researchers. To learn more about the Binary lead-free alloys were developed as the simplest state of the art and practice, along with the less common lead- alloys for soldering methods. Sn3.5Ag has been widely free options, please refer to the CALCE technical appendix studied because of its performance in terms of both [12]. manufacturability and reliability. George et al. [4] showed that Sn3.5Ag solder had a durability comparable to that of II. MISSING INFORMATION IN THE STATE OF ART o SAC305 solder in BGA packages under testing from -40 C to Since the decision to move to lead-free solders in o 185 C. Crandall [5] showed that Sn3.Ag solder had a better commercial applications, temperature cycling has been the thermal and vibration cycling durability (up to a maximum most studied loading condition (see Fig. 1). For this reason, o temperature of 50 C and a vibration level of 50G) than SAC- the durability of lead-free solders under standard temperature Mn and SnAg-Cu nano particles; however, Sn3.5Ag was cycling conditions specific to RoHS-compliant applications is worse than SAC305. well understood. However, many applications, such as Lead-free alternatives for high temperature applications aeronautic, military/space, automotive, and oil and gas primarily include Au-based alloys, Bi-based alloys, Cu-based exploration equipment, operate at very high (+150oC) and low alloys, Sb-based alloys, and Zn-based alloys [9]. Antimony (-60oC) temperatures, and there is very little research assessing content should be less than 5 wt.% in the Sn-Sb alloy to the reliability of lead-free solders in such environmental maintain excellent mechanical properties without the conditions. formation of brittle intermetallic compounds. The liquidus RoHS legislation includes an exemption of the use of high o temperature of 240 C for Sb-based alloys makes them melting temperature solder containing more than 85% lead, potential candidates for certain high temperature applications. which is typically used in harsh environments. This exemption However, for applications operating at higher temperatures may explain the lack of research; however, the move to lead- Au-based, Cu-based or Zn-based alloys should be considered. free electronics is imminent for all electronic products, and o Sn-4wt.%Cu alloy has a liquidus temperature of 300 C. RoHS-exempt applications will soon have to follow suit. For Although the high liquidus temperature of Cu-based alloy instance, the exemption on medical devices is set to expire in makes it an ideal choice for high temperature applications, the mid-2014, followed by other exempt applications. Therefore, formation of large volume of intermetallic compounds reduces there is a need to establish the durability of lead-free solders the solder joint reliability. Zn-based have been widely used as under harsh environments to ensure a smooth and reliable a high temperature solder for aluminum alloys or for structural lead-free transition. purposes. However, the brittle nature of the Zn-based alloys Most studies in the 21st century have focused on the thermal limits its operation in harsh operating environment. cycling durability of SAC alloys. A classification of the High temperature gold-based solders include gold (Au), number of IEEE publications based on the type of reliability gold-tin (AuSn), gold-silicon (AuSi), and gold-germanium testing for the timeframe 2004-2008 and 2008-2014 is shown (AuGe). Gold-based alloys have a high tensile strength, in Fig. 1 [12]. The poor durability of high silver SAC alloys superior thermal fatigue resistance, exceptional thermal under drop, shock, and vibration loads necessitated further conductivity, and resistance to corrosion and oxidation. From high strain rate studies. In the last few years, more studies a durability perspective, gold-based alloys have the highest have investigated the effect of drop/vibration durability of strength and longest durability. However, costs are one solder joints, and if this trend continues, as expected, in the concern, and low temperature tests have yet to be conducted. next few years, harsh environment industries will have Henkel claims to have a commercially available high sufficient reliability data to evaluate the long-term durability

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International Conference on challenges in IT, Engineering and Technology (ICCIET’2014) July 17-18, 2014 Phuket (Thailand) of solder interconnects under high strain rates and large strain been studied; however, the high cost of gold restricts the range applications. widespread use of gold-based lead-free solders in the industry. Power cycling Vibration test From a financial standpoint, gold-based lead-free solders are 1% 1% Drop test limited to niche markets, where cost is not one of the key 7% issues. Indium Corporation has published reliability data for a BiAgX solder system and has shown BiAgX solder to be more Others durable than high lead solder (Pb5Sn2.5Ag) under thermal 23% Temperature aging and temperature cycling conditions [14]. However, there cycling is a need for independent organizations to systematically 68% assess the durability of BiAgX solders. In addition to high temperature durability, the reliability under other harsh loading conditions needs to be assessed to successfully employ BiAgX solders in harsh environments. Henkel [15] has published on the development process of the new 90SiC solder (a) material and its advantages. However, no literature is publicly available on the reliability of these 90iSC solders. Finally, regardless of the solder, there are limitations as noted in Table I. Vibration test 19% TABLE I LIMITATIONS FOR SELECT HIGH TEMPERATURE SOLDERS, SINTERED SILVER, AND TLPS COMPOUNDS [16] Drop test Material Tm Limitations 15% Temperature Au12Ge 361˚C High cost cycling 66% Au3.2Si 363˚C High process temperature Zn6Al 381˚C Complicated processing Zn5.8Ge 390˚C High process temperature Sintered Relatively high cost 962˚C silver High pressure required for sintering Ag-In 600˚C Relatively high cost (b) Ag3Sn 480˚C Potentially long process duration Fig. 1 IEEE publications on solder interconnect durability, (a) 2004– Au-In 480˚C High cost 2008 and (b) 2008–2014 [12]. Au-Sn 530˚C Potentially long process duration Cu6Sn5 415˚C Cu Sn 670˚C Potentially long process duration Although lead-free solders perform as well or better than 3 Ni3Sn4 798˚C tin-lead solder under most conditions, the long-term reliability of these lead-free solders is not well documented. As stated by Strain energy models (see CALCE report [12]) are available Lasky [13], the long-term reliability of lead-free solders is still for SAC solders, but they have not been validated above a mystery, since most of the products with lead-free solders 125oC or below -60oC. For other solders, no models are have not been deployed for a long period of time. Estimation available. With regard to vibration- or mechanical-induced of the long-term durability of lead-free solders from existing fatigue, no validated failure models are available for high reliability data is a concern, as the estimation of the temperature solders. The strain range-based and strain energy- acceleration factors for harsh environments is challenging. based fatigue models still need to be experimentally validated A survey of IEEE studies shows that SAC305 is the most to predict the life expectancy under very high and low studied lead-free solder. Although research has shown that temperature conditions. Finally, the literature on the durability SAC305 can be reliably used in applications for temperatures of lead-free solders used in harsh environments primarily o o up to 200 C, the melting point of 217 C limits the application focuses on the estimation of reliability under a single loading of SAC305 in very harsh environments with temperatures condition. However, during use conditions, the products are o higher than 200 C. Additionally, the poor performance of subjected to more than one loading condition either SAC305 solders under high strain rate and large strain range concurrently or sequentially. The interactions of more than applications further reduces the chances of SAC305 becoming one loading condition, the order of application of these the de facto standard for harsh environment applications. loading conditions, and the time lapse between the Therefore, there is a need to develop a drop-in lead-free solder applications of multiple loading conditions, all play a role in replacement for high-lead solders to be used in a wide range of effective solder durability, as seen in the existing literature for extreme conditions. RoHS-compliant conditions. There is a lack of understanding Although high temperature lead-free solders are available in of how these multiple loading conditions affect durability the market, very few studies examine the durability of these under harsh conditions. Thus, there is a need to conduct more high temperature solders. Gold-based lead-free solders have studies under multiple loading conditions to develop factors

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International Conference on challenges in IT, Engineering and Technology (ICCIET’2014) July 17-18, 2014 Phuket (Thailand) and generate publicly available data. in safety critical applications such as aerospace [19] and military. For instance, a tin whisker event was reported on the III. RISKS IN ROHS RECAST COMPLIANCE NASA space shuttle in 2006 where the whiskers were not For harsh environment electronics, the primary risks in growing from tin-plated electrical components, since the going to ROHS arise from the fact that there is no drop-in Space Shuttle avionics pre-dated RoHS, but from tin-plated replacement for high-lead solders, and there has not been beryllium copper card guides. This tin whisker event may enough very low (-60oC) temperature testing or very long term have been a result of continuous growth for years. The (+10 year) testing. For consumer electronics, SAC305 has transition to lead-free electronics in aerospace would have been considered the de-facto industry standard for tin-lead more tin whisker susceptible components than lead-based solder replacement since the RoHS legislation was electronics, since any tin-plated component could be a source implemented. This motivated the electronics industry and of whiskers and lead is not present to mitigate whisker growth. research organizations to conduct extensive evaluation of Han et al. [20] quantified the likelihood of metal vapor arc SAC305 solders. However, since the harsh environment formation in tin whiskers that may result in catastrophic industry is still searching for a drop-in replacement, the failures. Sood et al. [21] and George et al. [22] showed that tin existing studies are scattered and there are no comprehensive whisker growth is a concern in electronics used in harsh studies on any particular harsh environment compliant solder. automotive applications that uses tin based finishes on the For instance, studies have shown that the bond shear strength connector pins. of BiAgX joints between the Ti/Ni/Au plated Si die and Cu substrate is up to 44% higher than the high lead-containing solder Pb5Sn2.5Ag; there is no decrease in bond strength after isothermal aging at 250oC for 500 hours; and BiAgX exhibits a bond shear strength up to 6.1 times that of Pb5Sn2.5Ag after 2000 cycles of temperature cycling from -55oC to 125oC [14]. However, there is no literature on the vibration durability of BiAgX solders. This lack of vibration data increases the risks associated with using BiAgX solders in a high temperature/vibration environment. As mentioned in the previous section, studies have shown Fig 3. Global military and aerospace supply chain (adopted from that SAC305 and Sn3.5Ag can be reliably used in applications [17]). for temperatures up to 200oC. Hence, depending on the Under prolonged exposure to low temperatures, lead-free requirement of the safety critical application (if maximum solders are susceptible to tin pest formation. Tin pest can temperature is below 200oC), appropriate acceleration factors result in embrittlement and disintegration, depending on the are developed from the literature. The harsh environment level and duration of exposure. The use of high tin content industries, particularly military and defense, are increasingly lead-free solders in applications where electronics are using commercially available off-the-shelf, RoHS compliant, subjected to harsh low temperatures for a prolonged duration, electronic parts [17]. However, the decision to use SAC305 or such as aerospace applications, increases the risk of tin pest Sn3.5Ag solder in safety critical applications must be made [18]. It has been shown that tin pest is suppressed when based on the time to failure under specific conditions. alloyed with elements readily soluble in tin, such as bismuth, An ad hoc sub-committee of the Lead-free Electronics in lead, or antimony. On the other hand, the risk of tin pest is Aerospace Project (LEAP) team called the Pb-free Electronics increased by alloying tin with insoluble elements such as zinc, Risk Mitigation (PERM) consortium has studied the dominant aluminum, manganese, or magnesium. The presence of lead in risks associated with lead-free technology in harsh high-lead solders reduces the probability of tin pest formation. environmental conditions. The areas of concerns included However, the removal of lead to comply with regulations reliability data, supply chain management (see Fig 2), would increase the probability of tin pest formation. With manufacturing complexity, and field support [18]. billions of solder joints in mission-critical circuit boards The reliability of solder interconnects is critical to evaluate exposed to cold conditions for many years, it is inevitable that during the transition to lead-free materials. Another aspect to some tin pest would form. The effect of the cold is consider is the risks associated with lead-free materials used in cumulative: it does not get reversed when the weather finishes and printed circuit boards. One of the risks associated becomes warm. Applications most at risk include with RoHS compliance during the lead-free transition for automobiles, mobile phone towers, and military equipment consumer electronics has been tin whisker shorting. Although [23]. While further study into tin pest is warranted, the risks associated with tin whisker growth have been particularly for electronic equipment that will have long or extensively studied for decades, the transition to high tin complete service lives at sub-zero temperatures, the failure content lead-free solders/finishes and the elimination of lead risk due to tin pest in the majority of electronic equipment has increased the probability of tin whisker growth, resulting appears to be very low. in a greater focus on failures due to tin whiskers. The risks due Another concern with the transition to lead-free electronics to tin whiskers are even greater while transitioning to lead-free is the higher probability of conductive anodic filament (CAF)

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International Conference on challenges in IT, Engineering and Technology (ICCIET’2014) July 17-18, 2014 Phuket (Thailand) formation due to higher processing temperatures [18]. In CAF, field use conditions [22]. Therefore, the harsh environment a conductive filament forms along the epoxy/glass interface, industry needs to systematically evaluate the effectiveness of a growing from the anode to the cathode under the presence of nickel underlayer under specific applications to reduce the risk humidity in a storage or use environment. Since military of implementation. Plating using pure tin in electronics was electronics are generally stored for prolonged durations in prohibited by the US military in the early 1990s and by NASA humid conditions, the risk due to CAF needs to be assessed in 1998 [29]. Aerospace manufacturers, including Boeing before transitioning to lead-free electronics. Although some Satellite Systems and Raytheon Systems Ltd., also followed studies have touched upon CAF failures in lead-free suit by prohibiting tin plating in their electronic products [30]. electronics, research has not examined the CAF failure Therefore, if tin whisker growth cannot be successfully probability under harsh conditions. eliminated under harsh environments, an industry-wide There is risk involved in redesigning products for lead-free prohibition of pure tin finishes should be considered, and compliance. Manufacturers need to verify and document the alternative non-tin finishes should be used. The alternatives, risks of re-engineering for compatible drop-in parts and the re- including NiPd, NiAu, NiPdAu, and Ag-based finishes, are design of assemblies and sub-assemblies for compliance. not prone to tin whiskering [27], [31]. Tin pest formation can be mitigated by alloying tin with IV. MITIGATION OF RISKS ASSOCIATED WITH ROHS RECAST elements readily soluble in tin, such as bismuth or antimony. COMPLIANCE Based on the status of tin pest research, more studies need to If lead-free technology is to be introduced into harsh evaluate the risks due to tin pest under harsh environments for environment applications, long-term reliability data and lead-free technology. In conclusion the use of pure tin in harsh compatibility data (this involves flux compatibility and alloy environment electronics can be detrimental to durability. mixing as well) should be acquired from the suppliers/manufacturers for a given set of conditions for the V. TRADE-OFFS IN NOT GOING LEAD-FREE specified applications. Using information from the existing Although harsh environment applications are exempt from lead-free databases from suppliers would assist companies in RoHS compliance, these applications account for only a conducting tests and thereby save time and money. If marginal share of the total electronics production [32]. sufficient reliability data are not present in the literature or Therefore, the majority of electronics have converted to lead- with suppliers, additional testing needs to be conducted to free soldering, primarily in the commercial market. The use of reduce the risks associated with using lead-free and other lead-free materials has proliferated to the point where many ROHS technologies. components/parts are no longer available in tin-lead (either The Pb-free Electronics Risk Mitigation (PERM) surface finishes or interconnection media). In fact, it is already Consortium [24] provides recommendations to optimize the nearly impossible to find the newer, high-density BGA cost/reliability risk trade-offs across product and requirement packages in a leaded version. In addition, it is expensive and boundaries throughout the supply chain. PERM also time consuming to seek aftermarket channels for the now recommends development of approaches for conveying and obsolete or soon-to-be obsolete leaded components. There is promoting the needs of high reliability, long-service-life users also a risk in getting „used‟ or counterfeit parts, due to the lack to the materials and components end of the electronics supply of a good distribution chain of obsolete parts. Furthermore, chain. applications that require lead-based support often need to go Although there is no effective way to prevent whisker through the same amount of time and expense to convert lead- formation, methods do exist to mitigate their growth. free parts to lead-based parts [33]. Market pressures impact Conformal coating, while not a panacea, provides a barrier to industries currently exempt due to the decreasing availability prevent whisker contact and a constraint to whisker growth. of lead-containing high-temperature solders (for use in However, it has been reported that under harsh environmental temperature intervals between 250oC and 350oC), thereby conditions, such as elevated temperature and humidity, or pressuring the switch to lead-free materials [34]. Moving to under imperfect surface coating, such as areas of thin exclusively lead-free components makes the most sense, coverage, tin whiskers grow and penetrate the conformal provided that the industry has sufficient reliability data and coating, which can result in product failure [25]. Conformal has assessed the risks of RoHS compliance. coating can be effective for mild loading and short durations; The introduction and adoption of RoHS has resulted in however, under harsh loading and long environmental extensive evaluation of lead-free technology. The knowledge exposures, the effectiveness of the coatings can be of lead-free solders‟ use is far beyond what was previously compromised [26]. Further studies also need to be conducted known about even lead-based solutions. Although earlier to determine the high temperature, high humidity, and high studies showed poor reliability of lead-free solders compared corrosion resistance of the intended conformal coatings. to tin-lead solders, improvements in processing technologies Another method to inhibit tin whisker growth is to use a nickel and the optimization of solder compositions have considerably underlayer by reducing the compressive stress buildup of the improved the solder reliability. For widely used ball grid Cu6Sn5 intermetallics associated with tin over a pure copper packages, SAC305 performs better than eutectic tin-solder in surface [27]. However, studies have shown that a nickel most cases. In a study by iNEMI [8] to assess the reliability of underlayer is ineffective under both controlled test [28] and lead-free alternatives, it was concluded that all the tested

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International Conference on challenges in IT, Engineering and Technology (ICCIET’2014) July 17-18, 2014 Phuket (Thailand) solders, including SAC alloys with low silver content and can be used to test for certain restricted substances [35]. microalloy additions, showed better thermal fatigue durability Systematic RoHS Compliance than eutectic tin-lead solder. Additionally, lead-free solders tend to perform better in components with smaller footprints and reduced pitches. The trend to miniaturization has been Product Planning advantageous for the lead-free transition in this respect. Since Supplier Manufacturing and Design for Analytical Testing Information Operations designs are moving to smaller connections, even as the Compliance number of connections is increasing, it would be beneficial for the harsh environment industries to become RoHS compliant Fig. 4 Steps involved in systematic approach to RoHS compliance [35]. [33].

Earlier adoption of lead-free alternatives will give harsh Complete segregation of RoHS and non-RoHS inventory environment manufacturers an advantage over their has to be implemented as a control strategy. To update the competitors. The cost of continuing Pb-based processing and RoHS inventory control, new part numbering schemes and maintaining materials and associated parts for a few years will databases needs to be created and physical material labeling result in a financial burden for the manufacturer. Rework of processes should be implemented. Components and materials parts containing lead-based solders with lead-free solders will received from suppliers should be subjected to random testing result in additional reliability issues from mixed solder for compliance to environmental requirements. Likewise, in- assemblies. process inventory should be labeled and segregated to RoHS and non-RoHS workstations through production lines, and VI. BUSINESS MODELS FOR ROHS COMPLIANCE associated documentation should provide material tracking Eventually, all manufacturers will need to demonstrate that and an audit trail. their products do not contain restricted substances. Large companies have developed their own research Additionally, manufacturers, suppliers, and importers will programs with a multitude of talent and resources to solve the need to document and maintain files showing RoHS problems of material and process conversion for RoHS conformity of the product and provide these documents to compliance. They work with contractors and material enforcement agencies. suppliers to implement RoHS compliance using a variety of For products that are exempt, a company can use the „grace reliability and test methods, as well as complex analytical period‟ to prepare for RoHS and other future requirements. tools such as vibration platforms, long term environmental However, there are disadvantages in waiting. These include: testing to failure, and electronic scanning microscopes to see the inability to buy technologies that may become obsolete the interfacing layers of RoHS compliant materials. These and more expensive; difficulties in funding suppliers that are sophisticated analysis tools and extensive DoE matrices were willing to manufacture and service older technologies; the used to evaluate a large number of candidate material possibility for counterfeit and „used‟ parts to get into the replacement and process parameters. supply stream; and the potential to fall behind the competition. Medium and smaller-size companies may not be able to The steps involved in a systematic approach to develop afford extensive programs, but could develop cost effective RoHS compliant systems are shown in Fig. 4. In the planning conversion programs using Six Sigma principles for RoHS stage, a formal document supporting the restricted substance conversion projects. Shina [36] provided a set of guidelines to compliance is developed and approved by the top successfully convert to RoHS and notes that manufacturers do management. The design engineering team would then specify not need to start over from the beginning to convert to lead- the procurement of RoHS compliant parts from approved free. There are many publications and research data publicly manufacturers. In addition to compliance certification from available. Based on the field use conditions, manufacturers the suppliers, manufacturers can conduct independent lab can use existing lead-free alternatives or a modified version of analysis to confirm the chemical composition. Suppliers need those alternatives. Further studies on a new lead-free to provide adequate tests and inspections to meet alternative should be carried out only after conducting an specifications. Quality and supply chain management ensures extensive literature and data survey. Use standard performance RoHS compliance by suppliers and manufacturers. Audit and criteria and test methods for the lead-free alternative. verification processes need to be carried out periodically to Standards for commercial lead-free electronics are already ensure that the compliance is maintained during the widely available. Standards for lead-based electronics under manufacturing operations. The employees must also be trained harsh environments may need to be modified to accommodate on the RoHS compliance requirements and the consequences for the lead-free transition. If required, new standards for the of not adhering to them. In the final phase, to confirm a testing of electronic products in a harsh environment needs to product‟s compliance, producers may choose to carry out be developed. Use the latest trend in lead-free technology to analytical testing of homogeneous materials in their products take advantage of the benefits of widespread usage. and/or specific components based on the risk that a restricted Additionally, implementation of a unique lead-free alternative substance may be present. The manufacturer should resort to may result in earlier obsolescence and higher cost in testing “high concern” materials instead of testing all the maintenance and part replacement during the lifetime of the components in an electronic product. The IEC 62321 standard

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International Conference on challenges in IT, Engineering and Technology (ICCIET’2014) July 17-18, 2014 Phuket (Thailand) product. Also, reduce the dependence on proprietary solders http://dx.doi.org/10.1108/03056121111155611 and finishes. Depending on the scale of application, RoHS [22] E. George and M. Pecht, “Tin whisker analysis in an automotive engine control unit”, Microelectronics Reliability, vol. 54, no. 1, pp. 214-219, implementation may be a multi-year project. January, 2014. http://dx.doi.org/10.1016/j.microrel.2013.07.134 [23] R. Lasky, “Lack of concern for tin pest as a reliability issue in mission REFERENCES critical products still hard to understand”, Indium Corporation Blogs, [1] E. Bastow and T. Jensen, “The proliferation of lead-free alloys”, SMTA January 6, 2014, accessed online: http://blogs.indium.com/blog/an- International Conference, October, 2009. interview-with-the-professor/lack-of-concern-for-tin-pest-as-a- [2] G. 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