Greening Consumer Electronics: Moving Away From Bromine and Chlorine

Presents case studies of seven electronics companies that have engineered environmental solutions that eliminate the use of most brominated and chlorinated chemicals that generate toxic materials. Discusses global standards and regulations

Developing the knowledge-based human resources that support the implementation of the National Dual Training System (NDTS): evaluation of TVET teacher's competency at MARA Training Institutions

Development in the world of technical and vocational education and training (TVET) on an ongoing basis is a challenge to the profession of the TVET-teachers to maintain their performance. The ability of teachers to identify the competencies required by their profession is very critical to enable them to make improvements in teaching and learning. For a broader perspective the competency needs of the labour market have to be matched by those developed within the vocational learning processes. Consequently, this study has focused on developing and validating the new empirical based TVET-teacher competency profile and evaluating teacher’s competency. This study combines both quantitative and qualitative research methodology that was designed to answer all the research questions. The new empirical based competency profile development and TVET-teacher evaluation was based upon an instructional design model. In addition, a modified Delphi technique has also been adopted throughout the process. Initially, 98 elements of competencies were listed by expert panel and rated by TVET institutions as important. Then, analysis using manual and statistical procedure found that 112 elements of competencies have emerged from seventeen (17) clusters of competencies. Prior to that, using the preliminary TVET-teacher competency profile, the level of TVETteacher competencies was found to be Proficient and the finding of 112 elements of competencies with 17 clusters was finally used to develop the new empirical based competency profile for MARA TVET-teacher. Mean score analysis of teacher competencies found that there were gaps in teacher competencies between MARA institutions (IKM) and other TVET institutions, where MARA-teacher was significantly better than other TVET teacher. ANOVA and t-test analysis showed that there were significant differences between teacher competencies among all TVET institutions in Malaysia. On the other hand, the study showed that teacher’s age, grade and year of experience are not significant predictors for TVET-teacher competency. In the context of mastering the competency, the study also found that three competencies are classified as most difficult or challenging, twelve competencies are classified as should be improved, and eight competencies are classified as needed to be trained. Lastly, to make NDTS implementation a reality for MARA the new empirical based competency profile and the framework for career development and training pathway were established. This Framework would serve as a significant tool to develop the knowledge based human resources needed. This will ensure that TVET-teachers at MARA are trained to be knowledgeable, competent, and professional and become a pedagogical leader on an ongoing basis towards a world class TVET-education system

Flexible and stretchable circuit technologies for space applications

Flexible and stretchable circuit technologies offer reduced volume and weight, increased electrical performance, larger design freedom and improved interconnect reliability. All of these advantages are appealing for space applications. In this paper, two example technologies, the ultra-thin chip package (UTCP) and stretchable moulded interconnect (SMI), are described. The UTCP technology results in a 60 µm thick chip package, including the embedding of a 20 µm thick chip, laser or protolithic via definition to the chip contacts and application of fan out metallization. Imec’s stretchable interconnect technology is inspired by conventional rigid and flexible printed circuit board (PCB) technology. Stretchable interconnects are realized by copper meanders supported by a flexible material e.g. polyimide. Elastic materials, predominantly silicone rubbers, are used to embed the conductors and the components, thus serving as circuit carrier. The possible advantages of these technologies with respect to space applications are discussed

Reworkable Epoxy Underfill Encapsulants

A reworkable epoxy underfill encapsulant is provided for use in an electronic packaged system which incorporates an integrated circuit, an organic printed wire board, and at least one eutectic solder joint formed therebetween. A preferred embodiment of the encapsulant includes: a cycloaliphatic diepoxide; an organic hardener; a curing accelerator; a silica filler; and an additive, with the additive providing thermal reworkability to the composition. A method is also provided for forming the aforementioned reworkable epoxy underfill encapsulants.Georgia Tech Research Corporatio

Joint Lead-Free Solder Test Program for High Reliability Military and Space Applications

Current and future space and defense systems face potential risks from the continued use of tin-lead solder, including: compliance with current environmental regulations, concerns about potential environmental legislation banning lead-containing products, reduced mission readiness, and component obsolescence with lead surface finishes. For example, the United States Environmental Protection Agency (USEPA) has lowered the Toxic Chemical Release reporting threshold for lead to 100 pounds. Overseas, the Waste Electrical and Electronic Equipment (WEEE) and the Restriction on Hazardous Substances (RoHS) Dicctives in Europe and similar mandates in Japan have instilled concern that a legislative body will prohibit the use of lead in aerospace/military electronics soldering. Any potential banning of lead compounds could reduce the supplier base and adversely affect the readiness of missions led by the National Aeronautics and Space Administration (NASA) and the U.S. Department of Defense (DoD). Before considering lead-free electronics for system upgrades or future designs, however, it is important for the DoD and NASA to know whether lead-free solders can meet their systems' requirements. No single lead-free solder is likely to qualify for all defense and space applications. Therefore, it is important to validate alternative solders for discrete applications. As a result of the need for comprehensive test data on the reliability of lead-free solders, a partnership was formed between the DoD, NASA, and several original equipment manufactures (OEMs) to conduct solder-joint reliability (laboratory) testing of three lead-free solder alloys on newly manufactured and reworked circuit cards to generate performance data for high-reliability (IPC Class 3) applications

Evolution of Pb-Free Solders

This chapter discusses the evolution of lead free (Pb-free) solder, from tin-silver-copper (SAC) system with silver content of 3.0, 3.8, and 4.0 to low SAC system such as SAC0307 and SAC105 and the emerge of high reliability Pb-free solder. The discussion covers the reason and the driving force of industries implementing this change. The solder composition has evolved further recently to fulfill high reliability requirement of certain sectors such as automotive, aerospace, and military which are preparing to go green in soldering technology. This kind of high reliability solder involves additional microalloying of tin (Sn)-based solder in making it to be more robust. In this chapter, the author will introduce the techniques used by solder makers and researchers in enhancing the Pb-free solder strength in the recent evolution. Recently, attention has been drawn to low temperature joining technology again such as silver sintered joint and liquid-phase diffusion bonding material used in high power density and high junction temperature-integrated circuits. Pb-free joining material is required to replace the high Pb solder, which is still commonly used in such high-power devices

Properties of Mixing SAC Solder Alloys with Bismuth-containing Solder Alloys for a Low Reflow Temperature Process

The subject of extensive research has been the establishing of lower temperature soldering of electronic assemblies that are similar to the once common yet still preferred eutectic Tin-Lead (SnPb) soldering manufacturing processes that are below 217˚C. This research opportunity will contribute data on mixed solder alloy assemblies that can be formed at lower process temperatures. There are many environmental and economic benefits of avoiding the current reliability concerns of assembling electronics at the standard high temperatures which peak at 230˚C 260˚C. To reduce this temperature the use of Bismuth containing solder pastes are mixing with the standard high temperature SAC solders for electronic assemblies. The materials evaluated are the (in weight percentages) 96.5Tin/3Silver/.5Copper (Sn/Ag/Cu) solder ball mixed with each solder paste, the eutectic 58Bismuth/42Tin (58Bi/42Sn), 57Bi/42Sn /1Ag and a propriety alloy that has a lower Bismuth content along with various micro alloys, 40-58Bi/Sn/X (X representing proprietary micro alloys or doping). In the assembly portion of this research the solder alloys were exposed to three different peak temperatures 180˚C, 195˚C, 205˚C. Another reflow profile attribute of focus was times above 138˚C the melting point of the eutectic Sn58Bi alloy. The ball and paste assembly portion of this research used the times above melting of 120sec and 240sec to represent process extremes and verify their significance on improving mixing level results. These times above melting did not consistently improve the mixing levels and therefore are not recommended or required during mixed low temperature solder assemblies. The results in this study suggest the recommended and optimum reflow profile to have a time above the melting point to be less than or equal to 90 seconds for mixed solder alloy assemblies in “low” (20mm a side) component is a SAC405 solder balled BGA with the dimensions of 42x28x0.8mm. With any large component the temperature gradient across the component is a risk factor and the results show that there are significantly differences of mixing from the center of the component to the edge due to an average 2.3 ˚C temperature difference during convection reflow. The average mixing % levels recorded for Tpeak= 180˚C for the solder pastes with a 58Bi = 47%, 57Bi = 47% and 40-58Bi = 44%. The average mixing % levels recorded for Tpeak= 195˚C for the solder pastes with a 58Bi = 69%, 57Bi = 77% and 40-58Bi = 57%. The conclusions found also match previous work identifying the reflow peak temperatures remain a significant factor on the mixing %. This work’s goal was to add to the knowledge of the electronics industry to better understanding the microstructure and mixing mechanisms of Bi/Sn/X-SAC solder joints for low temperature reflow assembly processes

Liquid-phase diffusion bonding and the development of a Cu-Ni/Sn composite solder paste for high temperature lead-free electrical connections

After gathering sufficient microstructural evidence that a practical high-temperature lead-free solder could be produced through liquid-phase diffusion bonding (LPDB) of gas-atomized Cu-Ni powder blended with SN100C (Sn-0.7Cu-0.05Ni, wt.%) commercial solder powder, additional research was completed to enable design of a prototype composite solder paste. By reviewing several experimental alternatives to LPDB for use as replacements and improvements to the currently-used high-Pb solders (which will inevitably be banned by the EU’s RoHS directive), the choice to pursue the prototype solder paste research was verified. One key difference between this research and that of others is the method of pre-alloying Cu with Ni before atomization of the metal powder particles. These Ni additions prevent a detrimental unit cell volume change from occurring in typical Sn-Cu solder alloys by suppressing the hexagonal-to-monoclinic isothermal phase transformation upon cooling during reflow to below 186ðC. Rapid diffusion of the Ni and Cu was explored in order to better design the composite paste’s suggested reflow profile. Research to study and maximize the grain boundary diffusion of Ni and its effect on the resulting intermetallic compounds helped determine the final composition of the composite paste for use in industry