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28 The PCB Magazine • September 2014 ALuMINuM BASE CIRCuIT TECHNOLOGy continues to military. Furthermore, the assembly makes it much more difficult for unscrupulous indi- viduals to extract and reuse components, inject- ing them into the supply chain as counterfeit devices [4] . F. Reliability Improvement Improvement in reliability is largely a by- product of various elements of the electrical, thermal and mechanical performance bene- fits just discussed, combined with the benefits that can be obtained by simple bypassing of a high-temperature lead-free soldering process. To this point, it is worth repeating what was mentioned earlier and that is that the soldering process is typically the largest cause of defects in assembly and that solder joints are the most common sites for failure of electronic intercon- nection systems [5,6] . Furthermore, in a solderless assembly, concern over tin whiskers, a topic that has returned to prominence in re- cent years, is relieved. Finally, CAF [7] (conductive anodic fila- ments), which is the growth of conductive fibers between ad- jacent vias in reinforced ma- terials and tin whiskers [8] are obviated by the ability to use homogeneous, unreinforced materials and elimination of solder respectively. G. Regulatory Compliance The EU's RoHS legislative mandate to eliminate lead from electronics solder has proven very costly [9] ; however, this stricture is automatically ac- commodated if one eliminates sol- der completely. The finished structure described is basically an all-copper interconnection sys- tem. On the finished product, only the surface sites required for making electrical connection to the other system elements, such as switches, connectors and the like, need to have a contact finish. The key point is that since neither copper nor aluminum is considered a problem, both the RoHS and REACH concerns should be obvi- ated provided the other materials selected and used in the assembly are compliant. Addition- ally, the material declaration process is greatly simplified. These same benefits hold true rela- tive to the use of conflict materials which is of growing concern among increasing numbers of both governmental and non-governmental or- ganizations (NGOs) as the structures completed as described are completely devoid of any pro- scribed or sanctioned materials. In short, the assemblies described allow a product to much more easily pass regulatory scrutiny. H. Environmental Friendliness During the last few decades, concern over the environment has moved steadily into the consciousness of government officials, business leaders and the consuming public around the world. The term social responsibility is also often used to describe the concern; however, the fact that the industry makes products that impact the envi- ronment at the lowest possible level has become increasingly important. With that in mind, consider an electronic struc- ture constructed principally of a material that is desirably and easily recycled, such as alumi- num, as well as the significant amount of energy that is used in traditional manufacturing in component and assembly preparation and in the sol- dering process—which can be saved when solder is not used. As suggested earlier, additional energy savings can be found by obviating the need for all of the process steps leading up to and following the soldering process. Discussion As has been shown, there are many advan- tages to making aluminum circuit assemblies in the manner described. That said, a recurring question is often raised: How does one test and rework such assemblies? The question is per- haps best addressed with another question: If the process is executed properly and the com- ponents are not subjected to thermal extremes, The key point is that since neither copper nor aluminum is considered a problem, both the RoHS and REACH concerns should be obviated provided the other materials selected and used in the assembly are compliant. " "