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SMT007-Oct2020

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12 SMT007 MAGAZINE I OCTOBER 2020 non-noble metals in alphabetical order (e.g., AgAuPdPtBiCuInSb). 4. List by the order of electromotive force series. Indium is not classified as a noble metal (in electromotive force, In = - 0.336 v; Ag = +0.80 v; Au = +1.42 v; e.g., AuPtPdAgCuBiSbIn). 5. Purely follow an alphabetical order of the name of elements in lieu of element sym- bols (e.g., antimony, bismuth, copper, indium, nickel, silver, tin). With considerable deliberations and debates, and in view of the past historical practice and the forward-looking convenience, our task group then reached the consensus to use the naming system starting with the matrix metal (i.e., naming lead-free alloys by starting with Sn elemental metal). This is the genesis of today's lead-free alloy designations in J-STD- 006 Table A-1. Future Work I hope that clarified the questions regard- ing the lead-free alloy designations being used in today's J-STD-006. Additionally, I want to take this opportunity to again mention the importance of future work for the task group to take on. In our recent past meetings, I have challenged the task group to address four questions: 1. As a task group, how can we make the J-STD-006 document more useful, complete, informative, and practical for the industry, including suppliers, users, or other interested parties? 2. Which area(s) should be added? 3. Which area(s) should be expanded? 4. What are the priorities? To this end, one recurring area that was brought up in our task group meetings was the differentiation and distinction between a dopant and an impurity. As more new alloys are being developed with intentionally added dopant(s) in a small weight percentage of the alloy composition, J-STD-006 bears the respon- sibility to provide a guide. 3. Minor elemental constituents, regardless of metallurgical nature (e.g., solid solu- tion, discrete particulate, doping element, intermetallic compound-forming element), are considered non-base metal. 4. Minor elemental constituents, regardless of metallurgical nature (e.g., solid solu- tion, discrete particulate, doping element, intermetallic compound-forming element), are considered either alloying elements or doping elements. 5. Inevitably, lead-free solder alloys fall in the Sn-based system (at least for the mainstream electronic packaging and SMT assembly industry sector.) 6. Individual companies and entities may have initiated their own naming systems or trademarks at their discretion. It is the companies' prerogative, for commercial purposes, to name solder alloys at their choice, which are formed independently from the list of Table A-1. 7. If needed, military drawings can be accommodated by an additional group of designations as a subset to reflect what have been used in the past in the electronics sector. Options for Alloy Designation or Naming System The task group has considered several options that were deemed plausible. Options included: 1. Following academic metallurgy, alloys are designated by element symbols, strictly, in alphabetical order (e.g., AgAuBiCuInNiSbSn). 2. Following the conventional practice or for practicality and convenience, alloys are named starting with the matrix metal, then followed with element symbols that are, strictly, in alphabetical order (e.g., SnAgAuBiCuInNiSb). 3. Some believe that noble metals should be listed first. Noble metals should be in alphabetical order first followed by

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