Issue link: https://iconnect007.uberflip.com/i/1415897
OCTOBER 2021 I SMT007 MAGAZINE 13 The answer is a resounding affirmation; reliability and manufacturability are closely linked. To have a sound manufacturability, four essential practices should be observed: 1. An adequate process window (e.g., reflow profile setting). 2. A sufficient material performance latitude (e.g., solder paste wetting ability). 3. Compatibility between process and material (e.g., reflow profile being in sync with properties of solder paste). 4. Process control. Each of the process steps must deliver an ad- equate process window and each of the mate- rials selected should possess an adequate per- formance latitude. is is particularly true in the reflow step—a narrow process window is expected to marginalize the process, which of- ten causes higher defect rates on the produc- tion floor and/or product reliability issues dur- ing service. Closing Thoughts To ensure the target reliability, a holistic ap- proach should be exercised to plan for reliabil- ity, to design for reliability, to select materials for reliability, to select components for reli- ability, and to manufacture for reliability. Ad- ditionally, utilizing the knowledge in known failure sources or mechanisms coupled with practicing the know-how to prevent likely fail- ure processes from occurring further enhance a product's reliability. Aer all, the Second Law of ermodynam- ics and the metallurgical Dislocation eory do not change. In a nutshell, the golden rule is to integrate three best practices: 1. Deliberately and systematically prevent likely known failure causes. 2. Diligently set up a robust manufacturing operation. 3. Prudently utilize the profound scientific and engineering principles to take care of the unknowns. ers, larger PCB size, thicker PCB) increases. Being free of degradation aer high tempera- ture processing, which may lead to production defects and/or product failure, such as the re- sult of pad-cratering, pad-liing, or de-lamina- tion, must be assured. On solder interconnections, the initial solder alloy selected to use is equally important to the solder joint integrity resulting from the manu- facturing-related factors. In combination, both dictate the quality and reliability of the result- ing solder interconnections. With respect to solder alloy, four fundamental correlations are worth noting: 1. e alloy composition determines the process temperature required. 2. e alloy's compositional makeup dominates the microstructure, which in turn reflects on the solder joint behavior during its service life. 3. e microstructure and its evolution dictate failure mechanisms. 4. An intrinsically inferior alloy cannot deliver a superior performance, i.e., the maximum performance is limited by the intrinsic properties of an alloy. From an SMT reliability perspective, the goal in selecting an optimal solder joint material is to deliver the plausible metallurgical properties and the anticipated behavior while not requir- ing an elevated process temperature, i.e., ren- dering the process temperature as close to that of SnPb eutectic alloy. To accomplish this goal under the established manufacturing infrastruc- ture, a lead-free composition must resort to the metallurgy of a quaternary alloy (not doping el- ements); I have presented this scientific pred- ication in my professional development cours- es at various international events and numerous locales spanning the last 25 years. How Does Manufacturability Play a Role? Is manufacturability a critical element of the product's reliability?