Thesis /

ROMDOC-THESIS-2017-825

Optimizarea procesului de contactare cu aliaje fără plumb

Cucu, Traian C.
2011-06-29

Abstract: Abstract In today’s SMT production landscape the tin-lead materials are progressively replaced by lead free materials. There is still work being done in order to harmonize across the globe the newly born lead free standards and requirements but yet, it seems obvious that lead free it is here to stay. One new challenge that came with the introduction of lead free technology is the broader range of materials that have been adopted as tin/lead replacements. The adoption of regional standards for lead free, to mention only the European ones: Directive on the restriction of the use of certain hazardous substances in electrical and electronic equipment RoHS - 2002/95/EC, Waste Electrical and Electronic Equipment Directive WEEE - 2002/96/EC, CE - 1907/2006 concerning the Registration, Evaluation, Authorization and Restriction of Chemicals (REACH), have helped to funnel the regional options and basically push forward the SAC family of alloys, a family that have showed good and consistent performance on all SMT applications. In parallel with these actions there is the need for continuous miniaturization driven by the extra features continuously added to all electronics and the market trend towards miniaturization and broad features electronics. All of these have stirred the market to have higher and higher component density needs and as a result the component manufacturers have complied bringing smaller SMD parts. This trend put an extra burden on PCB manufacturers too, to work with higher density boards and consequently lower pitch chips and smaller components (0.4 mm pitch BGA and 0201 are technologies that have been widely implemented and there is already work in progress to for 0.3 mm pitch and 01005 SMD). PhD thesis “OPTIMISATION METHODS OF LEAD FREE SOLDERING PROCESS” presents experimental and theoretical methods for optimization of the SMT processes based on solder paste characteristics. The aim is to achieve a better control of the soldering process, especially for fine features printing and reflow, and aid the final user to pick the right material that will deliver robust soldering process. The robustness of the process was considered by measuring the solder paste volume variability together with the process parameters for the printing process and the process parameters for the reflow process. A two directions approach have been used, one was considering a pool of different lead free alloys – using tin/lead as benchmark – while the other was concentrating on powder size for the same alloy. For the printing process the printing parameters have been studied based on different powder size in use and the importance of smaller intervals for the powder size gauging have been experimentally proven. The results of the theoretical studies and experimental researches have showed the advantages of non standard powder size deployment into the present production environment and the capabilities of such powders for the future technological developments, namely the capability of fine feature printing with lower process variability, being able to deliver less outliers into the printing process and a narrower distribution for the print volumes, especially for smaller apertures. The last part of the paper lists the author conclusions and contributions, suggestions for future developments generated by the thesis conclusions and today’s process capabilities, in the author’s opinion, for the implementations of such materials.

Keyword(s): Tehnologie electronică -- Teză de doctorat ; Tehnologii de contactare prin retopire -- Lipire prin retopire -- Teză de doctorat ; circuite imprimate -- Teză de doctorat ; Lipire fără plumb -- Teză de doctorat
OPAC: See record in BC-UPB Web OPAC
Full Text: see files

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