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March 2014 • SMT Magazine 89 emmanuelle guéné is electronics applications manager with InvenTec Performance chemicals in bry sur Marne, france. Steven Teh is asia applications manager with invenTeC in Selangor, Malaysia. feaTure rELIaBILITY aSSESSmENT OF NO-cLEaN aND WaTEr-SOLUBLE SOLDEr PaSTES, ParT 1 contin ues conclusion The purpose of the paper was to highlight the reliability differences between water-soluble and no-clean solder pastes to guide users in their choice. To achieve this goal, six lead-free pastes were extensively studied, three being water-sol- uble and three being no-clean. The first part of the study focused on printing performance. The pastes were characterized using standardized tests and internally developed tests: dynamic viscosity, tackiness, slump and solderballing. The influence of accelerated storage at elevated temperature, the influence of time and condi- tions between printing and reflow and the in- fluence of continuous shear according to time were shown. The printing performances were also eval- uated in a printer. Although the number of pastes studied was restricted, the water-solu- ble pastes generally yielded results below the no-clean pastes with sensitivity to tempera- ture and humidity, a tendency to slump dur- ing preheat and a narrower printing window. Water-soluble solder pastes must be stored, handled and used with more caution before reflow. In the second part of the paper, the reflow properties will be compared: wettability, reflow process window, anti-graping properties. Final- ly the residue cleanability with water, then with water and detergents will be examined. The cleanliness will be assessed using visual inspec- tion, ionic contamination and surface insula- tion resistance tests. SmT references 1. EFSOT Project. CliCk To View Video Interview Tim Jensen explains the effect of adding trace quan- tities of manganese to low- silver SaC alloys to provide the optimal balance of drop-test, thermal cycling, cost, and reliability, which characterizes Indium corpo- ration's SaCM solder paste. Sacm Explained by Real Time with... productronica

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