SMTA International Conference Proceedings


Authors: Dr. Xiaobai Wang and Christine Poon
Company: Kester Components Pte Ltd
Date Published: 9/25/2005   Conference: SMTA International

Abstract: Lead-free, no-clean fluxes have been challenged to achieve the similar soldering performance of leaded noclean fluxes in wave-soldering, yet, it has the additional requirement to overcome the intrinsic higher surface tension of lead-free SnAgCu or SnCu alloys, while optimizing the cosmetic appearance and residue level. The requisite for the no-clean flux in the lead-free wave soldering operation is to match the soldering performance of currently used no-clean flux in leaded wave soldering operation.

The conventional approach and common understanding in lead-free, no-clean flux selection is higher activity, higher solid content and better heat stability. However, there is no exact science in flux selection and thus, it is matter of trial and error. This paper attempts to put the flux selection in perspective in terms of various fluxes’ attributes and properties necessary for lead-free operations.

The fluxes were wavesolderedon test boards and graded on various soldering performance of icicles, bridging, solder balling, barrel fill on both leaded and lead-free wave soldering. The soldering performance will be used to address the type of no-clean flux that can qualify for lead-free operation and guide users in flux selection.

Key Words: lead-free, wave soldering, chemical flux

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