SMTA International Conference Proceedings


ISSUES AND CONCERNS IN CLEANING UNDER LOW PROFILE COMPONENTS

Authors: Rich Brooks, Mike Bixenman, D.B.A.
Company: Kyzen Corporation
Date Published: 10/24/2010   Conference: SMTA International


Abstract: The new technologies being implemented in the surface mount process today are increasing the challenges in the flux residue cleaning process. Some of these technology drivers are: -Low profile or flush mounted components (QFN style) -Miniaturization of the components & board size -Pb-free soldering flux residues (higher temperatures) -Halogen-free solder flux residues

The complete cleaning and removal of flux / soil residues under low profile components are becoming more critical, especially as the conductor spacing’s are decreasing and the power is increasing. If the residues are not completely removed, then the reliability of the circuit can be greatly affected. It is the combination of these technologies that make the cleaning process extremely difficult. Therefore, the cleaning process must be carefully examined and optimized to obtain maximum performance for removing the flux residues. The total cleaning process can be broken down into two subsets: the static cleaning rate and the dynamic cleaning rate.

Total Process Cleaning Rate = Static Cleaning Rate + Dynamic Cleaning Rate1

The Static Cleaning rate, in simple terms, is the cleaning agent’s ability to dissolve the reflowed flux residue. The Dynamic Cleaning rate involves the kinetic forces to remove the residue. This includes the Thermal energy and Impingement energy required to remove the flux residue. This paper will review cleaning problems brought about with the implementation of the latest technologies and explain how the cleaning process can be optimized to guarantee the reliability of the assemblies.



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