Determine Critical Cleaning Process Parameters for QFNsAuthors: Umut Tosun, M.S. Chem. Eng., Naveen Ravindran, M.S. Chem. Eng., and Michael McCutchen, M.S. Chem.
Company: ZESTRON America
Date Published: 4/17/2013 Conference: Symposium
Since the leads of the QFN package do not extend out from the component body, but are located underneath the component body, cleaning the flux residues after the soldering process becomes a challenge. The low standoff associated with such components, typically 1 mil, and the large thermal pad at the center of the component body pose barriers to the complete removal of flux residues. Partially removed or untouched residues can lead to component failure resulting from electrochemical migration via dendritic growth as well as electrical leakage currents.
This study is designed in two phases and will determine the critical cleaning process parameters for complete cleanliness underneath leadless devices or QFNs. Two groups of paste types will be used; lead-free water soluble and lead-free noclean. The cleaning process will employ an aqueous alkaline cleaning agent and spray-in-air cleaning equipment.
The goal of each phase is as follows:
Phase 1: Determine the critical wash process parameters and cleaning equipment settings for QFN components.
Phase 2: Utilizing process parameters from Phase 1, verify cleaning results by using an industry standard test board.
Cleanliness will be assessed via visual inspection for Phase 1 and visual inspection and Ion Chromatography analysis for Phase 2.
QFN, low standoff, cleaning agent, chemistry
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