Symposium Conference Proceedings

Cleaning Lead-Free No-Clean PCBA To Improve ICT Probe Contact Rate

Authors: Lee Kong Hui and Kangeyan Ramachandran
Company: Global Manufacturing Operations, Cisco Systems (Malaysia) Sdn. Bhd., and Assembly Science and Technology, Cisco Systems (Malaysia) Sdn. Bhd.
Date Published: 3/28/2017   Conference: Symposium

Abstract: Soldering flux materials such as liquid flux, paste flux, solder paste, solder cream, flux-coated and flux-cored solder wires and preforms are commonly use in electronic metallurgical interconnections for printed circuit board assembly (PCBA). Flux content is one of the major compositions in these material which helps to clean metal surfaces and reacts with the oxide layer during soldering, leaving a surface primed for good solder bond. While Flux is needed during soldering to enable good solder joint formation, flux residues left on site after soldering can be detrimental in preventing good probe contact during In-Circuit Test (ICT) or risk reacting with moisture in the presence of an applied voltage to cause electrochemical migration and electrical current leakage.

This presented paper is evaluating deep cleaning effect on Lead-Free No-Clean PCBA and its correlated product reliability to mitigate ball grid array rework and aging boards harden flux issue that had caused significant test points’ contact failures at ICT. Low profile components with a standoff height of less than 2mils had made it more challenging to clean a No-Clean PCBA as non-optimized cleaning process will induce the benign flux residues to become active again. Hence, evaluation samples were not only subject to complete normal production functional test, but had also went through Resistivity Of Solvent Extract (ROSE), Critical Cleanliness Control (C3), Ion Chromatography (IC) analysis and Enhanced Ongoing Reliability Test (eORT) to ensure end product reliability during field usage. Evaluation results is very promising as product reliability has been approximated to more than 10 years life expectancy. Although, there is no published literature reporting cleaning a No-Clean PCBA as a viable industry solution, the presented findings have shown the possibility of using deep cleaning process to clean No-Clean PCBA to improve ICT probe contact rate.

Key Words: 

Flux Residue, No-Clean, In-circuit Test (ICT), Test Point and Enhanced Ongoing Reliability Test (eORT)

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