The cleanliness of assembly components has become a significant concern in assembly operations. While the residues after assembly may not seem critical after the application of cleaning agents, they can cause failure in electrochemical analysis if the cleaning process is omitted.
For instance, like the growth of branches, issues such as electrolytic corrosion and leakage current under humid conditions can arise. Many bare boards may have passed existing cleanliness testing standards based on resistivity, yet OEM production facilities still experience high failure rates. These failures can often be traced back to liquid residues after the thermal air solder leveling process during non-ionic water dissolution and processing. Therefore, effective cleaning of residual flux and other contaminants is necessary.
Today, the understanding of bare board residues and their impact on electronic assembly is well-established, and there are better tools for measuring bare board cleanliness. However, OEM manufacturers may still be required to clean. When OEMs opt for no-clean assembly processes, they do not eliminate the need for cleaning but rather transfer the cleaning requirement to upstream board and component manufacturers, which may not always be understood by OEMs, selected manufacturers, or even customers. OEMs may not understand how to specify or measure cleanliness in procurement contracts. Thus, maintaining high cleanliness in cleaning residues during OEM assembly processes is safe and feasible.
Adopting a cleaning process in assembly operations has additional benefits beyond removing residual flux and other contaminants and maintaining cleanliness. For example, it allows for the removal of tin balls and facilitates the use of water-soluble masking agents, thereby altering the surface energy efficiency of applied coatings on components. This is particularly important in industries with high reliability and stringent requirements such as medical, safety, and military fields. Therefore, cleaning residual flux and other contaminants is absolutely necessary.
