The principle of PCBA board cleaning is essential for both surface mount technology (SMT) and through-hole technology (THT) assembly processes. Cleaning helps remove accumulated surface contaminants from the product during various manufacturing stages, thereby reducing the risk of surface contamination and enhancing product reliability.
When cleaning PCBA, it is crucial to ensure compatibility between the cleaning agent and the residues generated during the soldering process. This involves addressing the compatibility between flux residues and cleaning agents to facilitate easy removal of residues and achieve the desired cleanliness level. An effective cleaning process requires optimal matching of soldering temperature profiles, cleaning process parameters, solder pastes, and flux parameters.
For wave soldering, there may be residues of flux or solder mask that can cause visible dark stains, which may feel tacky when touched by hand and cannot be easily removed by conventional cleaning agents. Improper wave soldering temperature profiles, such as excessive preheating temperatures, can cause flux to glassify, rendering it ineffective and leaving unacceptable contaminants on the board. The removal of flux residues typically involves using alkaline cleaning agents with a high pH value, which contain metal ions that can promote chemical reactions to form lead salts. Some lead salts, such as Pb(NO)3, are soluble in water, while others are insoluble, leading to the formation of white precipitates on the surface of PCBA.
With technological advancements and changes in regulations, cleaning products will face increasing challenges, such as compliance with standards like CEE648 and REACH, which dictate the permissible use of certain chemical products in cleaning agents. In recent years, there has been a shift towards new cleaning agent technologies and equipment, such as chlorine-free solvents and water-based cleaning agents.
