Q1: Anyone has any ideas on how this post-SMT reflow solder joint could have changed to whitish joint? A1: Dunno. You need to tell us more. For instance: * What is the appearance of this white residue? [eg, glassy / coarse, milky colored / opaque, thin / thick film, hard / soft, color white, etc] * Where are these white residues located? [eg, pads only, solder mask only, every where, etc.] * What is the scope and extent of the problem? * What is your process, process materials, board fabrication, and process settings?
Q2: Why do some white residues pass ionic contamination tests and other white residues do not pass? A2: White residues are chemical compounds. Chemical compounds can be either ionic or nonionic. Ionic contamination testers only measure ionic compounds.
Q3: What can I tell my customer to make them feel comfortable about these white residues? A3: Tell them you plan to send the boards to a contract shop for cleaning and testing to assure that their boards absolutely immaculate.
Q4: What takes precedence to IPC-A-610C, 6.1 or 7.3? A4: Neither takes precidence. White residues are unacceptable, because they indicate a process that�s not well controlled.
reply »