³Ô¹Ïtv / ENGINEERING EXPLANATIONIPC-4554 / release checkpoints1Document basisSpecify the agreed IPC-4554 edition and amendment in the purchase requirement.2Measured quantityKeep total tin, free tin and intermetallic descriptions distinct.3Comparable inputsCalculate a ratio only after confirming compatible measurement definitions.4HistoryRetain packaging, storage and exposure information relevant to assembly acceptance.Conceptual illustration. Not to scale; examples are not process settings or acceptance limits.