Optimizing the DElta T of Your Assembly's Thermal Profile by Choosing the COrrect Heat Transfer method

摘要

A large delta T causes dissimilar times above liquidus for the soldr joints on the board. However, it is known that the longer the solder is kept in a liquid state, the more intermetallic matter will be produced. The amount of intermetallic matter is correlated to teh reliability of the joint and thus extended times above liquidus are considered a quality issue. The industry thus concentraltes more and more on the need to eliminate large delta T's. This paper examines the different heat transsfer methods: IR, Convection and Condensation as to their efficiency and the impact f certain parameters sucha as color, texture, material and shape on their heating performance. The theoretical ocnsideration and relevatnt test data yield a decision tree which will enable the user to decide which reflow method is appropriate for the particular assembly with regard to minimizing its delta T. Particularly in the case of BGA solderng, minimizing the time above liquidus will be one of the keys to reliable solder joints.