Process characterization for a surface mount rework system

A method is presented by which thermal characterization of a surface-mount rework system was achieved. The method includes identification of process variables and their classification as operator, setup, or use variables. Using a thermocoupled board, a data logger recorded the temperatures of the lead of a PLCC-52 and two adjacent sites, 0.075 in and 0.150 in from the solder joint. The test method chosen used a constant PLCC-52 solder joint temperature and measured the time required to meet the temperature with variables changed, incrementally, one at a time. For this system it was found that the bottom heater temperature had little effect on solder joint time to temperature, and that the system was relatively sensitive to vertical heater position and insensitive to lateral heater position within the range tested. The testing exposed the inadequacy of depending on hand attachment of thermocouples to circuits to study their dynamic thermal behavior.<>