Impact of Multiple Thermal Cycles on the Cleaning Process - Case Study
Multiple thermal cycles may be required for a variety of reasons in the production of PCBs. If the board includes mixed technology (SMT and through-hole), it will be processed through both a reflow oven and wave solder system. Also, depending on the complexity of the PCB design – inclusion of stacked components or double-sided circuitry, for example multiple reflows may be required.
As greater functionality from smaller components is sought, use of μBGAs (micro ball grid arrays) and CSP (chip scale packaging) is increasing. Due to package geometry, standoff height between the component and board decreases, thereby reducing component reliability resulting from mechanical shock. Reliability can be increased with the use of underfill. Underfill encapsulates the bottom side of the silicon chip, improving the package’s mechanical and thermal properties. However, underfills require a baking process for curing, adding a thermal cycle to the PCB manufacturing process.
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