Impact Of FPC Fabrication Process On SMD ReliabilityAuthors: Susie Johansson, John Dzarnoski, Yangjun Xing
Company: Starkey Hearing Technologies
Date Published: 10/13/2013 Conference: SMTA International
The flux cleaning process can require harsh cleaning chemistries when high temperature solder is used and when die have a very low standoff from the circuit board surface. Some typical vapor degreasing solvents have been found to attack flexible circuit boards at layer interfaces and reduce circuit board reliability. These solvents remain trapped in the circuit layers and can result in blistering and delamination of the circuit boards during subsequent assembly steps. Eliminating or reducing the occurrence of delamination on flexible circuit boards leads to an overall more robust circuit.
Certain board suppliers manufacture more robust boards that do not delaminate, but fabrication processes and material selection can be proprietary and some suppliers are unwilling to alter their processes. Consequently, an alternative method to prevent delamination that does not require specific assembly or materials information needed to be established. This paper described a process developed to circumvent or eliminate delamination caused by chemical solvent absorption that uses a post-assembly laser excising fabrication process.
Delamination, flexible printed circuits, FPC, vapor degreasing, laser excising, underfill
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