AR# 34410: Why "vented" parts in Xilinx cannot be immersed in solvents and can only be cleaned with DI water.
Why "vented" parts in Xilinx cannot be immersed in solvents and can only be cleaned with DI water.
SomepackagesinXilinx have a note added that it is a "vented" part and cannot be immersed in solvents and can only be cleaned with DI wateronly. Whyshouldit be cleaned with DIwater only?
Xilinx flip-chip packages are not hermetically sealed and exposure to cleaning solvents and chemicals or excessive moisture during boards assembly could pose serious package reliability concerns. Small vents are kept by design between the heatspreader (lid) and the organic substrate to allow for outgassing and moisture evaporation of epoxies in the lid adhesive and underfill material. Solvents or other corrosive chemicals could seep through these vents and attack the organic materials and components inside the package, and hence, are strongly discouraged during board assembly of Xilinx flipchip BGA packages. It is highly recommended to use either a no-clean solder paste or a water soluble solder paste. If cleaning is required, then a water soluble solder paste should be used. Most major PCB assembly subcontractors today have successfully developed the no-clean process in which post assembly washing is not required. That would be an ideal process. If cleaning is required as part of the process, then it is recommended to use a water soluble paste and then wash with deionized water in a washer, such as a Westek Triton III at 140F - 145F. Cleaning solutions or solvents are not recommended as some cleaning solutions may contain chemicals that could attack the heatspreader adhesive, thermal compound, or the components inside the package. For more clarification, refer to the following application note: http://www.xilinx.com/support/documentation/application_notes/xapp426.pdf