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Newbie denisb
Newbie
417 Views
Registered: ‎01-22-2019

Virtex-5 hermeticity

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We mount Virtex 5 FPGAs to PCBs.  The boards are then aqueously cleaned to remove any flux residue.  Does Xilinx recommend aqueous cleaning of the Virtex 5?  What cleaners do Xilinx recommend?  Does Xilinx recommend baking the assembled PCBs after cleaning to remove moisture?  What temperature and time does Xilinx recommend?  Does Xilinx have a method to seal the vent hole in the device cover to prevent liquids from wicking inside?  Does Xilinx have reliability data concerning processing chemistry seepage into the Virtex family of devices?

Thanks,

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Moderator
Moderator
354 Views
Registered: ‎05-02-2017

Re: Virtex-5 hermeticity

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hi @denisb

 

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

 

hope the above infroamtion clear's your query 

Regards
Chandra sekhar
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2 Replies
Moderator
Moderator
355 Views
Registered: ‎05-02-2017

Re: Virtex-5 hermeticity

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hi @denisb

 

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

 

hope the above infroamtion clear's your query 

Regards
Chandra sekhar
----------------------------------------------------------------------------------------------
Kindly note- Please mark the Answer as "Accept as solution" if solution provided is helpful.

Give Kudos to a post which you think is helpful and reply oriented.
----------------------------------------------------------------------------------------------
Newbie denisb
Newbie
341 Views
Registered: ‎01-22-2019

Re: Virtex-5 hermeticity

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Thanks.
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