Life expectancy of Aqueous Flux going LowZ

AI Thread Summary
The discussion centers on the life expectancy of water-soluble flux in low-Z applications, particularly regarding conductive material migration and its impact on low impedance bridges under varying humidity and temperature conditions. Participants highlight the significance of dendritic migration, noting that it can occur within a few hundred hours when a voltage difference exists between conductors. The conversation emphasizes the need for specific data on the failure rates of components with residual flux, especially under large BGAs where complete flux removal is challenging. Suggestions for further research include looking into industry studies and resources related to BGA reliability and PCB cleaning. The thread ultimately seeks to gather more empirical data on the longevity and reliability of aqueous flux in these contexts.
edwardtre
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Looking for any life expectancy data for water soluble flux going low Z. How long it takes for conductive material to migrate and cause low impedance bridges at any humidity or temperature.
 
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edwardtre said:
Looking for any life expectancy data for water soluble flux going low Z. How long it takes for conductive material to migrate and cause low impedance bridges at any humidity or temperature.

Welcome to the PF.

Are you asking specifically just about the flux aspect, or about dendritic migration of copper in general?

I did a Google search on dendritic migration pc board, and got some good hits:

https://www.google.com/search?sourc..._l=hp...0i22i30l5.0.0.1.13565...0.YrpWiZego6U

Once you have a voltage difference between conductors of a couple of volts or so, you can get dendritic migration to happen in a few hundred hours, depending on temperature and PC board cleanliness...
 
Thanks for the response. Specifically the conductive material that is part of the flux. Need to consider expected failure rate of a component with water soluble flux (OA) residue left under a BGA (BGA too large to allow for complete removal of flux (45mm part). Though I guess it could be a combination of the flux and exposed copper...
 
edwardtre said:
Thanks for the response. Specifically the conductive material that is part of the flux. Need to consider expected failure rate of a component with water soluble flux (OA) residue left under a BGA (BGA too large to allow for complete removal of flux (45mm part). Though I guess it could be a combination of the flux and exposed copper...

It seems like there should be some good PCBA industry studies on this. I Googled bga reliability pcb cleaning, and got some good hits. Maybe have a look at the hit list to see if you see any new information:

https://www.google.com/search?sourc...cleaning&gs_l=hp...0.0.0.9110...0.epKIo8N_xH8

:smile:
 

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