Homebrew PCBs

>I don't think it is a problem for tinning the board.

Paste with an acidic flux isn't a problem for tinning. Zinc Chloride 
can be washed off a board the same way Ferric Chloride can after 
etching. But for SMD work, where joints and components are involved, 
it's probably not the paste to use. However, there are plumber's pastes 
with non-acidic fluxes, at least so they claim. Here is the MSDS for a 
lead bearing plumber's paste with claimed non-acidic flux;

http://www.laco.com/pdfs/MSDS/SolderBrite_50-50_9_25_98_03_10_04.pdf

Here is one for a lead bearing paste with acidic flux;

http://www.palomar.edu/ehs/Facilities/Plum-Loy%2050-50.pdf

You can go to www.kester.com and view the MSDSs for real SMD solder 
pastes.