Since my bottle of Windex doesn’t list any ingredients, you would need to contact the manufacturer for details.

Depends on the solution. Some window cleaners are primarily alcohols; others contain a significant amount of weak organic acids. The alcohols can leave films, which won’t look pretty, but are rarely a conductivity issue. The weak organics are another story and will depend on the type and amount.

The bigger concern is lack of control. The manufacturer of the window cleaner may tweak their formulation and increase or decrease WOA content without informing you. It will have no influence on the ‘functionality’ of windows, but it could have a huge impact on your boards. In summation, don’t do it.

I would not recommend a window cleaner to remove flux residues. Window cleaners have different chemicals in them that could be dangerous to the functionality of the product.

Some of the cleaners have chlorine in them to make them cut through grease, or ammonia which when they dry will leave residues on the board surface which will be impacted by the moisture in the environment during the operational cycle of the product. These residues could and will impact the insulation resistance properties of the laminate material which will lead to signal integrity problems or worst case short on the surfaces of the boards.

Cleaners used to clean off fluxes must be evaluated to determine that they can in fact remove the fluxes and the materials the fluxes are made of and leave no residual residues which could be harmful to the functioning life of the product. There are test which can be conducted to determine board cleanliness and those test should be conducted when evaluating cleaning solvent selection.

I would not recommend using window cleaner, if you subject the PCBAs to even the basic cleanliness tests (ionic contamination, SIR, etc.) you will most likely find that, while it appears you removed the flux residue, there's a lot of "bad stuff" left on your board.

From your question, I assume you are a fan of survivor. You know the show where people are parachuted onto some tropical island and given “survival” task, like an emergency appendectomy with a conch shell.

But seriously, I suspect you are working with water soluble flux. These materials are generally cleanable with water alone, as long as you stay away from lead free materials, hence your apparent success with flux removal. Your question about ionics is most likely yes. Window cleaners use very common place materials (read low cost), and one can reasonably assume they will be ionic. Another concern is water “rinse-ability”. My experience with window cleaners is that they leave a film that will eventually either wear off or evaporate. This is generally not preferred at electronics assembly operations.

Obviously there is no data on effectiveness, compatibility of such materials and since generating such data is the responsibility of the cleaning agent supplier (in many cases), and you are not likely to get much help on that front from S.C. Johnson or their local agent, Walmart.

The real question you need to consider is this: are your savings in cleaning chemistry worth the price you will pay when one of your customers has a field failure and comes back to you as part of their investigation. One suspects that price may well be lost business in the future.