Indium Blog

Water Wash Solder Pastes and Halogen-Free

The question often arises as to whether or not a water wash solder paste should be halogen-free.  Since halogen-free is fundimentally an environmental issue, the key concern is all the materials that remain on the PCB when it is in the finished product.  Since the flux residue of a water wash solder paste needs to be cleaned after processing, there should be no residue remaining on the board.

I have also heard comments such as: "I need a halogen-free water wash solder paste because I don't want to risk halogen presence on the board if I don't end up properly cleaning it."   The issue here is that improperly cleaning a water wash paste is actually an electrical reliability issue (regardless of whether or not it contains halogens).  That residue remaining has a good chance of promoting corrosion and dendritic growth.  Making a halogen-free decision based on a lack of confidence in your process doesn't make sense to me!