I am a PCB Designer and I have to put a note on the assembly drawing to tell the assembler how to clean the board. This is new to me. Here is a sample note. Can someone give me some feedback on it? "Use water washable, no clean solder paste for the assembly. Wash in DI water following reflow." Thanks.
Water will not remove no clean flux residues because they are not water soluble. Solder paste with no clean flux should only be used when the assemblies do not need to be cleaned. That said, you can buy special cleaning solvents specifically for removing no clean flux residues if you must clean the assemblies and are stuck using the no clean paste. The better way to go if you need a clean assembly is to use solder paste that has water soluble flux in it.
As pointed-out above, the downside of telling your supplier how to perform a process can create problems: * It sets the cost of the operation ... I did what you told me to do * Materials selected may be incompatible ... I did what you told me to do * It may have unintended consequences ... I did what you told me to do * It may not work ... I did what you told me to do * It may be in conflict with other operations ... I did what you told me to do ... and on and on. This is why the US Military moved away from all those MIL-specs.
As an alternative, tell your supplier what you want, not what you want them to do. Consider defining the end result that you'd like in-order for your product to perform properly in its end-use environment. Such a definition might read like one of these: * Ionic materials less than xx �gm/in^2 of NaCl measured according to yyyy * Bromide less than xx ugm/in^2, Chloride less than xx ugm/in^2, Sulfates less than xx ugm/in^2 measured according to yyyy * per Telcordia GR-78-CORE, Generic Requirements for the Physical Design and Manufacture of Telecommunications Products and Equipment, latest issue * Nice and shiney, no sticky or tacky residues, ionic materials less than xx �gm/in^2 of NaCl measured according to yyyy