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Natrium Chloride (NaCl)

George Verboven

#12468

Natrium Chloride (NaCl) | 1 March, 1999

It seems to be that we have to much NaCl left on our assambled PCB's. The flux we use is from cobar. They say it can not be from the flux... So what can be the reason, what kind of problem may occer when there is to much NaCl.

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Justin Medernach

#12469

Re: Natrium Chloride (NaCl) | 1 March, 1999

| It seems to be that we have to much NaCl left on our assambled PCB's. | The flux we use is from cobar. They say it can not be from the flux... So what can be the reason, what kind of problem may occer when there is to much NaCl. | George, Are you sure it's Natrium Chloride and not Sodium Chloride on your PCBs. Don't take your flux suppliers word for it. Run some tests. Try to assemble a dummy product. Hand stuff some passive components in an old board if we're addressing your wave soldering process or place some passives on an old board if we're looking at a surface mount process. Take readings of the PCBs before and after population / reflow. Get a sample of some other type of flux system and run a comparison. This should give you an idea of where the culprit lies. If you're running a "clean" process, look into your cleaning effectivity.

Regards, Justin Medernach

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#12470

Re: Sodium Chloride (NaCl) | 1 March, 1999

| It seems to be that we have to much NaCl left on our assambled PCB's. | The flux we use is from cobar. They say it can not be from the flux... So what can be the reason, what kind of problem may occer when there is to much NaCl. | George: When someone says they have too much NaCl (sodium chloride, as Justin says) residues on their board, they�re really telling you is that you have bulk salts of chlorine, sulfur, bromine, and other stuff on your board. And that when taken together, they are equivalent to however much NaCl that they�re complaining about. And the spec they�re probably using is one either: ANSI-J-001B, MIL-P-28809, or MIL-STD-2000. It doesn�t matter which, because they each say pretty much the same thing: you must have LT 10.07 �gm/sq inch NaCl equivalent on your assembly. Alto the Bellcore TR-NWT-000078 spec is 6.5 ug/sq inch. And there's a ton of other specs. So, who knows. They probably used a bulk ionic contamination measurement tool, like an Ionograph or Omegameter, to measure how much salt went into solution when they slushed your board around in a tank of DI water and IPA.

These salts come from any or all of the following places:

1 Things your PCB fabricator left on the board, including the bromine compounds used to make the board meet UL flammability requirements, fluxes used in solder leveling, and plating and etching chemicals 2 Things your component suppliers left on the 100 or so parts you attached to the board 3 Things you put and left on the assembly during storage, handling, SMT and PTH assembly, and "cleaning." Depending on the flux you used, it�s possible that Cobar is correct in saying their flux isn't the culprit, but I wouldn�t bet on it.

Bottom line: Regardless of where they can from, you got caught shipping boards with too much contamination from those sources.

There are some thoughtful comments on this topic in the archives.

Good luck

Dave F

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