Q1: Can anyone explain to me about the effect of their mixture. A1: What is their �mixture�?
Q2: What enhancement does my BGA will have when using a WS paste flux with regards to corrosion, 25 years life cycle of the solder joint. A2: Tough to say, which board has the lower level of harmful contaminants?
Q3: What's the benefit in using a WS paste flux on a BGA with No Clean solder joint process? A4: Assuming you solder NC / paste, reflow water washable BGA / wash, you get to turn all your NC solder connections a milky, white color, after washing. [And potentially freak every inspector down stream from washing.]
Q4: Why can't I use a No Clean Flux only for that BGA, which has a no clean process from the supplier? A4: Dunno, contract requirements?
Q5: Do I have to use a WS because it's Class 3 and is an Aerospace Standard? A5: It�s probably because your customer requires WS, not necessarily because it�s Class III or aerospace. There�s probably a NASA [er, somebody like that] requirement for water washable flux. [See with low stand-off devices, like some QFP and some BGA, washing OA improperly potentially is far more damaging than using NC. Which; if you plan to use a garden house, Dawn, and a scrub brush; to clean the board is what you will do.]
Q6: Are all aerospace electronics products using Water Soluble for both flux and paste? A6: No. Look here: http://www.bmpcoe.org/bestpractices/external/itt/itt_7.html
For better understanding flux classifications, look here: http://www.alphametals.com/products/fluxes/PDF/jstd004.pdf
S1: I do know that Motorola is using a No Clean Eutectic Solder for their BGA's. R1: Yes, but what market and customer requirements is Motorola using NC flux to solder their BGA?
S2: The reason is that I'm planning to apply a No Clean instead of Water Soluble just on the BGA pads for soldering to get rid of the flux residue issue that we can't remove from our BGA. And will just switch back to WS paste once we got the proper cleaning system. R2: Has your contract officer approved your plan to use multiple flux formulations on this board? This could be a very dangerous combination of materials.
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