I have never used no-clean solder but I have used flux which left a highly conductive residue (unfortunately, I do not remember which kind it was - it may even have been plumber's flux because this circuit involved several large copper bus bars which had to be soldered together and to a PCB) The residue was conductive enough to cause the PCB to catch fire after several minutes of 48V DC bias being applied. I had previously heard of leakage current caused by flux but this must have been 100s of mA of "leakage" Of course, once extra flux is introduced it does not matter what kind of solder you use - if the extra flux is not "no-clean" then it would, of course, have to be cleaned anyway. Sean On Sun, Jul 31, 2011 at 3:24 PM, wrote: > Have any of you ever run into "conductivity problems" due to residue when= using "no-clean" solder. (Or do you find success without any cleaning?) > > The reason that I ask the question is related to surface mount resistors = with Ohm values greater than 1MegOhm (I.e. =A04.7M -- 10M have sometimes se= en resistances reduced significantly after solder process by our contract m= fgs. They say that they were using no-clean, lead-free -- but I can't be su= re). > > I wondered if this type of solder is recommended to post-clean in these s= ituations. > > I also suspect a liquid flux was used and may be the reason. But am not s= ure. > > Any pointers or advice would be appreciated. > > Sent on the Sprint=AE Now Network from my BlackBerry=AE > > -----Original Message----- > From: PICdude > Sender: piclist-bounces@mit.edu > Date: Sun, 31 Jul 2011 08:59:47 > To: > Reply-To: "Microcontroller discussion list - Public." > Subject: Re: [EE] Solder > > Did a bunch of research on this a few years ago, and here's a quick summa= ry... > > There are 3 general types of solder flux: Rosin (RA or RMA), no-clean, > and water-soluble. > > Rosin is the common hobbyist type stuff. =A0No matter what anyone says > they do or don't do, rosin flux should be cleaned and I've personally > verified it's a bit conductive and causes issues. =A0A small > flux-remover pen works fine. > > Water-soluble flux needs to be cleaned and requires de-ionized water. > Usually used by large-scale operations. > > No-clean is awesome stuff, and really the only option for BGA's etc > where you can't get under the chip to clean. =A0There are flux removers > for this, but really just for aesthetics. > > There are several types of solder compositions, apart from leaded and > lead-free. =A0They have different melting points with 63/37 having the > lowest melting point of any leaded solder. =A0But 63/37 or 60/40 will > dissolve gold/silver, so you may want to try some different > composition if you have a need for that. > > Other consideration is amount of flux in the core. =A0Generally more is > merrier, but smaller diameters solders can't hold as much. > > On the subject of diameters, I like thinner as it's easier to work > with, especially for surface-mount stuff. =A0I use 0.020" for 99% of > stuff I do, which goes up to soldering TO-220's and soldeirng 18-gauge > wires. =A0I do keep some 0.031" solder on hand for soldering thicker > wires, but haven't needed that in the past couple years. > > I've tried a few brands/types and really like Kester 245, no-clean, > 0.020", 2.2% flux. =A0Digikey is VERY expensive for solder, so I get it > from all-spec... http://www.all-spec.com/products/KW24510.html > > Cheers, > -Neil. > > > > Quoting Josh Koffman : > >> Hi all. >> >> I'm in a position I haven't been in for quite a while...I need to buy >> solder in wire form. It's been about 10 years since I've had to buy >> solder wire, and I'm not sure what to get. The roll I'm almost through >> is a roll of Multicore 63/37, that says "362 Flux" on it. It's 0.81mm >> (0.032") thick. >> >> I'll be using this for general assembly and rework, non ROHS compliant. >> >> Any recommendations? Digikey seems to have a number of options, but >> only two options in a half pound spool. Both are from MG, one is >> labelled Rosin Activated, and one No Clean. Here they are: >> >> http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=3D473-1= 133-ND >> and >> http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=3D473-1= 125-ND >> >> Any thoughts? >> >> Thanks! >> >> Josh >> -- >> A common mistake that people make when trying to design something >> completely foolproof is to underestimate the ingenuity of complete >> fools. >> =A0 =A0 =A0 =A0 -Douglas Adams >> >> -- >> http://www.piclist.com PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >> > > > > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .