Have any of you ever run into "conductivity problems" due to residue when u= sing "no-clean" solder. (Or do you find success without any cleaning?) The reason that I ask the question is related to surface mount resistors wi= th Ohm values greater than 1MegOhm (I.e. 4.7M -- 10M have sometimes seen r= esistances reduced significantly after solder process by our contract mfgs.= They say that they were using no-clean, lead-free -- but I can't be sure).= =20 I wondered if this type of solder is recommended to post-clean in these sit= uations.=20 I also suspect a liquid flux was used and may be the reason. But am not sur= e.=20 Any pointers or advice would be appreciated.=20 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=20 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 summary= .... There are 3 general types of solder flux: Rosin (RA or RMA), no-clean, =20 and water-soluble. Rosin is the common hobbyist type stuff. No matter what anyone says =20 they do or don't do, rosin flux should be cleaned and I've personally =20 verified it's a bit conductive and causes issues. A small =20 flux-remover pen works fine. Water-soluble flux needs to be cleaned and requires de-ionized water. =20 Usually used by large-scale operations. No-clean is awesome stuff, and really the only option for BGA's etc =20 where you can't get under the chip to clean. There are flux removers =20 for this, but really just for aesthetics. There are several types of solder compositions, apart from leaded and =20 lead-free. They have different melting points with 63/37 having the =20 lowest melting point of any leaded solder. But 63/37 or 60/40 will =20 dissolve gold/silver, so you may want to try some different =20 composition if you have a need for that. Other consideration is amount of flux in the core. Generally more is =20 merrier, but smaller diameters solders can't hold as much. On the subject of diameters, I like thinner as it's easier to work =20 with, especially for surface-mount stuff. I use 0.020" for 99% of =20 stuff I do, which goes up to soldering TO-220's and soldeirng 18-gauge =20 wires. I do keep some 0.031" solder on hand for soldering thicker =20 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, =20 0.020", 2.2% flux. Digikey is VERY expensive for solder, so I get it =20 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=3D473-11= 33-ND > and > http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=3D473-11= 25-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 > --=20 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 .