7670	2012-08-11 16:38:55	Reginald Beardsle...	Flux residue deemed harmful
Message	Date	From	Subject
FWIW While living in Houston, I had a couple of cheap VCRs die after about 1 year. In disassembling one to scavenge parts I observed a tremendous amount of flux residue. This got me to wondering whether the hygroscopic nature of rosin fluxes might be a factor. In the last few weeks I have "repaired" an IR remote, a WWVB sync clock and an AM/FM/CD/cassette by the simple act of removing all visible traces of rosin flux w/ a spray of isopropyl alcohol, an old tooth brush and a paper towel to blot up the liquid. All of the devices were completely nonfunctional. The CD player reported "No Disc". Initially intermittently for CD-Rs but eventually consistently for replicated discs also. I've always cleaned my boards this way when I build something. If you're not doing it, you might want to start making a habit of it especially if you're building things w/ microcontrollers and other digital logic. While 3 for 3 is not a strong statistic, I'm beginning to suspect that this is the primary cause of consumer electronics failures followed by electrolytics. Have Fun! Reg
7671	2012-08-11 17:31:56	Ivan Makarov	Re: Flux residue deemed harmful
I found by experience water soluble flux is hygroscopic and must be cleaned. It develops conductance with time. With rosin flux I did not have any problems but I clean it too for aesthetic reasons. Regards, Ivan
7672	2012-08-11 17:43:20	Dean Blake	Re: Flux residue deemed harmful
Good point! I'm a builder and I always use a flux remover after I'm done with my circuit or kit etc... but failures as you mentioned.. could be K4DSB Dean To: emrfd@yahoogroups.com From: pulaskite@yahoo.com Date: Sat, 11 Aug 2012 09:37:46 -0700 Subject: [emrfd] Flux residue deemed harmful FWIW While living in Houston, I had a couple of cheap VCRs die after about 1 year. In disassembling one to scavenge parts I observed a tremendous amount of flux residue. This got me to wondering whether the hygroscopic nature of rosin fluxes might be a factor. In the last few weeks I have "repaired" an IR remote, a WWVB sync clock and an AM/FM/CD/cassette by the simple act of removing all visible traces of rosin flux w/ a spray of isopropyl alcohol, an old tooth brush and a paper towel to blot up the liquid. All of the devices were completely nonfunctional. The CD player reported "No Disc". Initially intermittently for CD-Rs but eventually consistently for replicated discs also. I've always cleaned my boards this way when I build something. If you're not doing it, you might want to start making a habit of it especially if you're building things w/ microcontrollers and other digital logic. While 3 for 3 is not a strong statistic, I'm beginning to suspect that this is the primary cause of consumer electronics failures followed by electrolytics. Have Fun! Reg [Non-text portions of this message have been removed]
7673	2012-08-11 23:34:43	Mark	Re: Flux residue deemed harmful
Hi, I suspect that what you are really accomplishing is the removal of tin whiskers which are appearing now in some lead-free solder formulations. 73, Mark/n7eku
7674	2012-08-13 12:37:23	Gary, WB9JPS	Re: Flux residue deemed harmful
IPC standards absolutely require flux removal after assembly. This is for reliability. Otherwise, long-term corrosion will almost always result. You will find no counter-arguments among manufacturing engineers
7675	2012-08-13 20:15:48	Reginald Beardsle...	Re: Flux residue deemed harmful
Tin whiskers seem a pretty remote likelihood based on this: http://nepp.nasa.gov/whisker/background/index.htm It's primarily associated w/ tin electroplating. My observation is that cheap consumer devices are the most prone to early failure. With the exception of CD-ROM drives, I've not observed either premature failure or flux residue on computers. Personal experience has been a period of erratic operation followed by failure. That and the restoration of operation by cleaning are consistent w/ the flux residue affecting the noise margin of digital logic. The remote and the clock are both 3 V. Don't know about the CD player. The IR remote had the most flux and failed in ~6 months. The CD player had a single blob of flux on the controller board at one corner of the logic chip. It functioned w/o problems for 7-8 years. The clock was intermediate. Still 3 samples is such a small data set it's merely anecdotal. I plan to construct a spray setup that will allow cleaning devices w/ minimal disassembly and experiment. Repairing most consumer electronics has become non-economic. However, if a significant fraction of the failures can be repaired by removing the case and hosing the device down w/ alcohol that might change. Have Fun! Reg
7676	2012-08-14 10:31:41	Mark	Re: Flux residue deemed harmful
Well, That was not a very good article to discount the problem of tin whiskers in lead free solder; it was a study and recommendation from nasa parts procurement of tin-electroplating of electronic components and part housings. The problem of tin whiskers in lead free solder is a known problem so much so that medical, space, and weapons electronics are still allowed to use lead containing solder. Actually in the paper they are recommending lead containing solder dipping of tin plated parts to solve the problem. I imagine in consumer goods it mostly comes with the earlier formulations of lead-free solder. Hopefully by now they have better lead free solder. Also hopefully better for re-flow work as at work we have had too many ball solder chips with poor soldering in computers and other equipment -- one more problem in addition to cheapo electrolytic capacitors! If it was a flux corrosi
7677	2012-08-14 10:38:32	Matt Palmer	Re: Flux residue deemed harmful
Most parts self mitigate on tin whiskers based on spacing. You need extremely fine pitch parts and high density BGAs to get into that problem. Matt W8ESE
7678	2012-08-14 21:21:49	Reginald Beardsle...	Re: Flux residue deemed harmful
I thought it significant that all the cases cited for all metals were electroplated finishes. For example, hot dip galvanizing doesn't exhibit whisker growth but tin electroplate does. It would be interesting to know if reflowed tin plating exhibits whisker growth. I strongly suspect zinc whiskers are the reason for the high failure rate I've experienced w/ optical drives. There was no evidence of corrosion, so that's not a factor in my examples. I'm not sure that conductivity is the issue. It could be a change in dielectric constant causing increased capacitive loading. I'm trying to figure out how to run some tests w/o introducing additional variables. Current candidate is parallel wires on a microscope slide but I'm still puzzling over how to hold them in place securely. I don't consider lead particularly hazardous except when it's molten. I wash my hands before I eat or handle food. So I'm not adopting lead free solder ever. Have Fun! Reg
7679	2012-08-15 04:47:52	Russell Shaw	Re: Flux residue deemed harmful

7680	2012-08-15 05:40:14	Paul Anderson	Re: Flux residue deemed harmful
Tin whiskers up to a centimeter in length have been observed: http://nepp.nasa.gov/whisker/background/index.htm They grow pretty long. -----
7681	2012-08-15 07:32:05	Dave	Re: Flux residue deemed harmful

7682	2012-08-15 08:50:35	William Carver	Re: Flux residue deemed harmful
Dave, I've "known" about tin whiskers for a long time but never seen an explanation of how they form. Thanks for the explanation. W7AAZ