Karen, OK thanks. One more general chemistry question: If you have weak acids in solution, and you pass that solution through a DI column, will the weak acid be removed from solution as quickly as a strong acid? Thanks, Bob Kondner -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Karen Tellefsen Sent: Monday, April 23, 2012 11:32 AM To: [log in to unmask] Subject: Re: [TN] No-Clean Flux The acids in no clean fluxes are usually sparingly soluble in water, particularly adipic. The pH paper is a qualitative test. Spraying phenolphthalein on .the board will contaminate it and the board will need to be cleaned even if excess acid is not found. If you want a quantitative test, use IC. There are ways to extract small areas if you want to look for localized contamination., Karen Tellefsen - Electrical Testing [log in to unmask] 908-791-3069 Re: [TN] No-Clean Flux Robert Kondner to: TechNet 04/23/2012 11:10 AM Sent by: TechNet <[log in to unmask]> Please respond to rkondner Karen, Thanks. Are these acids soluble in water? Can a collection of rinse water be used to determine the "Quality" of the heating process? Kind of like a simplified ionic contamination test? Maybe a rinse with a basic phenolphthalein solution (pink) and if it turns clear "You Have Acid". Is there any way to calculate if such a test would have sufficient accuracy in the range of interest? Bob K. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Karen Tellefsen Sent: Monday, April 23, 2012 10:52 AM To: [log in to unmask] Subject: Re: [TN] No-Clean Flux pH paper slightly dampened with DI water. I've used it and it works. Some of the organic acid activators will be left behind after soldering, but most of them should have sublimed during processing. Additionally, some organic acids are worse than others; malic is worse than succinic is worse than adipic. Karen Tellefsen - Electrical Testing [log in to unmask] 908-791-3069 Re: [TN] No-Clean Flux Robert Kondner to: TechNet 04/23/2012 10:43 AM Sent by: TechNet <[log in to unmask]> Please respond to rkondner Hi, Are there any spray on chemical indicator that can be used to detect for activated flux? Something like a litmus or phenolphthalein solution? Bob K. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Ellis Sent: Monday, April 23, 2012 10:28 AM To: [log in to unmask] Subject: Re: [TN] No-Clean Flux I agree 100% with Doug. The important point is to ensure that the carboxylic acids are sublimed. This starts to happen at temperatures around 180°C but it takes time as well as temperature. It is therefore essential to limit the quantity to the minimum necessary to do the job and confine to the joint area. What is positive is that soldering irons operate at a higher temperature than wave or reflow, so that residues that spread outside the joint area will probably be heated sufficiently to ensure sufficient sublimation. Another important point is to ensure that all the alcohol has evaporated before starting the retouch, so that the latent heat of evaporation would otherwise cool down the flux and allow it to spread before sublimation takes place. This requires the operator to wait a few minutes between dosing the flux and picking up the soldering iron. It is common to have a row of fluxed assemblies and, as one is added at one end, a circuit is picked up at the other end for soldering. I don't know whether it is still available, but a flux with a crimson dye showed where unheated flux was applied and was quite common in days of yore. The dye sublimated with the activators. Brian On 23/04/2012 16:42, Woolley, Mark D. (Mark) wrote: > I have an issue with one of the assembly houses we use. They are > using a No-clean flux that contains adipit and succinic acids (per the > MSDS) in an alcohol base. > > Is it allowed to leave flux on the PWB that HAS NOT BEEN DEACTIVATED > BY HIGH TEMPERATURES OF SOLDERING? > > I am not talking about the flux used in the solder paste or wave > soldered flus. I am talking about the flux used at rework and > touch-up of the PWB. > > > > I havce seen papers detailing corrosion on PWBs using "no-clean" > fluxes and I have seen it on some of our products. This usually > pccurs near the periphery of the PWB where the wave solder flux is > protected by the pallet used to pass the PWB through the solder wave. > > > > Any opinions and references will be appreciated. I can give the > manufacturer and flux type to individuals, but don't want to put it in > a global email. > > > > Thanks > > mark > > > > > > mark > > Mark Woolley |PTRL Laboratory | Avaya | 1300 West 120th Ave | > Westminster, CO 80234 USA | > > Voice (Lab): (303) 538-2166 | email: [log in to unmask] | > > > > > ______________________________________________________________________ > This email has been scanned by the Symantec Email Security.cloud service. > For more information please contact helpdesk at x2960 or > [log in to unmask] > ______________________________________________________________________ > ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. 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