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#31 |
R.I.P
Join Date: Feb 2001
Location: USA
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I have been having failures of copperweld leads, both on film caps and resistors (solder joints look fine, no connection when measured with ohm meter).
jneutron, do you have any idea of a reasonable service life to expect for these kind of parts? What type of replacement schedule should I work out for these things?
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Candidates for the Darwin Award should not read this author. |
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#32 |
diyAudio Member
Join Date: May 2003
Location: quebec
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I never heard about the problem with gold , how do you solder gold plated connectors ?
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#33 | |||||
diyAudio Member
Join Date: Jan 2004
Location: In fear
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Quote:
I have developed production procedures in a mil environment, for every soldering process known to man (with the exception of fluxless submerged ultrasonic soldering), and the solder materials I have personally used is basically the indalloy catalog, from 60C melts to 395C. The biggest hurdle I've had to face in all that time, is to develop the visual workmanship criteria AND teach the reliability people and the inspectors what it is they are looking at. Because, most of the alloys I've used CANNOT form a shiny surface finish when it solidifies, regardless of the solder process parameters. Hydrogen belt furnace, vacuum DAP sealer, focused infrared, vapor phase....all of these techniques, regardless of operator expertise, are unable to produce a shiny 50/50 lead indium surface..this is just one alloy as an example. BTW, many times the explanation is inaccurate, but the end result is the same..this is one such case. If the joint looks like that and a eutectic lead tin is being used, something is wrong..the inspector doesn't necessarily need to know the technical details to be able to kick it out. Note: While it's great to have inspectors who will kick out rejects based on appearance alone, it does make it harder when the good solder joints happen to look like the example being used for a bad one. You end up trying to explain to them why what you called a reject in the past, suddenly is no longer a reject? Then you end up trying to explain eutectic vs non, phase diagrams, flux modification of surface energy....things they do not have the background to understand...deer in the headlight.. Man, been there, done that. When you find an inspector who can understand that stuff, gold.....gold I tell ya...keep em, promote em..pay em well.. Quote:
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Cheers, John
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I hate all these smart gadgets..I refuse to buy things that are smarter than me. I've made a list of those things... Cabbage just made the list. |
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#34 | ||
diyAudio Member
Join Date: Jan 2004
Location: In fear
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Quote:
Sometimes platers will use 10 microinches of nickel as a flash prior to the gold. It acts as a diffusion barrier to the gold. Perhaps the parts are aged, and the underlying nickel has oxidized. Initial soldering may be alloying to the gold with an underlying oxide barrier remaining intact. The oxide layer being so thin, is not visible, and the gold overlaying may be supporting the meniscus and hiding the lack of a metallurgical bond to the nickel. Same can happen with gold over copper I guess, but I've not used that as it is not good for 6 month shelf solderability nor steam age tests. If this is the case, do a dip using R flux in a 60/40 pot set to 250C. Remove the lead very slowly, allowing surface tension to pull the soldercoat very thin. Then, inspect for de-wet. If the gold is too thin allowing oxygen to diffuse to the flash, you'll see it here. If that's the case, you need a two step dip process. First dip is to clear the gold. Second is for refurbishing the de-wet areas. That will need an RA flux....DO NOT DO THIS FOR STRANDED LEADS IN A MIL ENVIRO, WICKING WILL KILL YA. Repeat the aggresive flux dip until the dewets go away. This should work for both matte gold and shiny gold, as the RA will clear the organics from the shiny levelers.. Service life is difficult to predict, as it's not clear what the underlying problem is. My guess is an underlying oxide layer being hidden by the gold/solder meniscus. Quote:
For internal use, amps and such, I'd worry about the places where heat is involved. Cheers, John
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I hate all these smart gadgets..I refuse to buy things that are smarter than me. I've made a list of those things... Cabbage just made the list. |
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