Gold Embrittlement in solder joints
Gold Embrittlement in solder joints
(OP)
Iknow that gold will cause lead-tin solder joints to become brittle over time, NASA tells me so. They have specific procedures to avoid it. Has anyone seen anything in writing that goes into any detail as to what the mechanism is and when to worry about it? Thanks.
Rick Schmidt
ricksintuc@yahoo.com
Mining, Mechanical and Electronics engineer.
RE: Gold Embrittlement in solder joints
1. Lead-tin is normally matched by lead-tin. About 7 years ago, the computer manufacturers recommended that SIMMs shall have that kind of match to avoid gold plated or gold contacts at SIMMs. They have been working there for 7 years without any problem.
2. Perhaps, if you contact SIMMs manufacturers that may have some information about this since they practically faced this problem.
Try Computer Shopper listed SIMMs Manufacturers or over
http://www.thomasregister.com
RE: Gold Embrittlement in solder joints
Rick Schmidt
ricksintuc@yahoo.com
Mining, Mechanical and Electronics engineer.
RE: Gold Embrittlement in solder joints
Darn frustrating too, you pay extra for the components, and then have to purchase and maintain equipment, and pay staff to remove it before the componet can be used.
That said, IPC 610 level three does not suggest that gold should not be used for high specification assemblies, and until an alternative finish with equal to or better solderability and shelf life properties than gold (sorry all those reps trying to sell tin, silver, and organic finishes), and as flat a surface, gold looks likely to stay with us.
Don't be scared of it though, gold joints are all around us, controlling lifts, computer systems, nuclear powerstations (now I'm scaring myself), and I know that boards I've made are actually floating around in satellites
Steve Bull
PCB and Quality Engineer
RE: Gold Embrittlement in solder joints
http://www.techplate.com
http://www.techplate.com/specchart1rev.htm
http://www.ipc.org/html/A600F.htm
http://standards.nasa.gov/stdsearch.taf?discpln=9
etc. for more info on somewhat related sites to finishes
RE: Gold Embrittlement in solder joints
5.4.1 Gold Removal:
Gold shall be removed from solder terminals plated with 2.5 um [0.0984 mil] or greater gold thickness.
Before soldering to any gold plated surface, you must first remove the gold to conform to IPC-610. This is due to gold embrittlement of the solder connection. An acceptable method is to tin the surface and then remove the tinning with solder wick. Once is enough to leach out the gold.
Tin-lead solder normally used in electronics is not compatible with gold plating. Gold readily alloys with tin-lead, but when the gold concentration exceeds a few percent
the alloy becomes weak during thermal cycling. This phenomenon is called gold embrittlement. As long as the gold plating thickness is small (20-30 µin) this is not considered a problem. For thickness above 100 µin, indium based alloys rather than tin-lead solder are recommended
to ensure the integrity of solder joints.
-- Greg Robinson, CQE, Thoratec Corporation
RE: Gold Embrittlement in solder joints
http://www.reliabilityanalysislab.com/Resistors.asp
http://home.cfl.rr.com/bjp/Plating.htm