Ed,
Text book "Microelectronics Packaging Handbook" by R. Tummala et.al p.742
stated that:
The ductility of the this (60/40 solder)solder with about 8% to 10%
dissolved gold is practically zero.  Although pure gold coatings provide an
excellent surface for soldering, the coating thickness has to be kept to a
minimum and under close control.

The book also has list of references regarding the same issue...Good luck.

jk
At 03:28 PM 4/5/99 -0600, you wrote:
>Please don't blast me on bringing this subject up again.  I have searched
>the TechNet archives and found lots of good information, and also noted that
>it is a somewhat sensitive subject, having been around for 30+ years.  We
>have a condition that I believe is clearly unreliable based on what I have
>read.  The condition is:
>
>- 4 lead LCCC's (leadless with castellations)
>- Approximately 50 microinches of glod plating on untinned castellations.
>- Untinned parts mass reflow soldered onto PWB's (parts were supplied on
>tape and reel, so subcontractors did not see that they were untinned).
>- Microsectioning shows a 50 to 100 microinch layer of Au/Sn intermetallic
>after soldering, on top of copper/nickel surface.  Au concentration averages
>about 25% in this intermetallic region.
>- These assemblies will be subjected to high vibration and long term (years)
>thermal cycling in actual use.
>
>Replacement of these parts would be expensive since they are on many boards
>installed in closed and tested boxes. For this reason, mangement is hoping
>that testing will qualify this condition.  I hate to see the affected
>program waste time and money, and am afraid they might even get a warm fuzzy
>and fly these parts.
>
>Can any of the numerous industry experts in this group give me something
>concrete to present to the program such as actual experiences or obtainable
>reports?  Is the above condition a no-brainer or is it not as bad as it
>looks to me?  I tried getting copies of the 2 reports listed in the
>J-STD-001 Handbook, but struck out.
>
>Thank you for your time.
>
>Ed Knowles
>Lockheed Martin
>[log in to unmask]
>
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