Well, I guess my REAL question should have been:
"Has anyone experienced switch contact failures using the IPC recommended
150 knoop, 118uin. Nickel min, 31.5uin. Gold min. for edge connectors?"
Joyce on IPC TechNet suggested that Switch Contacts may be different than
Edge Connectors, where I had assumed they would be the same.

IPC doesn't seem to make any distinction for anything other than:
- Gold for Edge Connectors
- Gold to be Soldered
- Gold for Wire Bonding
- Gold Immersion (ENIG)

So what fab dwg note do YOU use for Switch Contacts???

Jack

On Wed, Apr 14, 2010 at 5:03 PM, Gary Koven <[log in to unmask]> wrote:

>  Jack,
>
>
>
> Last time I had to do it was in 1998, 12 years ago, I went by IPC-2221
> Class 2 and the vendor didn’t whine.
>
>
>
> IPC-2221, page 20, Table 4-3 delineates the different usages of gold, and
> for your switch, I imagine one of these two is correct:
>
> Class 1 and 2 Gold (min) for edge-board connectors and areas not to be
> soldered = 0.8um (31.5uin)
>
> Class 3 (MIL-SPEC and med-spec) calls for 1.3um (51.1uin)
>
> Gold (max) on areas to be soldered = 0.8um (31.5uin) for Class 1,2,3
>
>
>
> Table 4-4 (Gold Plating Uses) on the same page specifies minimum purity
> 99.0%, Knoop hardness 130-200 and a letter “S” signifying “suitable” for
> Contacts.
>
>
>
> Other arcana in the MIL-SPEC may be of use. I believe MIL-G-45204 in my old
> IPC-2221 became MIL-DTL-45204D in 2007.
>
>
>
> Dunno about your last two questions.  I don’t have a current copy of
> IPC-2221.
>
>
>
> Dunno if anybody’s gonna pay to grind out a cross-section to send to the
> x-ray or the beta-backscatter to measure how thick the gold **really** is,
> or make the vendor issue a CofC for the purity of the gold – in the Class 3
> world when it’s mission-critical they sometimes do both.
>
>
>
> Anyway it’ll be interesting to see what others say about this.
>
>
>
> Gary
>
> Designing since 1975
>
>
>
> *From:* DesignerCouncil [mailto:[log in to unmask]] *On Behalf Of *Jack
> Olson
>
> *Sent:* Wednesday, April 14, 2010 5:14 PM
> *To:* [log in to unmask]
> *Subject:* [DC] Question for "Old-Timers" about Gold
>
>
>
> ya know, every time I think I know enough about a particular subject,
> something comes along to make me realize there is more to it....
>
>
>
> I need to order some boards using a fabrication drawing that hasn't been
> updated in over fifteen years.
>
> We need Hard Gold Electroplating for a rotary switch contacts.
>
> One of the notes calls for gold knoop hardness 200-300, thickness 130-230
> uin. 93.7% purity
>
> The last FAI report showed gold thickness of 160 uin. All other historical
> records are lost in the shifting sands of time
>
>
>
> Our vendor has knoop hardness 150, 99.7% purity and says gold requirement
> is too thick.
>
>
>
> IPC says knoop 150, gold minimum 31.5 uin. for edge connector fingers,
> which I assume is the same for contacts (doesn't seem to be addressed)
>
>
>
> Printed Circuits Handbook says knoop 150,  thickness 25-50 uin for
> non-military, 99.8% gold purity
>
>
>
> Has gold plating changed that much since then?
>
> Is there a danger of wear-out if I get 50uin. gold plating when our old
> boards were 160 uin.?
>
>
>
> surfin' the learnin' curve,
>
> Jack
>
>
> ______________________________________________________________________
> This email has been scanned by the MessageLabs Email Security System.
> For more information please contact helpdesk at x2960 or [log in to unmask]
> ______________________________________________________________________
>
> -------------------------------------------------------------------------------
> DesignerCouncil Mail List provided as a service by IPC using LISTSERV 1.8e
>
> To unsubscribe, send a message to [log in to unmask] with following text in
> the BODY (NOT the subject field):
> SIGNOFF DesignerCouncil
> To temporarily stop/(start) delivery of DesignerCouncil for vacation breaks
> send: SET DesignerCouncil NOMAIL/(MAIL)
> Search previous postings at: http://listserv.ipc.org/archives
>
> Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16for additional information, or contact Keach Sasamori at
> [log in to unmask] or 847-615-7100 ext. 2815
> -------------------------------------------------------------------------------
>
>
>

______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________

---------------------------------------------------------------------------------
DesignerCouncil Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF DesignerCouncil.
To temporarily stop/(restart) delivery of DesignerCouncil send: SET DesignerCouncil NOMAIL/(MAIL)
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
---------------------------------------------------------------------------------