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April 2010

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Thu, 15 Apr 2010 00:43:54 -0700
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...I mean 'extinguish' of course..

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From: "Inge" <[log in to unmask]>
Sent: den 15 April 2010 00:39
To: <[log in to unmask]>
Subject: Re: [TN] Question for "Old-Timers" about Gold

> Showing off?  It's just fun to share the little I know.  It's a remarkable 
> time we live in today.  There are no engineers left at my company, 
> engineers who are interested in all about switches (and other 
> electromechanical components).  On the other hand, I live partly in the 
> past myself,  having very shallow knowledge about today's central 
> technology with numerous applications based on semiconductors.  I've tried 
> to understand how a Intel processor works, but  must admit it's too 
> advanced for my old skull. And I would never be able to design a modern 
> DSP or a X-band up/down converter, to take example.  I had a look at one 
> of our library shelves the other day.  I estimated about 30 meters of 
> technical literature for design of electronics, but only a few books about 
> chemistry, mechanics and components !  It seems as if old-timer's 
> knowledge is not needed much today.
>
> TN is still a exciting forum, all kind of themes are discussed.  I'm very 
> grateful to such persons as Brian Ellis, John Burke, Wayne Thayer, Dave 
> Hillman, Iona Tempea, Steven Creswick, Victor Hernandez, George Wenger, 
> Mike Fenner, John Maxwell III, Joyce Koo, Denny Fritz, Steve Gregory, 
> Dewey Whittaker, It Depends,  and a dozen more.  You keep my curiosity 
> alive. Thanks to you all.
>
> I would like to see someone of you who started TN or have been members 
> from the very start, to write some kind of a retrospective essay about 
> TechNet, kind of baton for the change-over to next decade.  When those 
> real enthusiasts retire, I'm afraid TN will distinguish.
>
> Inge
>
> --------------------------------------------------
> From: "Jack Olson" <[log in to unmask]>
> Sent: den 14 April 2010 15:43
> To: <[log in to unmask]>
> Subject: Re: [TN] Question for "Old-Timers" about Gold
>
>> Well, now you are showing off!
>>
>> I believe the modern "impurity" is a .2% cobalt to add hardness,
>>
>> so I guess my questions for curiosity should have been
>> "did standard knoop hardness change over the years?"
>> and
>> "has gold thickness been gradually reduced over the years?"
>> but my REAL question is:
>> "Has anyone experienced switch contact failures using the IPC
>> recommended 150 knoop, 118uin. Nickel min, 31.5uin. Gold min.?"
>> thanks,
>> jack
>>
>> On Wed, Apr 14, 2010 at 5:19 PM, Inge <[log in to unmask]> wrote:
>>
>>> Jack,
>>> like you say, it's more to it....gold thickness is not the one and only
>>> parameter.  Other factors are contact asperity, contact geometry, 
>>> contact
>>> area vs. current, wipe pressure, switch slide coefficient, underlying
>>> plating, life expectancy and at least half a dozen more parameters. I 
>>> was
>>> specialist on electromechanical and manual switches decades ago, don't
>>> remember all details, but I can tell you this: if you count on gold
>>> thickness only, you don't know what you are shipping.  93.7% Au? We did 
>>> not
>>> name that Gold at all. We talked about maximum 0.1% impurities.  The 
>>> more
>>> impurities, the higher the friction coefficient. Well, I don't know what
>>> level of quality you speak for. I was in the HiRel, so maybe I'm too
>>> demanding. Anyway,  My advice (which you will probably frown at) is
>>> basic metal ?? your wiper
>>> 300 uinches of pure Nickel
>>> 25 uinches of Rhodium over Nickel
>>> 5 uinches of soft gold (gold works as 'lubricant')
>>>
>>> The above based on a qualified switch mechanism.  If that is not the 
>>> case,
>>> not even 160 uinches of gold  will work for a very long life.  160 
>>> uinches!
>>> Never heard of such a lot of gold. When extrem current switching is 
>>> actual,
>>> one use to work with mercury switches, microswitches or like.
>>>
>>> Don't listen to me, I'm from an era when we dismantled switches and 
>>> relays
>>> and measured all contact parameters and stored the  test data for 
>>> minimum 10
>>> years. And all our own test equipments were sent to a qualfied reference
>>> lab. Madness?
>>>
>>> Inge
>>>
>>> --------------------------------------------------
>>> From: "Jack Olson" <[log in to unmask]>
>>> Sent: den 14 April 2010 14:14
>>> To: <[log in to unmask]>
>>> Subject: [TN] 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
>>>>
>>>>
>>>> ______________________________________________________________________
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>>>
>>>
>>
>>
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>
>
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> -----------------------------------------------------  


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