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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