Re: May be silly question, but: Lost my qq(´) and qq(´) key
- Date: Mon, 08 Apr 2019 13:25:24 -0500
- From: rlharris@xxxxxxxxxx
- Subject: Re: May be silly question, but: Lost my qq(´) and qq(´) key
On 2019.04.08 05:29, Martin wrote:
since a few days, my qq(´) and qq(´)¹ don't work with a single
press. I have to press twice.
The problem most likely is oxidation of the electrical contacts of the
key switch. The silver or gold plating of the contact surfaces may be
compromised by mechanical wear.
Back in the 1970's, keyswitches were rated in terms of tens of millions
or hundreds of millions of keystrokes; keyswitches of today are rated in
terms of tens of thousands or hundreds of thousands of keystrokes.
Search and read the manufacturer specification sheets for keyswitches.
A factor which exacerbates the situation is the ongoing effort to reduce
energy consumption; nowadays voltages across keyswitch contacts can be
too low to break through oxidation and the currents flowing through
contacts may be too low to burn off the oxidation.
Research years ago by Honeywell Corporation revealed that gold-plated
contacts are not always a good approach. Though gold does not oxidize,
the presence of oil vapour in the atmosphere can result in formation of
an insulating polymer on gold contact surfaces. Silver contacts appear
to be the proper approach; silver oxide is conductive.
Mechanic design of the contacts also is a factor; when the contacts are
bars or rods which cross at an angle, the contact pressure is higher
pressure than if the contacts are in the shape of buttons. The pressure
helps break through oxidation.
Some manufacturers offer "lifetime" keyboards; but the lifetime in view
appears to be that of the keyboard and not of the user. Keyboards today
can have a useful lifetime measured in months. Much depends upon the
environment in which the keyboard is used, particularly the atmospheric
The proper approach to the problem of low voltage and low current would
be to design keyboards in which the keyswitch contact voltage and
current are an order-of-magnitude higher than the voltage and current of
the logic circuitry.