Editing Metal contact switch (section)

===Chatter===
When the switch contacts close, they rebound from the impact; this is referred to as '''contact bounce'''. Through operator or spring pressure they are driven to their closed position, but they repeatedly bounce back until they are drained of kinetic energy and settle into a stationary closed position. This bounce is subtle but significant: the [[keyboard controller]] will see the key being struck rapidly in succession. Switch manufacturers aim to keep this bounce at a minimum, and most keyboard switches are specified to bounce for no more than 5 milliseconds.

This in itself is not a great disadvantage; keyboard controllers are programmed to ignore the 5 millisecond period after a switch is first detected, and wait until the switch settles before reporting a keystroke.

However, contact-based switches exhibit a failure mode where the bounce lasts longer than expected, causing repeated keystrokes to appear. This is usually only on the order of one or two spurious keystrokes, but this is nonetheless a very visible and persistent problem. The generation of spurious keystrokes due to excessive contact bounce is referred to as '''chatter'''. Injecting the switch with a substance such as WD-40 can be all that is required to resolve this problem; chatter in both Cherry MX and Futaba clicky switches has been resolved using this method, without any need for switch disassembly (in the latter case, the switch was injected first with WD-40 and then 99% by weight isopropyl alcohol (IPA), which together with repeatedly working the switch, resolved a persistent chatter defect in a sealed switch<ref name="Herb-Palm" />). Where dirt is the cause, the current Keyboard Company recommendation is WD-40 Electrical Contact Cleaner Spray<ref>Correspondence with the Keyboard Company, 2016-09-21</ref> (a separate product to regular WD-40), and use of a dedicated contact cleaner substance has also seen mention on the forum along with IPA.<ref>Deskthority — [https://deskthority.net/keyboards-f2/alps-appreciation-t12915-990.html#p329242 Alps Appreciation] (page 34)</ref>