3.1.3 Mechanical Isolation

When multiple buttons are present in a system, it is possible for undesirable mechanical interaction between different buttons to occur. For example, when pressing button A, the contiguous metal surface may deform in such a manner that a significant amount of movement occurs over the neighboring button B sensor, and could appear as an unintended button press of button B. The following principles can be applied to reduce the mechanical crosstalk between adjacent buttons during an active press:

1. Physical supports between buttons or standoffs can facilitate stronger metal deformation on the button that is pressed, as shown in Figure 5.
2. Ensuring a larger physical deflection for the intended button. From an electrical perspective, a large signal-to-noise ratio between a true button press versus an undesired detection is the easiest way to detect the correct button press event. Using thinner metal or selecting materials with a low Young’s modulus ensures that metals are easier to deform and have less impact on the neighboring buttons. For example, aluminum is more flexible than many stainless steel alloys.
3. Increasing the distance or adding grooves between adjacent buttons improves mechanical isolation. For cross-talk minimization, button-to-button separation should also be greater than one coil diameter.