Instructions and Precautions for Handling Domes

General Handling Instructions – Metal Domes

• Most of our metal domes are designed to be depressed to flat and no further. Depressing a dome past flat (the outer-perimeter or feet of the dome) can cause loss in tactile feel and/or the dome to fail. However, in some applications more travel is required. Unless the dome was designed to overtravel (such as the M-Series), always place the dome on a hard flat surface. The contact area must be level with the outer perimeter or feet of the dome. Failure to do this may result in a bistable dome.
• Always use a tool when placing metal domes. Do not use your fingers as this could contaminate the dome.
• Domes should not be unsupported when activated. Always place on a flat hard surface. Never activate a dome when all feet are not evenly supported.
• Domes should not be rubbed with a sharp object.
• Dome “Nesting” – Double doming occurs when two or more domes “nest” together when placed. Double doming can be detected through force testing your applications. Both the SureShot Automated Dome Placement Machine and the Dart Dome Placement Pen (manually operated) eliminate double doming.
• Reflow Soldering – Metal dome contacts are designed to flex when actuated, therefore should not to be soldered as this may damage the dome. Always perform reflow soldering of other components prior to placing domes on the PCB.

General Handling Instructions – Peel-N-Place Arrays

• Before applying a Peel-N-Place array, it is essential to have a clean surface area to ensure proper adhesion and minimize contamination. Snaptron recommends that you keep all surfaces clean, dry and free of debris. Isopropyl alcohol can be used with a non-lint cloth.
• Do not stretch or overtension the Peel-N-Place array when applying to your surface area. This could affect the placement tolerances of the dome positions and adversely affect adhesion. The use of an application fixture is highly recommended.

Definitions

• Travel: The total distance the dome switch moves from its relaxed state to electrical contact.
• Over-travel: Actuating the dome past its designed travel. For most domes, this is beyond the flat plane of the foot. Domes can be designed to over-travel.
• Transition Ring: The transition ring is the visible ring on the top of the dome, where the dome radius transitions into the feet/legs of the dome. The transition ring is the hinge point of the dome that forces the dome back to its original shape after the dome has been depressed or snapped over.
• Bi-Stable: The condition of a dome where, when actuated and then released, the dome does not return to its original condition. In this state, the dome exhibits two (2) stable conditions.

Damage Can Occur to the Dome by Any of the Following Means:

• Over-traveling the dome past its designed travel can cause damage to the transition ring. For most domes this means traveling the dome past the flat plane of the feet. Actuating the dome between the fingers with the center being unsupported is an example of over-travel.
• Denting the transition ring can be caused by actuating the dome with a sharp object such as a pen or fingernail. (Rubbing the finger across the dome with the fingernail, for example.)
• Depressing the dome with a rigid, flat surface that is equal to or greater than the transition ring diameter can cause damage to the transition ring. (Too large of an actuator, for example.)
• Depressing the dome across the full width of the dome with some type of roller can cause damage to the transition ring.
• Actuating the dome when all of the feet are not evenly supported can cause damage to the transition ring. These are the most common causes of damage to the metal domes during assembly; yet do not include all sources caused by general rough handling.