1. Tactile feedback

Membrane switches can be divided into two types: tactile feedback and non-tactile feedback. There are two kinds of structures for non-tactile types: flat and embossed buttons.

Non-tactile membrane switches do not have any requirements on handfeel, but they require high sensitivity. They can be turned on with a light touch, but the circuit can't turn on when the button is not pressed. Therefore, a reasonable isolation point must be added to the lower circuit.

The buttons of the early non-tactile membrane switches use colors to show the position, shape and size. People recognize the operation visually. In order to facilitate operation and improve accuracy, the graphic overlay was later designed with embossed buttons. In recent years, many flat non-tactile membrane switches have been changed to capacitive membrane switches.

There are many structural forms of tactile membrane switches. The most popular ones are die-pressing key and metal dome.

For die-pressing key, it is produced by heating the mold with hydraulic pressure, causing the key to bulge slightly, higher than graphic overlay, which forms a three-dimensional button. The material is PET with very good toughness and heat shrinkability, and is hot-pressed. This kind of membrane switch has a very good handfeel and sensitivity. However, be careful not to put it in a high temperature environment for a long time. High temperature will weaken the handfeel.

If the contacts are directly printed on graphic overlay, the deformation after high-temperature aging must be taken into consideration. If the high-temperature baking time is too long, the deformation will be large, which will cause great trouble to the assembly of the membrane switch. If the time is too short, the contacts will not have enough aging time, and they will easily wear out, shortening the service life.

For metal domes, they are fixed on the lower circuit to be as the upper circuit. When we press the metal dome, it is connected to the other pole of the lower circuit to form a loop. The buttons can be designed in various ways to make the product more stable and reliable. It also enhances the decorative effect.

The design of the fixed layer can be divided into two forms: punching at the corresponding key position (the hole diameter is smaller than the metal dome) or embossing. The punching design has a crisper feel and even strength, while the embossing design has better overall sealing.

There is another structure. Metal domes can directly be installed on upper circuit to improve the handfeel. When there are many keys, and the overall shape is small, and there is no space for wiring, the upper and lower circuit structures are designed to adopt this structure. This is good, but the sensitivity is slightly weak. The pressing force should be strong. The time for releasing the finger is slightly longer. Sometimes there are a pressing feeling and the sound of metal dome, but the circuit is not turned on.

2. Shape

The graphic overlay can be designed as a flat surface, convex spherical surface, or convex flat surface. The shape can be circular, square, triangular, or other irregular shapes.

When the keys are flat or embossed, the upper adhesive must be thickened. It allows the metal dome to have enough space to move freely. If the handfeel is not good, add a small spacer under the button.

3. Water resistance

There are two types of waterproof structures. The waterproofness is generally designed as a zigzag embedded structure. There are two parts that are made of exactly the same material. The circuit is embedded in the panel. This structure is popular, and waterproof glue must be added on each layer.

The other structure is to use materials with the same thickness as the upper and lower circuits and isolation layers. The circuit part is embedded inside into a whole.