Conductive Carbon Pills / Gold Pills

Most of us know that there is conductive requirement to silicone rubber keypad. And we also have known that the keypad itself is not conductive. So how to make the keypad be conductive? There are several ways to achieve this. To add the conductive carbon pills, carbon rings, gold pills, Ni pills on back side of the keys, then when we press down the rubber keys, they will contact the conductive pads on the circuit board and then trigger electrical function. For the gold pill, it is not the real gold. It is just gold plated metal pill. The gold pill has very low impedance which can be low to 1ohm around. For the Ni pill, its impedance can be controlled within 5ohm. As to the carbon pill, its impedance can be high to 10ohm around. So, their surface resistances will determine the application of them. For some precision function control applications, like the defense, aerospace, medical, marine, automotive etc., which usually asked to use gold pills. By the way, the gold pills also have more longer life. For automotive application, it usually also uses Ni pill, which also has low impedance, but the cost is more lower. As to the carbon pill, which is the commonly used one in the most of fields. Its cost is the lowest one. Except for the conductive pills, it also can print the conductive ink on backside of rubber key. You can understand this as the 'printed pill'. The impedance for the printed conductive ink pill is usually less than 500ohm and the normal carbon pill's impedance is usually less than 10ohm. In addition, the carbon pill does also have dimension requirement. As per the standard, its dimensions are usually between Φ2.0mm and Φ8.0mm. It will be increased each time by 0.5mm. The common used is within Φ3.0mm and Φ5.0mm.

Actuation Force / Snap Ratio

Usually speaking, the travel of the rubber key is inversely proportional to resilience force. More bigger key travel, more less of the resilience force for keys. Vice versa. When the rubber key's sideling wall thickness fixed, the bigger of the angle between the sideling wall and key, the more higher of the actuation force will be, and then the more bigger of the resilience force is. By the way, more higher of the silicone material hardness, more higher of key's actuation force. LuphiTouch® can design and manufacture the silicone rubber keypads with the actuation force from 20g to 500g. But in the market commercial application, the common used actuation force is between 120g and 320g. Usually speaking it needs high actuation force keypads for industrial control field, and the low actuation force for consumer electronics and household appliances etc.

For the raw material, the hardness lies from shore A 10°-80°. The commonly used hardness usually are from 50° to 65°. LuphiTouch always use the high quality imported raw materials. The brands we used include Dow Corning from USA, ShinEtsu from Japan etc.