Why the Conductive Carbon Pill Fall Off From the Rubber Button

Conductive Carbon Pill also called as cabon pill, carbon graphites pill, which is widely used in rubber button, silicone rubber keypad.

Conductive carbon pill are usually made of silicone conductive material containing carbon.The conductive carbon pill is co-molded with rubber button, silicone keypad .When the conductive carbon pill contact with the circuit, the circuit is closed on the PCB, and achieve conduction of rubber button.

Generally, rubber button has different conductive ways: conductive carbon pills , conductive ink printing, metal pills, metal dome and nickel pill.

Conductive carbon pill is the most common conductive way.But why some conductive carbon pill falling off from the rubber button?

Rubber Keypad vulcanization temperature is too low.

While compression molding the rubber keypads, we should control the temperature at 160°C-170°C. The lower temperature will affect carbon pill stick to the rubber keypad bottom.

Rubber Keypad vulcanization time is too short.

The vulcanization time for rubber keypad molding should base on the the thickness of rubber button. If the rubber button is thickness, we can increase the vulcanization time to make sure rubber keypad full vulcanization and guarantee carbon pills firmly combined with the rubber button.

If the rubber keypad doesn’t get full vulcanization, the rubber keypad is easy to have indentation when we pinch the silicone keypad surface.

Conductive Carbon Pills are contaminated or become damp.

Carbon pills for rubber keypad should keep from moisture or contamination. The damp carbon pills or dirty carbon pill will affect the joint with rubber keypad. So the factory environment should keep clean.

Rubber keypad compression molding vent incompletely.

Incomplete venting during rubber keypad molding will cause falling carbon pills.

Higher Molding Temperature

If the rubber keypad molding is too high, silicone material will flow quickly in mould cavities and keypad shape forms quickly, which will affect carbon pills combine with rubber button.

Carbon Pills don’t get full vulcanization.

Good carbon pills should vulcanized fully in order to make sure them stick to the silicone keypad.

Lower rubber keypad molding pressure and insufficient silicone material

To stick two things together, pressure should be put on. To make sure carbon pills and rubber keypad stick firmly, rubber keypad compression molding should keep sufficient pressure and has enough silicone material.