Silicone rubber keypads: Conductive points for functionality

Silicone for keypad manufacturing

In user interface design, silicone keypads have become the preferred choice for various consumer and commercial applications. However, the inherent non-conductive nature of silicone raises a challenge in ensuring functionality. Engineers overcame this limitation by developing two primary approaches: carbon pills and printed carbon ink.

Read this article to learn how engineers achieve conductivity for silicone keypads following two standard engineering approaches.

Carbon pills & printed carbon ink: Approaches that make silicone conductive

As silicone rubber is non-conductive, conductive points are added between the buttons and the underlying circuit board. Two standard methods suitable for this purpose are carbon pills and printed carbon ink, each differing in form and application:

Carbon pills:

  • Form: Carbon pills are pre-formed small discs or domes composed of compressed carbon material.
  • Application: These pills provide conductivity within silicone rubber keypads, inserted between the keypad and the PCB board using a precision jig.

Silicone keypads and conductive pills are manufactured similarly. The material composition is a mixture of silicone and conductive material. On a normal conductive pill, carbon is used as a conductive material. When the silicone key is pressed, the carbon particles in the pill are squeezed together, allowing electricity flow.

Carbon pills deliver the required conductivity and durability, making them suitable for applications where reliability is crucial. They are installed directly and are cost-effective for mass production.

Printed carbon ink:

  • Form: Printed carbon ink involves using specialized conductive ink containing carbon particles.
  • Application: This ink is deposited onto specific areas of the silicone keypad through advanced printing techniques such as screen printing or inkjet printing, forming a pattern of carbon-based conductive traces.

Printed carbon ink offers flexibility in design and layout compared to carbon pills. Engineers can create custom conductive traces to meet specific application requirements. It also provides excellent conductivity while allowing for complex designs and customization and is suitable for applications where space constraints or design aesthetics are important considerations.

Quick Comparison

Carbon pills and printed carbon ink offer practical solutions for achieving conductivity in silicone rubber keypads. The choice between the two depends on factors such as specific application requirements, budget constraints, and manufacturing capabilities. 

Let’s see the difference in a table for a quick overview.


Apsect Carbon pills Printed carbon ink
Form Pre-formed small discs or domes composed of compressed carbon material Specialized conductive ink containing carbon particles
Application Inserted between keypad and PCB board using a precision jig Deposited onto silicone keypad using advanced printing techniques
Installation complexity Requires precise insertion process with a jig The printing process may require specialized equipment and expertise
Customization potential Limited customization due to pre-formed nature Offers greater flexibility in design and layout due to the printing process
Cost Generally cost-effective for mass production Cost may vary depending on ink type, equipment, and complexity of design

Carbon pills are best for applications where simplicity, reliability, and cost-effectiveness are important. Whereas, printed carbon ink offers design flexibility and customization options, making it suitable for applications where aesthetics and intricate patterns are desired.

In short, carbon pills and printed carbon ink are engineering approaches that enable engineers to make silicone conductive and provide a durable keypad for equipment. By understanding the strengths and considerations of each method, engineers can select the most appropriate solution for their unique application requirements.