Conductive Silicone Rubber | What Kind Of Rubber Is Used On A Stylus?

Conductive Silicone Rubber is a crucial material in the manufacturing of stylus pen tips, particularly for touchscreen devices. Its ability to conduct electricity while maintaining flexibility and durability makes it ideal for this application. Silicone rubber is a versatile elastomer known for its excellent thermal stability, flexibility, and resistance to chemicals and environmental factors. When enhanced with conductive properties, it becomes an ideal material for applications requiring touch sensitivity, such as stylus pen tips for touchscreens. 

Types of Conductive Silicone Rubber
Carbon Black Conductive Silicone Rubber: 

Composition: Contains carbon black particles dispersed within the silicone matrix.
Properties: Provides moderate conductivity, good flexibility, and fair durability. Carbon black is a common choice due to its cost-effectiveness and ease of processing.
Applications: Widely used in stylus pen tips, touchscreens, EMI/RFI shielding gaskets, and flexible circuits.

Nickel Metal Particle Conductive Silicone Rubber:

Composition: Contains metal particles (such as nickel) dispersed in silicone.
Properties: Offers higher conductivity compared to carbon black variants. It provides good electrical and thermal conductivity, but it is more expensive.
Applications: Suitable for applications requiring higher electrical conductivity, such as sensitive electronic components and medical devices.

Non Conductive Silicone Rubber Coated With Conductive Ink:

Composition: Firstly compression molded general silicone rubber tip, then spray black conductive ink layer to make it to be conductive.

Properties: More smooth writing feeling on screen, no scratch, but limited lifetime, the conductive ink layer will gradually wear off after around 7000 times writing. Price is between above two materials.

Applications: Frequently used equipment such as tablet PC, personal use.

Material	Lifetime/Lifespan/Service Life	Writing Experience	Manufacture Process	Price	Picture Reference
Carbon Black Conductive Silicone Rubber	Average	The writing feel is a bit astringent and not smooth enough, which may leave slight writing scratches on the screen	Use silicone mixed with conductive black carbon powder to mold (compression molding) and form the final shape of stylus tip.	Relatively  Cheap
Silicone Rubber Coated With Conductive Ink	Limited - around 7000 times	Excellent smooth - the best	Use common non conductive silicone to mold (compression molding) and form the final shape of stylus tip firstly, then spray black conductive ink to surface of the tip to make it be conductive.	Medium Level
Nickel Conductive Silicone Rubber	Good	Smooth - good	Use silicone mixed with conductive nickel powder to mold (compression molding) and form the final shape of stylus tip.	Much More Expensive

(Note: Different conductive material for stylus tip, different net weight. Hardness of conductive carbon silicone rubber and conductive nickel silicone rubber is limited, 60 Shore A - 70 Shore A, without other choices, the conductive pen tips are very easy to crack when hardness higher than 70 Shore A. If you require lower hardness, only one material choice - silicone rubber with conductive ink spraying.)

Properties of Conductive Silicone Rubber
Electrical Conductivity: The primary property required for stylus pen tips. Conductive silicone rubber enables precise touchscreen interactions by conducting electrical signals from the stylus to the device.
Flexibility: Maintains the necessary flexibility to mimic the feel of a pen or pencil on the screen while ensuring durability against repeated use.
Durability: Resistant to wear and tear, ensuring a long lifespan for the stylus tip without degradation in performance.
Chemical Resistance: Silicone rubber inherently resists moisture, oxidation, but cannot resist chemicals, use the silicone rubber stylus in daily environment. 
Temperature Stability: Maintains its properties across a wide temperature range, critical for stylus pens used in diverse climates. -20℃~200℃.

Applications of Conductive Silicone Rubber in Stylus Pen Tips
Conductive silicone rubber is extensively used in stylus pen tips due to its specific properties:

Tablets and Smartphones: Enhances accuracy and responsiveness for drawing, writing, and navigating touchscreen interfaces.

Signature Capture Devices: Facilitates precise signature recording in electronic transactions and documentation.

Industrial Touchscreens: Supports control panels and devices used in manufacturing and automation.

Manufacturing Process of Conductive Silicone Rubber Stylus Tips
The manufacturing of conductive silicone rubber stylus tips involves several key steps:
Material Selection: Choosing the appropriate type of conductive silicone rubber based on the desired conductivity level, flexibility, price, and durability.
Formulation: Mixing silicone base with conductive additives or fillers in precise ratios to achieve the desired electrical properties.
Molding: Compression molding the silicone rubber into the desired stylus tip shape. This process ensures consistency and precision in the final product.
Curing: Heating the molded parts to cure the silicone rubber, achieving the final mechanical and electrical properties.
Finishing: Trimming excess material, inspecting for quality assurance, and possibly applying a protective coating or texture to enhance user experience.

Challenges and Considerations in Manufacturing
Material Compatibility: Ensuring compatibility between the conductive additives and the silicone base to maintain consistent electrical properties.
Precision Molding: Achieving precise dimensions and shapes to fit various stylus pen designs and touchscreen devices.
Quality Control: Implementing rigorous quality control measures to detect defects early in the manufacturing process.
Cost Considerations: Balancing performance requirements with cost-effectiveness in material selection and manufacturing processes.