Liquid silicone for soft, durable ear tips
Injection-molded liquid silicone rubber (LSR) produces earbud tips that are soft, skin-safe and non-irritating, and that retain their shape after thousands of insertions and removals, meeting ever-higher user expectations.
Ear tips are the part that comes into direct contact with the body, determining wearing comfort, acoustic seal and even active noise cancellation performance. A poor-quality ear tip can harden, discolor or tear at the edge after just a few months.
For active noise-canceling earbuds, the ear tip is also part of the acoustic system: a poor seal lets low-frequency noise leak in, forcing the noise-cancellation algorithm to work harder and drain the battery. That is why the tip material is evaluated together with the acoustic design.
Advantages of liquid silicone over solid rubber
Liquid silicone has low viscosity and flows easily into the mold, enabling walls as thin as 0.2–0.3 mm and fine details. The injection molding process is automated, curing in a hot mold in just a few tens of seconds, with little flash and almost no post-processing required.
- A wide hardness range from Shore A 10 to Shore A 70.
- Heat resistance from -50 to 200°C, with no deformation when left in a car in the sun.
- Skin-contact certification per ISO 10993 for medical grades.
- Good resistance to UV, sweat and skin oils.
Choosing the right hardness for each tip type
In-ear tips
A hardness of Shore A 20–40 provides a soft feel that conforms to the ear canal and creates a good seal for bass. Multi-flange thin-wall designs require materials with high tear strength.
Ear wings and ear hooks
Shore A 40–60 is typically used to hold shape and prevent slipping during vigorous activity. Two layers of different hardness can be overmolded.
Common defects when molding ear tips
- Air bubbles at thin edges due to poor mold venting.
- Sticking to the mold when the mold surface has not been properly treated.
- Residual silicone odor due to the lack of post-curing.
- Dust-attracting surfaces, which call for an LSR grade with a dry-touch surface.
Post-curing for about 4 hours at 200°C removes volatiles, stabilizes mechanical properties and meets the volatile content requirements of export customers.
Color and surface finish
Liquid silicone can be colored with dedicated pigment pastes at a ratio of 1–2%, producing uniform color matched to the brand's palette. The tip surface can be given a matte texture from the mold or an additional soft-touch silicone coating to reduce dust pickup and enhance the premium feel. For export products, it is also advisable to test color fastness under UV and resistance to yellowing after long-term exposure to sweat, cosmetics and sunscreen.
AMS distributes liquid silicone rubber from Shin-Etsu and Dow to consumer electronics component molders. Contact AMS Vietnam to receive data sheets and samples.
