Silicone connector package

Liquid silicone rubber (LSR) encapsulation injection molding, also commonly known as connector secondary encapsulation or overmolding.

This is a high-precision manufacturing process used to provide ultimate sealing and protection for electronic connectors.

Process Core: Liquid Silicone (LSR) Injection Molding

This is a process of injecting liquid silicone into a mold containing connectors to shape and solidify them.

Basic process flow:

Preparation stage:

Prefabrication of connectors: Firstly, the metal terminals of the connector have been fixed in the plastic shell through injection molding (usually using high-temperature plastics such as PBT, PA6T, PPS, etc.), forming a "primary wire harness".

Mold design: Produce high-precision metal molds based on the final 3D structure of the product. Mold design is the key to this process, requiring precise calculation of runner, sprue, and exhaust.

Injection molding stage:

Accurately place the prefabricated connector (primary wire harness) into the lower mold of the LSR injection mold.

Closing the mold, the upper and lower molds form a closed cavity that matches the shape of the final product. This cavity is the space that silicone will fill in the future.

By using a dedicated LSR injection molding machine, the liquid silicone of two components (A+B) is mixed in precise proportions at low temperatures, and then injected into the heated mold cavity through a metering pump and injection system (the mold temperature is usually between 150 ° C and 200 ° C).

Sulfurization (curing) stage:

Liquid silicone gel undergoes cross-linking reaction (vulcanization) in heated molds, transforming from liquid to solid elastomer. This process is very fast, usually taking only a few tens of seconds.

Open the mold and take out the finished product - a connector perfectly wrapped and sealed with silicone.

Why use liquid silicone to wrap the connector? Core advantages:

Excellent sealing performance (waterproof and dustproof)

This is the main purpose. After vulcanization, liquid silicone can form a seamless and integrated sealing body with the plastic shell of the connector and the outside of the cable. It can easily meet high protection standards such as IP67, IP68, and even IP69K, preventing moisture, dust, and chemicals from entering the interior of the connector.

Excellent environmental resistance

High and low temperature resistance: Silicone can maintain elasticity within the range of -50 ° C to+200 ° C, without becoming brittle or melting, making it suitable for harsh environments such as engine compartments.

Weather resistance: UV and ozone resistance, long-term outdoor performance does not deteriorate.

Chemical stability: resistant to most chemicals, salt spray, and detergents.

Excellent electrical insulation

Silicone is an excellent insulating material that can prevent short circuits and ensure the safety and reliability of electrical connections.

Buffer and stress relief

The encapsulated silicone gel can absorb mechanical vibrations and impacts, protecting the fragile metal terminals inside. At the same time, it forms a flexible stress relief structure at the cable outlet to prevent the cable from breaking due to repeated bending.

Soft Touch and Safety

Provides a comfortable tactile sensation and, as a non-conductive material, increases operational safety.

Key Technologies and Challenges

Adhesive issue: Silicone does not adhere to most engineering plastics (such as PBT, Nylon) themselves. This is one of the biggest challenges in the process. The solution includes:

Physical structure design: Design mechanical interlocking structures such as inverted buckles and grooves on the plastic shell.

Use adhesive: Apply glue (such as silicone adhesive primer) to the plastic surface before injection molding.

Choose special materials: Use special grades of plastic that can chemically bond with silicone.

Mold and equipment:

Requires high-precision molds and specialized LSR injection molding machines (usually equipped with cold runner systems to reduce waste).

The exhaust requirements for molds are extremely high, as LSR has excellent fluidity and is prone to trapping air.

Raw material control:

LSR is a two-component material that requires precise mixing and metering ratios to ensure complete curing and stable performance.

Main application areas

This process is almost ubiquitous in all industries that require high reliability connections:

Automotive industry: sensor connectors, ECU control unit connectors, high-voltage connectors for new energy vehicle battery packs/motors, on-board camera connectors, etc.

Consumer electronics: smartwatch charging interface, underwater camera connector, drone outdoor connector.

Medical equipment: medical monitoring equipment cables, wearable medical sensor connectors (silicone has biocompatibility).

Industrial equipment: connectors for outdoor communication base stations, industrial robots, and automation control equipment.

Home appliances: high-end washing machine electrical control board connectors, water heater heating pipe connectors, etc.