Analysis of Micro-volume Liquid Silicone Overmolding Process Technology

I. Overview of Micro-LSR Overmolding Process

Micro-LSR overmolding is a high-end manufacturing process combining liquid silicone rubber (LSR) with precision injection molding technology, suitable for the production of tiny, complex, or high-precision parts. This process involves injecting a trace amount of liquid silicone rubber (typically only a few milligrams to a few grams) into a mold, bonding it with plastic, metal, or other substrates to form a monolithic overmolded structure. Its core lies in achieving high-precision molding through precise temperature control, mold design, and automated equipment, while retaining the excellent properties of LSR, such as temperature resistance (-50℃ to 200℃), biocompatibility, and chemical stability.

[Image of Micro-LSR overmolding process]

II. Advantages and Key Characteristics of Micro-LSR Overmolding Technology

Ultra-High Precision and Complex Molding

Micro-injection molding can achieve micron-level tolerances, making it particularly suitable for size-sensitive products such as micro-sensors and medical catheters. For example, the thickness of the waterproof sealing ring for a mobile phone SIM card tray can be controlled within 0.2mm, with a burr-free surface.

Material Performance and Environmental Friendliness

LSR is plasticizer-free and meets medical-grade (FDA) and food contact standards (LFGB). Its curing process takes only seconds to minutes, and its combustion products are non-toxic (only CO₂ and water vapor are produced), meeting the safety requirements of the automotive and aerospace industries.

Automation and High-Efficiency Production

Closed-loop controlled injection molding equipment enables fully automated production. A high-speed, high-precision vision inspection system is installed on the production line to monitor the appearance, dimensions, and position of the overmolded products in real time. It can automatically identify product defects such as insufficient glue, bubbles, and flash, and automatically reject unqualified products.

Multi-Material Bonding Capability

Through two-stage injection molding technology, LSR can be directly bonded to substrates such as PC, ABS, and metal without the need for glue or mechanical fixation. For example, the metal pins and silicone sealing layer of automotive electronic connectors can be molded in one step, avoiding the risk of delamination associated with traditional processes.

III. Typical Applications of Micro-Liquid Silicone Overmolding

Automotive Industry: High-Reliability Sealing Components

Headlight Sealing Rings: Traditional rubber is prone to aging, leading to water ingress into headlights. LSR overmolding creates a seamless seal at the edge of the PC headlight cover, withstanding extreme temperature differences from -40℃ to 150℃, extending its lifespan to over 10 years.

Electronic Sensor Housings: A 0.5mm thick LSR layer is applied to the surface of an aluminum alloy housing, achieving waterproof and dustproof (IP68) protection and resisting oil corrosion from the engine compartment.

Consumer Electronics: Miniature Waterproof Components

Type-C Interface Waterproof Rings: LSR overmolding ensures the interface remains leak-free for 30 minutes in 1 meter of water, with a insertion/removal life exceeding 10,000 cycles, widely used in high-end mobile phones and wearable devices.

Micro-liquid silicone overmolding, with its precision, safety, and versatility, is becoming one of the core technologies in high-end manufacturing. Donghao Plastics, with its rich experience and advanced technology, has successfully overcome some technical challenges, achieving high-level manufacturing of micro-liquid silicone overmolding products. In the future, Donghao Plastics will continue to dedicate itself to technological innovation, further improve production efficiency and product quality, and provide customers with better solutions.