Molded sheet conductive silicone rubber | When precision molding meets conductive elastomers - the "universal substrate" for military and high-end electronic EMI sealing

1、 Molding vs Extrusion: Why do we need "sheet"?

There are two main molding processes for conductive silicone rubber products: compression molding and extrusion molding. Both have their own strengths, but their application scenarios are completely different.

Extrusion molding is suitable for large quantities of continuous sealing strips with equal cross-sections, such as regular long strip sealing requirements for cabinet door frames, panel seams, etc. Its advantages are high efficiency and low cost, but its limitations are also obvious: fixed cross-section, continuous length, and the need for splicing or secondary processing when encountering corners or irregular structures.

Compression molding is the process of placing mixed conductive silicone rubber raw materials into precision molds and completing vulcanization and shaping under high temperature and high pressure conditions. Molded sheet metal is a typical product of this process - it does not pursue "continuity", but rather "completeness". A molded sheet can be die cut into pads of any shape: circular, square, irregular, flange pads, customized irregular parts.

The core advantage of molded sheet metal can be summarized in one sentence: buy a sheet and cut it as you want. For the sealing needs of small batches, multiple varieties, and irregular structures, molded sheets provide flexibility that cannot be replaced by extrusion molding.

More importantly, compression molding has no joints. For sealing rings or irregular gaskets formed by extrusion bonding, the joint is precisely the weakest link of electromagnetic leakage - the gasket formed by die-cutting of molded sheet metal does not have this problem at all.

2、 Data Speaking: The "Hard Index" of Conductive Silicone Rubber for Molded Plates

The performance of conductive silicone rubber for molded sheet metal ultimately needs to be answered with data.

Conductivity is the core indicator for measuring whether the conductive channel of a material is unobstructed. Different filler systems correspond to different volume resistivity ranges: the volume resistivity of silver plated aluminum system can be as low as 0.008 Ω· cm, silver filled system is about 0.01 Ω· cm, and nickel plated graphite system is usually around 0.1 Ω· cm. Advanced Institute Technology can flexibly select packing systems based on customer requirements for shielding effectiveness and cost.

The shielding effectiveness determines how much electromagnetic waves a material can 'block'. At the 10GHz frequency point, the shielding effectiveness of the copper silver plating system can reach up to 120dB. Conductive rubber sheets can be made into various thicknesses of sheets, molded products, and flat liners for die-cutting. In the frequency range of 20MHz-10GHz, the overall shielding effect can reach over 90dB. The shielding effectiveness of molded conductive rubber can suppress electromagnetic interference with frequencies up to 40GHz.

The working temperature range determines the environment in which the material can work. The conductive silicone rubber of the molded sheet can be used for a long time in a wide temperature range of -55 ℃ to 160 ℃ (silicone rubber substrate). By using fluorosilicone rubber matrix, it can also withstand the erosion of fuel and solvents.

Compression permanent deformation is related to long-term sealing reliability. The optimal compression of the board is between 7% and 15%. After 100 ℃ x 70 hours of thermal aging, the compression permanent deformation of high-quality products can be controlled within 30%.

3、 Three major application battlefields: from military chassis to 5G base stations

Military and aerospace industries are the most dominant fields for molded sheet conductive silicone rubber. Conductive rubber products have been proven through practice to be widely used in military electronic equipment such as aviation, aerospace, and ships, and can replace traditional sealing rubber while completing environmental sealing and electromagnetic shielding sealing. Molded conductive rubber can be made into plates of various thicknesses, used for electromagnetic shielding and sealing of small and medium-sized military electronic chassis, cabinets, shelters, microwave waveguide systems, and other equipment. The product complies with the US military standard MIL-DTL-83528 (formerly MIL-G-83528), providing full chain support from materials to certification for military customers.

5G communication and data centers are one of the areas with the highest demand for molded sheet conductive silicone rubber. Reliable EMI shielding and environmental sealing are required at the gaps of communication cabinets, RF modules, and base station equipment. Conductive rubber is widely used in fields such as anti electromagnetic information leakage, anti electromagnetic interference, electromagnetic compatibility, and electromagnetic sealing. At the joint of the door panel of the AAU/RRU equipment chassis in the 5G base station, the molded sheet can be cut into the desired cushion shape, with a working temperature range covering -40 ℃ to 125 ℃. Excellent electromagnetic shielding effectiveness (up to 90dB or more) and environmental sealing ability effectively solve the electromagnetic compatibility problem in high-frequency signal transmission.

Automotive electronics and industrial control are the fastest-growing application directions for molded sheet conductive silicone rubber. Vehicle electronic control modules, sensors, industrial chassis, etc. have dual requirements for electromagnetic compatibility and sealing protection. The molded sheet can be cut into various shapes of gaskets for flange EMI shielding and pressure sealing. In high reliability scenarios such as medical electronics and power equipment, molded sheet metal is also widely used in areas that require both EMI shielding and sealing protection.

4、 Selection points: How to choose the right molded sheet metal?

When engineers select molded sheet conductive silicone rubber, it is recommended to start from the following dimensions:

The packing system is the first choice. The copper silver plating system provides the highest shielding efficiency (up to 120dB), suitable for military and high-end communication scenarios; The silver plated aluminum system has excellent galvanic compatibility in aluminum chassis scenarios; The nickel plated graphite system has outstanding cost-effectiveness and is suitable for commercial equipment and general industrial scenarios.

The thickness and hardness determine the installation adaptability. The thickness of the board can be customized according to customer needs. The hardness is usually adjustable between Shore A 45-85. Softer boards have better adhesion and lower closing force; Harder boards have better wear resistance and are more suitable for high-pressure scenarios.

Environmental tolerance is crucial for long-term reliability. It is necessary to evaluate the working temperature range (standard silicone rubber -55 ℃ to 160 ℃, fluorosilicone rubber can withstand fuel and solvents), chemical corrosion risk, and flame retardant level requirements.

The processing method determines the final form. The molded sheet can be further die cut into various shapes of gaskets, O-rings, and irregular seals. Advanced Institute Technology provides one-stop services from sheet metal supply to die-cutting processing.

Advanced Institute Technology provides full process technical support from material selection, sample trial production to batch delivery.

The global conductive silicone rubber market is expected to grow to $13.09 billion by 2033. Driven by the upgrading of military electronics, deployment of 5G/6G communication, growth of automotive electronics, and precision of industrial equipment, molded sheet conductive silicone rubber is becoming the preferred solution for more and more engineers to meet non-standard EMI sealing requirements due to its unique advantages of "flexible cutting, no joints, and high precision".