Silicone rubber sheet is currently one of the most widely used products in the electronics industry. It is mainly used for sensing and conducting heat, and is one of the best materials selected specifically for using gaps to transfer heat. During use, it can not only fill gaps and connect heating and cooling parts, but also effectively improve the efficiency and stability of the heat transfer system. It also uses silicone material to provide insulation, shock absorption, sealing, and protection, which can meet the needs of various small and medium-sized electronic devices with good thermal conductivity systems. It is currently a relatively traditional type of thermal filling material.

However, in actual use, different product quality problems also arise, among which the more common ones are the failure of thermal conductivity sensors and the decrease in product aging life. Among these problems, aging life is the main factor. So, what are the phenomena that affect the service life of thermal conductivity silicone sheets?

What does "aging and hardening" of thermal pads refer to?
During the use of organic silicon thermal conductive gaskets, the hardness will increase due to long-term exposure to high temperatures, which will seriously affect the effectiveness and service life of the gasket, and also cause damage to electronic and electrical equipment.

What are the hazards of later hardening of thermal pads?
Due to the fact that such thermal conductive materials are often used in precision and complex electronic and electrical products, the common hazards in the event of such problems are as follows:
1. After the gasket becomes hard, it is not only inconvenient for construction, but also reduces the adhesion, seriously increases the thermal resistance, and reduces the heat dissipation effect.
2. After construction, the gasket becomes hard, and it is easy for the gasket to crack or even powder, which shortens the lifespan of the gasket and seriously reduces the heat dissipation effect.
3. In the later stage of hardening, there may be separation between the gasket and the protected components, resulting in direct exposure of the components. This can easily cause product short circuits, thermal oxidation, rust, etc., affecting the lifespan of the components.

What factors cause later hardening?
Organic silicon thermal conductive gasket is a composite material, which is prepared by mixing an additive organic silicon elastomer that provides high elasticity and a thermal conductive filler that provides thermal conductivity. So the main influencing factors are as follows:

1. Excessive crosslinking agent (this factor is the highest and also the most prone to problems):
Generally speaking, when adding hydrogen containing silicone oil, the molar ratio of hydrogen to vinyl group should be controlled at (1.2-1.8): 1, where hydrogen containing silicone oil includes side hydrogen and end hydrogen. Many people mistakenly believe that adding a little more hydrogen to the silicone oil will increase its strength and decrease its hardness, so they will add too much hydrogen to the silicone oil. As a result, the rebound elasticity of the gel decreases, the surface viscosity decreases, and the hardness increases rapidly after aging.

2. The volatile components in hydrogen containing silicone oil are generally high, up to about 12%. Some of these volatile components are cyclic siloxane monomers (DMC), while others are hydrogen containing small molecule monomers (linear or cyclic). The characteristics of these hydrogen containing small molecules are low activity at medium and low temperatures, and slow reaction at high temperatures, resulting in increased hardness in later stages or after aging.

3. When the volatile matter in vinyl silicone oil and hydrogen containing silicone oil is high, these small molecules will escape during the aging process, which is equivalent to a decrease in the amount of system oil. This not only causes the gasket to harden, but also reduces the thermal conductivity. After volatilization, the contact interface of the gasket will dry out and the surface viscosity will decrease.

4. The powder factor is due to the different chemical additives added to the raw materials, resulting in different quality and extraction standards for each type of powder. Therefore, one of the factors that cause quality problems with silicone rubber gaskets is also included.

How to solve this problem?
Calculate the molar ratio of hydrogen to vinyl and control it at (1.2-1.8): 1. The amount of hydrogen silicone oil added should not be too high, generally below 0.9 relative to vinyl. This can ensure stable hardness and maintain product resilience.

Regarding liquid silicone rubber, please refer to our website for details: IOTA Liquid Silicone Rubber