Adhesive-capable Thermal Interface (Dispensable TIM) Materials

The dispensing TIM can be used for many types of applications: thin bond line (thermally conductive silicone grease, dispensing thermally conductive phase change material PCM) and gap filler (thermally conductive gel).
The dispensing TIM may all look the same, but their uses and requirements are different. Thermal grease and thermal gel are not interchangeable.
As with any TIM, it is important to understand whether you need a material to reduce the contact resistance between the two contact interfaces as much as possible, or whether you need something to fill the gap.
Thin Bond Line Application Requirements
• Designed to compress to the thinnest possible thickness
• Thermal resistance and thermal conductivity are indicators of performance, but more important is the thickness of the bond line
• Interfaces and grease are clamped (springs, screws, clamps, etc.)
• Maintaining mechanical stability-no outflow or pumping out
Application Requirements for Gap Filler
• Designed to provide low thermal resistance through high thermal conductivity
• Compliance with requirements to absorb changes in gap dimensions
• Mechanical stability-does not run off or pump out
Types of Materials and R & D Trends for Thin Bond Line Applications
• Thermal Grease thermal grease-early thermal grease has a low bond line thickness, thus achieving low thermal resistance, but due to the use of small molecular silicone materials as the matrix, such materials in long-term practical application will become dry and hard, silicone oil overflow and other issues. With the continuous exploration and innovation of research and development personnel in recent years, thermal conductive silicone grease with higher and higher thermal conductivity (6-8 W/m K), low thermal resistance (0.06 ℃/W), low bond line thickness (25 µm) and excellent reliability has been developed and can be stably supplied. The difficulties and trends in the development of this type of material are how to balance the four points mentioned above.
PCM thermal conductive phase change TIM-PCM has always been the strongest competitor of thermal conductive silicone grease in high-end applications. Based on PCM's convenient application operability (sheet-shaped easy-to-manual patch, coatable steel screen printing like thermal conductive silicone grease, and dispensing process construction), PCM has excellent long-term reliability and will not cause common drying and hardening problems of silicone grease in practical applications. At present, the performance of PCM in the market is also gradually improving. The highest thermal conductivity of mass-produced PCM that can be stably supplied can reach 8 W/m K, low thermal resistance (0.04 ℃/W) and low bond line thickness of 25 µm). PCM with 10 W/m K and lower thermal resistance is also being developed simultaneously by major companies. The biggest challenge of this kind of material is how to realize high thermal conductivity, low thermal resistance and higher reliability under the condition of ensuring the same thickness of low bond line.
• Silicone free non-silicon thermal grease-small molecules based on silicone oil can cause some damage to some electronic devices, so in recent years, more and more applications require non-silicon thermal grease.
Types of application materials (silicone and non-silicon) and trends for Gap Filler
Pre-cure thermal gel single-component pre-cured thermal conductivity gel, the current market single-component pre-cured insulation thermal conductivity gel thermal conductivity market has achieved the highest thermal conductivity of 12 W/m K and above. The challenge of research and development is how to balance high thermal conductivity, stable high-speed dispensing rate and long-term reliability of gel products.
Curable thermal gel single-component post-curing thermal conductivity gel. In recent years, due to the rapid development of optical communication, more and more applications require very low or even no small molecule silicone oil volatilization of thermal conductivity gap materials, so the development direction of thermal conductivity gel turns to post-curing single-component. In this way, in practical application, thermal conductivity gel undergoes crosslinking reaction to form high molecular polymer, taking into account the application requirements of high flow rate dispensing process and low volatile and low permeability oil. The technical challenge of this kind of material is how to take into account the life cycle of low temperature storage, preferably at least half a year at room temperature, and the stable dispensing rate after long-term storage. The technical direction of this kind of material uses latent catalyst, but there are few manufacturers on the market that can supply latent catalyst stably. At present, the thermal conductivity of the single-component curable thermal conductive gel that can be stably supplied on the market can reach 6-8 W/m · K.
2-component thermal gel two-component thermal conductive gel, due to the storage and application of single-component post-curing thermal conductive gel is subject to many restrictions, especially for large-scale application scenarios such as electric vehicle battery packs, in order to improve the dispensing efficiency, scientific researchers have provided two-component thermal conductive gel for the market, which can realize the initial dispensing rate 2-3 times that of single-component gel, while taking into account better long-term reliability. At present, the thermal conductivity of the two-component thermal conductive gel that can be stably supplied on the market can reach 12 W/m · K.. 14-16 W/m · K products are under active development. The technical difficulty of the two-component thermal conductive gel is how to take into account the high dispensing rate and try not to appear or reduce the probability of oil powder separation in the life cycle.