Dispensable TIM materials

The dispensing TIM can be used for many types of applications: thin bond line (thermal conductive silicone grease, dispensing thermal conductive phase change material PCM) and gap filler (thermal conductive gel).
Dispensible TIMs may look the same, but their uses and requirements are different. Thermal conductive silicone grease and thermal conductive gel are not interchangeable.
Like any TIM, it is important to understand whether you need a material to minimize the contact resistance between two contact interfaces, or if 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 performance indicators, but more importantly, the thickness of the bond line
Interface and grease are clamped (springs, screws, clips, etc.)
• Maintain mechanical stability - will not flow or pump out
Application requirements for Gap Filler
Designed to provide low thermal resistance through high thermal conductivity
Meet requirements to absorb changes in gap size
Mechanical stability - will not flow out or pump out
Types of materials and research and development trends suitable for Thin Bond Line applications
Thermal Grease thermal conductive silicone grease - Early thermal conductive silicone grease had a low bond line thickness, achieving low thermal resistance. However, due to the use of small molecule organic silicon materials as the matrix, this type of material may experience problems such as drying and hardening, and silicone oil overflow in long-term practical applications. With the continuous exploration and innovation of R&D personnel in recent years, thermal conductive silicone grease with increasingly high thermal conductivity (6-8W/m · K), low thermal resistance (0.06 ℃/W), low bond line thickness (25 µ m), and excellent reliability has been developed and can be stably supplied. The research and development difficulties and trends 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 the convenient application operability of PCM (the sheet shape is easy to manually mount, the coating can be used for steel screen printing like thermal conductive silicone grease, and can also be used for dispensing process construction), it also has excellent long-term reliability. PCM will not encounter the 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 stably supply can reach 8W/m · K, with low thermal resistance (0.04 ℃/W) and a low bond line thickness of 25 µ m. Major companies are also developing PCM materials with 10W/m · K and lower thermal resistance simultaneously. The biggest challenge for this type of material is how to achieve high thermal conductivity, low thermal resistance, and higher reliability while ensuring that the thickness of the low bond line remains unchanged.
Silicon free non silicon thermal conductive silicone grease - Small molecules based on silicone oil can cause some damage to certain electronic devices, so in recent years, there has been an increasing demand for non silicon thermal conductive silicone grease.
Types (organic silicon and non silicon) and development trend of Applied Materials suitable for Gap Filler
• Pre cure thermal gel One component pre cured thermal conductive gel. At present, the thermal conductivity of one component pre cured insulating thermal conductive gel in the market has reached the highest of 12W/m · K and above. The challenge of R&D is how to give consideration to high thermal conductivity, stable high-speed dispensing rate and long-term reliability of gel products.
• Curable thermal gel single component post curing thermal conductive gel. In recent years, due to the rapid development of optical communication, more and more applications have very low requirements or even no thermal conductive gap materials volatilized by small molecular silicone oil, so the development direction of thermal conductive gel turns to post curing single component, so in practical applications, the thermal conductive gel crosslinks to form polymer, It takes into account the application requirements of high flow rate dispensing process and low volatility and low permeability oil. The technical challenge of this type of material lies in how to balance low-temperature storage with a life cycle of at least six months at room temperature and a stable dispensing rate after long-term storage. The technical direction of this type of material mostly adopts latent catalysts, but there are very few manufacturers in the market that can stably supply latent catalysts. At present, the thermal conductivity of one component curable thermal conductive gel that can be stably supplied in the market can reach 6-8W/m · K.
• 2-component thermal gel two-component thermal conductive gel, because the storage and application of single component post curing thermal conductive gel are subject to many restrictions, especially for large-scale application scenarios such as electric vehicle battery packs, in order to improve dispensing efficiency, scientific researchers have provided two-component thermal conductive gel for the market, which can achieve an initial dispensing rate of 2-3 times that of single component gel, while giving consideration to better long-term reliability. At present, the thermal conductivity of two-component thermal conductive gel that can be stably supplied in the market can reach 12W/m · K. 14-16W/m · K products are actively being developed. The technical difficulty of two-component thermal conductive gel is how to give consideration to the high spot gel rate and try not to appear or reduce the probability of oil powder separation in the life cycle.