Thermal Gap Pads vs Thermal Conductive Paste
Thermal Interface Materials (TIM) are used to conduct heat between two or more thermally manufactured components. Considering that up to 90% of the gap may exist in the contact area, the presence of TIM becomes critical.So what’s the difference between Thermal Gap Pads vs Thermal Conductive Paste?
One of the key roles of TIM is to transfer heat to the surrounding environment through thermal conduction. The ultimate goal of this process is to protect the component from adverse heat-related reactions. Through the application of TIM, heat is transferred and dispersed more efficiently, preventing damage to equipment or performance degradation that may result from overheating.
Thermal interface materials need to possess two key properties, thermal impedance and thermal conductivity. Thermal impedance is the efficiency with which a material transfers heat to the surrounding area, i.e. how efficiently it is able to induce the transfer of heat from one place to another. Thermal conductivity, on the other hand, is a material’s natural ability to transfer heat and directly affects how quickly and effectively heat is transferred.
By optimising these two key properties, thermal interface materials enable efficient heat dissipation in electronic devices, ensuring that components maintain a suitable temperature range during operation. This is essential for improving device stability, extending lifetime and ensuring consistent performance.
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Choosing between thermal gap pads and thermal paste
When choosing between thermal gap pads and thermal paste, it is vital to understand the nature and needs of the application. Materials that fill the thermal interface, such as gap pads and thermal paste, play an important role in different applications and have their own advantages and scenarios.
Thermal Gap Pads are soft and comfortable pads that reduce component stress and dampen vibration, in addition to providing excellent thermal performance. Their thermal conductivity typically ranges from 1 to 6.5 W/mK, while standard thicknesses typically range from 0.010″ to 0.200″, but can be thicker. When selecting a thermally conductive pad material, it is critical to consider the design requirements. For example, glass fibre and aluminium carriers are common choices, while shear-resistant Kapton and PEN films are also suitable for applications where there is a risk of shear.
Thermal Gap Pads
Advantages of Pads
Ease of Application: Thermally conductive pads are easier to apply than solder pastes that require specialised application equipment. They simply need to be placed on the application with relative pressure.
Ease of Manufacturing: Thermally conductive pads are used in heating elements to avoid pad bonding, making the manufacturer’s job easier. In contrast, thermally conductive pads are less likely to move out of their initial position than thermally conductive pastes.
Standardised heat dissipation capability: Compared to liquid thermal paste, thermal pads have a more standardised heat dissipation capability on the pad surface, making standardisation easier to achieve. Thermal pads respond to the temperature of the heating component by softening after application, thus filling the interface gap on the application surface.
Disadvantages of Pads
Adhesion Issues: When a thermally conductive pad adheres to a heat sink, it is usually moulded to one of the heat-generating surfaces it is in contact with. This means that if the heat sink or other nearby components move, the pad must be replaced.
Single Use: Thermal pads cannot be used multiple times and once removed, each component needs to be handled very carefully, especially if the pad adheres to other components of the application. This can add cost and complexity to the manufacturing process.
thermal conductive paste
Multiple application methods: Compared to thermal pads, thermal paste offers a similar solution, but as a liquid, it can be used in a variety of ways. Through dispensers (syringes, tubes, etc.), the paste can be applied directly to the central processing unit (CPU) or heat sink, filling even the smallest interfacial air gaps to ensure effective heat transfer and preservation.
Stability: Thermally conductive pastes do not flow and remain stable under strong vibrations. They are able to maintain stability over time.
EFFICIENCY: Since the heat transfer capacity is inversely proportional to the amount of thermal interface material used, very little thermally conductive paste is required, e.g., THERM-A-GAP GEL30 or GEL8010. this allows for a low thermal impedance at both thin gaps and thick gaps, using common heat sinks.
Low Outgassing: When products are applied near cameras or optics, it is critical to select a thermal paste that meets NASA outgassing standards. Low outgassing ensures that outgassed silicone will not condense on cameras or other optical devices.
APPLICATION TECHNICAL REQUIREMENTS: When using a thermally conductive paste, it is important to ensure that the entire surface area is covered as needed and that an adequate amount is used. Whilst less is usually better, using too little will not adequately fill any air gaps that may exist.
Liquid state can lead to mess: The liquid nature of thermally conductive pastes can lead to mess and wasted material during application. Therefore, care and precision are key to ensure that the right amount of thermal paste is applied accurately to avoid wastage.
Which is better:Thermal Gap Pads vs Thermal Conductive Paste
Can I use thermal paste instead of thermal pads?
Thermal paste or gel can be a reasonable alternative to thermal pads. Compared to thermal pads, thermal paste offers automation capabilities, lower impedance (in the case of some materials), and the ability to be more consistent on irregular surfaces. The use of thermal paste may need to be considered in the following situations:
Higher Production Demand: If your production demand exceeds 5,000 parts/year, a thermally conductive paste may be a more appropriate choice.
Complex Pattern Designs: If the part design involves complex patterns, thermal paste may be more convenient for automated applications.
Part fragility: If the part is fragile because the solder paste produces low mechanical stress, a thermally conductive paste may be more suitable.
Suppose the intent is to replace a thermal pad with a thermally conductive paste. In that case, some recommended products include Chomerics Therm-a-Gap Gel 75 (high thermal conductivity), Gel 30, or 8010 (used in automotive applications with ultra-low compression).
Are thermal pads better than thermal paste?
The choice between thermal pads and thermal paste is not a clear-cut “better” choice, but rather depends on the specific needs of the application. Thermal pads have historically been used for a wide range of applications and are particularly good at vibration suppression and space filling. Their hand-applied nature makes them potentially more challenging in terms of surface consistency.
In contrast, thermal paste offers automation capabilities, lower impedance, and the ability to provide higher consistency on irregular surfaces. As a result, thermal paste may be more appropriate where production needs are greater, part design is more complex, or part fragility is higher.
Overall, the choice depends on the requirements of the particular application, and the advantages of both thermal pads and thermal paste need to be considered together and the choice made accordingly.