Phase Change Material
Remains solid at room temperature for easy placement, then softens as temperature rises to fill microscopic gaps. Its ultra-thin interface reduces thermal resistance while supporting cooling performance and long-term reliability.
Phase Change Material Selection Guide
Select a phase change material according to its phase change temperature, operating temperature, initial thickness, bond line thickness, thermal resistance, assembly pressure, insulation requirements and product form. The material must soften sufficiently and wet the contact surfaces during operation to reduce interface thermal resistance effectively.
Check the Phase Change Temperature
The phase change temperature determines when the material begins to soften from its solid state. Select it according to the component’s actual operating temperature after startup.
- Component startup and steady-state temperatures
- Heat sink surface temperature
- Phase Change Temperature
- Low-temperature startup time
- Ability to complete the first thermal cycle
If the interface temperature remains below the phase change temperature for an extended period, the material may not soften sufficiently or wet the contact surfaces. Actual thermal resistance may therefore be higher than expected.
Choose the Initial Material Thickness
The initial thickness must accommodate surface flatness, assembly tolerances and local height differences without adding unnecessary distance to the heat-transfer path.
- Chip and heat sink flatness
- Initial contact gap
- Mechanical assembly tolerances
- Available sheet thicknesses
- Actual compressed condition after installation
Phase change materials mainly fill microscopic surface roughness and very small gaps. They are not intended to replace thick thermal gap pads where significant height differences exist. Select the material according to surface flatness, mechanical tolerances and available thicknesses.
Compare BLT and Thermal Resistance
After reaching its phase change temperature under pressure, the material forms an ultra-thin bond line thickness (BLT). A thinner BLT generally shortens the heat-transfer path.
- Minimum BLT
- Actual clamping pressure
- Contact area after compression
- Thermal resistance at different thicknesses
- Interface stability after thermal cycling
Initial sheet thickness is not the same as the BLT after phase change and compression. Compare the final BLT and thermal resistance of different products at the specified temperature and pressure.
Evaluate Thermal Conductivity and Actual Thermal Resistance
Thermal conductivity indicates the heat-transfer capability of the material itself. Actual cooling performance also depends on BLT, installation pressure, surface roughness and wetting.
- Thermal conductivity
- Thermal resistance at a specified pressure
- Component power and heat flux
- Contact area
- Steady-state and peak temperatures
Do not compare thermal conductivity alone. For phase change materials, the ability to form a thin, complete contact interface is often more critical than a single conductivity value in the datasheet.
Confirm Assembly Pressure
Appropriate pressure helps the softened material displace air, wet the contact surfaces and form a stable BLT.
- Heat sink fastening method
- Screw locations and pressure uniformity
- Allowable chip pressure
- Risk of PCB bending
- Material displacement after phase change
Insufficient pressure may cause poor local contact, while excessive pressure may increase mechanical stress on the chip, solder joints and PCB. Validate pressure and thermal resistance using the actual assembly.
Choose the Material Form and Processing Method
Phase change materials are available in rolls, sheets and custom die-cut parts for manual installation and automated mass production.
- Rolls or sheets
- Custom die-cut dimensions
- Holes and custom profiles
- Release-liner design
- Manual or automated placement
- Positioning accuracy and handling method
For small, narrow or multi-hole shapes, confirm die-cutting tolerances, liner release and automated handling stability to prevent stretching, damage or misalignment during placement.
Check Electrical Insulation
Electrical properties may be measured at a specific material thickness and under specific test conditions. Do not apply them directly to every thickness. Confirm the actual operating voltage, application thickness and safety requirements before final selection.
- Operating voltage
- Surface resistivity
- Volume resistivity
- Actual material thickness
- Distance between the metal heat sink and component
Electrical specifications obtained at a specific test thickness cannot be applied directly to every sheet thickness. The electrical data for PCM900 on the website is specified at a test thickness of 1.0 mm. Confirm performance at the actual thickness and against applicable safety requirements.
Assess Environment and Reliability
The material must maintain interface contact and thermal performance after thermal cycling and prolonged operation while reducing the risk of pump-out and dry-out.
- Long-term operating temperature
- Thermal cycling
- Continuous clamping pressure
- Vibration and shock
- Pump-out risk
- Dry-out risk
- Change in thermal resistance after aging
“Pump-out resistant” does not mean the material will never move under every pressure, temperature or mechanical design. Validate it through prolonged operation and thermal cycling in the actual assembly.
Confirm Material Compatibility
For optical components, precision contacts and contamination-sensitive equipment, further confirm the resin system, volatile substances and compatibility with surrounding materials.
- Silicone or non-silicone
- Risk of optical and contact contamination
- Vacuum or sealed environments
- Compatibility with metals and plastics
- Cleanliness and outgassing requirements
Non-silicone does not automatically mean low outgassing or compliance with ASTM E595. For vacuum, optical or aerospace applications, confirm the test data for the specific product.
Validate Samples in the Device
Datasheets support initial screening. Final selection requires validation under the actual power, pressure, thickness and thermal-cycling conditions.
- Actual component temperature rise
- Thermal resistance after the first phase change
- BLT after compression
- Hot spots and temperature distribution
- Material displacement or overflow
- Interface condition after disassembly
- Long-term operating stability
Testing should include cold startup, the first temperature-induced phase change and subsequent thermal cycling. Testing only the material’s best condition after heating may overlook cooling performance during equipment startup.
Quick Selection Guide
| Need | Selection Direction |
|---|---|
| Operating temperature consistently reaches the phase change point | Select a product with a phase change temperature suited to the equipment |
| Flat contact surfaces with a very small gap | Suitable for phase change materials |
| Significant height differences or large gaps | Evaluate thermal gap pads or liquid gap fillers |
| Ultra-thin interface and low thermal resistance required | Compare post-phase-change BLT and thermal resistance at the specified pressure |
| Limited component pressure tolerance | Select a product that wets fully under lower pressure |
| Clean, fast assembly required | Select sheets or custom die-cut parts |
| High-volume automated placement required | Select rolls and structures suitable for automated handling |
| Near optical components or precision contacts | Evaluate non-silicone and low-outgassing test data |
| Electrical isolation required | Confirm insulation specifications at the actual thickness |
| Repeated long-term thermal cycling | Evaluate pump-out, dry-out and thermal resistance after aging |
Choose the Right Phase Change Material
A solid sheet at room temperature for easy cutting, positioning and automated placement. At the phase change temperature, it softens and wets the contact surfaces, forming an ultra-thin BLT that fills microscopic gaps and reduces interface thermal resistance and long-term pump-out and dry-out risks.
Low Interface Thermal Resistance
Forms an ultra-thin BLT after phase change to shorten the heat-transfer path.
Microscopic Gap Filling
Softens and wets the surfaces to fill fine irregularities and air gaps.
Easy Processing
Available in silicone and non-silicone formulations.
Long-Term Reliability
Reduces the effects of pump-out and dry-out on cooling performance.
electrical insulation
Combines efficient heat transfer with isolation between components and metal heat sinks.
AI Servers
high-performance computing
networking equipment
gaming consoles
Power modules
automotive electronics
Phase Change Material Installation
Clean the surfaces
Clean the component and heat-sink surfaces.
Remove the bottom liner
Peel off the first release liner.
Align and place
Position the pad at the installation site.
Remove the top liner
Peel off the upper release liner.
Apply Even Pressure
Install the heat sink and apply pressure evenly.
Feature Overview
Non-Silicone
Reduce Siloxane Outgassing and Contact Contamination
Evaluate material outgassing, condensable substances and water-vapor regain to reduce the risk of contaminating lenses, sensors and precision components in vacuum or sealed environments.
Low Interface Thermal Resistance
Ultra-Thin BLT Shortens the Heat-Transfer Path
After softening, the material fills microscopic surface irregularities, removes air gaps and forms an ultra-thin interface to improve heat transfer from the heat source to the heat sink.
Pump-Out Resistance
Maintains Interface Stability After Thermal Cycling
A stable phase change base material reduces the risk of gradual pump-out, displacement and increased thermal resistance caused by prolonged thermal cycling and pressure changes.
Dry-Out Resistance
Reduces Dry-Out During Prolonged Operation
The material maintains the required interface wetting and thermal performance after repeated temperature cycling and prolonged use, improving long-term cooling reliability.
Electrical Insulation
Heat Transfer with Electrical Isolation
High volume resistivity and dielectric breakdown voltage provide electrical isolation between components and metal heat sinks, suiting power devices and high-voltage electronic modules.
Automated Assembly
Solid Sheets Simplify High-Volume Placement
Remains solid at room temperature and requires no dispensing equipment. It can be supplied in rolls, sheets and custom die-cut parts for clean, fast, automated mass production.
Phase Change Material FAQs
How Do Phase Change Materials Differ from Thermal Grease?
Phase change materials are solid sheets at room temperature and support direct cutting, placement and automated assembly. They soften and wet the interface only after heating. Thermal grease flows at room temperature and fills gaps effectively, but requires dispensing equipment and volume control, with greater attention to pump-out, overflow and process cleanliness.
How Do Phase Change Materials Differ from Thermal Gap Pads?
Phase change materials suit flat surfaces and very small gaps, forming an ultra-thin BLT after phase change for low interface thermal resistance. Thermal gap pads fill larger height differences and mechanical tolerances while providing cushioning and compressibility.
Can the Material Conduct Heat Below Its Phase Change Temperature?
The material still conducts heat, but below its phase change temperature it may not soften sufficiently, wet the surfaces or eliminate microscopic gaps. Actual interface thermal resistance may therefore be higher than after a complete phase change.
How Should Phase Change Material Thickness Be Selected?
Select thickness according to contact-surface flatness, roughness, assembly tolerances and required BLT. The material must provide complete contact but should not be used to fill significant gaps. Available thicknesses and forms vary by product.
What Is the Difference Between Initial Thickness and BLT?
Initial thickness is the sheet thickness before installation. BLT is the final interface thickness between the heat source and heat sink after phase change and compression. Actual BLT is a key factor when evaluating thermal resistance.