When semiconductor manufacturers select substrate materials for a new design, they consider data on several thermal properties that are commonly available: maximum heat capacity, thermal shock resistance, and thermal conductivity.
In this blog, we’ll walk you through what these properties mean in the context of material selection for semiconductor substrates and explain why they don’t provide enough information to pick the right material.
Click here to download a comprehensive guide on substrate material thermal evaluation.
What substrate thermal data is available now?
Heat capacity measures a material’s stability across temperature ranges. Yet, the maximum use temperature of a material really depends on how it's used. For example, a metallized substrate under compressive stress will tolerate a lower maximum temperature than one without any load. Importantly, standard tests for thermal stability typically do not involve actual loads on the samples.
The thermal shock resistance test determines how materials react to abrupt temperature changes. Materials that perform well in these tests are ideal for environments with rapid temperature fluctuations, such as in aerospace applications, which differ significantly from the gradual heat increases seen in electronic device operations.
Thermal conductivity refers to the material's ability to transfer heat efficiently. Although materials with high thermal conductivity are excellent for use as heat sinks and spreaders, they don’t prevent localized overheating, known as hot spots.
Application-base thermal resistance value on insulating substrates helps to optimize design for high performance computing applications.
Current industry standard for measuring thermal conductivity
Thermal conductivity is critical for understanding how materials transfer heat. Accurate measurement of these properties is essential for various applications, including electronics, construction, and manufacturing. Here are the most common methods of how thermal conductivity is measured during manufacturing:
ASTM C518 Heat Testing: ASTM C518 is a standard test method developed by the American Society for Testing and Materials (ASTM) for measuring the steady-state thermal transmission properties of thermal insulation.
This test involves placing a sample material between two plates at different temperatures. The heat flow through the material is measured to determine its thermal conductivity.
It is widely used for testing the thermal properties of insulation materials, construction materials, and other products requiring precise thermal management.
Laser Flash Analysis (LFA): LFA measures thermal diffusivity by subjecting a small sample to a short laser pulse. The temperature response on the opposite surface is recorded to determine thermal diffusivity.
This is a non-contact method, suitable for a wide range of materials, and provides rapid results. Commonly used in research and development for materials such as metals, ceramics, and polymers.
Guarded Hot Plate Method: Similar to ASTM C518, this method involves placing the sample between two plates. One plate is heated, and the other is kept at a constant lower temperature. The heat flow through the sample is measured.
This method provides high accuracy and is often used for materials with low thermal conductivity.
Commonly used in the insulation industry and for materials requiring precise thermal conductivity measurements.
Limitation on established test methods
The most common methods to measure thermal properties are the ASTM C518 heat testing, which quantify the heat flow through materials to determine thermal conductivity.
The GHP method is considered the gold standard for testing insulator materials, but it comes with some limitations:
❌ While we can measure the thermal conductivity of individual materials in metallized (direct copper bonding) substrates, there’s no comprehensive methods to assess the substrate’s overall thermal characteristics.
❌ There are also no established test methods for evaluating the static thermal properties of semiconductor components in mounted form.
❌ Typically, thermal tests are done during manufacturing on sample pieces crafted into a standardized geometry, not on the final product. Geometric differences and varied processing techniques (like machining or pressing) mean that the actual property values of a finished part might differ from those measured in a test sample.
❌ Thermal performance can be significantly affected by the conditions under which ceramic is used, such as under heavy compression loads.
Lowering overall production and testing costs by including thermal resistance measurement for each individual substrate in power module design.
Ask us for more tips on evaluating thermal properties in substrate materials
If you want to improve device performance and be the first to overcome thermal challenges in next-generation power devices, you need to have access to the thermal resistance (Rth) in metallized substrates.
This will change the way you design.
Click here to download a comprehensive guide on substrate material thermal evaluation.
Email us at [email protected] or call us on 1-800-292-6286 to discuss your application with our engineering team.