Thermal material characterization

TIMs - thermal interface materials - are the key component to ensure thermal performance and reliability of electronics. Every application comes with unique TIM requirements and good choices can only be made based on good data. We acquire such data.

Application-related characterization of TIMs is described in the standard ASTM D5470 and the measurement system TIMA 5 fully implements that standard. This includes precise heat flow control, thickness resolution in 1 µm range and sample compression of up to 3.4 MPa (500 PSI).

Bulk thermal properties

Characterization of TIMs, provided in different thicknesses, allows to directly determine the bulk thermal conductivity and the thermal interface resistance. This applies to most classes of TIMs, especially silicon-based pastes, pads and curing gap fillers. But with smart sample preparation and treatment, adhesives, molding compound, underfill material and similar materials are characterizable this way, too.

Effective thermal properties

The overall thermal resistance and effective thermal conductivity can be determined as function of the temperature or mechanical load (compression or tension). Also laminates or compounds are feasible samples for such analyses.

Aging investigation

The durability of TIMs is an essential material characteristic. Depending on their application, TIMs can see greatly different operation temperatures and mechanical loads. It is important to evaluate the expectable lifetime by conducting purposeful aging tests that load TIMs periodically by varying the gap width, the clamping pressure or the operating temperature. With our TIMA 5, the TIM's thermal performance can be monitored in-situ to observe the process of degradation, in particular through pump-out, dry-out and delamination, with maximum detail.

Out of the box

Beyond standards and standardized measurements, TIMs may face several challenges that need proper attention. What about tilted surfaces? Can we find out how  much faster the grease will pump out at 10% tilt? Or can we check if this metal-based TIM needs 500 or rather 5000 cycles to fully burn-in? Is it possible to quantify, how much better is the thermal contact resistance between these substrates with the aid of liquid metal?

Well, yes we can. These are mere examples, but we are not limited to prescribed procedures from international standards.

The thermal properties of liquids are relevant for coolant fluids or similar applications, where the liquid is supposed to carry out a specific task such as conducting and carrying heat away from a source. Thermal characterization of liquids, on the contrary, is not limited to such applications.

Materials like epoxy resins often serve purposes where the thermal performance is an important factor. Characterizing these materials in liquid and solid state, as well as during the curing process may provide insights on the effectiveness of filler particles, the chemical formula or the applied curing temperature profile.

Bulk thermal properties

Using the 3-omega method in our measurement system TOCS allows to easily characterize liquids, pastes, glues – viscous material in general – and to determine their bulk thermal conductivity and diffusivity at a go. These measurements can be done spatially resolved, temperature-dependent, repeatedly over a period of time and even while applying a temperature gradient through the sample.

This way, the impact of filler particle concentration can be quantified, the pace and quality of the curing at different temperatures be compared and many more fascinating correlations be explored.

Thermal characterization of solids can come with challenges. Depending on the material class, high thermal conductivities are to be determined, thin layers to be characterized or anisotropy to be considered. We have serveral methods and measurement systems at hand to cope with all of that.

Metals, semiconductors and ceramics

Characterization of metals and alloys is challenging due to considerably high thermal conductivities. Common steady-state methods are eligible for low conductivities only and alternative transient methods don't provide the thermal conductivity as result, but the thermal diffusivity only.

We developed the measurement system LaTIMA which provides qualified in-plane thermal conducitivity determination by means of steady state method. Furthermore, the same samples can be used to determine the thermal diffusivity, delivering great added value and the possibility to calculate the volumetric heat capacity.

Sintered and printed metals

Sintered silver is engaging the market of electronics as attach material and has already found a wide spectrum of applications. Still, the quality of sinter paste and the sintering process with all its dependencies greatly varies and needs proper quality assessment and characterization. Also 3D-printed metal parts become increasingly popular due to more knowledge of the physics and processes. The thermal conductivity and diffusivity are great quality indicators and can easily be measured using LaTIMA. Moreover, being an partly thermographic measurement system, inhomogeniety or hidden flaws can be detected along with the characterization.

Anisotropic substrates

Characterizing GFRP or CFRP (glass or carbon fiber-reinforced polymers) such as commonly used for circuit boards requires understanding of the targeted application. Which responsibility the substrate has to bear dictates the intensity of thermal investigations. In many cases anisotropic properties like heat spreading capabilites are to be considered and also the transient behavior is influential in terms of reliability. We provide all necessary means to characterize thermal properties with regard to their anisotropic behavior, including in-plane and through-plane thermal conductivity and thermal diffusivity.

Thin layers and laminates

Only few measurement systems allow reliable thermal testing of thin layers. Laserflash system promise much, especially with regard to a wide range of feasible material classes. Though, available systems usually fail in case of high thermal conductivities and thin layers - samples that are increasingly relevant in electronics.

Because of that, we use a high performance laser with pulse widths in nanoseconds range. Using this excitation source, determination of the diffusivity of thin to very thin layers is no problem anymore - and our offer to you.

The thermal interface resistance between two joint solid materials can occasionally range in the same order as the actual thermal resistance through the two joint materials. This interface property therefore is essential to characterize. Besides the effective overall diffusivity of the compound material laserflash analysis also offers insights about the interface resistance between the joint materials. Don't let interfaces set boundaries to you. We will assist.