نقل قول

فهرست مطالب

Phase Change Materials for PCB Heat Dissipation

Nowadays, electronic devices are capable of performing very complex calculations just within the size of their components. As a result, during operation, printed circuit boards (PCBs) generally have high thermal loads. One of the main reasons for this is overheating, which affects the performance, reduces the life span, and causes unexpected failures of the device. Therefore, مدیریت حرارتی PCB has become a key factor limiting system reliability, performance, and miniaturization.

Traditional thermal interface materials (such as thermal grease and silicone pads) are increasingly showing limitations in handling instantaneous high heat loads, long-term reliability, and the need for ultra-low interface thermal resistance. Phase change materials, as a thermal management solution based on physical phase change mechanisms, have established an important position in the field of high-end PCB heat dissipation due to their unique thermophysical properties.

The article discusses phase change materials (PCMs) as a superior-level thermal management solution for PCBs. It explains their working principle, integration, capacity for high heat loads, and also recent trends and areas where they are becoming common in next-generation electronics.

مواد تغییر فاز دهنده

What are Phase Change Materials for PCB Heat Dissipation

Phase change materials are developed to capture large amounts of heat energy in the phase transition from solid to liquid and then release this stored heat in the solidification process. The phase transition temperature typically falls within the operating range of electronic devices; therefore, they may be thermally coupled to such devices. 

When one device rapidly heats up, the phase change material melts, absorbing the heat without allowing significant increases in temperature. Upon cooling, the phase change material solidifies and releases its heat over time. The above-described heat absorption/solidification cycle acts as a thermal barrier, protecting اجزای حساس from rapid temperature fluctuations, while maintaining stable operation of the overall system.

Thermophysical Mechanism of Phase Change Materials (PCMs)

Phase change materials (PCMs) used in thermal management of the printed circuit boards (PCBs) are mostly based on thesolid-to-liquid phase change at a set temperature. This involves two major processes of thermophysics:

  1. Latent Heat Absorption: When the PCM reaches the phase change temperature, the substance undergoes a transition from the solid to the liquid/paste state. This is an isothermal process where the latent heat is absorbed by the substance in tens to hundreds of joules per gram, and the temperature of the substance remains relatively constant. Therefore, the substance acts as a thermal buffer to reduce the peak power of the electronics during the transition.
  2. Interface Wetting and Filling: Above the phase change temperature, the fluidity of PCM is significantly enhanced and is able to wet and fill microscopic voids and flatness imperfections present in the interfaces of heat-generating devices like chips and heat sinks like heat pipes and housings. It allows maximum air displacement because air has lower thermal conductivity of around 0.026 W/m.K, thereby significantly reducing contact thermal resistance.

 

Together, the two methods make it possible for PCMs to simultaneously handle efficient steady-state conduction and transient thermal-shock situations. In practical implementations, the phase-change temperature in a PCM is set up marginally higher than the nominal operating temperature of the device being protected in order for the device to be in a thermally conductive post-transition mode when working in its normal environment.

Main Material Systems and Product Forms in Phase Change Material

Early phase change materials, such as paraffin waxes, were preferred for their heat storage capabilities; however, early PCMs exhibited a very poor thermal conductivity.

The most recent advancements in phase change materials include enhancing early phase change materials with high-conductivity fillers (graphite flake, CNTs, metal oxides, and polymer composites) as well as developing nano-enhanced phase change materials, which exhibit faster thermal conduction characteristics and increased response times. 

Researchers are also developing the thermally conductive yet electrically non-conductive PCMl configurations so that they will be able to coexist with sensitive PCBs. The development of these new technologies allows phase change materials to not only store heat but also aid in providing a more uniform temperature distribution across the PCB.

1. Paraffin-Based Composite Phase Change Materials

This category is the dominant commercial system. Refined paraffin is chosen as the phase change material, and the thermal conductivity is increased by adding fillers that possess a large thermal conductivity value. Some of these materials include alumina, boron nitride, graphite sheets, and carbon fibers. Polymers or microporous supporting structures can be combined to retain shape stability when it is in a liquid state. Its thermal conductivity varies between 1.5 to 8.0 W/mK, while its phase-change temperature can be adjusted depending on the carbon chain length of paraffin. Its range varies between 40°C to 80°C.

2. Metal-Based Low-Melting-Point Alloys

Typical alloys of gallium, indium, tin, and other related elements are either liquid or near-liquid at room temperatures. The most popular use of these alloys is based on their exceptionally high intrinsic thermal conductivity (>20 W/mK). Electrically conductive, possibly corrosive to some metals, with the potential of leakage, these alloys must be encapsulated in sealed cavities or metal foil packaging. The alloys are rather costly. The applications of these alloys are limited to situations where there is high heat flux density, such as direct-contact liquid cooling applications in some military electronics and high-performance computation chips.

3. Main Product Forms

  • Phase Change thermal Pads: The most popular kind, pre-manufactured in the form of sheets, with mild adhesive properties for easier mounting and removal. These materials change phases when a force is applied to them, thus adapting to the surface.

  • Phase Change Thermal Paste: Conceptually similar to the common silicone grease, but with higher fluidity at the phase change temperature and low initial thermal resistance, but not necessarily stable in the long term.

  • Encapsulated Phase-Change Sheets: These components provide a means of encapsulating PCM, with a focus on low-melting-point alloys, inside a metallized polymer film. Such encapsulated phase-change sheets address any leakage issues associated with this component.

Integration of Phase Change Materials into PCB Design

In order to make effective use of phase change materials, they must be located in close proximity to those elements (components) generating the most heat. In Thermal Engineering, several common methods for integrating phase change materials exist:

Using Phase Change Material films or pads

These are very thin and are positioned between heat spreaders and the اجزا. These are soft compressible layers that are positioned immediately above the آی‌سی‌ها or power modules. Once the IC begins heating up, the phase change material captures all of the additional heat generated by the IC prior to reaching the heat spreader; thus, stabilizing temperatures across the IC during rapid changes in temperature.

Micro-encapsulated Phase Change Materials on the PCB Substrate

Using this technique, PCM droplets are encapsulated in a polymer shell and then embedded within the PCB resin layers. The polymer shell provides complete leak resistance while allowing precise placement of thermal storage anywhere within the PCB stack.

Read more: PCB substrate materials

Strategic positioning of Phase Change Material cavities

Small compartmented areas containing the phase change material can be machined or molded into the PCB. These cavities are designed to function as a local thermal reservoir surrounding high-power components to provide improved temperature distribution and minimize impact on circuit routing.

Insulation using Phase Change Material interfaces in battery-powered electronic systems.

Using phase change material as an insulating interface between battery modules reduces the increase in temperature during the charge/discharge cycle and enhances the efficiency of the battery, extends the life of the energy storage system, and prevents overheating of the system.

Operational Scenarios Where Phase Change Material Offers the Highest Benefit

In the place of constant high temperature, phase change materials should be applied to processes with variable high temperature, i.e., intermittent or cyclical peaking heating. They are mainly to play the role of softening the sudden increase in temperature during brief bursts of high performance.

High-performance Processors

Temporary workload bursts are mainly experienced by the high-performance processors. The graphics processors (GPUs) and central processing units (CPUs) are often switching between low and high power levels at very short intervals. Rapid workload changes are causing phase change material to absorb the extra heat generated, thus eliminating the thermal throttling and ensuring stable performance.

Telecommunication, Power electronics, and 5G

Pulses are formed by some of the devices, such as RF amplifiers and antenna modules, which also produce heat as a result of the different transmission loads. phase change materials are used in telecommunication where the component temperature needs to be kept within a safe range, and the airflow is inadequate due to the tight casing.

High-power Charging of Battery Cells

LiBs, when subjected to high charging rates, become hot, and this heat is absorbed by phase change material layers that surround the cells. The goal is to reduce the risk of thermal runaway, enhance safety, and slow down the aging process.

High-powered LED Lighting Components

Since the LEDs are enclosed, they become very hot, ultimately causing a reduction in the lightness and color shift. In such cases, phase change materials absorb the heat for a shorter time frame to get the optical performance and elongate the life of the product.

Limitations in Cooling Aerospace Parts

Cooling by standard air is not viable during peak altitudes. During such periods, phase change materials work as a passive thermal protection in a way that sensitive elements that are vital for the mission are stored in a stable state during the high loads.

Complementary Role Alongside Traditional Cooling Solutions

The primary benefit of using phase change materials as a thermal buffer, however, is that it does not remove the heat from the device. Once the phase change material has melted completely, it loses its ability to absorb heat and therefore needs to be used in conjunction with other heat removal strategies (e.g., copper planes, vapor chamber, etc.) or airflow to dissipate the heat to the ambient environment.

نتیجه‌گیری

There has been a vital role of phase change materials in the decrement of rapid thermal changes in modern PCBs.

They are appropriate for compact and high-performance equipment because of their ability to dissipate heat under essential working conditions, as they are combined with lightweight and passive functionality.

Recent innovations in phase change material technology are making them one of the critical contributors to the upcoming thermal management in the electronic industry, even though they are most effective when used with conventional heat-dissipation methods. Their contribution will be expanded further because the needs of the industry will demand increased efficiency, higher power density, and stability of the products.

Need help managing thermal spikes in high-power PCB designs?
Talk to FS PCBA engineers about advanced PCB materials, layout strategies, and thermal optimization.

سوالات متداول

The melting point is set to the highest safe working temperature of the critical components. Thermal simulations performed by engineers help to ensure that the phase change material is activated when the heat is just about to reach the critical areas, not causing a delay in heat absorption.

Phase change materials are designed to undergo thousands of melting and solidification cycles without any deterioration and thus, in general, have the same lifetime as the electronic device. They do not require servicing or replacement when they are properly encapsulated.

Yes. The use of phase change materials can lead to the obsolescence of the active cooling systems, such as fans that draw power, by vanquishing the temperature spikes. This is a circumstantial way of cutting down on energy consumption, more so in battery-operated electronics.

The advent of soft and thin-film phase change material composites has enabled the embedding of these materials in bendable circuits and wearable systems. These flexible designs retain the thermal resistance of the device even under flexing or compressing conditions.

دریافت قیمت

وبلاگ‌های مرتبط