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PCB thermal conductivity – method to improve PCB performance

PCB-thermal-conductivity---method-to-improve-PCB-performance

What is effective PCB thermal conductivity?

Understanding the thermal behavior of PCB is very important and quite challenging for experts working in the field of electronics. Due to this, it is essential to have a solid understanding of efficient thermal management throughout the planning stage of PCB design. This can be done with the help of the effective PCB thermal conductivity planning technique. The capacity or rate at which heat is transported is determined by the effective PCB thermal conductivity of a material.

PCBs transfer the heat that is created by their surroundings to the components of the board after they have absorbed heat from their surroundings. The effective PCB thermal conductivity of PCBs is dependent on the efficiency through which heat is transported to the components, which is denoted by the symbol Keff.

Experts are able to develop more accurate models with the assistance of thermal analysis and modeling. During the process of designing a PCB, these models and assumptions play a significant part in determining the effective PCB thermal conductivity of the circuit.

The importance of PCB conductivity

Effective PCB thermal conductivity has a significant functionality impact on both the performance and longevity of PCBs. PCB always produce heat because of all of their constituent parts. When the heat is generated by the components, it is necessary to remove the heat from the PCB. That is why engineers use a variety of techniques to remove the high voltage(knowing about high voltage PCB) signal or heat and improve the thermal conductivity of PCBs. During this procedure, a variety of different factors play a role, each of which contributes to the PCB’s high performance and long-lasting quality. These elements include traces, vias, heatsinks, fans, and so on.

Functional deterioration

There are conditions or temperatures at which material begins to break down. When PCB is exposed to such high temperatures, their components began to lose their shape. As a result of this, PCB functionality is highly affected. Because of this, the effective heat conductivity of PCBs is of the utmost significance.

Protect PCB from fire

An environment with a high temperature can have a significant impact on electronic equipment and components, and when this occurs, the electronic gadgets themselves can sometimes spark a fire. Engineers always prefer to integrate efficient PCB thermal conductivity technologies in order to keep the temperature on the PCB at a regular level.

Protect-PCB-from-fire

Delamination control

PCB laminate is a technique that is carried out by engineers during the fabrication design phase. During this process, stackup layers are brought together to form a single structure. After the process has been finished, the structure of the PCB may be susceptible to the problem of functional deterioration. Because of this, engineers and other experts give a high priority to selecting the appropriate material throughout the lamination process.

Factors affecting the effective PCB thermal conductivity

In the process of fabricating printed circuit boards (PCBs), a variety of materials are required, and each material on a PCB has its own unique ability to transfer heat. Changes in the heat conductance of PCBs are observed by specialists or trained experts with the aid of a process known as PCB thermal conductivity.

To determine or have a better understanding of how well PCBs transfer heat, professionals and industry experts conduct a number of trials and investigations. The effective PCB thermal conductivity is determined by specialists based on a variety of different factors.

Size of the component

In printed circuit board construction, the size of the components is a crucial factor. As the size of the components decreases, their ability to function and their capacity to release heat also change. For instance, a MOSFET heat pad paired with a SOT-23 package takes up much less area than a TO-220 package. Because of this, the components and the sizes of those components have a significant impact on how efficiently they transfer heat.

Inside layers of copper

Due to its significant impact on heat loss, the inside copper layers of a PCB can also significantly impact its effective thermal conductivity. If a PCB contains numerous inner layers, then the rate at which heat is transferred will be reduced. The rate of PCB thermal conductivity varies from material to material due to these differences. 

FR-4 has a thermal conductivity value of 0.25 m-K, while copper has a value of 355 W/m-K.
It is extremely beneficial for effective PCB thermal conductivity to have a good conductor and fewer inner copper layers in PCBs.

Thermal vias

In order to effectively remove heat from the component, PCB thermal conductivity must be effective. Thermal vias are a specialized kind of hole that can be used to remove heat from a component or to minimize the amount of heat that it generates. This method is quite effective because it creates a greater number of holes through which the heat or steam can escape. Therefore, we are able to claim that the functionality of the PCB will rise if it contains a greater number of thermal vias. This is because more thermal vias equal more functionality.
PCB-thermal-conductivity-must-be-effective

Trace geometries

Copper traces are used in printed circuit boards (PCBs) to create electrical paths that help to connect two points. It is ideal for effective PCB thermal conductivity if the copper traces are of good grade and run along from one end to the other for a long period of time. If the taces were discontinued in PCB, this would have a significant impact on the value of PCB.

How to test the thermal conductivity of FR4 PCB dielectric material?

The samples of an FR4-type PCB dielectric material need to be obtained first for the testing, and then the PCB thermal conductivity needs to be measured utilizing a technique known as C-Therm Modified Transient Plane Source (MTPS). Experts and other trained professionals make use of this method when conducting advanced levels of testing.

The MTPS method makes use of a unique guard ring technology, which creates a unidirectional flow of heat and, as a consequence, enables measurement that is accurate and exact for thermal conductivity. The direct measurement of the PCB thermal conductivity anisotropy is the method that most experts and researchers recommend using since it produces more accurate results. Positioning the sensor over the various surfaces of material provides straight forward analysis of anisotropic materials.

Professionals must first collect data for three different samples before they can implement the Through-plane PCB thermal conductivity method. In order to acquire more accurate results, these samples are obtained using three separate experiments consisting of fifteen measurements each. The through-plane PCB thermal conductivity is determined by taking the average of the three samples and having experts create a report on their findings.

In each test, highly trained and experienced engineers professionally measure the relative standard deviation, which is found to be less than one percent for each of the three samples. The relative standard error that has been reported is 0.7%.

The next step that the professional follows is to prepare an in-plane report of the PCB thermal conductivity of the bulk material, which is followed by three separate tests, each of which consists of five measurements. In-plane PCB thermal conductivity is measured using three different methods, and the relative standard deviation was determined to be 0.6%.

How to estimate thermal conductivity of a PCB?

During the manufacturing of printed circuit boards (PCBs), it is extremely important that every material have a high heat conductivity. PCB thermal conductivity measures how well heat is transferred between PCB components, such as heat moving between hot and cool regions on a PCB. 

Datasheets of various materials are a resource that is utilized by professionals. The datasheets of the materials provide comprehensive information on how well the substrate transfers heat. After obtaining an understanding of the stackup and determining the amount of copper used in the layout, the next step is to calculate the substrate’s rate of heat transfer.

To directly compute this, professionals make use of a variety of methods and approaches. However, the strategy that uses a weighted average is the most effective method. The method of averaging techniques provides information regarding the amount of copper and substrate that is used in PCBs. The effective PCB thermal conductivity is calculated by engineers using an average volume-weighted procedure of PCB material parameters.

Factors that affect the heat transfer rate of PCBs can also impact the thermal resistance of the boards. The effective thermal conductivity of an electronic component can be determined by its traces, stackup materials, copper layers, vias, and thermal pad. The following equation is useful for determining both the direction of thickness and the resistance of the material.
R = T/A.keff
T = board thickness
A = board area

Calculating the board cross-sectional area is helpful in calculating the thermal resistance of a PCB and also in determining the surface direction along the sectional area of the board. Following this approach, you will be able to determine the temperature distribution rate of PCBs. The rate of heat transfer can be calculated by taking the temperature gradient and dividing it by the thermal resistance.

Copper thermal pads and reliefs are a crucial part of the heat removal process. When heat is transferred into a heat sink, it is possible to remove it from the system by allowing air to circulate across the surface of the heat sink. During the process of PCB design, it is possible to reduce the number of active cooling measures necessary as well as their size by selecting an appropriate stack up design and material for the substrate.

●The professional should determine the most effective technique of cooling, whether thermal paste or a thermal pad should be used to bond with a heat sink.

●The amount of heat produced by an active component is directly proportional to that component’s rate of speed. As a result, engineers have come to the conclusion that PCBs need some additional cooling components.

●The layer stack also plays an essential part in the heat conductivity of the effective PCB. Because of this, it’s crucial to pay a lot of attention to assembling the layer stack in the correct order.

How to improve PCB thermal conductivity?

Professionals apply the below-mentioned techniques to improve PCB thermal conductivity

   ★ Heat sinks
All of the components that are utilized in the process of PCB design generate heat. It is an absolute necessity to add some sort of heat or thermal energy dissipation mechanism into the PCB design. PCBs are currently contributing to an improvement in thermal conductivity. Heat sinks are designed to dissipate heat in a way that is safe for printed circuit boards (PCBs).

   ★ Thermal resistance components
Improving the PCB thermal conductivity can be done in a variety of methods, one of the most effective and best of which is by selecting components or materials that are heat-resistant. When it comes to maximizing the thermal conductivity of PCBs, industry experts recommend using thick copper panels. These components are capable of handling larger levels of current, and they can also resist higher temperatures for longer periods of time.

   ★ Fans
The majority of modern electronic devices remove heat with the help of fans, and the performance of these fans is important to improving PCB thermal conductivity. As a result of this, fans help to improve the PCB thermal conductivity, which helps prevent overheating.

   ★ Increase layers of plates
Most engineers like thicker PCB panels for PCB thermal conductivity because they increase the PCB thermal conductivity . The reason is that these plates need a lot of electricity to heat up, which lowers the possibility of warping and disruption.

    ★ Keeping a proper gap between components
On a printed circuit board (PCB), determining the component spacing is strongly recommended. Crosstalk is possible and can occur if the components on the PCB are placed too close to one another. During cross-talk, separate components could start interacting with each other in ways that are not desirable. Because of this, the circuit’s trace resistance goes up, which causes it to generate more heat. Therefore, engineers pay additional attention to the space between components in order to improve PCB thermal conductivity.

     ★ Applying Laminates
Utilizing laminates is a useful strategy for increasing the thermal resistance of PCBs. The use of these laminations helps to protect the PCB from being damaged by high temperatures. High-temperature PCB laminates offer the components of the PCB protection from heat, helping to improve PCB thermal conductivity and durability.

     ★ RTI and MOT utilization to the fullest potential
RTI stands for “relative thermal index,” which is an indicator of the highest temperature of any material can withstand or handle without experiencing a decrease in its performance. RTI is measured in degrees Celsius.
A maximum operating temperature (MOT) is the highest temperature that a given circuit board configuration is able to sustain without experiencing any changes to its properties. MOT refers to the maximum temperature that a device can operate at.

These two terms have a major impact during the construction process (PCBs) and in the process of improving PCB thermal conductivity. Because of this, engineers constantly make sure to keep these two measures in mind while trying to improve the heat resistance and increase the durability of PCBs.

Pcb-thermal-conducticity

Conclusion

By utilizing the strategies of effective thermal conductivity, engineers have discovered solutions to PCBs’ complex difficulties. Selecting the best material for PCBs is the ideal strategy, according to the majority of specialists. High thermal conductivity materials may efficiently remove heat from the board and maintain the board’s normal temperature. The primary problem arises when there are no appropriate means of removing heat before the PCB degradation process begins. The functionality of PCBs is greatly influenced by PCB heat conductivity, which is the main cause.

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