Basic Knowledge of Thermal Management (2) -Background to the Need of Thermal Management-


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Basic Knowledge of Thermal Management (2) -Background to the Need of Thermal Management-

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Thermal management is an important process to ensure the characteristics, life, and safety of equipment and systems. "Basic Knowledge of Thermal Management" explains the basics for implementing the necessary thermal management in three parts, "Basic Knowledge of Heat," "Background to the Need of Thermal Management," and "Thermal Design and Management." This issue is the second part, i.e. "Background to the Need of Thermal Management."

Increased Importance of Thermal Management

Although thermal management has always been necessary, its importance has been increasing in recent years due to the downsizing and high performance of equipment and systems.
Here are some examples.
  • Reduced heat dissipation areas and paths due to the high density mounting of devices
  • Increased heat resistance due to the downsizing of components with the same performance
  • Increased heat generation due to increased processing speeds of semiconductor elements
  • Increased heat generation due to the miniaturization (increased integration) of semiconductor integrated circuits
As shown by the above, in today's electronic equipment design, thermal design has become as important as electrical design.

Impact of Heat on Components and Equipment

You can perhaps understand intuitively that components and equipment becoming hot is not preferable. Heat-related problems due to generated heat or exposure to the high temperature of nearby heating elements are shown below. Issues associated with heat can be classified into functional, mechanical, and operator-related problems.

熱が部品や機器に与える影響,热量对零件和设备的影响,Effect of heat on parts and equipment img

Functional Problems

The life of electronic components basically becomes shorter at higher operating temperatures. For example, the life of aluminum electrolytic capacitors is known to be halved if the temperature rises by 10°C. This is because the rate at which the electrolyte liquid in capacitors diffuses to the sealing rubber is accelerated by heat. This results in a significant decrease in capacitance and consequently the lack of capacitance required by the circuit, leading to a circuit malfunction.
The graph below shows an example of the relationship between the operating temperature and estimated life of aluminum electrolytic capacitors with 105°C and 2000 h values guaranteed. The graph shows that the higher the temperature, the shorter the estimated life, and as described earlier, the estimated life of aluminum electrolytic capacitors is halved by a temperature rise of 10°C.
Heat, which has an impact on component functions and reduces their life, is therefore an important factor affecting reliability.

電解液が封口ゴムを徐々に浸透する画像,电解液的图像逐渐渗入密封橡胶,Image of electrolyte gradually penetrating the sealing rubber img105°C2000時間保証品による推定寿命のグラフ,带有105°C 2000小时保修的预计寿命图,Graph of estimated life with 105 ° C 2000 hours warranty img

Mechanical Problems

Thermal stress is generated by temperature rises on structures that consist of multiple elements, such as electronic components, modules, and printed circuit boards mounted with these. This is because these elements have different thermal expansion coefficients. Simply put, thermal stress is large when elements with significantly different thermal expansion coefficients are combined. The repetition of a normal temperature (or low temperature) state and a high temperature state, i.e., repetition of thermal stress, causes thermal fatigue leading to mechanical degradation and destruction. Heat, which becomes mechanical stress, induces component degradation and failure, thereby having an impact on reliability.

熱が機械的ストレスとなり部品の劣化や故障を誘発する画像,热量引起机械应力并导致零件劣化和故障的图像,Image that heat causes mechanical stress and induces deterioration and failure of parts img

Operator-related Problems

A person can suffer from burns if he/she touches a high temperature object. In recent years, low temperature burns have also become a problem. Low temperature burns often progress without being recognized due to lack of pain and therefore tend to become more severe than ordinary burns.

Some reported cases involve familiar items such as a "kotatsu" (a table with a built-in electric heater underneath and covered with a quilt), hot-water bottles, pocket warmers, as well as mobile information equipment such as smartphones. In one case, keeping a smartphone in a pocket for hours resulted in a low temperature burn due to the heat generated by the smartphone. It has also been confirmed that a temperature of 44°C, which is a fairly warm temperature for a hot springs, can cause low temperature burns if it acts on the skin for six or more hours.

Relationship between temperatures and time that cause burns
やけどの原因となる温度と時間の関係を表したグラフ,导致烫伤的温度与时间的关系,A graph showing the relationship between temperature and time that causes burns img

As is clear from the above, the heat of equipment touched or carried by people gives rise to safety problems concerning the human body. Heat generation can also cause ignition, leading to a fire.

Impact of Heat on Society and Company Activities

The impact of the above-mentioned functional, mechanical, and operator-related problems due to heat is not limited to components and products. For example, home appliances can cause burns to people or fires that lead to the loss of homes, assets, and even human lives.
Products sold in large quantities causing problems can also lead to social issues. The company that sold the products will naturally suffer from a poorer image, incur substantial costs for recalls, compensation, etc., be legally penalized depending on the problems, and bear great social responsibilities.


In recent years, the temperature of final products tends to increase due to the downsizing (high-density components) and high performance of equipment and systems. Heat generation can cause problems to products and systems, thereby possibly having an impact on companies and society. Thermal management is therefore very important not only for ensuring the performance and reliability of products but also for society and company activities.

The next issue will explain thermal design and management.

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