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A Mutual Understanding of Thermal Design
2021.01.20
Points of this article
・In addition to thermal design satisfying current requirements and the establishment of evaluation criteria, mutual understanding of thermal design is also necessary for thermal design optimization.
・Moreover, it is essential that engineers "come to grips with" thermal design.
・By improving design quality, reductions both in use of manpower and in costs are possible.
In the previous article, the need for thermal design that follows changing design trends was explained. This article explains how the thermal design of recent years will not take effect if it is not based on mutual understanding among all the engineering divisions involved in equipment design. If this prologue that precedes a detailed explanation of thermal design has been somewhat long, it is because of the need to understand not only the engineering aspects of thermal design issues in recent years, but also the closely related environment and system aspects surrounding thermal design.
A Mutual Understanding of Thermal Design
Product design involves, broadly, electronic circuit design, mounting board (PCB) design, mechanical design, and software design. Conventionally, these are each performed by specialized design engineers and sections in charge, allocating tasks appropriately; for example, an electronic circuit design engineer selects components that satisfy product specs and designs the circuit, whereas a software designer develops software to run on the hardware, a PCB design engineer designs the PCB taking into account appropriate component positioning and layout, the PCB size, and so on. And, a mechanical design engineer designs housings, structures and the like.
When considering the thermal design that is being sought in such a situation, if each design engineer does not incorporate thermal design into his own design area and share this with other designers to achieve a unified product design, it can be said that arriving at a product with an optimized thermal design will be difficult.
For example, fanless specs are studied as a way to cope with the equipment trends of miniaturization, quieter operation, and reduced costs. Where fans are present, they will probably be the responsibility of the mechanical design engineer, who normally handles matters relating to cooling in a housing; but when fans are eliminated, which design engineer will be dealing with cooling? This diagram cites examples of how different design engineers could handle thermal design.

As the reader has probably noticed on seeing the above diagram, each of the design engineers reduces heat generation within his own scope or category, or uses measures to increase heat dissipation, and these various measures are interrelated to achieve a fanless design. Often this requires communication between engineers, and without mutual understanding, the intentions of the individual engineers cannot be expected to bear fruit. Moreover, there is increased possibility that an engineer may be alerted to something he would not have been aware of working in his own area, and consequently may hit upon a more effective solution.
What Becomes Possible through Optimization of Thermal Design Based on Mutual Understanding
There is the term “design quality.” Put simply, when prototypes are fabricated according to a design and no problems arise, so that mass production begins in a short period, and no problems arise in the marketplace as well, the design is said to be a high-quality design. While not limited to thermal design, design of high quality is universally desired. Hence improvement of design quality is important, and in addition to the thermal design satisfying current requests, the establishment of evaluation criteria, and the mutual understanding with respect to thermal design that have been described up till now, it is essential that engineers “come to grips with” thermal design.
As a practical matter, shortages of manpower and cost prioritization are real problems; but enhancing design quality ultimately leads to resolution of these problems as well. Improvement of design quality can reduce the number of prototype cycles, as indicated in the diagram below. This results in significant cost reduction, and by reducing the repetition of tasks, manpower use as well as costs can be decreased.

From the next article, we will explain the fundamentals of thermal design and heat dissipation.
【Download Documents】 Thermal Design of Semiconductor Components in Electronics
Thermal design has become a new issue in the design of electronic equipment in recent years, as thermal countermeasures have been the focus of attention. Although heat has been an important consideration for some time, the requirements for electronic equipment have changed in recent years, making it necessary to review conventional thermal countermeasures. This handbook describes thermal design based on the assumption that ICs and transistors are basically used in electronic equipment.
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Electrical Circuit Design
- Soldering Techniques and Solder Types
- Seven Tools for Soldering
- Seven Techniques for Printed Circuit Board Reworking
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Basic Alternating Current (AC)
- AC Circuits: Alternating Current, Waveforms, and Formulas
- Complex Numbers in AC Circuit
- Electrical Reactance
- What is Impedance? AC Circuit Analysis and Design
- Impedance Measurement: How to Choose Methods and Improve Accuracy
- Impedance Matching: Why It Matters for Power Transfer and Signal Reflections
- Resonant Circuits: Resonant Frequency and Q Factor
- RLC Circuit: Series and Parallel, Applied circuits
- What is AC Power? Active Power, Reactive Power, Apparent Power
- Power Factor: Calculation and Efficiency Improvement
- What is PFC?
- Boundary Current Mode (BCM) PFC: Examples of Efficiency Improvement Using Diodes
- Continuous Current Mode (CCM) PFC: Examples of Efficiency Improvement Using Diode
- LED Illumination Circuits:Example of Efficiency Improvement and Noise Reduction Using MOSFETs
- PFC Circuits for Air Conditioners:Example of Efficiency Improvement Using MOSFETs and Diodes
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Basic Direct Current (DC)
- Ohm’s Law: Voltage, Current, and Resistance
- Electric Current and Voltage in DC Circuits
- Kirchhoff’s Circuit Laws
- What Is Mesh Analysis (Mesh Current Method)?
- What Is Nodal Analysis (Nodal Voltage Analysis)?
- Thevenin’s Theorem: DC Circuit Analysis
- Norton’s Theorem: Equivalent Circuit Analysis
- What Is the Superposition Theorem?
- What Is the Δ–Y Transformation (Y–Δ Transformation)?
- Voltage Divider Circuit
- Current Divider and the Current Divider Rule
Thermal design
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About Thermal Design
- Changes in Engineering Trends and Thermal Design
- A Mutual Understanding of Thermal Design
- Fundamentals of Thermal Resistance and Heat Dissipation: About Thermal Resistance
- Fundamentals of Thermal Resistance and Heat Dissipation: Heat Transmission and Heat Dissipation Paths
- Fundamentals of Thermal Resistance and Heat Dissipation : Thermal Resistance in Conduction
- Fundamentals of Thermal Resistance and Heat Dissipation : Thermal Resistance in Convection
- Fundamentals of Thermal Resistance and Heat Dissipation : Thermal Resistance in Emission
- Thermal Resistance Data: JEDEC Standards, Thermal Resistance Measurement Environments, and Circuit Boards
- Thermal Resistance Data: Actual Data Example
- Thermal Resistance Data: Definitions of Thermal Resistance, Thermal Characterization Parameters
- Thermal Resistance Data: θJA and ΨJT in Estimation of TJ: Part 1
- Thermal Resistance Data: θJA and ΨJT in Estimation of TJ: Part 2
- Surface Temperature Measurements: Methods for Fastening Thermocouples
- Surface Temperature Measurements: Thermocouple Mounting Position
- Surface Temperature Measurements: Treatment of Thermocouple Tips
- Surface Temperature Measurements: Influence of the Thermocouple
- Estimating TJ: Basic Calculation Equations
- Estimating TJ: Calculation Example Using θJA
- Estimating TJ: Calculation Example Using ΨJT
- Estimating TJ: Calculation Example Using Transient Thermal Resistance
- Estimation of Heat Dissipation Area in Surface Mounting and Points to be Noted
- Surface Temperature Measurements: Thermocouple Types
- Summary
- Collection of Important Points Relating to Thermal Design
Switching Noise
- Procedures in Noise Countermeasures
- What is EMC?
-
Dealing with Noise Using Capacitors
- Understanding the Frequency Characteristics of Capacitors, Relative to ESR and ESL
- Measures to Address Noise Using Capacitors
- Effective Use of Decoupling (Bypass) Capacitors Point 1
- Effective Use of Decoupling Capacitors Point 2
- Effective Use of Decoupling Capacitors, Other Matters to be Noted
- Effective Use of Decoupling Capacitors, Summary
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Dealing with Noise Using Inductors
- Frequency-Impedance Characteristics of Inductors and Determination of Inductor’s Resonance Frequency
- Basic Characteristics of Ferrite Beads and Inductors and Noise Countermeasures Using Them
- Dealing with Noise Using Common Mode Filters
- Points to be Noted: Crosstalk and Noise from GND Lines
- Summary of Dealing with Noise Using Inductors
- Other Noise Countermeasures
- Basics of EMC – Summary
Simulation
- Thermal Simulation of PTC Heaters
- Thermal Simulation of Linear Regulators
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Foundations of Electronic Circuit Simulation Introduction
- About SPICE
- SPICE Simulators and SPICE Models
- Types of SPICE simulation: DC Analysis, AC Analysis, Transient Analysis
- Types of SPICE simulation: Monte Carlo
- Convergence Properties and Stability of SPICE Simulations
- Types of SPICE Model
- SPICE Device Models: Diode Example–Part 1
- SPICE Device Models: Diode Example–Part 2
- SPICE Subcircuit Models: MOSFET Example―Part 1
- SPICE Subcircuit Models: MOSFET Example―Part 2
- SPICE Subcircuit Models: Models Using Mathematical Expressions
- About Thermal Models
- About Thermal Dynamic Model
- Summary
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About the ROHM Solution Simulator
- How to Access the ROHM Solution Simulator
- Trying Out the ROHM Solution Simulator (1)
- Trying Out the ROHM Solution Simulator (2)
- Starting a Simulation Circuit in the ROHM Solution Simulator
- ROHM Solution Simulator Toolbar Functions and Basic Operations
- ROHM Solution Simulator: User Interface
- Execution of Simulations
- Method for Displaying Simulation Results
- Simulation Result Display Tool: Wavebox
- Simulation Results Display Tool: Waveform Viewer
- Customization of Simulations
- Exporting Circuit Data to PartQuest™ Explorer
- Purchasing Samples for Evaluation
- Optimization of PFC Circuits
- Optimization of Inverter Circuits
- About Thermal Simulations of DC-DC Converters
- Circuit-Theory-Based Design Simulation