Flexible PCB Thermal Isolation for High-Speed Electric Devices

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Solution Overview

Problem

The challenge is to design an electric device with both high heat generation and low heat generation electric elements on a printed circuit board without exceeding the low operational temperature limits of the latter, while maintaining compact dimensions and enabling high-speed communication between them without impedance mismatch.

Innovation Solution

The solution involves a substrate with rigid and flexible portions, where the high heat generation element is on one rigid portion and low heat generation elements are on separate rigid portions connected by a flexible portion with wiring for thermal isolation and high-speed communication.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the dimensions of the printed circuit board are minimized, then the size of the entire electric device is reduced, but the operation specifications of small heat generation electric elements may not be satisfied due to heat from large heat generation elements

Engineering Contradiction:

Improvedevice sizeVSAvoidoperation temperature of small heat generation elements

Core Design Contradiction:

Volume of moving objectVSTemperature

Solution Approach 1:

The printed circuit board is divided into a first board and a second board that are independently formed and then connected. The large heat generation element is mounted on the first board while small heat generation elements are mounted on the second board, physically separating heat sources to prevent thermal interference while maintaining compact overall dimensions.

Inventive Principle:

Principle #1Segmentation

2Temperature

If a cooling fan is formed on the casing to radiate heat from large heat generation elements, then heat dissipation is improved, but operation noise increases

Engineering Contradiction:

Improveheat dissipationVSAvoidoperation noise

Core Design Contradiction:

TemperatureVSObject-generated harmful factors

Solution Approach 1:

The cooling fan is extracted from the casing and relocated to the rear surface of the printed circuit board. This allows the fan to be positioned closer to the heat generation elements for more efficient heat dissipation while reducing noise impact within the device housing, as the fan operates outside the main device volume.

Inventive Principle:

Principle #2Taking out (Extraction)

3Temperature

If the printed circuit board is divided into two independent boards to isolate heat, then heat affecting small elements is prevented, but impedance mismatch occurs due to contact resistance when connecting with a connector

Engineering Contradiction:

Improvethermal isolationVSAvoidhigh speed communication

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

A flexible printed circuit board is used as an intermediary connection between the first board (with large heat generation element) and the second board (with small heat generation elements). This flexible board provides both mechanical connection for thermal isolation and electrical connection with controlled impedance to maintain high speed communication without mismatch issues.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Temperature

If a large heat radiation fin is added to radiate heat from large heat generation elements, then heat dissipation is improved, but the dimensions of the device increase

Engineering Contradiction:

Improveheat dissipationVSAvoiddevice size

Core Design Contradiction:

TemperatureVSVolume of moving object

Solution Approach 1:

The heat radiation function is merged with the existing printed circuit board structure by adding heat radiation fins to the board itself rather than as a separate component. This integrates thermal management into the structural design, achieving effective heat dissipation without increasing overall device volume.

Inventive Principle:

Principle #5Merging (Combining)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This configuration effectively isolates heat from the high heat generation element, preventing temperature exceedance in low heat generation elements and allows for high-speed communication without impedance issues, while maintaining a compact device size.

Implementation Method 1

thermal conduction from the first electric element to the second electric element is limited by the flexible portion

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS7623347B2Electric device having first and second electric elements

Publication Date: 2009.11.24 DENSO CORP

AI summary

An electric device includes: first and second electric elements, wherein electric power consumption and operation temperature limit of the first electric element is larger than the second electric element; a substrate made of a rigid flexible board; and a casing that accommodates the substrate with the first and second electric elements. The substrate includes first and second rigid portions and a flexible portion. The first and second electric elements are disposed on the first and second rigid portion, respectively. The flexible portion connects the first and second rigid portions. The thickness of the flexible portion is smaller than the first and second rigid portions. The flexible portion further includes a wiring for electrically coupling the first and second electric elements so that high speed communication is performed between the first and second electric elements.