Plastically Deformable Fixing Element for PCB Component Thermal Alignment

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Solution Overview

Problem

In electrical circuits with multiple components to be cooled, the varying heights due to manufacturing tolerances lead to reduced thermal contact and increased thermal resistance when using a common heat sink, causing mechanical stress and potential damage, especially in smaller packaging variants.

Innovation Solution

A plastically deformable fixing element is used to align heat dissipation surfaces of components to the same plane, compensating for different component heights through elastic deformation, allowing for uniform pressure distribution and stress-free arrangement, which enables a precise press fit and improved thermal contact without mechanical stress.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If a common heat sink is used to cool multiple components, then heat dissipation is achieved, but thermal contact is reduced due to varying component heights

Engineering Contradiction:
Improvethermal contactVSAvoidcomponent height variation
Core Design Contradiction:
TemperatureVSManufacturing precision

Solution Approach 1:

The patent applies compliant mounting structures that change their mechanical parameters (flexibility, elasticity) to accommodate variations in component height. These structures allow the heat sink to maintain consistent thermal contact with components of different heights by deforming elastically, thereby resolving the contradiction between heat dissipation effectiveness and manufacturing tolerance variations.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent introduces compliant mounting structures as intermediary elements between the rigid heat sink and the components with varying heights. These intermediaries absorb the height variations through their compliance, ensuring that the heat sink maintains uniform thermal contact with all components regardless of their individual height differences.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Temperature

If pressure is applied to achieve uniform thermal contact, then thermal contact improves, but mechanical stress increases in solder joints

Engineering Contradiction:
Improvethermal contactVSAvoidsolder joint integrity
Core Design Contradiction:
TemperatureVSReliability

Solution Approach 1:

The patent transforms the mounting structure from rigid to compliant, allowing it to deform elastically under pressure. This parameter change enables the structure to apply sufficient pressure for uniform thermal contact while distributing the mechanical stress through deformation, thereby protecting the solder joints from excessive stress and maintaining reliability.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The compliant mounting structures act as cushioning elements that are designed to deform before the excessive stress reaches the solder joints. This beforehand cushioning protects the fragile solder connections by absorbing and distributing the mechanical stress, preventing solder joint failure while still achieving the necessary pressure for thermal contact.

Inventive Principle:
Principle #11Beforehand cushioning (Prior cushioning)

3Temperature

If elastic deformation is used to compensate for height differences, then thermal contact uniformity improves, but component displacement under vibration increases

Engineering Contradiction:
Improvethermal contact uniformityVSAvoidvibration-induced displacement
Core Design Contradiction:
TemperatureVSObject-affected harmful factors

Solution Approach 1:

The patent optimizes the compliance parameters of the mounting structures to provide sufficient elasticity for height compensation while maintaining enough rigidity to resist vibration-induced displacement. By carefully tuning the mechanical properties (elastic modulus, geometry) of these structures, the system achieves both uniform thermal contact and vibration resistance.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent employs dynamic mounting structures that can adapt their stiffness characteristics. These structures are designed to be compliant under static or low-frequency conditions to accommodate height variations, yet sufficiently rigid under high-frequency vibration conditions to prevent component displacement, thus resolving the contradiction between thermal contact uniformity and vibration resistance.

Inventive Principle:
Principle #15Dynamics

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 solution ensures consistent thermal contact across all components, enhances mechanical resilience, and extends the service life of the electrical circuit by maintaining uniform pressure distribution and resistance to shock and vibration, while avoiding mechanical stress and solder joint failure.

Implementation Method 1

A plastically deformable fixing element is used to align heat dissipation surfaces of components to the same plane, compensating for different component heights through elastic deformation

Methodology Applied
Scientific EffectElastic deformation: Elasticity

Implementation Method 2

allowing for uniform pressure distribution and stress-free arrangement, which enables a precise press fit and improved thermal contact

Methodology Applied
Scientific EffectPressure distribution: Pressure Increase

Implementation Method 3

ensures consistent thermal contact across all components, enhances mechanical resilience, and extends the service life of the electrical circuit by maintaining uniform pressure distribution

Methodology Applied
Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentEP2609795B1Method for populating a circuit board with a plurality of components and electrical circuit having a circuit board and a plurality of components mounted thereon
Publication Date: 2015.10.14 ROBERT BOSCH GMBH
  • EP2609795B1 patent drawingFigure 1

AI summary

The invention relates to a method for populating a circuit board with a plurality of components. The method comprises the steps of: providing the components with push-through contacts extending at least in end segments of the push-through contacts in a direction perpendicular to the heat emitting surfaces of the components, and providing the circuit board with contact holes for receiving push-through contacts. At least one plastically deformable fixing element is further mounted on the circuit board. The components are mounted on the fixing element and the push-through contacts are inserted into the corresponding contact holes of the circuit board. A flat surface displaces the heat surfaces of the components toward the circuit board, plastically deforming the fixing element, until all heat emitting surfaces of the components lie in the same plane. The invention further relates to an electrical circuit having a circuit board, wherein heat emitting surfaces are connected to the circuit board by means of at least one plastically deformable fixing element, wherein the heat emitting surfaces are flush with each other because the fixing element that has been correspondingly plastically deformed compensates for the different component thicknesses.