PCBA Thermal Cover and Strap for IC Heat Removal
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Solution Overview
Problem
Convection-based cooling methods are not practicable in high vacuum applications such as space, where heat from integrated circuits (ICs) needs to be efficiently removed without mechanical stress and solder fatigue, especially with differential thermal expansion and contraction.
Innovation Solution
A printed circuit board assembly (PCBA) incorporating a thermal cover and thermal strap for thermal conduction, where the thermal cover is thermally coupled to the IC package and mechanically urges it into contact with a socket, and the thermal strap provides a conductive pathway for heat removal, using materials like copper or thermally conductive composites to facilitate relaxed manufacturing tolerances and relative movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If convection-based cooling methods are used, then heat removal is effective in atmospheric conditions, but the method becomes impracticable in high vacuum applications such as space
Solution Approach 1:
The patent replaces convection-based cooling (which requires fluid medium) with thermal conduction through solid thermal straps and heat sinks. This substitution eliminates dependence on atmospheric conditions, enabling effective heat removal in high vacuum environments where convection cannot occur.
Solution Approach 2:
The patent introduces thermal straps as intermediary components that provide a direct conductive pathway between the IC package and heat sink. These thermal straps act as mediators to transfer heat through solid contact, bypassing the need for convective heat transfer through air or other gases.
2Temperature
If rigid thermal contact methods are used, then thermal conduction is effective, but mechanical stress and solder fatigue increase due to differential thermal expansion
Solution Approach 1:
The patent employs flexible thermal straps instead of rigid thermal contact methods. These flexible straps can accommodate differential thermal expansion between the IC package and heat sink without generating excessive mechanical stress or causing solder fatigue, while still maintaining effective thermal conduction.
Solution Approach 2:
The patent changes the mechanical properties of the thermal contact interface by using compliant thermal strap materials. This parameter change allows the thermal contact interface to deform elastically under thermal expansion, maintaining thermal contact while reducing mechanical stress on solder joints.
3Temperature
If tight manufacturing tolerances are enforced for thermal contact, then heat transfer efficiency improves, but manufacturing complexity and cost increase
Solution Approach 1:
The flexible thermal straps inherently compensate for manufacturing tolerances through their compliance. Even with variations in assembly positioning or component dimensions, the flexible straps can deform to maintain adequate thermal contact, eliminating the need for tight manufacturing tolerances while preserving heat transfer efficiency.
Solution Approach 2:
The patent designs the thermal strap system with built-in compliance that cushions against manufacturing variations. The flexible material acts as a buffer that absorbs dimensional tolerances and assembly variations, ensuring consistent thermal performance without requiring precision manufacturing.
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 effectively removes heat from ICs using thermal conduction, comparable to or better than solder-based connections, reducing mechanical stress and solder fatigue, and allows the use of Land Grid Array (LGA) packages in applications where convection cooling is not feasible, such as in space, without requiring reworking to Ball Grid Array (BGA) or Column Grid Array (CGA) packages.
Implementation Method 1
The disclosure describes a printed circuit board assembly (PCBA) including a thermal management mechanism for removing heat from an integrated circuit (IC) package using thermal conduction
Implementation Method 2
The thermal strap also may be made of relatively compliant material, such as copper, a copper alloy, or a thermally conductive composite material, which may facilitate relaxed manufacturing tolerances and relative movement
Data Source
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AI summary
A printed circuit board assembly (PCBA) may include a printed circuit board (PCB), a socket mechanically and electrically coupled to the PCB, and an integrated circuit package electrically coupled to the socket. The PCBA also may include a thermal cover comprising a thermally conductive material and a thermal strap thermally coupled to the thermal cover. The thermal cover may be thermally coupled to the integrated circuit package and mechanically urge the integrated circuit package in contact with the socket, and the thermal strap may include a thermally conductive material.