Angled Circuit Card Guides for Thermal Coupling and Alignment
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Solution Overview
Problem
Existing methods for installing line-replaceable units (LRUs) face challenges such as labor-intensive installation, poor dimensional alignment, preload stress due to stack-up tolerances causing circuit card bending, expensive specialized components, and supply chain issues, particularly in densely packed environments with multiple circuit cards.
Innovation Solution
A system utilizing machined rails in the LRU chassis at a 60-degree angle with externally accessible fasteners at a 30-degree angle, providing thermal and structural coupling, and incorporating soft fabric-over-foam gaskets for electrical grounding, allowing easy assembly and enhanced heat dissipation through the chassis as a secondary heatsink.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If spring-finger card guides are used for alignment, then circuit cards can be installed in parallel, but labor-intensive installation and poor dimensional alignment occur
Solution Approach 1:
The patent replaces the mechanical spring-finger card guide system with a precision-machined rail system featuring 60-degree angled rails and corresponding 30-degree angled fasteners. This substitution eliminates the need for spring-finger mechanisms while achieving both ease of installation and precise dimensional alignment through the geometric relationship between the angled rails and fasteners.
Solution Approach 2:
The patent introduces specific angular parameters (60-degree rails, 30-degree fasteners) to the mounting system. These parameter changes create a geometric locking mechanism that guides the circuit card into precise alignment while allowing straightforward fastener installation, simultaneously improving both installation ease and dimensional precision.
2Strength
If mechanical devices like Wedgelocks are used to lock circuit cards, then clamping force for heat transfer is provided, but displacement due to shock or vibration is not fully resisted
Solution Approach 1:
The patent employs a composite mounting system combining precision-machined rigid rails with compliant gasket materials. The rigid rails provide structural strength and precise positioning, while the gasket materials add compliance to handle thermal expansion and mechanical shocks, creating a composite structure that maintains clamping force under various operating conditions.
Solution Approach 2:
The patent incorporates gasket materials between the circuit card and mounting surfaces to provide beforehand cushioning. These compliant elements absorb shocks and vibrations before they can cause displacement or damage, while maintaining the necessary clamping force for thermal conduction throughout the operational life of the device.
3Temperature
If larger heat sinks are used to dissipate heat, then heat dissipation capacity increases, but the size of the LRU increases beyond ARINC-600 guidelines
Solution Approach 1:
The patent merges the heat sink function with the structural mounting system. The precision-machined rails and mounting structure are designed to serve dual purposes: providing mechanical support and alignment while simultaneously acting as heat dissipation pathways. This integration eliminates the need for separate, bulky heat sinks, maintaining compact LRU dimensions within ARINC-600 guidelines.
Solution Approach 2:
The mounting structure is designed with multi-functionality, serving as both the mechanical support system and the thermal management system. The same rigid rails and fasteners that provide precise alignment and secure mounting also conduct heat away from the circuit cards, eliminating the need for dedicated heat sink components and reducing overall LRU volume.
4Ease of manufacture
If externally accessible fasteners are used, then assembly is simplified, but structural rigidity may be compromised
Solution Approach 1:
The patent uses 3D-printed mounting brackets with complex three-dimensional geometries that provide internal reinforcement and optimized stress distribution. These brackets feature integrated mounting holes for external fastener access while maintaining internal structural rigidity through geometric design elements that distribute loads efficiently across the mounting structure.
Solution Approach 2:
The patent optimizes fastener parameters including length, diameter, thread pitch, and material properties to achieve the required structural rigidity while allowing external access. The precision-machined rails are designed with specific tolerances and surface finishes that enhance the rigidity of the overall assembly, compensating for the use of externally accessible fasteners.
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
Facilitates efficient and cost-effective installation with improved thermal management and electrical grounding, reducing training and labor costs while enhancing cooling efficiency and structural rigidity.
Implementation Method 1
the heat sink may include a corresponding mateable surface configured to mate to and thermally couple with a mateable surface of the chassis
Implementation Method 2
the chassis may include vents defined by the outer surfaces and configured to receive air for convectively cooling the heat sink
Data Source
AI summary
A system is disclosed for thermal coupling and fastening of circuit card assemblies of line-replaceable units (LRUs). The LRU may include a chassis configured to house one or more circuit card assemblies. The chassis may include external coupling features configured to receive fasteners. The circuit card assembly may include a heat sink with corresponding coupling features configured to align with the external coupling features and to receive the fasteners. The chassis may include a mateable surface. The circuit card assembly may include a corresponding mateable surface configured to mate to and thermally couple with the mateable surface of the chassis. The chassis may include an electrically conducting surface and the circuit card assembly may include a corresponding electrically conducting surface.