Laser Weldable Brackets for Heat Sink Attachment to EMI Shields
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Solution Overview
Problem
Existing methods for attaching heat sinks to EMI shields, such as board level shields, face challenges in maintaining even pressure and retention force, particularly at elevated temperatures and during impacts, with conventional adhesives delaminating and mechanical fasteners providing uneven pressure.
Innovation Solution
The use of laser weldable brackets that constrain movement of the heat sink in the X and Y directions, pressing down on the thermal interface material and being laser welded to the EMI shield to ensure proper contact and retention, providing a reliable retention force even after severe drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional adhesives are used to attach heat sinks to EMI shields, then the assembly process is simple, but the retention force is lost at elevated temperatures causing delamination
Solution Approach 1:
The patent replaces chemical bonding (adhesives) with mechanical bonding (laser welding) to attach the bracket to the EMI shield. This substitution eliminates the temperature sensitivity of adhesive bonds while providing a reliable mechanical connection that maintains retention force at elevated temperatures and during impact events.
Solution Approach 2:
The solution uses a composite attachment system combining a metal bracket (laser weldable to EMI shield) with thermal interface material (between heat sink and EMI shield). This composite approach separates the retention function (handled by the welded bracket) from the thermal conduction function (handled by the TIM), allowing each component to optimize its specific function without the limitations of single-material solutions.
2Force
If mechanical fasteners are used to attach heat sinks to EMI shields, then retention force is provided, but the pressure distribution is uneven affecting thermal interface performance
Solution Approach 1:
The patent introduces a compliant bracket as an intermediary component between the EMI shield and heat sink. This bracket acts as a mediator that distributes the retention force uniformly across the thermal interface material, eliminating the localized pressure points created by direct mechanical fasteners while maintaining adequate retention force.
Solution Approach 2:
The solution changes the physical state and properties of the bracket material to be compliant and laser weldable. By selecting a bracket material that is both laser weldable to the EMI shield and compliant enough to distribute pressure evenly, the system achieves uniform pressure distribution while maintaining strong retention force.
3Force
If clips or mechanical fasteners are used for attachment, then retention is provided, but extensive EMI shield area is required reducing assembly compactness
Solution Approach 1:
The patent segments the attachment function from the EMI shield by introducing a separate bracket component. This segmentation allows the bracket to provide the retention function using minimal EMI shield area, as the bracket itself bears the retention load rather than requiring large EMI shield surfaces for direct attachment.
Solution Approach 2:
The solution transitions from a two-dimensional attachment approach (direct attachment to EMI shield surface) to a three-dimensional approach using a vertical bracket structure. This dimensional change allows retention force to be applied through the bracket's height and structure rather than requiring extensive EMI shield surface area.
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 interface performance, maintains retention force during impacts, and allows for a more compact assembly by eliminating the need for extensive EMI shield area, compared to conventional clips and mechanical fasteners.
Implementation Method 1
A bracket may then be laser welded to the EMI shield to complete the assembly
Implementation Method 2
The thermal interface material may be used to fill the gap between thermal transfer surfaces, in order to increase thermal transfer efficiency
Data Source
AI summary
According to various aspects, exemplary embodiments are disclosed of laser weldable brackets for attachment of heat sinks to EMI shields, such as a board level shield, etc. In an exemplary embodiment, an assembly generally includes an electromagnetic interference (EMI) shield, a heat sink, and a bracket laser weldable to the EMI shield for attachment of the heat sink to the EMI shield. In another exemplary embodiment, a method of attaching a heat sink to an EMI generally includes laser welding a bracket to the EMI shield whereby the bracket retains the heat sink in place relative to the EMI shield.