Flexible Wing Heat Spreading Lid for TIM Strain Mitigation
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Solution Overview
Problem
In electronic modules, thermal interface material (TIM) strain occurs due to differential thermal expansion between the chip package and the lid, leading to potential TIM failure, which reduces heat dissipation and can cause overheating, especially as lid thickness increases for better heat spreading, and the elimination of the organic carrier core further exacerbates this issue.
Innovation Solution
A heat spreading lid design featuring a flexible wing portion that moves independently with the TIM, strategically thinned at the corners of the die to reduce strain, and an increased volume of TIM material at the periphery, allowing the lid to flex and accommodate thermal expansion without increasing stiffness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If lid thickness is increased to improve heat spreading, then thermal performance is improved, but lid stiffness increases which lowers lid-to-die compliance and increases TIM strain
Solution Approach 1:
The lid is segmented into a rigid main body and a flexible wing portion. The wing portion is strategically positioned at the corners of the die where TIM strain is greatest. This segmentation allows the main lid body to maintain high stiffness for effective heat spreading while the wing portion provides localized flexibility to accommodate thermal expansion and reduce TIM strain.
Solution Approach 2:
The lid exhibits non-uniform mechanical properties: the main body has high stiffness and thickness for optimal heat spreading, while the wing portions at the corners have reduced thickness and increased flexibility. This local quality variation allows the lid to simultaneously achieve high thermal performance and low TIM strain in critical areas.
2Power
If die area increases, then processing power improves, but TIM strain increases
Solution Approach 1:
The wing portions are specifically positioned at the corners of the die, which are the locations of greatest TIM strain for larger die areas. This segmentation allows the flexible regions to be strategically placed where they are most needed to accommodate the increased thermal expansion of larger dies.
Solution Approach 2:
The solution addresses the two-dimensional expansion problem by introducing a vertical dimension - the wing portions can deflect vertically to accommodate thermal expansion, transforming the constraint from a planar stress problem to a three-dimensional deformation problem that better absorbs thermal stresses.
3Ease of manufacture
If organic carrier core is eliminated to reduce cost, then manufacturing cost decreases, but CPI increases and TIM strain increases
Solution Approach 1:
The flexible wing portions act as a substitute for the organic carrier core's compliance function. By segmenting the lid structure to include flexible regions, the design compensates for the increased CPI caused by eliminating the organic carrier core, maintaining TIM reliability without the added cost.
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 design reduces TIM strain by up to 42% and maintains thermal performance, preventing TIM failure and overheating, even with increased lid thickness, while minimizing the risk of interconnect cracking.
Implementation Method 1
TIM (thermal interface material) is used in electronic modules to allow for heat transport from an IC (integrated circuit), referred to as 'a die', to a heat spreading component
Implementation Method 2
CPI occurs during thermal expansion and/or contraction, such as lid assembly curing, accelerated reliability cycling and power on off cycling million, and the organic carrier or circuit card may have a higher coefficient of expansion
Data Source
AI summary
A heat spreading lid, including a lid body, a wing portion, where the wing portion flexibly moves independently from the lid body.