AlSiC Stiffener and Sealing Structure for Lidless Package Warpage
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Solution Overview
Problem
Electronic component packages experience warpage due to temperature differentials caused by varying thermal coefficients of expansion, which is exacerbated by high power heat sources and liquid cooling solutions, posing challenges in maintaining structural integrity and thermal management in high-density server environments.
Innovation Solution
A weight-optimized stiffener made of AlSiC, with an irregularly shaped outer periphery and central aperture, is coupled to a substrate to provide warpage control, and combined with a top plate and O-ring sealing, enabling direct liquid cooling and minimizing thermal mass.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a stiffener is added to control warpage, then warpage control is improved, but weight increases
Solution Approach 1:
The stiffener is made from aluminum silicon carbide composite material, which combines the low density and high strength of aluminum with the high strength-to-weight ratio and dimensional stability of silicon carbide. This composite material provides effective warpage control while minimizing the weight increase that would result from using traditional solid metal stiffeners.
Solution Approach 2:
The stiffener features an irregularly shaped outer periphery with varying thickness distribution, concentrating material where structural support is most needed to control warpage while removing material from areas where it is less critical. This localized quality approach optimizes the balance between warpage control and weight reduction.
2Temperature
If liquid cooling is implemented, then thermal management is improved, but thermal expansion warpage worsens
Solution Approach 1:
The aluminum silicon carbide composite stiffener has a coefficient of thermal expansion that can be tailored by adjusting the silicon carbide content and distribution. This allows the stiffener to better match the thermal expansion characteristics of the substrate and electronic components, reducing differential thermal expansion and associated warpage when liquid cooling is applied.
Solution Approach 2:
The stiffener design incorporates specific geometric parameters including irregular outer periphery, varying thickness, and central aperture configuration that are optimized to compensate for thermal expansion effects. These parameter changes allow the structure to maintain dimensional stability under the thermal loads imposed by liquid cooling systems.
3Temperature
If a central aperture is added for cooling, then heat transfer is improved, but structural strength decreases
Solution Approach 1:
The aluminum silicon carbide composite material provides high strength-to-weight ratio and exceptional structural integrity, allowing the inclusion of a central aperture for liquid cooling flow without significantly compromising the overall strength of the stiffener. The composite's inherent strength compensates for the stress concentration that would normally result from the aperture.
Solution Approach 2:
The stiffener employs varying thickness distribution with material concentrated at the periphery and around the aperture boundary where structural strength is most needed, while the central region contains the aperture for cooling. This local quality differentiation maintains structural integrity while enabling effective heat transfer through the cooling channels.
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
The solution effectively controls warpage and enhances thermal management, allowing for efficient heat transfer and reduced weight, while maintaining structural integrity and compatibility with high-density server environments.
Implementation Method 1
Due to differences in the thermal coefficient of expansion (CTE) of the various package components, the electronic component package may warp as the temperature of the electronic component package changes
Implementation Method 2
Because liquid is many times better at storing and transferring heat than air, liquid cooling solutions can provide immediate and measurable benefits to compute efficiency, density and performance
Data Source
Figure 1
Figure 2A~2D
Figure 3A~3B
AI summary
A weight optimized stiffener for use in a semiconductor device is disclosed herein. In one example, the stiffener is made of AlSiC for its weight and thermal properties. An O-ring provides sealing between a top surface of the stiffener and a component of the semiconductor device and adhesive provides sealing between a bottom surface of the stiffener and another component of the semiconductor device. The stiffener provides warpage control for a lidless package while enabling direct liquid cooling of a chip or substrate.