Liquid Cooler Integrated with Flexible Chip Package
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Solution Overview
Problem
Conventional semiconductor packaging technologies face challenges in effectively cooling high-power density chip modules due to thermal expansion mismatch between silicon chips and organic substrates, leading to mechanical stresses, warpage, and reduced reliability, especially in liquid cooling systems where attachment complexities result in non-uniform thermal resistance and mechanical instability.
Innovation Solution
Integrating a metallic liquid cooler device directly to the backside of a flip-chip mounted IC on a flexible substrate, coupled mechanically through a metallic stiffener structure bonded to the substrate, providing both thermal and mechanical rigidity and ensuring controlled compressive forces to maintain the cooler's position and integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a liquid cooler device is attached to a flexible organic carrier substrate, then cooling effectiveness is improved, but mechanical stability deteriorates due to CTE mismatch and substrate flexibility
Solution Approach 1:
A stiffener member is introduced as an intermediary component between the liquid cooler device and the flexible organic carrier substrate. The stiffener member has a first surface bonded to the substrate and a second surface bonded to the cooler device, acting as a mediator that provides mechanical stability while allowing thermal coupling. This resolves the contradiction by decoupling the mechanical support function from the flexible substrate while maintaining the thermal connection.
Solution Approach 2:
The package structure employs composite material construction by combining the flexible organic carrier substrate with a rigid stiffener member (typically metallic). This composite structure leverages the flexibility and electrical connectivity of the organic substrate while the rigid stiffener provides mechanical stability and dimensional control, resolving the mechanical instability issue while preserving cooling effectiveness.
2Productivity
If the flexible substrate is used to mount the chip, then integration density is improved, but warpage increases due to CTE mismatch during thermal cycling
Solution Approach 1:
The stiffener member serves as a mediator that compensates for the CTE mismatch between the silicon chip and the flexible organic substrate. During thermal cycling, the stiffener member absorbs and distributes the differential expansion forces, preventing warpage while allowing the flexible substrate to maintain its high integration density mounting capabilities.
Solution Approach 2:
The stiffener member modifies the mechanical parameters of the package structure by introducing a rigid element with different CTE characteristics. This changes the overall thermal-mechanical behavior of the assembly, reducing warpage through parameter optimization while preserving the benefits of the flexible substrate for high-density integration.
3Ease of manufacture
If conventional attachment methods are used for liquid coolers, then ease of manufacture is improved, but thermal performance deteriorates due to non-uniform bond lines
Solution Approach 1:
The stiffener member acts as an intermediary that provides a large, flat bonding surface for attaching the liquid cooler device. This intermediary structure enables uniform thermal contact and consistent bond line thickness across the interface, improving thermal performance while maintaining ease of manufacture through standardized bonding processes.
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 approach enhances thermal performance by reducing thermal resistance and mechanical stresses, improving reliability by maintaining a uniform bond line and minimizing the weight and size of the cooler, thus addressing the limitations of conventional liquid cooling systems.
Implementation Method 1
a metallic stiffener structure that is bonded to the flexible package substrate to provide mechanical rigidity to the flexible package substrate
Implementation Method 2
the liquid cooler device is thermally coupled directly to the back side of an integrated circuit chip
Data Source
AI summary
Semiconductor package structures are provided which are designed to have liquid coolers integrally packaged with first level chip modules. In particular, apparatus for integrally packaging a liquid cooler device within a first level chip package structure include structures in which a liquid cooler device is thermally coupled directly to the back side of an integrated circuit chip flip-chip mounted on flexible chip carrier substrate. The liquid cooler device is mechanically coupled to the package substrate through a metallic stiffener structure that is bonded to the flexible package substrate to provide mechanical rigidity to the flexible package substrate.