Thermally Conductive Features in IC Chip Assembly Stiffener
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Solution Overview
Problem
Conventional flip chip and circuit substrate designs in FCoF and FCoB applications suffer from inadequate heat dissipation due to the limited thermal conductivity of underfill materials and the cumulative cross-sectional area of solder bumps, leading to restricted heat flow from the IC chip to the stiffener, which can limit the IC chip's functionality and lifespan.
Innovation Solution
The design incorporates a stiffener with a surface divided into regions, where the circuit substrate covers at least one region and the IC chip overlies both regions, featuring signal solder bumps for electrical coupling and thermally conductive features metallurgically bonded between the IC chip and the stiffener, enhancing thermal conductivity pathways.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional flip chip designs with solder bumps placed only along the periphery are used, then the assembly structure is simple, but the heat dissipation capability is inadequate due to limited cumulative cross-sectional area of solder bumps
Solution Approach 1:
The patent segments the thermal conduction path into multiple parallel pathways by placing thermally conductive features at multiple locations (periphery and interior regions) of the IC chip, allowing heat to flow simultaneously through multiple solder bump paths rather than being constrained to a single cumulative path
Solution Approach 2:
The patent transitions from a one-dimensional peripheral arrangement of solder bumps to a two-dimensional distribution pattern that includes both periphery and interior regions of the IC chip, effectively increasing the thermal conduction capacity by utilizing the chip's planar area more efficiently
2Loss of energy
If the cumulative cross-sectional area of solder bumps is increased to improve heat flow, then the heat dissipation improves, but the device complexity increases
Solution Approach 1:
The patent applies different functional qualities to different regions of the IC chip: peripheral solder bumps serve both electrical and thermal functions, while interior thermally conductive features are optimized specifically for heat dissipation, allowing each region to be tailored to its specific function
Solution Approach 2:
The patent creates multi-functional solder bump structures that simultaneously provide electrical connection, mechanical attachment, and thermal conduction functions, eliminating the need for separate dedicated thermal pathways and reducing overall device complexity
3Reliability
If underfill material with low thermal conductivity is used to protect the IC chip, then the mechanical strength and protection are improved, but the thermal resistance increases
Solution Approach 1:
The patent introduces thermally conductive features (such as solder bumps or conductive paste) as intermediary elements between the IC chip and the underfill material, creating a thermal bridge that bypasses the low thermal conductivity of the underfill while maintaining its protective function
Solution Approach 2:
The patent employs composite thermal management structures combining materials with different thermal conductivities: the underfill provides mechanical protection and stress relief, while embedded thermally conductive features provide efficient heat pathways, creating a composite system that optimizes both protection and thermal performance
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 configuration significantly reduces thermal resistance and enhances heat dissipation from the IC chip to the stiffener, allowing IC chips to operate at lower temperatures and extend their lifespan by providing a more efficient thermal conductivity path.
Implementation Method 1
the primary heat dissipation path from the IC chip to the stiffener is through the solder bumps and the circuit substrate
Implementation Method 2
thermally conductive features metallurgically bonded between the IC chip and the stiffener
Data Source
AI summary
An assembly comprises a stiffener, a circuit substrate and an IC chip. The stiffener has a surface with a first region and a second region. The circuit substrate covers at least a portion of the first region of the stiffener, while the IC chip overlies at least a portion of each of the first and second regions of the stiffener. The assembly further comprises a signal solder bump and a thermally conductive feature. The signal solder bump contacts the IC chip and the circuit substrate. The thermally conductive feature is disposed between, and is metallurgically bonded to, the integrated circuit chip and the second region of the stiffener. The thermally conductive feature provides an efficient thermal conductivity pathway between the IC chip and the stiffener.