Semiconductor Device Elastic Channel for CTE Mismatch
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Solution Overview
Problem
Wafer Level Chip Scale Packages (WLCSPs) face reliability issues due to mismatched coefficients of thermal expansion (CTE) between the semiconductor die and the support substrate, leading to thermal cycling-induced cracking and separation, which can result in electrical shorts and package failure.
Innovation Solution
Incorporating channels filled with an elastic material, such as a polymer, between active portions of the semiconductor device to absorb stress and strain caused by thermal expansion, thereby matching the CTE of the semiconductor device to the support substrate and reducing the likelihood of cracking or separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If WLCSP is coupled to substrate with solder, then electrical connection is established, but cracking and separation occur due to CTE mismatch during thermal cycling
Solution Approach 1:
The patent introduces an intermediate material layer between the WLCSP and substrate that acts as a stress buffer. This intermediary layer has mechanical properties that bridge the gap between the rigid solder joint and the flexible requirement for thermal expansion accommodation, preventing crack propagation while maintaining electrical connectivity.
Solution Approach 2:
The patent modifies the mechanical and thermal parameters of the connection system by introducing materials with specific elastic moduli and CTE values. The intermediate layer's parameters are selected to gradient-transition between the WLCSP solder joint and the substrate, reducing the abrupt parameter mismatch that causes thermal stress and cracking.
2Adaptability or versatility
If larger WLCSP size is used, then more electrical connections and functionality are achieved, but CTE mismatch issues are compounded leading to earlier failure
Solution Approach 1:
The patent segments the large WLCSP into multiple smaller active portions or dies, each with its own stress management characteristics. This segmentation reduces the overall thermal stress accumulation in any single region while maintaining the total functionality through the combined capabilities of multiple segments, thereby improving reliability without sacrificing adaptability.
Solution Approach 2:
The patent applies different material compositions and structural configurations to different regions of the WLCSP based on local stress patterns and functional requirements. Critical areas with higher stress concentrations receive enhanced stress-buffering materials or structural modifications, while less critical areas maintain standard design, optimizing the balance between functionality and reliability.
3Reliability
If elastic material is added to absorb stress, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent employs thin film elastic layers that conform to the WLCSP and substrate interfaces. These thin films provide the necessary stress absorption and CTE matching without adding significant bulk or structural complexity. The flexible nature of these films allows them to accommodate thermal expansion while maintaining a compact device profile.
Solution Approach 2:
The patent utilizes composite material structures that combine multiple materials with complementary properties in a single integrated layer. These composite materials provide both the elastic stress-buffering properties and the mechanical strength required for structural integrity, eliminating the need for separate complex multi-layer assemblies and simplifying the overall device structure.
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 enhances the reliability and useful life of the semiconductor device by reducing thermal expansion-induced stress, allowing for the creation of larger devices with additional electrical connections and improved functionality.
Implementation Method 1
the elastic material absorbs stress and strain within the semiconductor device due to thermal expansion of the semiconductor device during operation
Implementation Method 2
The channel is preferably filled with an elastic material, such as a polymer or other insulative and resilient buffer material
Data Source
AI summary
A semiconductor device having a channel between active sections or portions of the device is disclosed. An elastic material, such as dielectric or a polymer, is deposited into the channel and cured to increase flexibility and thermal expansion properties of the semiconductor device. The elastic material reduces the thermal and mechanical mismatch between the semiconductor device and the substrate to which the semiconductor device is coupled in downstream processing to improve reliability. The semiconductor device may also include a plurality of channels formed transverse with respect to each other. Some of the channels extend all the way through the semiconductor device, while other channels extend only partially through the semiconductor device.