Thermally Conductive Layer for Semiconductor Die Heat Dissipation
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Solution Overview
Problem
Semiconductor devices face challenges with heat dissipation and thermal stress due to thermally non-conductive encapsulants, which can reduce performance, reliability, and lifetime, and increase manufacturing costs, especially as die sizes shrink and pin counts increase.
Innovation Solution
A thermally conductive layer is introduced between the semiconductor die and the build-up interconnect structure, with openings to accommodate bumps and reduce package height, minimizing thermal stress and interconnect resistance while allowing for efficient heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thermally non-conductive encapsulant is used to cover the semiconductor die and interconnect structure, then the semiconductor device is protected from environmental factors, but heat dissipation is impaired and thermal stress increases
Solution Approach 1:
The encapsulant is segmented into two distinct layers: a first encapsulant layer that is thermally non-conductive providing environmental protection, and a second encapsulant layer that is thermally conductive providing heat dissipation. This segmentation allows each layer to perform its specialized function without compromising the other, resolving the contradiction between protection and heat dissipation.
Solution Approach 2:
Different regions of the encapsulant structure are assigned different thermal conductivity properties. The first encapsulant layer has low thermal conductivity for protection, while the second encapsulant layer has high thermal conductivity for heat dissipation. This local differentiation of material properties enables simultaneous achievement of environmental protection and effective thermal management.
2Area of moving object
If the semiconductor die size is reduced to achieve smaller footprint devices, then device density and integration are improved, but heat dissipation becomes more challenging and thermal stress increases
Solution Approach 1:
The dual-layer encapsulant structure segments thermal management functions from structural protection functions, allowing the semiconductor die to be miniaturized without compromising heat dissipation capability. The thermally conductive second layer specifically addresses heat removal from the reduced-size die.
Solution Approach 2:
The encapsulant system uses composite material architecture with two layers of different thermal conductivity characteristics. This composite structure enables effective heat dissipation from miniaturized die while maintaining the protective enclosure, resolving the scaling contradiction.
3Ease of manufacture
If there is a mismatch in the coefficient of thermal expansion between the encapsulant, semiconductor die, and build-up interconnect structure, then manufacturing is simplified, but thermal stress causes defects and warpage
Solution Approach 1:
The encapsulant is segmented into two layers that can independently manage different aspects of thermal stress. The first layer provides structural protection while the second layer is optimized for thermal management, allowing each layer to be tailored to minimize thermal expansion mismatch with specific components.
Solution Approach 2:
The two-layer encapsulant structure acts as an intermediary system between the semiconductor die and the external environment. By introducing this intermediate thermal management layer, thermal stress is distributed and reduced, preventing direct transmission of expansion mismatch forces between components with different CTE values.
4Stress or pressure
If an underfill material is used to absorb thermal stress, then stress-induced defects are reduced, but heat dissipation remains insufficient due to the material's thermal non-conductivity
Solution Approach 1:
The encapsulant is segmented into two distinct layers: the first encapsulant layer provides stress absorption similar to underfill functionality, while the second encapsulant layer provides the thermally conductive heat dissipation pathway that was missing in traditional underfill approaches.
Solution Approach 2:
The dual-layer encapsulant uses composite material architecture where one layer handles mechanical stress and the other handles thermal conduction. This composite approach combines the benefits of stress-absorbing underfill materials with thermally conductive materials, eliminating the need for separate underfill and thermal management components.
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 effectively dissipates heat, reduces thermal stress, and minimizes interconnect resistance, enhancing the performance and reliability of semiconductor devices while reducing manufacturing costs and void formation.
Implementation Method 1
a thermally conductive layer is introduced between the semiconductor die and the build-up interconnect structure
Data Source
AI summary
A semiconductor device has a thermally conductive layer with a plurality of openings formed over a temporary carrier. The thermally conductive layer includes electrically non-conductive material. A semiconductor die has a plurality of bumps formed over contact pads on the die. The semiconductor die is mounted over the thermally conductive layer so that the bumps are disposed at least partially within the openings in the thermally conductive layer. An encapsulant is deposited over the die and thermally conductive layer. The temporary carrier is removed to expose the bumps. A first interconnect structure is formed over the encapsulant, semiconductor die, and bumps. The bumps are electrically connected to the first interconnect structure. A heat sink or shielding layer can be formed over the semiconductor die. A second interconnect structure can be formed over the encapsulant and electrically connected to the first interconnect structure through conductive vias formed in the encapsulant.