IC Package Cavities with Dual-Modulus Die Encapsulation
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Solution Overview
Problem
Integrated circuit packaging faces challenges in accommodating stress-sensitive semiconductor devices, as materials with high modulus of elasticity can cause mechanical and thermomechanical stress-related failures, while using low modulus materials for encapsulation may compromise rigidity and lead to adhesion issues with the outer housing, and hermetic packaging is costly and prone to wire bond short circuits.
Innovation Solution
The solution involves encapsulating a stress-sensitive die with a low modulus material in a cavity within the IC package housing, allowing it to move and absorb stresses, while using a high modulus material for the outer housing, and ensuring the low modulus material is not confined by the housing, thereby maintaining its ability to absorb stresses effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high modulus material is used for encapsulation, then rigidity of the package is improved, but mechanical and thermomechanical stress on stress-sensitive devices increases causing failures
Solution Approach 1:
The patent applies different materials with different modulus values to different regions: a low modulus material (first material) is applied locally around the stress-sensitive device to absorb mechanical stresses, while a high modulus material (second material) is used for the outer housing to provide overall rigidity. This local differentiation allows each region to have the material properties needed for its specific function.
Solution Approach 2:
The patent uses a composite structure combining two materials with different mechanical properties. The first material (low modulus) and second material (high modulus) are applied in layers or regions to create a composite encapsulation system that simultaneously provides stress absorption and structural rigidity, resolving the contradiction between these two opposing requirements.
2Reliability
If low modulus material is used for encapsulation, then stress absorption is improved, but adhesion to outer housing deteriorates causing separation issues
Solution Approach 1:
The patent creates a composite structure where the low modulus first material is applied in contact with the stress-sensitive device, and the high modulus second material is applied over it to form the outer housing. The interface between these two materials provides both stress absorption (from the first material) and adhesion (from the second material bonding to the housing), resolving the adhesion problem while maintaining stress absorption capabilities.
3Reliability
If hermetic packaging is used, then protection from external environment is improved, but cost increases and wire bond short circuit risk increases
Solution Approach 1:
The patent changes the encapsulation approach from hermetic sealing to stress-absorbing encapsulation using low modulus material. This parameter change in material selection and encapsulation philosophy provides adequate protection for stress-sensitive devices without the high costs and manufacturing complexities of hermetic packaging, while also reducing wire bond short circuit risks through the compliant material interface.
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 allows for the independent encapsulation of vertically stacked dies with different materials, ensuring the stress-sensitive devices are protected from mechanical stresses without compromising the rigidity of the package, and enabling proper operation of optical devices by selecting appropriate materials that allow light transmission.
Implementation Method 1
a low modulus material that is free to move and absorb stresses experienced by the IC package so as to protect the die encased therein
Data Source
AI summary
Integrated circuit packaging with cavities and methods of manufacturing the same are disclosed. An example apparatus includes a semiconductor die and a housing enclosing portions of the semiconductor die. The housing defines an opening that extends from a surface of the semiconductor die to an external environment, the housing formed of a first material. The example apparatus includes a second material disposed within the opening to block exposure of the semiconductor die to the external environment.