IC Package Air Cavity Reduces Molding Stress
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Solution Overview
Problem
Conventional semiconductor packaging techniques induce significant stresses on sensitive regions of integrated circuit dies due to thermal mismatch and encapsulant adherence, leading to issues like parametric shifts, cracking, and hysteresis, which existing solutions such as cavity packages, low stress mold compounds, and soft overcoats only partially address.
Innovation Solution
Creating an air cavity around the semiconductor device within the package by using a thermally decomposable sacrificial layer and a structural layer in the molding compound, which decomposes and outgasses during the encapsulation process, thereby reducing molding-induced stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an encapsulant material is used to cover the die, then the die is protected and packaged, but molding-induced stresses are generated on stress sensitive areas of the die
Solution Approach 1:
The patent segments the encapsulant structure by introducing an air cavity that divides the molding compound into separate regions. This segmentation allows the molding compound to be isolated from direct contact with stress-sensitive areas of the die, thereby reducing molding-induced stresses while maintaining protective encapsulation of non-sensitive regions.
Solution Approach 2:
The patent introduces an intermediary air cavity between the molding compound and the die's stress-sensitive areas. This air cavity acts as a mediator that prevents direct stress transmission from the rigid molding compound to the sensitive die regions, while still allowing the encapsulant to provide overall protection.
2Ease of manufacture
If conventional packaging methods are used, then manufacturing is simple and cost-effective, but stresses cause parametric shifts, cracking, and hysteresis
Solution Approach 1:
The patent applies preliminary action by forming the air cavity structure within the molding compound during the packaging process itself, rather than requiring separate post-processing steps. The cavity is created by positioning a sacrificial material before molding, which is later removed to create the stress-relieving air space, thus maintaining manufacturing simplicity while improving die integrity.
3Stress or pressure
If existing stress reduction techniques are applied, then some stress is reduced, but compressive and bending-induced stresses remain significant
Solution Approach 1:
The patent applies local quality by creating air cavities specifically positioned over stress-sensitive areas of the die rather than uniformly across the entire die surface. This localized approach allows the molding compound to maintain structural integrity in non-sensitive regions while providing stress relief precisely where needed on the die surface.
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
The air cavity effectively minimizes both in-plane and compressive stresses on the die, improving the reliability and performance of integrated circuit packages by isolating the effects of mold compound shrinkage and thermal mismatch.
Implementation Method 1
heating the encapsulant material, wherein the sacrificial layer decomposes and outgasses through the structural layer and the encapsulant material, thereby leaving an air cavity
Data Source
AI summary
An integrated circuit package includes a carrier, an integrated circuit die attached to the carrier, and a molding compound surrounding the integrated circuit die. The integrated circuit die includes a bottom surface attached to the carrier, a top surface including at least one stress sensitive area, and side surfaces. The molding compound has a top air cavity formed over the at least one stress sensitive area, and a side air cavity formed on the side surfaces of the integrated circuit die. The integrated circuit package may further include a top structural layer surrounding the top air cavity. The air cavities reduce molding-induced stresses in integrated circuit packages.