Solder-Sealed Die Cavity for Stress-Sensitive Semiconductor Packaging
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Solution Overview
Problem
Stress-sensitive semiconductor components experience adverse changes in electrical properties due to mechanical stress from mold compounds and filler particles during packaging, leading to non-uniform performance across devices.
Innovation Solution
The use of a flip-chip mounting technique with a solder seal to create a cavity around the stress-sensitive component, reducing mechanical stress by spacing it from mold compound and filler particles, and employing a chip-scale package design with trenches or cantilever structures to further isolate the component.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If mold compound with filler particles is used to encapsulate semiconductor devices, then the package provides mechanical support and protection, but the filler particles concentrate and apply compressive and shear stress to stress-sensitive components, degrading their electrical properties
Solution Approach 1:
A stress relief layer is introduced as an intermediary between the mold compound and the stress-sensitive component. This layer acts as a buffer that absorbs and distributes the mechanical stress from the mold compound, preventing direct transmission of compressive and shear forces to the sensitive component while maintaining the protective encapsulation function.
Solution Approach 2:
The patent segments the encapsulation structure by dividing it into distinct functional layers: the outer mold compound layer providing mechanical support, the intermediate stress relief layer reducing stress transmission, and the inner region protecting the stress-sensitive component. This segmentation allows each layer to perform its specific function independently.
2Strength
If large filler particles are used in mold compound, then the mechanical strength and rigidity of the package are improved, but the stress concentration effect is amplified, applying more pressure against stress-sensitive components
Solution Approach 1:
The stress relief layer serves as a mediator that decouples the relationship between large filler particles and the stress-sensitive component. It allows the use of large filler particles for structural strength while preventing their stress concentration effect from reaching the sensitive component, as the intermediate layer absorbs and redistributes these forces.
Solution Approach 2:
The patent changes the mechanical parameters (such as elasticity modulus and viscosity) of the stress relief layer to optimize its stress-absorbing properties. By carefully selecting materials with appropriate parameter ranges, the layer can effectively cushion against stress from large filler particles while maintaining overall package integrity.
3Ease of manufacture
If random placement of large filler particles occurs in mold compound, then the manufacturing process remains simple, but the force distribution on stress-sensitive components becomes non-uniform, resulting in non-uniform performance across devices
Solution Approach 1:
The stress relief layer acts as a uniform intermediary that standardizes the stress distribution across all devices in a batch. Even though filler particles are randomly placed, the intermediate layer ensures that stress is distributed uniformly to the stress-sensitive components, eliminating the non-uniform performance variation that would otherwise occur.
Solution Approach 2:
The stress relief layer provides a homogeneous mechanical environment across the entire package area. Its uniform material properties ensure that all stress-sensitive components, regardless of their specific position or the random distribution of filler particles nearby, experience consistent stress levels, thereby achieving uniform performance across devices.
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 effectively reduces or eliminates mechanical stress on stress-sensitive components, ensuring consistent electrical characteristics across devices and preventing adverse changes due to packaging processes.
Implementation Method 1
a solder seal bonded to and extending from the first surface of the first semiconductor die which is flip chip mounted to the third surface of the second semiconductor die, the solder seal at least partially surrounding the component
Data Source
AI summary
A method includes forming a stress sensitive component on a first semiconductor die; forming a solder seal on the first semiconductor die, the solder seal extending from a first surface of the first semiconductor die, and surrounding the stress sensitive component, the solder seal having an interior surface that surrounds the stress sensitive component and having an exterior surface facing away from the stress sensitive component; flip chip mounting the first semiconductor die to a first surface of a second semiconductor die, the stress sensitive component facing the first surface of the second semiconductor die; and forming a solder joint between the solder seal and the first surface of the second semiconductor die.