Semiconductor Package Buffer Layers for Delamination Control
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Solution Overview
Problem
Conventional semiconductor device packages face delamination issues due to mismatched thermo-mechanical properties of materials used in the die, die attach, metal lead frame, metal wires, and protective coverings, leading to interfacial delamination and cracking under temperature excursions.
Innovation Solution
The implementation of a conductive buffer layer with limited or no solid solubility between the metal layer and the conductive submount, balancing interfacial stresses by reducing bonding strength at the lower interface to match that at the upper interface, thereby preventing delamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If dissimilar materials are used in the die, die attach, metal lead frame, metal wires, and protective coverings to achieve functional requirements, then device functionality is improved, but stress imbalance and interfacial delamination occur due to mismatched thermo-mechanical properties
Solution Approach 1:
A conductive buffer layer is introduced as an intermediary between the metal layer and conductive submount. This buffer layer has limited or no solid solubility with the metal layer material, creating a controlled bonding interface that balances interfacial stresses. The buffer layer acts as a mediator that prevents direct contact between dissimilar materials, thereby reducing stress imbalance and preventing delamination while maintaining electrical conductivity.
2Reliability
If strong bonding is used at the metal layer to conductive submount interface to ensure electrical connection, then electrical conductivity is improved, but stress imbalance increases leading to delamination at other interfaces
Solution Approach 1:
The bonding strength parameter at the metal layer to conductive submount interface is modified by introducing a conductive buffer layer with limited or no solid solubility. This changes the bonding characteristics from strong direct bonding to controlled intermediate bonding, which reduces the stress imbalance across different interfaces while maintaining sufficient electrical conductivity for reliable operation.
3Strength
If material solid solubility is increased at bonding interfaces to improve adhesion, then bonding strength is improved, but stress imbalance and delamination susceptibility increase due to thermo-mechanical property mismatch
Solution Approach 1:
The conductive buffer layer serves as an intermediary that deliberately limits solid solubility with the metal layer material. This limited solubility creates a controlled bonding interface with optimized adhesion strength that balances the thermo-mechanical stresses, preventing the excessive bonding that would lead to stress concentration and delamination at other interfaces.
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 significantly enhances the reliability of power discrete packages and power modules by reducing stress imbalances at bonding interfaces, minimizing delamination, and improving adhesion between the mold structure and metal layers.
Implementation Method 1
The second material of the conductive buffer layer has limited or no solid solubility with respect to the first material of the metal layer
Data Source
AI summary
A semiconductor device package includes a conductive submount, a metal layer comprising a first material on the conductive submount, and at least one conductive buffer layer comprising a second material on the metal layer. The conductive buffer layer may be between the metal layer and the conductive submount, or may be between the metal layer and a transistor die on the conductive submount. The second material of the conductive buffer layer has limited or no solid solubility with respect to the first material of the metal layer. Related packages and fabrication techniques are also discussed.