Semiconductor Package Lid Bonding With Dual-Stiffness Adhesives
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Solution Overview
Problem
Existing semiconductor packages face challenges in maintaining structural integrity and heat transfer efficiency due to warping of lids and mismatch in thermal expansion coefficients, leading to potential cracking and reduced reliability.
Innovation Solution
A semiconductor package design utilizing two adhesives with differing stiffnesses, where a high-stiffness adhesive supports the lid and improves bonding, while a low-stiffness adhesive mitigates thermal expansion mismatch, enhancing the seal and reducing voids in the heat transfer layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single adhesive is used to bond the lid to the substrate, then the bonding process is simple, but the lid warping and thermal expansion mismatch cause structural integrity issues
Solution Approach 1:
The bonding process is segmented into two distinct adhesive applications: a first adhesive applied between the lid and the package structure, and a second adhesive applied between the lid and the substrate. This segmentation allows each adhesive to be optimized for its specific function, resolving the contradiction between process simplicity and structural integrity.
Solution Approach 2:
Different adhesive materials are selected for different locations based on local requirements. The first adhesive (higher stiffness) is used where structural support is needed, while the second adhesive (lower stiffness) is used where flexibility for thermal expansion is required. This local differentiation resolves the contradiction by tailoring adhesive properties to specific functional needs.
2Strength
If a high-stiffness adhesive is used to support the lid, then warping is reduced, but thermal expansion mismatch causes cracking
Solution Approach 1:
The support function is segmented between two adhesives with different stiffness properties. The first high-stiffness adhesive provides the necessary lid support strength, while the second low-stiffness adhesive accommodates thermal expansion differences, preventing cracking. This segmentation resolves the contradiction by distributing different mechanical functions to different materials.
Solution Approach 2:
The stiffness parameter of the adhesive is changed between the two bonding locations. The first adhesive has higher stiffness (Young's modulus) for structural support, while the second adhesive has lower stiffness for thermal compatibility. This parameter variation resolves the contradiction between strength and cracking resistance.
3Strength
If adhesive material is increased to improve bonding, then bonding strength improves, but void formation in heat transfer layer increases
Solution Approach 1:
The adhesive application is localized to specific areas rather than being applied uniformly throughout. The first adhesive is applied in a first area between the lid and package structure, and the second adhesive is applied in a second area between the lid and substrate. This localized application provides sufficient bonding strength while minimizing void formation in the heat transfer layer.
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 design improves heat transfer efficiency and long-term reliability by minimizing warping and cracking, thereby optimizing the package's structural integrity and performance.
Implementation Method 1
A first adhesive of a high stiffness, which encircles the package structure, is disposed between the lid and the substrate
Implementation Method 2
The second adhesive may mitigate the mismatch between the coefficient of thermal expansion of the lid and the coefficient of thermal expansion of the substrate
Implementation Method 3
heat transfer from the semiconductor dies, through the metal layer and the heat transfer layer, to the lid is improved
Data Source
AI summary
A semiconductor package including two different adhesives and a method of forming are provided. The semiconductor package may include a package component having a semiconductor die bonded to a substrate, a first adhesive over the substrate, a heat transfer layer on the package component, and a lid attached to the substrate by a second adhesive. The first adhesive may encircle the package component and the heat transfer layer. The lid may include a top portion on the heat transfer layer and the first adhesive, and a bottom portion attached to the substrate and encircling the first adhesive. A material of the second adhesive may be different from a material of the first adhesive.