Dual-Material Package Lid Structure for Thermal Stress Reliability
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Solution Overview
Problem
Conventional package assemblies face issues with material cracking and delamination due to stress, particularly in large reticle sizes, which affect package reliability, and finding suitable materials with appropriate thermal expansion properties is challenging.
Innovation Solution
A package assembly with a dual lid structure, comprising an outer lid and an inner lid, where the inner lid is made of a low coefficient of thermal expansion material, such as INVAR36, is designed to mitigate stress and cover high CTE regions, while the outer lid is polished to accommodate the inner lid and provide additional support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional single lid structure is used, then the device complexity is low, but the reliability deteriorates due to material cracking and delamination from thermal stress
Solution Approach 1:
The lid is divided into two separate lids: an outer lid and an inner lid. The outer lid has a first coefficient of thermal expansion (CTE) and the inner lid has a second CTE that is lower than the first CTE. This segmentation allows each lid to handle different thermal stress levels, with the inner lid specifically protecting high CTE regions from stress-induced cracking and delamination.
Solution Approach 2:
The dual lid structure combines materials with different thermal expansion properties. The outer lid material and inner lid material are selected to have different CTE values, creating a composite structure that better matches the thermal expansion characteristics of the underlying polymer materials, thereby reducing thermal stress.
2Reliability
If materials with appropriate thermal expansion properties are selected, then the reliability improves, but finding suitable materials becomes more challenging
Solution Approach 1:
The inner lid is specifically positioned to cover high CTE regions of the package assembly. By providing targeted protection only where it is most needed (high CTE regions susceptible to stress), the design optimizes material usage and simplifies the selection process by focusing on specific critical areas rather than requiring all materials to have perfect thermal expansion matching throughout.
3Manufacturing precision
If the outer lid is polished to accommodate the inner lid, then the manufacturing precision improves, but the ease of manufacture deteriorates
Solution Approach 1:
The outer lid is polished in advance to create a recessed portion that will accommodate the inner lid. This preliminary preparation of the outer lid surface ensures proper fit and alignment before final assembly, allowing the inner lid to be subsequently attached in the recessed area with precise positioning.
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 dual lid structure effectively reduces the risk of polymer material cracking and delamination, enhancing the reliability of the package assembly by managing thermal stress more efficiently.
Implementation Method 1
the inner lid is made of a low coefficient of thermal expansion material, such as INVAR36, is designed to mitigate stress and cover high CTE regions
Data Source
AI summary
A package assembly includes a package substrate, an interposer module on the package substrate, and a package lid on the interposer module and attached to the package substrate. The package lid includes an outer lid including an outer lid material and including an outer lid plate portion. The package lid further includes an inner lid including an inner lid material different than the outer lid material and including an inner lid plate portion attached to a bottom surface of the outer lid plate portion.