Bare Die Package Displacement Constraint for Warpage Control
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Solution Overview
Problem
Bare die packages experience excessive substrate warpage due to thermal expansion mismatch between the die and package substrate, leading to improper electrical contact and potential damage to the die when secured between a socket and heat sink, as they lack the structural support provided by an integrated heat spreader.
Innovation Solution
A displacement constraint, such as a plurality of rigid members or a frame, is fixedly attached to the package substrate or heat sink to provide structural support and prevent excessive substrate warpage, minimizing thermal expansion-induced bending.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a bare die package is secured between a socket and heat sink, then thermal management is achieved, but excessive substrate warpage occurs due to thermal expansion mismatch
Solution Approach 1:
A displacement constraint structure is introduced as an intermediary element between the package substrate and the heat sink. This constraint acts as a mediator that prevents the substrate from warping during thermal cycling while still allowing effective heat transfer from the die to the heat sink.
Solution Approach 2:
The invention changes the mechanical parameters of the packaging system by adding a displacement constraint that limits the substrate's degree of freedom. This constraint modifies the thermal-mechanical behavior of the system, preventing excessive warpage while maintaining thermal management functionality.
2Stability of the object's composition
If an integrated heat spreader is added to provide structural support, then substrate warpage is minimized, but device complexity increases
Solution Approach 1:
The invention extracts only the necessary structural support function from the integrated heat spreader concept. Instead of adding a full IHS assembly, a simplified displacement constraint is used that provides the essential warpage prevention functionality without the additional complexity of a complete heat spreader structure.
Solution Approach 2:
The displacement constraint is applied locally at critical positions on the package substrate rather than using a comprehensive IHS structure. This localized approach provides sufficient structural support to prevent warpage while minimizing the addition of complex components.
3Stability of the object's composition
If a compressible gasket is placed between the package substrate and heat sink, then some structural support is provided, but sufficient structural support is still lacking to prevent warpage
Solution Approach 1:
Instead of using a compressible gasket that relies on compression to provide support, the invention uses a rigid displacement constraint that actively prevents displacement. This inverts the approach from passive compression-based support to active constraint-based support, providing significantly stronger structural support.
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 displacement constraint effectively minimizes substrate warpage, ensuring stable electrical contact and reducing the risk of damage to the package substrate and die by providing adequate structural support during assembly.
Implementation Method 1
Die 110 and package substrate 120 are typically made from different materials, and hence both have different coefficients of thermal expansion (CTE). At the package assembly process, the die 110 does not expand as much as the package substrate 120, thus causing the package substrate 120 to bend away from the die 110
Data Source
AI summary
Embodiments of the present invention describe a bare die package and its methods of fabrication. The bare die package comprises a die electrically coupled to a package substrate, and a displacement constraint. In an embodiment of the present invention, the displacement constraint is a plurality of members fixedly attached onto the package substrate and surrounds the die. When the bare die package is secured between a socket and a heat sink, the plurality of members provide structural support to the package substrate and prevent excessive substrate warpage.