Split Stiffener Architecture for Microelectronic Package Warpage
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Solution Overview
Problem
Warpage in thin microelectronic package structures due to differences in temperature coefficients of thermal expansion (CTE) between devices and package substrates, exacerbated by temperature processing like solder reflow, leads to reliability issues and yield loss.
Innovation Solution
Incorporating a metal stiffener with two sections on opposite sides of an opening on the substrate, where a non-conductive adhesive is used to attach the stiffener, and a grounding structure is employed to ground the stiffener to the substrate, allowing for enhanced mechanical strength and reduced warpage without consuming additional real estate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a metal stiffener is added to reduce warpage, then mechanical strength and warpage resistance are improved, but package real estate is consumed
Solution Approach 1:
The stiffener is divided into two separate sections positioned on opposite sides of the opening, allowing the package to achieve the necessary mechanical strength and warpage resistance while consuming less real estate than a single large stiffener would require
Solution Approach 2:
The stiffener sections are strategically positioned adjacent to components that require support, providing localized reinforcement exactly where needed to prevent warpage during temperature processing, rather than using a large stiffener that would occupy unnecessary package area
2Ease of manufacture
If temperature processing is performed for solder reflow, then device assembly is completed, but warpage increases due to CTE differences
Solution Approach 1:
The stiffener sections are attached to the substrate before temperature processing, creating a pre-existing mechanical reinforcement structure that counteracts the warpage forces generated during solder reflow and other temperature processing operations
Solution Approach 2:
The stiffener material is selected to have thermal and mechanical properties that compensate for the CTE mismatch between the device and substrate, allowing the structure to maintain dimensional stability during temperature cycling without requiring additional real estate
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 solution effectively reduces warpage and enhances mechanical strength while maintaining electrical performance, allowing for closer component packing without increasing the package size, thus addressing the reliability and yield concerns.
Implementation Method 1
a non-conductive adhesive is used to attach the stiffener
Implementation Method 2
a grounding structure is employed to ground the stiffener to the substrate
Implementation Method 3
Temperature coefficients of thermal expansion (CTE) may differ between a device and a package substrate, which contributes to the problem
Data Source
AI summary
Methods of forming microelectronic package structures, and structures formed thereby, are described. Those methods/structures may include attaching a stiffener on a substrate, wherein a first section of the stiffener and a second section of the stiffener are on opposite sides of an opening. At least one component may be attached on the substrate within the opening, wherein the at least one component is disposed between the first section of the stiffener and the second section of the stiffener, and wherein the stiffener comprises a grounding structure disposed on the substrate.