BGA Warpage Control via Segmented Frame Stiffener
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Solution Overview
Problem
Ball grid array (BGA) packages experience warpage due to thermal expansion mismatches between materials, leading to connectivity issues with printed circuit boards (PCBs), especially in larger packages where warpage results in significant displacement of connectors, rendering the package unusable.
Innovation Solution
A warpage control frame is integrated into the BGA assembly, mounted on the substrate opposing the lid, comprising a mechanical structure that reduces warpage by counteracting internal stresses and CTE mismatches between the package substrate, chip, and lid, with configurations including cross members that span or traverse the substrate to maintain structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the BGA package size is increased, then the electronic devices become smaller and more capable, but the package warpage increases due to thermal expansion mismatches
Solution Approach 1:
The warpage control frame is divided into multiple segments including a perimeter frame and internal cross members that span the substrate. This segmentation allows the frame to effectively counteract thermal stresses across different regions of the large footprint package, preventing overall warpage while maintaining the large package size needed for advanced electronic devices
Solution Approach 2:
The frame structure modifies the mechanical parameters of the package by introducing a rigid perimeter and internal support members. This changes the stress distribution parameters throughout the package, counteracting the thermal expansion mismatches between the substrate, copper layers, and chip that would otherwise cause warpage in larger packages
2Area of stationary object
If the package footprint is made larger, then more connectors can be accommodated, but the displacement of connectors at the outer extremes increases
Solution Approach 1:
The frame is segmented into a perimeter portion and multiple internal cross members that divide the large footprint into smaller effective zones. This segmentation ensures that connectors at the outer extremes remain properly positioned by providing local support that prevents excessive displacement, while still allowing the overall package footprint to be large enough to accommodate numerous connectors
Solution Approach 2:
The frame structure adds a dimensional element to the package design by introducing a rigid boundary layer around the perimeter and spanning across the substrate. This dimensional addition creates a stable reference framework that maintains connector position accuracy across the large footprint area
3Adaptability or versatility
If metal components are incorporated into the package, then electrical functionality is enhanced, but internal stresses increase during lamination or adhesion steps
Solution Approach 1:
The warpage control frame acts as an intermediary structural element between the metal components and the substrate. During lamination or adhesion steps, the frame provides a stable framework that distributes and reduces internal stresses, preventing excessive warpage while allowing the metal components to maintain their electrical functionality
4Shape
If a rigid perimeter frame is added to control warpage, then substrate flatness is improved, but device complexity increases
Solution Approach 1:
The frame is segmented into a perimeter portion and optional internal cross members, allowing for a modular design that can be tailored to specific package requirements. This segmentation achieves substrate flatness control while managing complexity by only adding structural elements where needed rather than creating a fully enclosed complex framework
Solution Approach 2:
The frame structure applies local quality control by concentrating rigid support at the perimeter and key internal locations where warpage stresses are most problematic. This localized approach maintains substrate flatness where critical while avoiding unnecessary complexity in regions where the substrate is already stable
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 warpage control frame effectively minimizes substrate warpage, ensuring reliable connection to PCBs by maintaining package flatness and reducing internal stresses, thereby enhancing the structural performance and usability of BGA packages.
Implementation Method 1
package warpage has been observed during the elevated temperature processes due to the different coefficient of thermal expansion ('CTE') properties between the flip-chip package substrate material, copper conductor layers, the chip itself, and other substrate assembly materials
Data Source
AI summary
A chip package and methods of manufacturing the same are disclosed. In particular, a chip package comprising a ball grid array is disclosed in which the chip package includes a package substrate supporting the ball grid array and in which the chip package further includes a warpage control frame that helps to minimize or mitigate warpage of the chip package.