BGA Package Ground Ring for Thermal Conduction and Backside Grounding
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Solution Overview
Problem
Current thermally enhanced flip-chip BGA packages face challenges in heat dissipation and backside grounding, particularly in Silicon On Insulator (SOI) devices, leading to thermal stresses and mechanical separation, which affect electrical performance and reliability.
Innovation Solution
The implementation of a BGA package with a heat spreader and an electrically continuous annulus of conductive material extending from the substrate ground ring to the heat spreader, allowing for improved thermal conduction and backside electrical contact, including coupling the backside of the IC to a ground ring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the BGA substrate uses a non-conductive adhesive underfill material to protect contacts and mechanically lock the flip-chip, then the mechanical strength and protection of contacts are improved, but the thermal conduction path is blocked due to the poor thermal properties of the substrate and underfill material
Solution Approach 1:
The invention divides the thermal management function into separate components: the underfill material maintains its protective and mechanical locking functions, while a dedicated thermal via system provides the thermal conduction path. The substrate is segmented into functional zones with thermal vias creating vertical heat paths through the substrate layers, separating the mechanical support function from the thermal management function.
Solution Approach 2:
The invention introduces thermal vias as intermediary elements that bridge the gap between the chip and the external environment for heat transfer. These vias act as thermal conduits through the non-conductive underfill material and substrate, enabling heat to bypass the thermal barriers and travel from the chip junction through the substrate to external heat sinks or ground planes.
2Reliability
If SOI devices use a thin insulating layer between silicon and substrate to reduce electrical charge and improve performance, then the electrical performance and energy efficiency are improved, but heat dissipation is impaired and thermal stresses increase
Solution Approach 1:
The invention addresses the heat dissipation problem by creating vertical thermal paths through the substrate using thermal vias, moving heat management from a two-dimensional plane to a three-dimensional structure. The thermal vias extend through multiple substrate layers, providing heat escape routes in the vertical dimension that bypass the insulating layer's thermal resistance.
Solution Approach 2:
The invention applies different material properties to different regions of the substrate. Thermal vias are strategically placed in specific locations beneath or near the SOI device to provide localized heat extraction paths. The substrate structure is modified locally to create thermal conduction channels while maintaining the insulating layer's electrical isolation properties in other areas.
3Productivity
If the high density of flip-chip BGA is used to achieve high interconnection density, then the number of balls per package volume is improved, but the concentration of excess heat generated during operation increases
Solution Approach 1:
The invention divides the heat dissipation function into multiple distributed thermal vias throughout the substrate, creating numerous localized heat extraction points. This segmentation of thermal management allows heat from densely packed chips to be distributed and removed through multiple paths, preventing heat concentration in any single region.
Solution Approach 2:
The invention addresses heat concentration by creating vertical thermal paths through the substrate using thermal vias, moving heat management from a two-dimensional surface problem to a three-dimensional solution. The thermal vias extend heat conduction into the vertical dimension, providing escape routes for heat that would otherwise concentrate in the high-density chip array plane.
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 configuration enhances thermal paths for heat dissipation and provides improved backside grounding, reducing thermal stresses and mechanical separation, thereby enhancing the reliability and performance of semiconductor devices.
Implementation Method 1
improved thermal conduction and backside electrical contact, including coupling the backside of the IC to a ground ring
Implementation Method 2
electrically continuous annulus of conductive material extending from the substrate ground ring to the heat spreader
Data Source
AI summary
The invention provides thermally enhanced BGAs and methods for their fabrication with a ground ring suitable for operably coupling to either the frontside or backside, or both, of an IC chip mounted on a substrate. The methods and devices of the invention disclosed include the fabrication of a ground ring on the surface of a BGA substrate prepared for receiving the frontside of the chip. A heat spreader has ground ring corresponding to substrate round ring and is attached at the backside of the chip with a conductive material. A conductive material is interposed between the heat spreader and substrate ground rings, electrically coupling them. Thus, the backside of the chip may be electrically connected to the ground ring as well as, or instead of, the frontside.