BGA Package Layout With PCB Cutout for Lower Stack Height
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Solution Overview
Problem
Conventional ball grid array (BGA) packaging in information handling systems results in increased substrate layer count and overall thickness, making it difficult to reduce the system's thickness without compromising performance or functionality, due to the need for circuit paths to traverse all internal layers.
Innovation Solution
The BGA device is affixed to the substrate with the ball grid array on the top side, allowing the cold plate to extend through a cutout area in the PCB, reducing the overall stack height by 'hiding' the depth of the BGA and cold plate within the PCB, and using a backplate for mechanical stability to eliminate tension on solder connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional BGA packaging is used with the BGA on the bottom side of the substrate, then the circuit paths can be routed through internal layers, but the substrate layer count increases and the overall thickness increases
Solution Approach 1:
The patent inverts the conventional BGA placement by positioning the ball grid array on the top side of the substrate instead of the bottom side. This inversion allows circuit paths to be routed on the same side as the BGA, eliminating the need for paths to traverse through all internal substrate layers, thereby reducing the required substrate layer count and overall thickness while maintaining connectivity reliability
Solution Approach 2:
The patent changes the dimensional arrangement by placing the BGA on the top surface rather than the bottom surface of the substrate. This dimensional repositioning enables circuit paths to remain on the top side of the substrate, avoiding the need to route through multiple internal layers in the vertical dimension, thus reducing substrate thickness requirements
2Length of stationary object
If the substrate layer count is reduced to decrease thickness, then the system becomes thinner, but circuit path routing becomes more difficult
Solution Approach 1:
By inverting the conventional design and placing the BGA on the top side of the substrate, the patent enables circuit paths to be routed on the same side as the BGA connections. This eliminates the complexity of routing paths through multiple internal layers, making circuit path routing easier even with reduced substrate layer count
3Length of stationary object
If the BGA and cold plate depth is hidden within the PCB to reduce stack height, then the overall system thickness decreases, but mechanical stability may be compromised
Solution Approach 1:
The patent applies nesting by positioning the cold plate within the PCB structure, specifically extending the cold plate through a cutout area in the PCB. This allows the cold plate depth to be 'hidden' within the PCB, reducing the overall stack height while the PCB itself provides mechanical support and stability to the assembly
4Reliability
If solder connections are used to attach the BGA to the PCB, then electrical connectivity is achieved, but tension on the solder connections can cause reliability issues
Solution Approach 1:
The patent introduces a backplate that acts as a counterweight or support structure to offset the tension forces on the solder connections. The backplate provides mechanical support to the BGA assembly, counteracting the tensile stresses that would otherwise be placed on the solder joints, thereby maintaining both electrical connectivity and mechanical strength
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 reduces the substrate layer count, decreases the overall cost of the BGA device, and allows for a thinner information handling system design without compromising performance, as the circuit paths do not need to traverse all internal layers, and thermal contact is maintained for effective heat dissipation.
Implementation Method 1
a die that is bonded via a first surface of the die to a first surface of the substrate
Implementation Method 2
The integrated circuit device may be bonded to a first surface of the PCB via the BGA
Implementation Method 3
thermal contact is maintained for effective heat dissipation
Data Source
AI summary
An information handling system includes a printed circuit board (PCB) and an integrated circuit device. The integrated circuit device includes a substrate and a die that is bonded via a first surface of the die to a first surface of the substrate. The substrate includes a ball grid array (BGA) on the first surface of the substrate. The integrated circuit device is bonded to a first surface of the PCB via the BGA. The die is collocated with the cutout area.