Liquid Metal PCB Interconnect With Surface Pins for Reworkable CPU Packages
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Solution Overview
Problem
Current BGA and LGA packaging technologies face challenges such as warpage and stress on solder joints, destructive removal processes, and space and height constraints, which complicate replacement and repair, and increase the risk of component failure.
Innovation Solution
A substrate-to-board interconnect using a thin dielectric sheet with liquid metal and surface pins, where the dielectric sheet is attached to a system-on-chip or CPU substrate package, and magnet and guideposts are used for alignment, allowing for electrical communication between the substrate and the board without the need for reflow processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If BGA packaging technology is used, then the package size is reduced, but the solder joints are subjected to warpage stress and replacement becomes destructive
Solution Approach 1:
The invention separates the interconnection function from the package substrate by introducing an interposer with through-holes. The BGA balls connect to the interposer rather than directly to the PCB, segmenting the stress path and isolating the solder joints from warpage stresses.
Solution Approach 2:
The interposer acts as an intermediary component between the BGA package and the PCB. It mediates the mechanical and electrical connection, absorbing stress and enabling non-destructive replacement without directly transmitting warpage forces to the solder joints.
2Volume of moving object
If BGA packages are direct soldered onto PCB, then the package size is smaller, but replacement and repair require destructive removal processes
Solution Approach 1:
The interposer creates a separable interface between the BGA package and PCB. The BGA balls solder to the interposer, which can then be removed as a unit from the PCB without damaging the PCB traces or requiring complex rework equipment.
Solution Approach 2:
The interposer serves as a removable intermediary that simplifies replacement. The entire interposer assembly can be detached and replaced without destructive processes, making repair and upgrade straightforward while maintaining the compact BGA form factor.
3Ease of repair
If LGA packages with socket and lid are used, then replacement and repair are easier, but the device occupies larger real estate and height
Solution Approach 1:
The invention merges the interconnect function with a thin dielectric layer containing through-holes, eliminating the need for separate socket and lid components. This integration achieves easy replacement without the bulk of traditional LGA packaging.
Solution Approach 2:
The solution transitions from the three-dimensional socket-lid structure to a planar interposer with through-holes. The electrical connections are established through the thickness of the thin dielectric layer rather than requiring a tall socket structure, reducing height while maintaining replaceability.
4Ease of repair
If LGA packages are used, then replacement is easier, but compression force increases with pin count and package size
Solution Approach 1:
The interposer segments the connection points into discrete through-holes distributed across its surface. This distributes the compression force across multiple small contact points rather than requiring concentrated force on a large socket, reducing the overall compression force needed.
Solution Approach 2:
The thin dielectric interposer acts as a flexible medium that can deform slightly under compression to establish reliable electrical contact through the through-holes. This flexibility reduces the rigid compression force requirements compared to traditional LGA sockets.
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 enables non-destructive replacement and repair of components, reduces stress on solder joints, and conserves space and height, improving the reliability and maintainability of electronic assemblies.
Implementation Method 1
individual holes of the plurality of holes having a liquid metal (LM) therein... enabling electrical communication between the substrate and the board
Implementation Method 2
magnet and guideposts are used for alignment
Data Source
AI summary
A substrate to printed circuit board (PCB) interconnect with liquid metal and surface pins. A thin dielectric sheet with drilled openings is adjacent to the bottom of a system on chip or CPU package substrate. Holes in the dielectric sheet have a liquid metal (LM) therein, the holes correspond to landing metal pads on the package substrate. The PCB includes surface pins in an arrangement to match the LM filled holes. A pick and place assembly of the package substrate to the PCB can be done without needing a reflow step. A magnet ring can be positioned on the polyimide sheet and configured to pair with a metal plate on the PCB. Guideposts around the periphery of the package substrate may be used to assist in alignment during assembly.