Compression Contact Test Socket for High-Speed BGA Signal Integrity
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Solution Overview
Problem
Conventional cantilevered beam contacts in BGA test sockets suffer from signal losses, signal reflection, impedance mismatching, misalignment, and limited adaptability to different solder ball sizes, and lack integration of capacitors and resistors, hindering high-performance integrated circuit testing.
Innovation Solution
A conductive compression contact socket with a PCB substrate and insulative housing, using conductive elastomer buttons and flexible retention members to establish direct, uniform connections, allowing for embedded capacitors and resistors, and accommodating various solder ball sizes without increasing footprint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional cantilevered beam contacts are used in BGA test sockets, then the socket structure is simple and manufacturing is easier, but signal loss increases and performance speed is limited to about 24 GHz
Solution Approach 1:
The patent changes the contact mechanism from cantilevered beam to compression contact, and changes the signal transmission medium from irregular cantilever shape to controlled impedance coaxial structure. This parameter change enables performance speed beyond 50 GHz by reducing signal loss through improved geometric consistency and impedance control.
Solution Approach 2:
The patent employs a composite structure combining conductive elastomer material with coaxial transmission geometry. The conductive elastomer provides both electrical conductivity and mechanical compliance, while the coaxial structure provides controlled impedance for high-speed signal transmission, achieving both low signal loss and high performance speed.
2Reliability
If cantilevered beam contacts are used, then the socket body thickness is reduced, but signal reflection increases and impedance matching becomes difficult due to irregular shape
Solution Approach 1:
The patent adopts a coaxial cylindrical geometry for the compression contact assembly, replacing the irregular cantilevered beam shape. This curved/symmetric geometry provides uniform impedance characteristics along the signal path, eliminating signal reflection issues and simplifying impedance matching while accommodating the required socket body thickness.
Solution Approach 2:
The patent changes the contact geometry from irregular cantilever shape to uniform coaxial cylinder, and changes the contact mechanism from cantilever deflection to compression. This parameter change achieves reliable impedance matching beyond 50 GHz by providing consistent geometric parameters throughout the signal transmission path.
3Ease of operation
If cantilevered beam contacts are used, then the contact length can be adjusted for retention force, but the contacts move or tilt within socket openings causing misalignment and damage
Solution Approach 1:
The patent replaces the mechanical cantilevered beam system with a compression contact system. Instead of relying on beam deflection and friction for retention, the compression contact uses axial compressive force through a coaxial structure, eliminating lateral movement and tilting while maintaining proper alignment and positioning stability.
4Loss of energy
If conventional sockets are used, then the interconnection is achieved, but the electrical signal path increases causing inherent signal losses
Solution Approach 1:
The patent uses a coaxial cylindrical structure for the compression contact, which provides the most efficient and direct signal transmission path. This symmetric curved geometry minimizes the electrical signal path length compared to irregular cantilever shapes, reducing inherent signal losses while maintaining the required interconnection function.
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
Reduces signal loss and reflection, enhances performance speed beyond 50 GHz, improves impedance matching, and facilitates daisy-chain testing with improved power integrity and adaptability.
Implementation Method 1
adhered to the top surface of each filled via is an electrically conductive compression contact
Implementation Method 2
establish electrical connectivity from the array of solder ball contacts of the DUT, through the conductive compression contacts and associated filled vias
Implementation Method 3
The flexible retention member may extend around the circumference of the socket aperture and grip the solder ball of the integrated circuit
Data Source
AI summary
A test socket for an electronic circuit device with protruding circuit contacts, the test socket including an underlying PCB substrate with an overlaying electrically insulative housing, where the PCB substrate includes an array of electrically conductive vias extending therethrough, and the housing includes an array of socket apertures which align with the PCB vias and contain resiliently compressible electrically conductive compression contacts therein that connect electrically with the conductive vias of the PBC substrate. The socket apertures each have peripheral retention flaps which engage and retain the protruding circuit contacts of the electronic circuit device in electrical engagement with the conductive compression contacts within the socket apertures during testing.