Controlled Impedance High-Density Interconnection Structures
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Solution Overview
Problem
High-speed electronic signal transmission in IC packaging and probing systems faces challenges due to signal degradation caused by discontinuities in traditional interconnection schemes, particularly at the chip-to-package interface, leading to issues with impedance control and signal integrity as pin counts increase.
Innovation Solution
The development of controlled impedance high-density interconnection structures using flexible microstrip circuits with fine-pitch and coarse-pitch terminals arranged in specific configurations, such as stair-step formations, to maintain seamless signal transitions and minimize signal degradation, employing flexible insulating materials like polyimide film and polyetherimide to ensure consistent impedance across multiple circuit layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional wire bonds are used to interconnect chip to package, then the interconnection structure is simple and easy to manufacture, but signal degradation occurs due to excessive inductance and capacitance at interconnection transitions
Solution Approach 1:
The interconnection structure is divided into multiple circuit layers with fine-pitch terminals on one surface and coarse-pitch terminals on another surface. Each layer is bonded together using adhesive layers, creating a segmented architecture that separates signal transmission functions from interconnection functions, thereby maintaining signal integrity while managing complexity.
Solution Approach 2:
The invention transitions from planar interconnections to a three-dimensional multi-layer structure. Circuit layers are stacked with fine-pitch terminals on the first surface and coarse-pitch terminals on the second surface, utilizing the vertical dimension to achieve pitch transformation and controlled impedance without excessive lead length.
2Quantity of substance
If pin count increases to handle high-density interconnections, then more signals can be transmitted, but the number of available interconnection solutions drops off rapidly
Solution Approach 1:
The circuit layer structure serves multiple functions simultaneously: it provides pitch transformation from fine-pitch to coarse-pitch terminals, maintains controlled impedance for signal integrity, enables high-pin count interconnections, and facilitates redistribution of signals. This multi-functional design makes the solution adaptable to various high-density interconnection requirements.
Solution Approach 2:
The invention changes the pitch parameter from fine-pitch at one surface to coarse-pitch at another surface through the multi-layer circuit structure. This parameter transformation allows high-pin count signals to be redistributed to appropriate interconnection points while maintaining controlled impedance throughout the signal path.
3Reliability
If feature sizes and spacing of conductors are changed to control impedance, then impedance matching can be achieved, but the design becomes extremely challenging using current design practices
Solution Approach 1:
The circuit layers are designed with pre-calculated conductor widths, spacing, and dielectric thicknesses to achieve controlled impedance before assembly. The fine-pitch and coarse-pitch terminal configurations are predetermined to maintain characteristic impedance across the interconnection structure, eliminating the need for complex post-assembly impedance matching adjustments.
4Reliability
If lead length is shortened to reduce inductance effects at high signal speeds, then signal degradation is minimized, but the acceptable lead length becomes extremely short
Solution Approach 1:
The invention uses vertical stacking of circuit layers to achieve pitch transformation and signal redistribution without requiring long horizontal lead lengths. The fine-pitch terminals connect to fine-pitch pads on the chip, and coarse-pitch terminals provide access points on the opposite surface, minimizing the electrical path length while accommodating pin count requirements.
Data Source
AI summary
An interconnection structure suitable for use as an IC package, probe head or other electrical termination of high density where uninterrupted controlled impedance is desired is described.