Impedance Compensation in Flip Chip RF Interconnects

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Solution Overview

Problem

Flip chip connections in RF communications face significant parasitic effects at millimeter wave frequencies, requiring proper impedance compensation to achieve desired impedance matching, which existing technologies struggle to address effectively.

Innovation Solution

The implementation of connector strips with uneven widths and strategically placed cavities to adjust impedance, utilizing Smith charts for determining the necessary adjustments to match the impedance of transmission lines to either high or low impedance, depending on capacitive or inductive nature, ensuring a 50-ohm impedance match.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If flip chip connection is used for short signal propagation path and low loss, then signal transmission quality is improved, but parasitic effects increase significantly at millimeter wave frequencies

Engineering Contradiction:

Improvesignal lossVSAvoidparasitic effects

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The connector strip is designed with non-uniform width where the first portion has a first width and the second portion has a second width different from the first width. This local variation in geometric quality allows different sections to serve different impedance matching functions, compensating for parasitic effects at millimeter wave frequencies while maintaining low signal loss.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The impedance of the transmission line is adjusted by changing the geometric parameters of the connector strip, specifically the width of different portions. By varying the width parameter along the strip, the impedance profile is optimized to compensate for parasitic effects and achieve desired impedance matching at millimeter wave frequencies.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If conventional uniform connector strips are used, then manufacturing is simple, but impedance matching cannot be achieved at millimeter wave frequencies

Engineering Contradiction:

Improveconnector strip fabricationVSAvoidimpedance matching precision

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The connector strip incorporates local geometric variations with different width portions to achieve precise impedance matching. These localized structural modifications enable accurate impedance control at millimeter wave frequencies while remaining compatible with conventional PCB manufacturing processes.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS10553551B2Impedance compensation of flip chip connection for RF communications

Publication Date: 2020.02.04 SWIFTLINK TECH INC

AI summary

A flip chip IC device utilized in RF transceivers includes a bare die having a number of metalized pads and each metalized pad has a solder ball deposited thereon. The flip chip IC device further includes a substrate having a number of connector pads corresponding to the metalized pads. The connector pads are connected to one or more electronic components disposed on the substrate via a number of connector strips. The bare die is flipped up-side-down such that the metalized solder pads are aligned and connected with the connector pads of the substrate via the solder balls. At least one of the connector strips includes a strip section having an uneven strip width configured to compensate an impedance of a transmission line formed based on a connection between a metalized pad of the bare die and a connector pad of the substrate to match predetermined impedance.