Differential Trace Pair Neck-Down for BGA Routing

Solution Overview

Problem

Conventional differential trace pairs face challenges in transmitting data at high speeds due to impedance variations and manufacturing difficulties when narrowing traces to fit through Ball Grid Array (BGA) pin fields, leading to issues like signal reflections and increased Bit Error Rate at 25 G transmission rates.

Innovation Solution

The design includes a differential trace pair with a first portion outside the connection pad array and a second portion with a smaller width extending through the array, featuring connection pad channels to maintain impedance matching and accommodate the BGA pin field, reducing impedance discontinuities and manufacturing complexities.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the differential trace pair is narrowed to fit through the BGA pin field, then the trace pair can be routed through the connection pad array, but the manufacturing precision becomes difficult to achieve and impedance variations increase

Engineering Contradiction:

Improverouting capability through BGA pin fieldVSAvoidtrace width consistency

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent applies local quality by creating a neck-down region with reduced trace width specifically at the connection pad array location, while maintaining the original wider trace width in other regions. This localized modification allows the trace pair to fit through the BGA pin field without requiring the entire trace pair to be manufactured at the difficult thin width, thereby resolving the manufacturing precision issue while maintaining routing capability.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The differential trace pair is segmented into multiple regions with different widths: a first region with wider traces outside the connection pad array, and a second neck-down region with narrower traces through the connection pad array. This segmentation allows each region to be optimized independently, with the wider regions being easier to manufacture and the narrow region specifically adapted for routing through the BGA pin field.

Inventive Principle:

Principle #1Segmentation

2Reliability

If the trace width is reduced to 4-5.5 mils for 10G transmission, then the impedance can be maintained, but the trace becomes too thin for reliable manufacturing at 25G rates

Engineering Contradiction:

Improvesignal transmission reliabilityVSAvoidtrace fabrication feasibility

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent applies local quality by creating a neck-down region with reduced trace width specifically at the connection pad array location, while maintaining the original wider trace width in other regions. This localized modification allows the trace pair to fit through the BGA pin field without requiring the entire trace pair to be manufactured at the difficult thin width, thereby resolving the manufacturing precision issue while maintaining routing capability.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the trace width parameter locally in the neck-down region while maintaining different parameters in other regions. By adjusting only the specific segment that needs to pass through the connection pad array, the patent achieves the necessary geometric adaptation without compromising the manufacturability of the majority of the trace pair structure.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If the differential trace pair width is increased for 25G transmission to reduce losses, then the signal quality improves, but the trace pair cannot fit through the BGA pin field

Engineering Contradiction:

Improvesignal transmission qualityVSAvoidrouting capability through connection pad array

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent applies local quality by creating a neck-down region with reduced trace width specifically at the connection pad array location, while maintaining the original wider trace width in other regions. This localized modification allows the trace pair to fit through the BGA pin field without requiring the entire trace pair to be manufactured at the difficult thin width, thereby resolving the manufacturing precision issue while maintaining routing capability.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The differential trace pair is segmented into multiple regions with different widths: a first region with wider traces outside the connection pad array, and a second neck-down region with narrower traces through the connection pad array. This segmentation allows each region to be optimized independently, with the wider regions being easier to manufacture and the narrow region specifically adapted for routing through the BGA pin field.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS9936572B2Differential trace pair system

Publication Date: 2018.04.03 DELL PROD LP

AI summary

A differential trace pair system includes a board having a first board structure member and a second board structure member. A differential trace pair in the board includes a first differential trace pair portion of a first width outside the board structure, and a second differential trace pair portion of a second width extending through the board structure. A first outer edge and a second outer edge of the second differential trace pair portion define the second width that is less than the first width. A first board structure member channel is defined by the first outer edge adjacent the first board structure member, a second board structure member channel is defined by the second outer edge adjacent the second board structure member and the first and second board structure member channels provide a third width of the second differential trace pair portion that is less than the second width.