Back-Drilling Multi-Layer PCBs Using Conductive Electrical Sensing

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Solution Overview

Problem

The variability in layer thicknesses of multilayer circuit boards poses challenges in effectively removing stub portions and detecting slivers during back drilling, leading to signal integrity issues and reduced bandwidth in high-speed data transmission.

Innovation Solution

A progressive reciprocating back drill process with dynamic electrical sensing using a conductive cutting device, which controls stub length and eliminates slivers by referencing a contact layer to accurately determine drilling depth and detect any remaining conductive material.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If back drilling is performed to remove stub portions, then signal quality is improved, but manufacturing precision deteriorates due to variable layer thicknesses

Engineering Contradiction:

Improvesignal qualityVSAvoiddrilling depth control

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The system employs electrical sensing feedback during the back-drilling process to detect the contact layer in real-time. The conductive cutting device interacts with the contact layer to provide positional feedback, allowing the drilling depth to be dynamically adjusted and controlled, thereby ensuring consistent stub removal despite variable layer thicknesses

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces purely mechanical depth control with an electrical sensing system. The conductive cutting device uses electrical interaction with the contact layer to determine drilling depth, substituting mechanical measurements with electrical detection to achieve more precise and reliable depth control

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Length of moving object

If drilling depth is increased to remove all stubs, then stub length is reduced, but signal layer connection reliability deteriorates

Engineering Contradiction:

Improvestub lengthVSAvoidsignal layer connection

Core Design Contradiction:

Length of moving objectVSReliability

Solution Approach 1:

The electrical sensing feedback mechanism continuously monitors the drilling depth by detecting the contact layer. This feedback prevents over-drilling by stopping the cutting device when the contact layer is reached, ensuring that the stub is removed while maintaining the integrity of the signal layer connection

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The contact layer serves as a self-referencing feature that automatically indicates the correct drilling depth. The conductive cutting device uses the contact layer's position to self-regulate the drilling process, eliminating the need for external depth measurement systems

Inventive Principle:

Principle #25Self-service

3Reliability

If conventional back drilling is used, then stub removal is achieved, but slivers are generated causing signal integrity issues

Engineering Contradiction:

Improvestub removalVSAvoidsliver generation

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent replaces conventional mechanical drilling with a controlled cutting process using a conductive cutting device. This substitution allows for more precise material removal that reduces the generation of slivers and chips, thereby minimizing harmful factors while maintaining stub removal effectiveness

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system changes the cutting parameters dynamically based on real-time electrical feedback. By adjusting the cutting depth and speed according to the detected contact layer position, the process optimizes material removal while minimizing sliver generation

Inventive Principle:

Principle #35Parameter changes

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 approach ensures consistent and minimal stub length reduction, enhancing signal-to-noise ratio and reducing the likelihood of signal layer damage, while effectively detecting and addressing slivers to improve electronic system performance.

Implementation Method 1

dynamic electrical sensing using a conductive cutting device, which controls stub length and eliminates slivers by referencing a contact layer to accurately determine drilling depth

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS11690177B2Methods and systems for back-drilling a multi-layer circuit board

Publication Date: 2023.06.27 NEXTGIN TECH BV

AI summary

Methods and systems for making a multi-layer circuit board are disclosed, including electrically connecting a boring device with a plated multi-layered circuit board; cutting a first bore having a first diameter through a first layer of the plated multi-layered circuit board; reciprocally extending a second cutting device a first predetermined distance into a barrel plated multi-layered circuit board and retracting the cutting device a second predetermined distance that is less than the first predetermined distance to form a second bore; after each retraction, sensing for electrical contact indicating a closed circuit between the cutting device and the plated multi-layered circuit board; if a closed circuit is sensed, determining if the second bore has reached an expected depth of a contact layer; and if the expected depth of the contact layer has not been reached, determining that a sliver has been formed in the barrel.