PCB Plated Through Holes With Precision Stub Removal

Solution Overview

Problem

Existing methods for forming plated through holes in printed circuit boards (PCBs) result in excessive conductive material, known as stubs, which cause signal distortion and integrity issues, especially in high-speed signal transmission due to the stub effect.

Innovation Solution

A method involving multiple drilling steps with varying diameters and conductive material application to form plated through holes, ensuring that the conductive material is strategically removed or maintained to minimize stub formation, thereby improving signal integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a plated via structure extends completely through the PCB to connect proximate adjacent layers, then electrical connectivity between layers is achieved, but excessive conductive material (stubs) is formed causing signal distortion

Engineering Contradiction:

Improveelectrical connectivityVSAvoidstub effect

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The via structure is segmented into two separate conductive paths: a first conductive path from the first surface to the first internal layer, and a second conductive path from the second surface to the second internal layer. This segmentation eliminates the continuous through-hole stub that causes signal distortion, as each conductive path terminates at its respective internal layer without extending completely through the PCB.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the PCB have different via structures tailored to their specific needs. The first via structure connects the first surface to the first internal layer, while the second via structure connects the second surface to the second internal layer. This local differentiation allows each via to provide connectivity only where needed, eliminating unnecessary conductive material in each region.

Inventive Principle:

Principle #3Local quality

2Reliability

If signal is transmitted through a plated via structure with stubs, then electrical connectivity is maintained, but signal integrity deteriorates due to reflections and delays

Engineering Contradiction:

Improveelectrical connectivityVSAvoidsignal integrity

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The via structure is segmented into two separate conductive paths: a first conductive path from the first surface to the first internal layer, and a second conductive path from the second surface to the second internal layer. This segmentation eliminates the continuous through-hole stub that causes signal distortion, as each conductive path terminates at its respective internal layer without extending completely through the PCB.

Inventive Principle:

Principle #1Segmentation

3Ease of manufacture

If conventional drilling and plating methods are used, then plated through holes are formed, but stubs with excessive conductive material remain causing harmful effects

Engineering Contradiction:

Improveplated through hole formationVSAvoidstub effect

Core Design Contradiction:

Ease of manufactureVSObject-generated harmful factors

Solution Approach 1:

The via structure is segmented into two separate conductive paths: a first conductive path from the first surface to the first internal layer, and a second conductive path from the second surface to the second internal layer. This segmentation eliminates the continuous through-hole stub that causes signal distortion, as each conductive path terminates at its respective internal layer without extending completely through the PCB.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of drilling a single continuous hole through the entire PCB and then attempting to remove stubs, the invention inverts the approach by drilling two separate holes of different depths from opposite surfaces. The first hole is drilled from the first surface to a first depth, and the second hole is drilled from the second surface to a second depth, with the deeper hole drilled after plating the shallower hole to ensure proper conductive material distribution.

Inventive Principle:

Principle #13The other way round (Inversion)

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

The method effectively reduces stub length and maintains signal integrity by controlling the distribution of conductive material within the plated through holes, enhancing the performance of high-speed signal transmission in PCBs.

Implementation Method 1

the walls of the remaining portion of the first hole 102 and the walls of the second hole 103 are plated with a thin layer of a conductive material 106

Methodology Applied

Scientific EffectElectroplating: Electroplating

Data Source

PatentUS12575036B2Method of forming high aspect ratio plated through holes

Publication Date: 2026.03.10 SANMINA CORP

AI summary

The present invention relates to printed circuit boards (PCBs), and more particularly, to methods of forming high aspect ratio through holes and high precision stub removal in a printed circuit board (PCB). The high precision stub removal processes may be utilized in removing long stubs and short stubs. In the methods, multiple holes of varying diameter and depth are drilled from an upper and/or lower surface of the printed circuit board utilizing drills of different diameters.