PCB Cavity Formation via Peelable Copper Barrier

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Solution Overview

Problem

The manufacturing of multilayer printed circuit boards with cavities faces challenges in controlling resin overflow during the lamination process, leading to difficulties in protecting electrically conductive traces and increasing production costs due to the need for additional protective measures like peelable films.

Innovation Solution

A method involving a core substrate with dielectric layers and copper layers, where a peelable metal layer is formed with a smooth surface that can be easily peeled off, reducing the need for additional protective films by enhancing the adhesive force between dielectric and trace layers, allowing for controlled cavity formation without resin overflow.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a peelable film is attached on the inner layer substrate to protect traces during lamination, then resin overflow is controlled and traces are protected, but manufacturing cost increases

Engineering Contradiction:

Improvetrace protectionVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The copper layer itself serves as the protective function by forming a protruding structure that extends into the cavity, eliminating the need for separate peelable films. The copper trace structure provides both electrical connectivity and physical protection during the lamination process, making the system self-sufficient.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The protective function is extracted from the copper trace by creating a protruding structure that extends into the cavity. This protruding copper structure is specifically designed to prevent resin overflow and protect underlying traces without requiring additional protective materials.

Inventive Principle:

Principle #2Taking out (Extraction)

2Productivity

If resin overflow during lamination is not controlled, then manufacturing process is simpler, but PCB must be discarded due to resin on traces

Engineering Contradiction:

Improvemanufacturing efficiencyVSAvoidPCB quality

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The protruding copper structure is formed in advance before the lamination process. This pre-formed structure acts as a barrier that prevents resin from reaching and contaminating the traces during hot pressing, ensuring PCB quality without compromising manufacturing efficiency.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The potential harm of resin overflow is converted into a benefit by using the copper protruding structure as a sacrificial barrier. The resin can flow against the protruding copper without damaging the actual traces, and the excess resin is easily removed after lamination, turning a potential defect into a protective mechanism.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Loss of time

If adhesive sheet is hot pressed without protective measures, then lamination process is faster, but resin overflow contaminates traces and requires discarding PCB

Engineering Contradiction:

Improvelamination timeVSAvoidresin control precision

Core Design Contradiction:

Loss of timeVSManufacturing precision

Solution Approach 1:

The protruding copper structure is prepared in advance to serve as a built-in protective barrier. This eliminates the need for additional protective films during lamination, maintaining fast processing speeds while ensuring precise resin control and preventing contamination of the traces.

Inventive Principle:

Principle #10Preliminary action

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 method enables the efficient formation of cavities in printed circuit boards while reducing manufacturing costs by eliminating the need for additional peelable films and improving the adhesive forces between layers, thus preventing resin overflow and protecting the traces effectively.

Implementation Method 1

surfaces of the first trace layer and the second dielectric layer, surfaces of the third trace layer and the fourth dielectric layer, and surfaces of the fourth trace layer and the fifth dielectric layer are roughened, respectively. Therefore, adhesive forces between the layers are increased

Methodology Applied

Scientific EffectAdhesion: Adhesive

Implementation Method 2

Methodology Applied

Scientific EffectSurface roughening: Abrasion

Implementation Method 3

the peelable metal layer has a smooth surface, and therefore, adhesive forces between the peelable metal layer and the second dielectric layer are weaker than adhesive forces between neighboring dielectric layers

Methodology Applied

Scientific EffectAdhesion: Adhesive

Data Source

PatentUS9439282B2Method for manufacturing printed circuit board

Publication Date: 2016.09.06 LEADING INTERCONNECT SEMICONDUCTOR TECHNOLOGY QINHUANGDAO CO LTD

AI summary

A printed circuit board includes a first trace layer, a first dielectric layer, a second trace layer, a second dielectric layer, a third trace layer, a third dielectric layer and a fourth trace layer arranged in that order. A cavity is defined in the printed circuit board running through from the fourth trace layer to the second dielectric layer. Portion of the second dielectric layer is exposed in the cavity. Surfaces of the fourth trace layer combining with the second dielectric layer, and surfaces of the second trace layer combining with the first dielectric layer, are all roughened to increase the strength of adhesion.