Blind Via Fabrication Using Photosensitive Cover Layer
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Solution Overview
Problem
Conventional laser drilling processes for forming blind via structures in circuit boards face issues with contamination and instability due to the corrosion of the rough oxide layer and non-uniformity in the copper foil layer, which affect the quality and stability of the subsequent processes.
Innovation Solution
A method involving a substrate with a conductive layer, a metal layer, and a dielectric layer, where a cover layer made of a photosensitive material is formed and irradiated with a laser beam to create blind via structures with different opening sizes, allowing for direct ablation and heat absorption, thereby simplifying the process and protecting the underlying layers from etchant corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rough oxide layer is formed on the copper foil layer before laser drilling, then the copper can be protected from oxidation, but the rough oxide layer cannot resist etchant corrosion and may be corroded through, affecting the stability of subsequent processes
Solution Approach 1:
A cover layer is introduced as an intermediary protective layer between the laser beam and the copper foil layer. This cover layer serves as a sacrificial protective barrier that prevents etchant from reaching and corroding the rough oxide layer and underlying copper structures, while still allowing laser processing to proceed effectively.
Solution Approach 2:
The cover layer is formed on the copper foil layer before laser drilling and etching processes. This preliminary protective action ensures that the underlying copper and oxide structures are protected from harmful etchant corrosion throughout the subsequent manufacturing steps.
2Ease of manufacture
If surface lithographing and etching processes are performed to form a thinned copper foil layer, then the copper foil can be prepared for via formation, but the thickness uniformity of the thinned copper foil layer may be affected by surface cleanness and etchant tumbling efficiency
Solution Approach 1:
The cover layer acts as a protective intermediary that prevents etchant from unevenly attacking the copper foil layer. By providing a uniform protective barrier, the cover layer ensures consistent etching conditions and maintains thickness uniformity across the copper foil layer during the via formation process.
Solution Approach 2:
The introduction of the cover layer changes the physical and chemical parameters of the surface, creating a uniform interface that improves etchant flow characteristics and ensures consistent etching rates across the entire copper foil layer, thereby maintaining thickness uniformity.
3Manufacturing precision
If multiple pre-processing steps are performed before laser drilling, then the copper foil layer can be prepared, but the production flow becomes complex and stability is affected
Solution Approach 1:
The cover layer formation step combines multiple functions: it protects the copper foil layer from oxidation, provides a uniform surface for laser processing, and acts as a barrier against etchant corrosion. By merging these protective functions into a single layer and process step, the overall production flow is simplified while maintaining preparation quality.
Solution Approach 2:
The cover layer serves multiple purposes simultaneously: oxidation protection, laser processing assistance, and etchant barrier. This multi-functional approach eliminates the need for separate processing steps for each function, thereby reducing production flow complexity while ensuring preparation quality.
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 formation of stable blind via structures with improved thickness uniformity and reduced contamination, allowing for a single-step laser processing and subsequent filling of conductive material without the need for additional etching or masking steps.
Implementation Method 1
the substrate formed with the cover layer is irradiated by a laser beam to form at least one blind via structure extending from the cover layer to the metal layer
Implementation Method 2
the cover layer and the conductive layer are directly heated by the laser beam, such that the cover layer and the conductive layer are ablated
Implementation Method 3
the dielectric layer under the conductive layer absorbs the heat of the conductive layer and is vaporized
Implementation Method 4
the dielectric layer under the conductive layer absorbs the heat of the conductive layer and is vaporized
Data Source
AI summary
A method for fabricating a blind via structure of a substrate is provided. First, a substrate is provided, which includes a conductive layer, a metal layer, and a dielectric layer disposed between the conductive layer and the metal layer. Next, a cover layer is formed on the conductive layer. Finally, the substrate formed with the cover layer is irradiated by a laser beam to form at least one blind via structure extending from the cover layer to the metal layer. The blind via structure includes a first opening, a second opening, and a third opening linking to one another. The first opening passes through the cover layer. The second opening passes through the conductive layer. The third opening passes through the dielectric layer. For example, a size of the first opening is greater than a size of the second opening and a size of the third opening.