Laser Cavity Formation in Multi-Layer PCBs
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Solution Overview
Problem
The existing methods for forming cavities in multi-layer printed circuit boards (PCBs) are prone to damage of the outer wall, leading to electrical shorts, delamination, and increased manufacturing costs, with limited design freedom due to the need for precise milling and the rarity of successful layer-by-layer applications.
Innovation Solution
A method using a laser to form cavities in PCBs by creating a cavity separation layer that can be easily removed, allowing for increased design freedom without the need for an etch stopper, thereby improving the accuracy and reliability of the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a punching machine is used to form a cavity in a multi-layer PCB, then the cavity can be formed, but the outer wall of the cavity is damaged leading to CAF short, delamination, and increased manufacturing costs
Solution Approach 1:
The patent replaces the mechanical punching system with a laser-based system. The laser beam forms the cavity by ablation rather than mechanical force, eliminating contact with the outer wall and preventing damage. The laser process creates a clean cavity without the mechanical stress that causes CAF short and delamination in traditional punching methods.
Solution Approach 2:
The patent introduces a cavity separation layer as an intermediary element. This layer is formed between the insulating layer and the cavity region, allowing the insulating layer to be cleanly separated and removed without damaging the cavity outer wall. The separation layer acts as a mediator that enables precise cavity formation while protecting the structural integrity of the surrounding areas.
2Manufacturing precision
If a milling bit is used to form a cavity with 5 μm precision, then the cavity can be formed, but the process precision requirement is too high for mass production
Solution Approach 1:
The patent replaces precision mechanical milling with laser processing. The laser system inherently provides precise positioning and cutting without the mechanical tolerance issues (50-100 μm) that plague milling operations. This substitution makes high-precision cavity formation feasible for mass production without requiring excessive process control.
Solution Approach 2:
The patent changes the processing parameters from mechanical (milling bit diameter, feed rate, depth of cut) to optical (laser power, pulse duration, scanning speed). This parameter transformation enables precise cavity formation with more controllable and consistent results across mass production, eliminating the need for extremely tight mechanical tolerances.
3Manufacturing precision
If an etch stopper is formed at the cavity boundary, then the cavity can be precisely defined, but the design freedom for cavity circuits is reduced
Solution Approach 1:
The patent uses a cavity separation layer as an intermediary instead of an etch stopper. This separation layer provides precise cavity definition through controlled adhesion rather than through etch resistance. The approach allows cavity circuits to extend to the boundary without requiring an etch stopper, thereby maintaining design freedom while achieving precise cavity boundaries.
Solution Approach 2:
Instead of using an etch stopper to prevent etching at the cavity boundary (positive control), the patent uses a cavity separation layer with controlled adhesion to enable clean separation (negative control). This inverted approach achieves precise cavity definition without restricting circuit design, as the separation occurs after circuit formation rather than preventing circuit deposition.
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 enables precise cavity formation without damaging the outer wall, reduces manufacturing costs, and enhances the design flexibility of PCBs by allowing for the easy removal of insulating layers and control of etch depth using a laser.
Implementation Method 1
a cavity is formed by using a laser
Data Source
AI summary
Disclosed are a printed circuit board and a method for manufacturing the same. The method for manufacturing the printed circuit board includes forming a base circuit board including a cavity circuit pattern in a cavity region on upper and lower portions of a substrate and internal circuit layers outside the cavity region, forming a cavity separation layer on the cavity circuit pattern, forming at least one pair of an insulating layer and a circuit layer on the base circuit board, cutting the insulating layer and the cavity separation layer provided on an etch stop pattern by controlling a focal length of a laser beam such that the laser beam reaches a surface of the base circuit board, and removing the insulating layer by separating the cavity separation layer to form the cavity. The cavity separation layer is formed on the cavity circuit pattern, and the resultant structure is cut to the cavity separation layer by using a laser so that the insulating layer is separated. Accordingly, the insulating layer in the cavity is easily removed.