Embedded PCB Traces via Laser Ablation and Electroless Plating
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Solution Overview
Problem
In printed circuit board (PCB) fabrication, voids can be entrapped between traces during prepreg lamination, and signal integrity and conductor impedance are difficult to control due to varying dielectric spacing, leading to fabrication failures and reliability issues with fine trace lines not adhering properly to the laminate surface.
Innovation Solution
Embedding PCB traces within a laminate substrate composed of a catalytic core material surrounded by a non-catalytic material, using laser ablation or plasma etching to form channels, and electroless copper plating to create controlled geometry and improve adhesion, thereby ensuring consistent trace impedance and adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If PCB traces are formed above a laminate surface using conventional photolithography and chemical copper etching, then the fabrication process is simple and straightforward, but the geometry of the traces varies across the length of the traces leading to poor signal propagation and trace impedance control
Solution Approach 1:
The patent replaces conventional mechanical/chemical trace formation methods (photolithography and chemical etching) with a direct-write laser-induced forward transfer (LIFT) process. This substitution enables precise control of trace geometry by using laser parameters and template design rather than chemical diffusion processes, directly resolving the contradiction between manufacturing precision and process complexity.
Solution Approach 2:
The patent changes the fundamental parameters of the trace formation process by using laser energy density, pulse duration, and template-substrate distance as controllable parameters instead of chemical concentration and exposure time. This allows precise control of trace geometry (width, height, depth) while maintaining a relatively simple single-step fabrication process.
2Manufacturing precision
If PCB traces are formed above a laminate surface, then the fabrication process is straightforward, but dielectric space above the PCB traces varies across the length and width of the board making it difficult to accurately control impedance
Solution Approach 1:
The patent creates traces with non-uniform cross-sectional geometry where the dielectric material is strategically placed around the conductor. By controlling the local distribution of dielectric material through template design and laser processing parameters, the patent achieves consistent impedance along the trace length while maintaining fabrication simplicity.
Solution Approach 2:
The patent uses a composite structure consisting of a metal conductor core surrounded by a dielectric material shell. This composite geometry, formed through the LIFT process, allows independent control of conductor and dielectric dimensions, enabling precise impedance control without complicating the fabrication process.
3Manufacturing precision
If trace widths and spaces are less than one mil with traces formed on the substrate surface, then fine trace lines can be created, but adhesion failures occur causing poor yields and reliability issues
Solution Approach 1:
The patent embeds the metal conductor trace within a dielectric material shell, creating a nested structure where the conductor is completely surrounded by the dielectric. This nesting provides mechanical support and strong adhesion for sub-mil traces, eliminating the adhesion failures that occur with surface-mounted fine traces while maintaining precise width and spacing control.
Solution Approach 2:
The patent transitions from two-dimensional surface traces to three-dimensional embedded traces. By adding the vertical dimension and embedding the conductor within the dielectric, the patent achieves both fine lateral dimensions (sub-mil width and spacing) and improved adhesion through the third dimension of embedding depth.
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 allows for better electrical performance by controlling trace geometry and adhesion, reducing fabrication failures and improving signal propagation and impedance consistency.
Implementation Method 1
The channels are ablated in the surface of catalytic core material 10
Implementation Method 2
electroless copper plating to create controlled geometry and improve adhesion
Data Source
AI summary
A printed circuit board includes a laminate substrate. The laminate substrate includes catalytic core material that resists metal plating except where a surface of the catalytic material is ablated. Metal traces are formed within in trace channels within the laminate substrate. The channels extend below the surface of the catalytic material.