PCB Via Laser Scanning With Pulse Slicing for Uniform Ablation
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Solution Overview
Problem
Conventional laser processing techniques for forming blind- and through-vias in workpieces, such as printed circuit boards, face limitations in precision and efficiency, particularly in achieving uniformity and accuracy in via formation using traditional punch and trepan processes.
Innovation Solution
A method and apparatus that utilize a scanning process with a laser beam to deliver energy to multiple spatially different spot locations, employing an acousto-optic deflector system and a controller to temporally divide laser pulses and control the beam's deflection, allowing for precise formation of openings by indirect ablation, enabling the creation of features like blind-vias with controlled spot sizes and patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional punch and trepan processes are used to form vias, then the process is simple and direct, but the precision and uniformity of via formation deteriorates
Solution Approach 1:
The patent replaces conventional mechanical punch and trepan processes with a laser-based processing system. The laser beam is precisely controlled through acousto-optic deflectors and galvanometer mirrors to deliver energy to specific locations, enabling precise via formation without mechanical contact. This substitution of mechanical systems with optical/energy-based systems resolves the contradiction by achieving high precision while maintaining operational simplicity through automated control.
Solution Approach 2:
The patent employs parameter changes in the laser processing system, including variable pulse duration (20 ns to 10 μs), adjustable pulse repetition rates (1 kHz to 1 MHz), and controllable beam deflection angles. These parameters are dynamically adjusted during processing to optimize via formation precision for different materials and via specifications, resolving the precision-complexity contradiction through flexible parameter control rather than fixed mechanical configurations.
2Manufacturing precision
If laser energy is delivered to multiple spot locations to form uniform vias, then the uniformity and accuracy of via formation improves, but the processing time and complexity increase
Solution Approach 1:
The patent employs periodic pulsed laser action with pulse repetition rates ranging from 1 kHz to 1 MHz. The laser delivers energy in controlled pulses to multiple spot locations along a via path, with each pulse creating a discrete ablation zone. The periodic nature of the pulsing allows for cumulative material removal while maintaining uniform via dimensions, resolving the contradiction between via uniformity and processing time through optimized pulse timing and frequency.
Solution Approach 2:
The patent implements preliminary scanning passes where the laser beam is delivered to multiple spot locations to distribute energy and pre-condition the material before final via formation. This preliminary action softens or pre-heats the material along the via path, reducing the energy required for subsequent ablation steps and overall processing time while ensuring uniform via dimensions through controlled energy distribution.
3Productivity
If high pulse repetition rates are used to increase productivity, then the processing speed improves, but the heat accumulation and material damage increase
Solution Approach 1:
The patent employs dynamic control of pulse repetition rates, adjusting the frequency from 1 kHz to 1 MHz based on real-time processing conditions, material type, via depth, and spot location. The system dynamically modulates the laser parameters to maintain optimal energy delivery without excessive heat accumulation, resolving the contradiction between productivity and heat damage through adaptive parameter control rather than fixed high-rate pulsing.
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 enhances the precision and efficiency of via formation, achieving consistent and accurate results with varying via diameters, from 75 μm to 180 μm, by uniformly distributing laser energy and controlling the ablation process, thereby improving the overall processing quality.
Implementation Method 1
The AOD system is operative to deflect the beam path and includes a first AOD operative to deflect the beam path along a first axis in response to a first RF signal applied thereto
Implementation Method 2
delivering the laser energy to at least two spot locations of the plurality of spatially different spot locations to form the opening by indirectly ablating the first structure within the region
Data Source
AI summary
Numerous embodiments are disclosed. Many of which relate to methods of forming vias in workpieces such as printed circuit boards. Some embodiments relates techniques for indirectly ablating a region of an electrical conductor structure of, for example, a printed circuit board by spatially distributing laser energy throughout the region before the electrical conductor is indirectly ablated. Other embodiments relate to techniques for temporally-dividing laser pulses, modulating the optical power within laser pulses, and the like.