PCB Via Laser Scanning With Acousto-Optic Pulse Slicing
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Solution Overview
Problem
Conventional laser processing methods for forming blind and through-vias in workpieces, such as printed circuit boards, are limited by inefficient scanning techniques that result in suboptimal via formation, particularly in terms of diameter and circularity.
Innovation Solution
A method and apparatus utilizing a beam of laser energy that is scanned across multiple spatially different spot locations, employing acousto-optic deflectors and controllers to control the scanning process, allowing for precise formation of features like openings and vias by ablating the workpiece structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional laser scanning techniques are used to form blind and through-vias, then the processing can be completed, but the via diameter and circularity are suboptimal
Solution Approach 1:
The patent segments a single laser pulse into multiple sub-pulses using an acousto-optic modulator (AOM). Each sub-pulse is delivered to a different spatial location within the via formation region, enabling precise control over the ablation pattern. This segmentation allows the laser energy to be distributed across multiple spot locations sequentially within one pulse duration, achieving superior via diameter and circularity control while maintaining high processing speed.
Solution Approach 2:
The patent employs dynamic control of the laser beam position by rapidly switching the AOM drive signal frequency during the pulse duration. The beam is dynamically redirected to different spatial locations corresponding to different frequencies, creating a scanning effect without mechanical movement. This dynamic approach enables precise via formation with optimized diameter and circularity while maintaining high productivity through electronic control rather than mechanical scanning.
2Manufacturing precision
If the laser beam is scanned across multiple spot locations to improve via quality, then the manufacturing precision improves, but the processing time increases
Solution Approach 1:
The patent uses periodic modulation of the AOM drive signal frequency to sequentially direct sub-pulses to different spatial locations. The frequency switching follows a predetermined pattern that corresponds to the desired via geometry, allowing multiple spot locations to be processed within a single pulse period. This periodic action enables high-precision via formation without requiring multiple separate pulses, thereby minimizing processing time.
Solution Approach 2:
The patent performs preliminary planning of the pulse slicing pattern and frequency switching sequence before actual processing. The scan pattern and sub-pulse timing are pre-calculated to optimize via formation, allowing the laser system to execute the predetermined pattern at high speed without real-time computation delays. This preliminary action ensures both high manufacturing precision and efficient processing by eliminating on-the-fly decision-making overhead.
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
Enables the formation of high-quality blind and through-vias with improved diameter and circularity, enhancing the precision and efficiency of laser processing.
Implementation Method 1
An acousto-optic deflector (AOD) system may be employed to deflect the beam path. The AOD system may include a first AOD operative to deflect the beam path along a first axis in response to a first RF signal applied thereto. The controller may be configured to control an operation of the AOD system whereby a frequency of the first RF signal is changed at least twice to temporally divide a common laser pulse incident upon the AOD system into a plurality of pulse slices
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
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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.