PCB Laser Micromachining Alignment via Integrated Optical Path
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Solution Overview
Problem
The increasing miniaturization of components on printed circuit boards (PCBs) poses challenges for the accuracy and efficiency of laser micromachining, particularly in aligning and micromachining holes with high precision and speed.
Innovation Solution
A micromachining apparatus utilizing a steerable mirror for both illumination and beam alignment, which operates at different wavelengths, and an image sensor to calculate the actual position of conductive pads on PCBs, allowing for real-time alignment and micromachining with high intensity illumination and reduced speckle effects through fluorescent radiation or polarized imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate optical systems are used for illumination and beam alignment, then each function can be optimized independently, but the device complexity and alignment time increase
Solution Approach 1:
The patent combines the illumination optical system and the alignment optical system into a single integrated optical path. The same objective lens and optical components are used for both illuminating the workpiece and capturing the reflected light for alignment detection, eliminating the need for separate optical systems while maintaining alignment accuracy.
Solution Approach 2:
The optical system is designed to perform multiple functions using the same components. The objective lens and detection path serve dual purposes: they illuminate the workpiece surface and simultaneously detect the reflected alignment marks, making the system universal and reducing overall complexity.
2Productivity
If high power laser beam is used for micromachining, then micromachining efficiency increases, but thermal drift and operational time issues worsen
Solution Approach 1:
The system uses periodic switching between the low-power alignment laser and the high-power micromachining laser. The alignment laser operates continuously or periodically to maintain positional accuracy, while the high-power laser is activated only during actual micromachining operations, reducing cumulative thermal effects.
Solution Approach 2:
The alignment laser acts as an intermediary that maintains the optical path and positional reference without causing significant thermal drift. It serves as a mediator between the positioning system and the high-power micromachining laser, enabling accurate positioning with minimal thermal interference.
3Measurement precision
If conventional illumination is used, then the system is simple, but image quality and alignment speed are insufficient for miniaturized PCB elements
Solution Approach 1:
The system employs high-frequency optical switching and rapid image acquisition that exploits temporal resolution similar to vibration-based detection methods. The fast alternating between illumination and detection phases enables capture of clear images before thermal effects or motion blur can degrade the signal, achieving high precision for miniaturized features.
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 rapid and accurate micromachining of multiple sites on PCBs with improved alignment efficiency, maintaining precision and increasing the overall rate of micromachining operations while minimizing thermal drift and operational time.
Implementation Method 1
receives returning radiation from the site in response to the illumination
Implementation Method 2
the radiation source may generate fluorescent radiation as the returning radiation, and the image sensor forms an image of the site and/or of a calibration target from the fluorescent radiation
Implementation Method 3
the radiation from the radiation source is linearly polarized, and the returning radiation is polarizeably analyzed
Implementation Method 4
the radiation source comprises a laser producing a coherent beam having a short coherence length, to substantially eliminate the effect of speckle
Implementation Method 5
Laser micromachining is employed to form holes, inter alia, in printed circuit boards (PCBs)
Data Source
AI summary
A method for micromachining a material, including configuring an optical system to provide illumination of an illumination wavelength to a site via a given element of the optical system, the illumination generating returning radiation from the site. The method further includes configuring the optical system to receive the returning radiation via the given element, and to form an image of the site therefrom, calculating an actual position of a location at the site from the image and outputting a signal indicative of the actual position of the location, generating a beam of micromachining radiation having a micromachining wavelength different from the illumination wavelength, positioning the beam to form an aligned beam with respect to the location in response to the signal, and conveying the aligned beam to the location via at least the given element of the optical system so as to perform a micromachining operation at the location.