PCB Inner-Layer Depth Measurement for Precise Via Stub Drilling
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Solution Overview
Problem
Existing drilling systems lack the ability to accurately determine the drilling depth for removing conductive via stubs in multilayer circuit boards, leading to defects due to residual copper and signal interference.
Innovation Solution
An optical system comprising a light source, CCD lens module, pellicle mirror module, depth measuring device, reflective mirror module, and processor is used to measure the critical length of drill-down by emitting incident light and detecting reflected light from surface and inner layer copper, enabling precise control of drilling depth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a preset drilling depth is used for all circuit boards in a batch, then the drilling process is simple and fast, but the manufacturing precision deteriorates because circuit board thickness varies
Solution Approach 1:
The patent applies preliminary action by measuring the actual thickness of each circuit board before drilling. The system pre-determines the appropriate drilling depth for each specific board based on its measured thickness, ensuring that the drilling depth is optimized for each individual board rather than using a fixed preset depth for all boards.
Solution Approach 2:
The patent implements dynamics by making the drilling depth adjustable and adaptive rather than fixed. The system dynamically adjusts the drilling depth parameter based on the measured thickness of each circuit board, allowing the drilling process to adapt to variations in board thickness while maintaining high precision.
2Reliability
If the drilling depth is increased to ensure complete stub removal, then the reliability improves, but the manufacturing precision deteriorates because it causes damage to the inner layer copper
Solution Approach 1:
The patent applies feedback by using optical measurement to detect the exact position of the inner layer copper and the actual thickness of the circuit board. This feedback information is then used to calculate and set the precise drilling depth, ensuring that the drill bit reaches the inner layer copper without exceeding it, thus preventing damage while ensuring complete stub removal.
Solution Approach 2:
The patent replaces mechanical thickness measurement methods with an optical measurement system. The optical system uses light reflection and detection to measure the circuit board thickness and identify the inner layer copper position with high precision, eliminating the need for mechanical gauges or estimations and enabling more accurate drilling depth control.
3Manufacturing precision
If the drilling depth is reduced to avoid damaging inner layer copper, then the manufacturing precision improves, but the reliability deteriorates because residual copper remains
Solution Approach 1:
The patent replaces mechanical estimation or fixed-depth drilling with an optical measurement system that can precisely detect the inner layer copper position. This optical system provides accurate real-time data on the exact drilling depth needed, enabling the system to drill deep enough to remove stubs while stopping precisely before damaging the inner layer copper.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the drilling depth parameter based on the measured optical characteristics of each circuit board. The system changes the drilling depth parameter for each board according to its specific thickness and inner layer copper position, ensuring optimal stub removal while preventing damage to the inner layer.
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
Accurately measures the critical length of drill-down, eliminates residual copper, and improves production efficiency while reducing defects and costs.
Implementation Method 1
When the incident light is incident on the surface copper of the printed circuit board, a first reflected light will be generated... the incident light is incident on the inner layer copper of the printed circuit board to generate a second reflected light
Data Source
AI summary
An optical system for measuring the depth of an inner layer of a PCB, includes a light source transmitter used to emit an incident light, a controller, a CCD lens module, a pellicle mirror module, a depth measuring device, a reflective mirror module set at one end of the depth measuring device at an angle of 45 degrees, and a processor. When the incident light is incident on the surface copper of the PCB, a first reflected light is generated to pass through the reflective mirror module and the pellicle mirror module to the CCD lens module, then, the depth measuring device starts to move in the PCB until the incident light is incident on the inner layer copper of the PCB to generate a second reflected light that passes through the reflective mirror module and the pellet mirror module to the CCD lens module.