Conductive Drill Bit Feedback for Precise PCB Back Drilling
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Solution Overview
Problem
Plated through holes in multilayer printed circuit boards act as bottlenecks and obstacles in high-speed signal transmission due to their nature as 'stubs' in transmission lines, causing signal integrity issues, and existing back drilling methods are process-dependent and difficult to control in terms of depth.
Innovation Solution
A drill bit with a conductive tip and a non-conductive film-covered edge is used to drill through holes, allowing for feedback time measurement of conductive layers, calculation of layer differences, and controlled depth drilling based on these measurements, independent of process flow, to accurately control drilling depth and improve machining efficiency and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If back drilling method is used to remove plated through holes, then signal integrity is improved, but process complexity increases and depth control becomes difficult
Solution Approach 1:
The patent applies feedback by using the conductive drill tip to detect conductive layers during drilling and using acoustic emission signals to monitor drilling depth in real-time. The system adjusts drilling parameters based on this feedback to achieve precise depth control and eliminate the need for complex post-processing back drilling operations.
Solution Approach 2:
The drill bit performs multiple functions simultaneously: it drills the hole, detects conductive layers through its conductive tip, and monitors drilling depth through acoustic emission. This self-service capability eliminates the need for separate depth measurement and back drilling processes, reducing overall process complexity.
2Reliability
If back drilling method is used, then plated through holes are removed, but depth control precision deteriorates
Solution Approach 1:
The system uses acoustic emission technology to provide real-time feedback on drilling depth and drill bit condition. This feedback mechanism enables precise depth control by continuously monitoring the drilling process and adjusting parameters to maintain manufacturing precision.
Solution Approach 2:
The patent replaces mechanical depth measurement methods with acoustic emission detection. This substitution provides more precise and reliable depth control by detecting acoustic signals generated during drilling, which correlate with drill bit position and condition.
3Reliability
If conventional drill bit with conductive coating is used, then electricity conduction is achieved, but drilling depth control and layer detection accuracy worsen
Solution Approach 1:
The drill bit features localized quality differentiation: the tip is conductive for detecting conductive layers, while the shaft is covered with non-conductive coating for stable acoustic emission detection. This local quality assignment optimizes both electricity conduction and measurement precision for their respective functions.
Solution Approach 2:
The drill bit is segmented into functional zones with different properties: a conductive tip section for layer detection and a non-conductive coated shaft section for acoustic monitoring. This segmentation allows each part to perform its specific function optimally without interference from the other.
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 method enables precise control of drilling depth, reducing dependence on board thickness and process flow, thereby enhancing machining efficiency and accuracy while minimizing signal distortion in high-speed signal transmission.
Implementation Method 1
the drill tip is capable of conducting electricity... a feedback time T of each conductive layer of the board to be processed is collected by the drill tip
Implementation Method 2
the drill edge is covered with a non-conductive film layer
Implementation Method 3
the method further includes: a feedback signal is obtained by the drill bit in real time during the process of drilling the through hole... the feedback signal includes acoustic emission signals
Data Source
AI summary
A method of using a drill bit includes: S11, drilling, by a drill bit, a through hole in a board to be processed, and collecting a feedback time T of each conducting layer of the board by a drill tip; S12, determining a target layer and a reference layer of the board, and calculating a time difference t between the target layer and the reference layer; S13, determining a distance H between the target layer and the reference layer according to the time difference t and a drilling speed v of the drill bit; and S14, performing a controlled depth drilling by starting from the reference layer on the basis of the through hole and taking the distance H as a drilling depth.