Laser Stacked Via Formation on HDI PCBs
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Solution Overview
Problem
The existing methods for forming stacked via-holes on high-density interconnection (HDI) printed circuit boards are prone to alignment and sizing errors due to the multi-step etching process, which introduces discrepancies in the formation of copper micro-vias.
Innovation Solution
A method involving the formation of copper-clad laminates on printed circuit boards, where first and second copper micro-vias are created using lasers, followed by the removal of resin layers using a second laser to form stacked via-holes, thereby simplifying the process and reducing errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an etching process is used to form copper micro-vias, then the via-holes can be created in the copper layers, but alignment and sizing errors occur due to multiple process steps
Solution Approach 1:
The patent replaces the traditional etching process (chemical/mechanical system involving photoresist application, exposure, development, and etching) with a laser-based direct writing system. The laser directly ablates the copper material to form micro-vias, eliminating the need for multiple etching steps and associated alignment procedures, thereby achieving higher precision and simpler process control.
Solution Approach 2:
The patent extracts and removes the intermediate photoresist layer and etching chemistry steps from the traditional via formation process. By using laser direct writing, only the essential copper ablation step remains, significantly reducing the number of process steps and potential sources of alignment error while maintaining via formation capability.
2Productivity
If multiple etching steps are used to form first and second copper micro-vias, then the stacked via-holes can be created, but manufacturing time increases due to process discrepancies
Solution Approach 1:
The patent merges the formation of first and second copper micro-vias into a single integrated laser writing process. Instead of performing separate etching operations for each copper layer, the laser system directly writes both sets of micro-vias in one continuous operation, eliminating the time-consuming intermediate steps and improving overall manufacturing efficiency.
Solution Approach 2:
The laser writing process operates continuously to form all required micro-vias without interruption. The laser beam moves seamlessly between different locations and depths, maintaining continuous useful action throughout the via formation process, thereby minimizing idle time and maximizing productivity compared to batch-wise etching operations.
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 achieves precise and efficient formation of stacked via-holes with improved concentricity and alignment, reducing manufacturing time and avoiding deformation issues associated with etching processes.
Implementation Method 1
removing corresponding resin layer portions of the first and second metal-clad laminates, using a second laser, in order to yield the respective stacked via-holes
Data Source
AI summary
A method for forming stacked via-holes on a printed circuit board includes the steps of: providing a printed circuit board having a conductive trace formed on a side surface thereof; forming a first copper-clad laminate on the side surface having the conductive trace; forming a number of first copper micro-via in a copper layer of the first copper-clad laminate; forming a second copper-clad laminate on the surface of the copper layer having the first copper micro-via of the first copper-clad laminate; forming a number of second copper micro-via in a copper layer of the second copper-clad laminate by a first laser on the basis of the first copper micro-via, each second copper micro-via being located corresponding to its correspondingly first copper micro-via; and removing corresponding resin layer portions of the first and second copper-clad laminates, using a second laser, to yield the respective stacked via-holes.