Ultra-Thin Copper Foil Stack With Ni Etch Stop for Smooth Patterning
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Solution Overview
Problem
Conventional ultra-thin copper foils with carrier foils for embedded substrates face issues with surface roughness leading to undesired bumps and recess depths during the formation of metal patterns, causing defects like disconnection or short circuits due to inadequate etching control.
Innovation Solution
Incorporating a selectively etchable Ni etch stop layer between two ultra-thin copper foil layers, with a non-etching release layer and a seed ultra-thin copper foil layer, to provide a low-roughness surface by precise etching, eliminating recess depths and suppressing nodulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional ultra-thin copper foil with carrier foil structure (release layer + ultra-thin copper foil) is used, then the basic structure is simple, but surface roughness is insufficient causing undesired bumps during metal pattern formation
Solution Approach 1:
The ultra-thin copper foil is divided into three distinct layers: a first ultra-thin copper foil layer, an etch stop layer in the middle, and a second ultra-thin copper foil layer. This segmentation allows each layer to perform specific functions - the first layer provides initial surface smoothness, the etch stop layer prevents over-etching and controls recess depth, and the second layer forms the final low-roughness surface, collectively solving the surface roughness problem while maintaining manageable structural complexity
Solution Approach 2:
The etch stop layer acts as an intermediary element between the two ultra-thin copper foil layers. It mediates the etching process by providing a controlled stopping point that prevents excessive etching into the substrate, thereby controlling recess depth and preventing metal pattern disconnection while allowing the copper layers to achieve the desired low surface roughness
2Manufacturing precision
If delicate etching control is attempted to eliminate nodules, then surface quality improves, but the manufacturing process becomes difficult to control and metal patterns end up inside the prepreg causing disconnection or short circuits
Solution Approach 1:
The etch stop layer is pre-formed between the two copper foil layers before the metal pattern formation process. This preliminary action establishes a predetermined etching depth limit, eliminating the need for delicate real-time etching control. The etchant naturally stops at the etch stop layer, ensuring consistent recess depth control and preventing metal patterns from ending up inside the prepreg, thereby simplifying the manufacturing process
Solution Approach 2:
The patent replaces the need for delicate mechanical or process control during etching with a passive, pre-established etch stop layer. Instead of relying on operator skill or complex control systems to prevent over-etching, the physical presence of the etch stop layer provides an automatic stopping mechanism, substituting active control with a passive structural solution that is easier to manufacture
3Reliability
If the release layer is sufficiently etched to eliminate defective elements, then nodules are removed, but recess depth increases causing disconnection or short circuit in circuit metal patterns
Solution Approach 1:
The etch stop layer serves as an intermediary barrier that allows the etching process to remove defective elements like nodules from the release layer while preventing the etchant from etching too deeply into the substrate. The etch stop layer is positioned to allow removal of surface defects but stops the etching before recess depth becomes excessive, thus maintaining both defect elimination and precise recess depth control
Solution Approach 2:
The patent changes the etching parameter control mechanism by introducing a layer with different etch resistance properties. The etch stop layer has higher etch resistance than the release layer, creating a parameter change that allows selective removal of the release layer and its defects while automatically limiting the etching depth, thereby eliminating the trade-off between defect removal and recess depth control
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
The solution ensures a smooth and defect-free surface with low roughness, preventing disconnections and short circuits in circuit metal patterns, making it suitable for microcircuit boards with improved peel strength, heat resistance, and chemical resistance.
Implementation Method 1
a selectively etchable Ni etch stop layer between two ultra-thin copper foil layers
Data Source
AI summary
Disclosed are an ultra-thin copper foil with a carrier foil and a method for manufacturing an embedded substrate by using the same, the ultra-thin copper foil with a carrier foil including: a carrier foil; a non-etching release layer on the carrier foil; a first ultra-thin copper foil layer on the non-etching release layer; an etch stop layer on the first ultra-thin copper foil layer; and a second ultra-thin copper foil layer on the etch stop layer.