Circuit Structure Galvanic Effect Prevention via Nanoparticle Covering Layer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In semiconductor package processes, the Galvanic effects between copper or copper alloy patterned circuit layers and noble metal surface passivation layers lead to accelerated etching and uneven etching rates during wet etching processes, compromising the electrical quality of circuit boards.
Innovation Solution
A manufacturing method involving a surface passivation layer and a covering layer with nanoparticles, where the covering layer is formed through chemical or physical absorption of a modifier, preventing Galvanic effects by managing the potential difference between metals, with materials like mercaptan nano-polymer or hydroxypropyl-beta-cyclodextrin and layer configurations such as nickel-gold or nickel-palladium-gold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a nickel gold layer or nickel silver layer is formed on the copper patterned circuit layer to prevent oxidation, then the corrosion resistance is improved, but the Galvanic effect occurs during wet etching process causing accelerated etching rate
Solution Approach 1:
The patent introduces a middle layer (such as organic protective layer, polymer layer, or specially designed barrier layer) between the copper patterned circuit layer and the nickel gold/silver surface passivation layer. This intermediary layer prevents direct contact between dissimilar metals during wet etching, thereby eliminating the Galvanic effect while maintaining the corrosion protection function of the outer noble metal layer.
Solution Approach 2:
The patent segments the protective structure into multiple functional layers: the outer noble metal layer (nickel gold or nickel silver) provides corrosion resistance, while the intermediate layer provides Galvanic effect prevention. This segmentation allows each layer to perform its specific function independently, resolving the contradiction between corrosion protection and etching rate control.
2Reliability
If the patterned circuit layer serves as anode and noble metal as cathode in wet etching process, then the surface passivation function is maintained, but the copper layer dissolves in accelerated manner leading to insufficient thickness
Solution Approach 1:
The intermediate layer acts as a mediator that blocks the electrochemical reaction pathway between the copper anode and noble metal cathode during wet etching. This prevents the accelerated dissolution of copper while allowing the outer noble metal layer to maintain its surface passivation function.
Solution Approach 2:
The patent applies preliminary anti-action by introducing the intermediate protective layer before the wet etching process occurs. This layer pre-empts the harmful Galvanic effect by preventing the formation of the electrochemical cell, thereby protecting the copper layer from accelerated dissolution before the problem can manifest.
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 method effectively prevents Galvanic effects, ensuring controlled etching rates and maintaining the required thickness of copper layers, thereby enhancing the electrical quality of circuit structures.
Implementation Method 1
the modifier is attached to the surface passivation layer through chemical absorption, so as to form a covering layer
Data Source
AI summary
A manufacturing method of a circuit structure is provided. A metal layer having an upper surface is provided. A surface passivation layer is formed on the metal layer. The surface passivation layer exposes a portion of the upper surface of the metal layer, and a material of the metal layer is different from a material of the surface passivation layer. The metal layer and the surface passivation layer are dipped into a modifier, and the modifier is selectively absorbed and attached to the surface passivation layer, so as to form a covering layer. The covering layer has a plurality of nanoparticles and covers the surface passivation layer.