Silicon Nitride Adhesion Layers for Smooth IC Package Solder Resist
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Solution Overview
Problem
Direct bonding of solder resist to electronic substrates can result in impurities and defects, and is not feasible in IC packages with electrolytic surface finishes, while traditional aqueous developers used for patterning solder resist leave ions that inhibit etching and cause surface roughness.
Innovation Solution
Using a silicon nitride adhesive layer to couple solder resist to a substrate with a surface finish, and employing a Tetramethylammonium hydroxide (TMAH) developer to create tapered openings without undercuts, which reduces flux trapping and surface roughness, enabling reliable bonding and smooth etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If direct bonding of solder resist to substrate is used, then bonding process is simple, but bonding reliability deteriorates due to impurities and defects
Solution Approach 1:
A silicon nitride adhesive layer is introduced as an intermediary between the solder resist and the substrate surface finish layer. This adhesive layer acts as a mediator that enables reliable bonding by preventing direct contact between the solder resist and the substrate, thereby avoiding impurity formation and bonding defects while maintaining process simplicity.
2Productivity
If aqueous developer is used for patterning solder resist, then development process is effective, but surface quality deteriorates due to ion deposition and roughness
Solution Approach 1:
The patent changes the chemical composition parameter of the developer from aqueous-based to organic-based (specifically TMAH - tetramethylammonium hydroxide). This parameter change eliminates the water component that causes ion deposition and surface roughness, while maintaining effective patterning capability through the organic chemistry of TMAH.
3Productivity
If aqueous developer is used for patterning, then development capability is sufficient, but etching performance deteriorates due to ion mask formation
Solution Approach 1:
The developer composition is changed from aqueous to organic (TMAH), which fundamentally alters the chemical properties. This parameter change eliminates ion mask formation that hinders etching, while preserving adequate development capability through the organic chemistry mechanisms of TMAH.
4Device complexity
If traditional bonding method is used, then process simplicity is maintained, but adhesion quality deteriorates due to impurities and defects
Solution Approach 1:
The silicon nitride adhesive layer serves as a mediator that improves adhesion quality by preventing direct bonding between solder resist and substrate. This intermediary layer eliminates impurity formation and bonding defects while adding minimal complexity to the overall process flow.
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 approach improves the bonding reliability and surface smoothness of solder resist, facilitating effective etching and assembly processes by eliminating ion masks and undercuts, thus enhancing the manufacturing precision and reliability of IC packages.
Implementation Method 1
an adhesive layer including silicon nitride coupled to a surface finish layer of a substrate, and solder resist coupled to the adhesive layer
Implementation Method 2
employing a Tetramethylammonium hydroxide (TMAH) developer to create tapered openings without undercuts
Data Source
AI summary
Methods, systems, apparatus, and articles of manufacture to produce integrated circuit (IC) packages having silicon nitride adhesion promoters are disclosed. An example IC package disclosed herein includes a metal layer on a substrate, a layer on the metal layer, the layer including silicon and nitrogen, and solder resist on the layer.