Circuit Substrate Curved Conductive Structures for Pitch Reduction
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Solution Overview
Problem
Conventional circuit substrates with high I/O count face limitations in reducing bump pitches and alignment accuracy requirements, leading to larger opening sizes and increased dimensions of conductive structures, which restrict the miniaturization of chip pad pitches.
Innovation Solution
The design incorporates conductive structures with curved protruding parts that increase bonding area without requiring wider protrusions, allowing for shorter pitches among conductive structures through integral formation and electroplating processes, bypassing alignment accuracy constraints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the openings of the patterned photoresist layer are formed to communicate with and completely expose openings of a dielectric layer, then alignment accuracy is improved, but the width of the openings of the patterned photoresist layer must be greater than the width of the openings of the dielectric layer or solder resist layer, preventing reduction of opening size and conductive structure dimensions
Solution Approach 1:
The patent applies curvature to the side walls of conductive structures, transforming them from flat vertical walls to curved surfaces. This curvature allows the conductive structures to self-align during the electroplating process, as the curved surfaces naturally guide the deposition process and compensate for alignment variations, enabling smaller opening widths while maintaining manufacturing precision
Solution Approach 2:
The patent replaces the mechanical alignment system (relying on precise photolithographic alignment between photoresist and dielectric layer openings) with an electrochemical self-alignment system. The electroplating process inherently self-aligns to the curved side walls of the conductive structures, eliminating the need for tight mechanical alignment tolerances and allowing smaller opening dimensions
2Length of moving object
If the bump pitches are shortened, then the pitches among chip pads on the chips can be correspondingly shortened, but the alignment accuracy requirement becomes more stringent, requiring larger opening sizes which prevents pitch reduction
Solution Approach 1:
The curved side walls of the conductive structures serve as self-aligning templates during electroplating. This curvature geometry inherently guides the electrochemical deposition process, providing tolerance to alignment variations and enabling the formation of conductive structures at reduced pitches without proportionally increasing alignment accuracy requirements
Solution Approach 2:
The patent changes the geometric parameter of the conductive structure side walls from flat to curved. This parameter change fundamentally alters the alignment mechanism from external photolithographic alignment to internal self-alignment during electroplating, allowing pitch reduction while maintaining manufacturing feasibility
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 enables the reduction of conductive structure pitches without increasing the width of protruding parts, enhancing bonding efficiency and reducing alignment errors, thus facilitating more compact and accurate circuit substrate fabrication.
Implementation Method 1
a plurality of conductive structures (150) are formed with use of the first patterned photoresist layer as a mask. Here, each of the conductive structures (150) is integrally formed
Data Source
AI summary
A circuit substrate includes a dielectric layer and a plurality of conductive structures. The dielectric layer has a plurality of conductive openings, a first surface, and a second surface opposite to the first surface. Each of the conductive openings connects the first surface and the second surface. The conductive openings are respectively filled with the conductive structures. Each of the conductive structures is integrally formed and includes a pad part, a connection part, and a protruding part. Each of the connection parts is connected to the corresponding pad part and the corresponding protruding part. Each of the protruding parts has a curved surface that protrudes from the second surface. A process for fabricating the circuit substrate is also provided.