Circuit Board Manufacturing via Layer Separation for Fine Bump Pitch
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Solution Overview
Problem
Current methods for manufacturing circuit boards face challenges in reducing the fine bump pitch due to limitations in exposure alignment accuracy, particularly with the solder plated over pad (SPOP) method, which restricts the miniaturization of metal bumps.
Innovation Solution
A method involving a substrate with a resin layer and multiple copper layers, where vias are formed and metal layers are deposited and patterned, allowing for the separation of layers and etching to create a void, enabling the first metal layer to protrude and reducing bump pitch without the need for precise exposure alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the solder plated over pad (SPOP) method is used to form metal bumps, then the alignment accuracy can be maintained, but the fine bump pitch cannot be reduced below a certain limit
Solution Approach 1:
The invention divides the metal bump formation process into multiple independent stages: first forming vias through the resin layer, then depositing metal layers within the vias, and finally separating the bottom layer from the resin layer to expose the metal bumps. This segmentation eliminates the need for single-step exposure alignment, enabling fine bump pitch below conventional limits while maintaining manufacturing precision through multi-step process control
Solution Approach 2:
The invention transitions from a planar 2D exposure alignment process to a 3D multi-layer construction process. By building metal structures vertically within vias and then separating layers, the method achieves fine pitch in the horizontal dimension without being constrained by exposure alignment accuracy, effectively adding a vertical dimension to the fabrication approach
2Quantity of substance
If the fine bump pitch is reduced to increase element density, then the packaging capacity is improved, but the exposure alignment accuracy becomes insufficient
Solution Approach 1:
The fabrication process is segmented into distinct operations: via formation, metal deposition, and layer separation. This eliminates the need for high-precision exposure alignment while achieving fine bump pitch, thereby enabling increased element density without being constrained by exposure alignment accuracy
Solution Approach 2:
The invention replaces the optical exposure alignment system with a mechanical/chemical process system involving laser drilling or milling for via formation, followed by controlled metal deposition and layer separation. This substitution removes the fundamental limitation of exposure alignment accuracy, enabling finer bump pitch and higher element density
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 enables the fabrication of circuit boards with a narrow bump pitch, enhancing packaging processes by increasing element density and allowing for pitches as low as 40 μm without the constraints of exposure alignment margins.
Implementation Method 1
the bottom layer includes a core layer, a first copper layer, a second copper layer and a release layer, in which the first copper layer is over the core layer, and the release layer is over the first copper layer, and the second copper layer is over the release layer
Implementation Method 2
forming the vias is conducted by laser drilling or exposure development
Data Source
AI summary
A method of manufacturing a circuit board includes: providing a substrate including a bottom layer and a resin layer over the bottom layer, the resin layer including a first surface in contact with the bottom layer and a second surface opposite to the first surface; forming a plurality of vias through the resin layer; depositing a first metal layer in the vias, the first metal layer filling a portion of each of the vias; depositing a second metal layer over the first metal layer and in the vias; forming a patterned metal layer over the second metal layer and extending from each of the vias to a position over the second surface; separating the bottom layer and the resin layer; and removing a portion of the resin layer from the first surface, so that the first metal layer protrudes from the resin layer.