Ringless IC Board Fabrication via Selective Metal Etching
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Solution Overview
Problem
Conventional IC board fabrication methods face challenges in reducing the size of the metal capture ring, which limits layout density and increases manufacturing costs due to alignment tolerances and adhesion issues between conductive lines and substrates, especially with the trend towards smaller and thinner IC products.
Innovation Solution
A method for fabricating an IC board without a ring structure by removing the second deposited metal layer, the first deposited metal layer, and the metal layer not masked by the second pattern photoresist layer, allowing for the formation of narrower conductive lines and increased layout density, involving a substrate with a metal layer, core through holes, and multiple photoresist layers for precise etching and electroplating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the metal capture ring size is reduced to increase layout density, then the circuit pitch is reduced and more circuits can be laid out, but the alignment tolerance requirements increase and manufacturing precision deteriorates
Solution Approach 1:
The patent removes the metal capture ring structure entirely from the IC board design. By extracting this unnecessary component, the layout density increases as the space previously occupied by the ring is now available for additional circuits or reduced pitch, without imposing any alignment tolerance constraints on via holes.
Solution Approach 2:
Instead of reducing the ring size while maintaining its function, the patent inverts the approach by completely eliminating the ring structure. This reversal allows the design to achieve higher density without the compromising factor of alignment tolerance, as the ring's protective function is replaced by alternative design approaches.
2Area of stationary object
If the metal capture ring size is reduced to decrease substrate size, then the package becomes smaller, but the alignment precision requirements increase and manufacturing becomes more difficult
Solution Approach 1:
By removing the metal capture ring structure, the substrate area is reduced as the space previously dedicated to the ring is now part of the usable layout area. This extraction eliminates the need for precise alignment between the ring and via holes, thereby reducing measurement precision requirements.
3Ease of manufacture
If conventional design rules are followed with a 50 μm metal ring, then alignment is easier and manufacturing is simpler, but layout density is reduced and circuit pitch is increased
Solution Approach 1:
The patent extracts and removes the metal capture ring from the design, thereby eliminating the trade-off between ease of manufacture and layout density. Without the ring structure, layout density increases as the space is freed up, while ease of manufacture is maintained through simplified process steps that do not require precise ring alignment.
4Reliability
If the conductive line width is increased to improve adhesion, then reliability improves, but the circuit pitch increases and layout density decreases
Solution Approach 1:
By removing the metal capture ring structure, the patent creates additional space that allows for reduced circuit pitch while maintaining adequate adhesion. The extraction of the ring provides extra area that compensates for the reduced line width, enabling both high reliability and high layout density to coexist.
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 circuit pitch, improves production yield, and decreases manufacturing costs by eliminating the need for a metal capture ring, enhancing layout density and product reliability.
Implementation Method 1
a first pattern photoresist layer is formed on the first depositing metal layer, and the first pattern photoresist layer has maintained a photoresist layer opening over the core through hole
Implementation Method 2
a first depositing metal layer is formed on the metal layer and a sidewall of the core through hole
Implementation Method 3
the metal layer, the first depositing metal layer, and the second depositing metal layer which have not being masked by the second pattern photoresist layer are etched
Data Source
AI summary
A method for fabricating an IC board without a ring structure is provided. In the method, after the completion of the core board (including the core through hole), the second pattern photoresist layer is used to mask over the first deposited metal layer, and a portion of the second deposited metal layer (this portion of the second deposited metal layer is to electrically couple to the conductive circuit of the core through hole). Later, the second deposited metal layer, the first deposited metal layer, the metal layer, and the substrate at the innermost layer which are not masked by the second pattern photoresist layer are removed. As a result, the substrate is exposed to form the ringless structure, and to couple a conductive line to the core board through hole.