Conductive Patterning Using Permanent Resist for High Aspect Ratio Traces
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Solution Overview
Problem
Existing patterning methods such as subtractive etch, semi-additive process (SAP), and modified semi-additive process (MSAP) face limitations in achieving high aspect ratio conductive trace patterning with narrow spaces, leading to reduced pattern density and inefficient heat dissipation in miniaturized IC packages.
Innovation Solution
The use of a permanent resist in conductive patterning processes allows for the formation of high aspect ratio patterns with narrower spaces between conductive lines, enabling higher line heights and narrower space widths, which is not achievable with traditional methods, by remaining as an integral part of the circuit product and serving as insulation between lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional patterning methods (subtractive etch, SAP, MSAP) are used, then the manufacturing process is simple and well-established, but the line height to space width ratio is limited and pattern density is reduced
Solution Approach 1:
A permanent resist layer is introduced as an intermediary structure between conductive traces. This resist layer serves multiple functions: it defines the pattern during fabrication, provides insulation between traces, and enables higher line heights by maintaining structural integrity during plating. The permanent resist acts as a mediator that resolves the contradiction between achieving high aspect ratios and maintaining process simplicity.
Solution Approach 2:
The invention changes the physical and chemical parameters of the resist material by using a permanent resist that remains in the final structure rather than being removed. This parameter change allows the resist to serve as both a patterning tool and a functional insulating layer, enabling higher line heights and narrower spaces without increasing process complexity.
2Temperature
If line height is increased to improve heat dissipation, then thermal management is improved, but space width between lines must increase reducing pattern density
Solution Approach 1:
The permanent resist layer serves as an intermediary that allows increased line height without proportionally increasing space width. The resist provides structural support and insulation, enabling taller conductive lines to be packed more closely together than would be possible with traditional methods, thus maintaining pattern density while improving heat dissipation.
3Area of stationary object
If space width between conductive lines is narrowed to increase pattern density, then IC package size is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The permanent resist layer performs multiple functions simultaneously: it defines the pattern during fabrication, serves as a spacer to maintain precise spacing between traces, and provides electrical insulation. This self-service capability of the resist layer enables narrow spacing without increasing manufacturing precision requirements, as the resist itself maintains the required dimensional accuracy.
4Productivity
If permanent resist is used to achieve high aspect ratio patterning, then pattern density and heat dissipation are improved, but the manufacturing process becomes more complex
Solution Approach 1:
The invention merges multiple functions into the permanent resist layer: patterning definition, spacing maintenance, and electrical insulation. By combining these functions into a single material layer that remains in the final structure, the process achieves high pattern density without adding significant complexity, as the same layer that defines the pattern also provides the insulating and spacing functions.
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 creation of smaller, higher-performance IC packages with improved heat dissipation and increased pattern density, enhancing the efficiency of inductive coils and reducing package size.
Implementation Method 1
The layer of permanent resist is exposed to a light and developed to pattern the layer of permanent resist
Implementation Method 2
An additional amount of the conductive material is plated over the patterned seed layer to create individual traces or coiled windings
Data Source
AI summary
A permanent resist, such as TMMF, is used when patterning conductive material on a substrate, enabling lines that have a higher line-to-space ratio (L/S) or a higher aspect ratio (T/L) or both. Pattern density can thus be increased, allowing for improved performance (e.g., greater efficiency, in the case of transformer coil patterning) and greater heat dissipation. As examples, the permanent-resist-based patterning fabrication methods can be used to create transformer coils within an integrated circuit (IC) module, or a routable lead frame for one or more IC dies.