Circuit Substrate Fabrication with Thickened Bonding Segments
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Solution Overview
Problem
Conventional circuit substrates face limitations in reducing the pitch between bonding pads due to the constraints on narrowing transitional segments and trace widths for electrical transmission and bonding area requirements, which hinders increased layout density.
Innovation Solution
A process involving a patterned conductive layer with bonding and plating segments, where a dielectric layer with openings exposes these segments, and a plating seed layer is used to form thickening conductive layers on bonding segments, expanding the bonding area and allowing for reduced pitch between adjacent bonding segments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the pitch between bonding segments is reduced to increase layout density, then the bonding pad density is improved, but the transitional segment width and trace width must be narrowed which limits the reduction extent due to electrical transmission requirements
Solution Approach 1:
The trace is divided into three distinct segments: bonding segment, transitional segment, and plating segment. Each segment serves a specific function and can be independently optimized. The bonding segment provides bonding area, the transitional segment connects adjacent bonding segments, and the plating segment provides current path for plating thickening conductive layers.
Solution Approach 2:
Different segments of the trace are given different properties and functions. The bonding segment is designed for bonding with conductive bumps, the transitional segment is optimized for electrical transmission between bonding segments, and the plating segment is designed to conduct current for electroplating the thickening conductive layers on the bonding segments.
2Quantity of substance
If the trace width is narrowed to reduce pitch between bonding segments, then the layout density is improved, but the bonding area of bonding segments is reduced which limits the reduction extent
Solution Approach 1:
The bonding segment is extended in the vertical dimension by forming thickening conductive layers through electroplating. This allows the bonding area to be increased in the thickness direction while keeping the planar footprint small, thereby enabling reduced pitch between adjacent bonding segments while maintaining sufficient bonding area.
Solution Approach 2:
The trace structure is changed from a single-layer planar trace to a multi-segment structure with vertical thickening. The plating segment provides current path for electroplating, which changes the dimensional parameters of the bonding segment by adding vertical thickness, thereby increasing bonding area without increasing planar dimensions.
3Quantity of substance
If large-sized openings on solder mask layer are applied to expose die bonding region, then the bonding pad density is improved, but the transitional segment must be narrowed which is unfavorable to pitch reduction
Solution Approach 1:
The dielectric layer is patterned with different types of openings: bonding openings that expose bonding segments and plating openings that expose plating segments. This segmentation allows the solder mask to be removed only where needed for bonding and plating, while preserving the transitional segments underneath for electrical transmission.
Solution Approach 2:
The plating segment acts as an intermediary that provides current path from the trace to the bonding segment. By exposing the plating segment through plating openings, current can be supplied to electroplate the thickening conductive layers on the bonding segment without needing to expose the entire bonding region or narrow the transitional segment.
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
The process effectively increases the widths and heights of bonding segments, expanding the bonding area and enabling a reduction in pitch between adjacent bonding segments, thereby enhancing layout density and interconnectivity.
Implementation Method 1
The plating seed layer is etched with use of the mask as an etching mask, so as to remove the portions of the plating seed layer on the corresponding bonding segments
Implementation Method 2
A thickening conductive layer is plated on each of the bonding segments through the plating seed layer and the traces with use of the mask as a plating mask
Data Source
AI summary
A process for fabricating a circuit substrate is provided. A dielectric layer is formed to cover a surface of a circuit stack and a patterned conductive layer, and has bonding openings exposing bonding segments of traces of the patterned conductive layer, and has plating openings exposing plating segments of the traces. A plating seed layer is formed to cover the surface of the circuit stack, the bonding segments, the plating segments, and the dielectric layer. A mask is formed to cover the plating layer and has mask openings exposing portions of the plating seed layer on the bonding segments. Portions of the plating seed layer on the bonding segments are removed with use of the mask as an etching mask. A thickening conductive layer is plated on each of the bonding segments with use of the mask as a plating mask. The mask and the plating seed layer are removed.