Circuit Device with Integrated Copper Redistribution Lines
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Solution Overview
Problem
Conventional CSP circuit devices face issues with poor joint reliability due to material differences between bumps and redistribution lines, thermal stress, and challenges in miniaturization, leading to disconnection and increased manufacturing costs.
Innovation Solution
The circuit device integrates connecting portions and redistribution lines made of rolled metal, which are continuous and formed as one piece, with the redistribution lines extending parallel to the circuit element's surface, and a method involving a semiconductor wafer and conductive foil with isolation trenches and filling resins to enhance joint reliability and facilitate miniaturization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bumps and redistribution lines are made of different materials to enable wire bonding, then connection functionality is achieved, but thermal stress occurs at the interface causing disconnection and poor joint reliability
Solution Approach 1:
The patent applies homogeneity by making both the connecting portion and redistribution line from the same material (copper), eliminating material interfaces and thermal stress. The connecting portion is formed by selectively removing insulation from the conductive foil, creating a homogeneous copper structure that extends continuously from the electrode connection point to the redistribution line, thereby preventing thermal stress-induced disconnection.
2Length of moving object
If bumps with diameter of 30 to 60 μm are formed by wire bonding, then connection is achieved, but miniaturization is limited as electrodes must be larger than bump diameter
Solution Approach 1:
The patent replaces the mechanical wire bonding process with a direct copper foil-based connecting structure. Instead of forming discrete bumps through mechanical wire bonding, the connecting portion is created by selectively removing insulation from the conductive foil, allowing the electrode size to be independent of connection structure dimensions and enabling miniaturization to minute electrode sizes.
3Reliability
If wire bonding technique is used to form bumps, then connection functionality is achieved, but manufacturing costs increase
Solution Approach 1:
The patent merges the connecting portion and redistribution line into a single integrated copper structure formed from the conductive foil. This eliminates the need for separate wire bonding processes and multiple material layers, simplifying manufacturing and reducing costs while maintaining connection functionality through the continuous copper structure.
4Reliability
If conventional CSP structure with peripheral electrodes is used, then circuit functionality is achieved, but the side of mounting substrate cannot be further miniaturized
Solution Approach 1:
The patent transitions from peripheral electrode arrangement to a structure where connecting portions extend vertically from the conductive foil to connect electrodes to redistribution lines. This dimensional change allows electrodes to be positioned at the periphery while enabling the mounting substrate area to be reduced, as the connections are formed through the thickness of the conductive foil rather than requiring lateral space.
Data Source
AI summary
A circuit device of preferred embodiments of the present invention includes: a circuit element with electrodes formed in a peripheral part thereof; connecting portions connected to surfaces of the electrodes; and redistribution lines which are continuous to the respective connecting portions and extended in parallel to the main surface of the circuit element. In preferred embodiments of the present invention, the connecting portions and the redistribution lines are integrally formed of one piece of metal. Accordingly, there is no place where different materials are connected in a portion between the connecting portions and the redistribution lines, thus improving a joint reliability of the entire device against a thermal stress or the like.