Semiconductor Package Ball Pitch Reduction via Dummy Balls
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Solution Overview
Problem
The miniaturization of semiconductor packages, such as WL-CSP/BGA/LGA, leads to increased costs due to narrower wiring pitches on printed circuit board substrates, as chip size reduction necessitates tighter ball pitches, and vice versa, making it challenging to balance chip size and PCB substrate costs.
Innovation Solution
A semiconductor package design featuring a rewiring layer, post electrodes, and a protective layer with balls connected to the rewiring layer, where balls on internal wiring paths are either non-connected or removed, allowing for reduced chip size without miniaturizing wiring widths on the PCB substrate, and enabling easy mounting by utilizing the land portions as wirings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If chip size is reduced to achieve miniaturization, then semiconductor package size decreases, but ball pitch becomes narrower which increases PCB substrate cost
Solution Approach 1:
The invention divides the ball array into functional segments: signal balls connected to the semiconductor chip and dummy balls not connected to the chip. This segmentation allows the ball pitch to be reduced for signal transmission while maintaining larger spacing for dummy balls that serve as PCB wiring paths, thus resolving the contradiction between chip miniaturization and PCB manufacturing cost
Solution Approach 2:
Dummy balls act as intermediaries between the signal balls and the PCB substrate wiring. These non-connected balls provide dedicated wiring paths on the PCB without requiring additional trace routing, thereby reducing PCB complexity and cost while enabling tighter ball pitch for the functional signal balls
2Length of moving object
If ball pitch is narrowed to reduce chip size, then semiconductor package becomes smaller, but PCB wiring paths become congested increasing substrate cost
Solution Approach 1:
The dummy balls serve multiple functions: they maintain the grid array pattern for mechanical alignment, provide dedicated wiring paths on the PCB substrate, and enable tighter pitch for signal balls without increasing PCB complexity. This multi-functionality resolves the contradiction by making the ball structure serve both packaging and PCB routing needs
3Quantity of substance
If wiring pitch on PCB is reduced to accommodate more balls, then more connections are possible, but manufacturing cost increases
Solution Approach 1:
The invention extracts the wiring path function from the signal balls and assigns it to separate dummy balls. This extraction allows signal balls to be densely packed for high connectivity while dummy balls provide dedicated, simplified wiring paths on the PCB, thereby increasing the number of connections without proportionally increasing PCB manufacturing cost
Data Source
AI summary
A semiconductor package includes: a semiconductor integrated circuit; an interlayer film disposed on the semiconductor integrated circuit; a rewiring layer disposed on the interlayer film; post electrodes disposed on the rewiring layer; a protective layer which is disposed on the interlayer film and covers the rewiring layer and the post electrodes; and a plurality of balls which is respectively disposed on the post electrodes and is connected to the rewiring layer, wherein balls existing on a wiring path of internal wirings connected to inner lands of a plurality of lands, which is arranged on a printed circuit board substrate to face the plurality of balls and is connectable to the plurality of balls, are non-connected to the rewiring layer.