Wiring Board Solder Resist Segmentation for Flip-Chip Pad Isolation
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Solution Overview
Problem
The narrow pitch and spacing between connection pads in semiconductor integrated circuit elements lead to electrical short circuits during flip-chip bonding due to solder spreading between adjacent pads, making it difficult to achieve reliable electrical connections.
Innovation Solution
A solder resist layer is deposited to fill the space between adjacent connection pads, allowing the solder to be adhered and melted without bridging between pads, ensuring proper formation of solder bumps on individual pads without electrical short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If connection pads are arranged with narrow pitch to achieve high-density wiring, then wiring density is improved, but solder spreads between adjacent pads causing electrical short circuits
Solution Approach 1:
The invention divides the continuous solder application area into isolated pad regions by introducing solder resist material between adjacent connection pads. This segmentation prevents solder from spreading across the space between pads, thereby avoiding electrical short circuits while maintaining narrow pitch arrangements for high-density wiring.
Solution Approach 2:
The solder resist layer acts as an intermediary substance deposited between adjacent connection pads. This intermediary material creates a physical barrier that prevents direct contact between solder on neighboring pads, enabling reliable electrical connections even when pads are arranged with narrow pitch spacing.
2Reliability
If solder resist layer is deposited between connection pads to prevent short circuits, then electrical connection reliability is improved, but manufacturing process complexity increases
Solution Approach 1:
The invention merges the solder resist formation process with the existing solder bump manufacturing process. The solder resist layer is deposited as part of the same manufacturing sequence that forms the solder bumps on connection pads, thereby preventing short circuits without requiring a completely separate manufacturing process.
Solution Approach 2:
The solder resist layer serves multiple functions: it prevents solder spreading between pads, defines the boundaries of connection pads, and provides a planar surface for uniform solder application. This multi-functionality reduces the need for additional specialized process steps, mitigating the increase in manufacturing complexity.
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 method enables high-density wiring with excellent electrical connection reliability, effectively connecting narrow-pitch electrode terminals to corresponding pads without electrical short circuits, ensuring reliable semiconductor element mounting.
Implementation Method 1
the solder is adhered and melted without bridging between pads
Implementation Method 2
the solder is adhered and melted without bridging between pads, ensuring proper formation of solder bumps on individual pads
Data Source
AI summary
In a wiring board, insulation layers and wiring conductors are alternately laminated, and a plurality of strip-shaped wiring conductors for connecting semiconductor elements are arranged side by side on the outermost insulation layer. Each of the wiring conductors partly has a connection pad to which the electrode terminals of the semiconductor elements are connected by flip-chip bonding. In the wiring board, a solder resist layer is deposited over the outermost insulation layer and the strip-shaped wiring conductors so as to have slit-shaped openings for exposing the upper surfaces of the connection pads. The solder resist layer fills up the space between the connection pads adjacent to each other and exposed within the slit-shaped openings.