Wiring Board External Terminal Design for High Density
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Solution Overview
Problem
Current methods for manufacturing multi-layer wiring boards fail to maximize wiring density in the outermost layer, leading to limitations in connection terminal miniaturization and increased risk of conduction and insulation failures due to narrow wiring widths.
Innovation Solution
The proposed solution involves a wiring board design with external connection terminals projected through the outermost wiring layer, allowing for increased wiring density and reliability by optimizing the placement and formation of connection pads and solder resist openings, using techniques such as electroless copper plating and laser processing to enhance positional accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If openings of solder resist layer are formed to cover the entire connection pad for reliability, then insulation reliability is improved, but wiring density cannot be maximized due to space occupation by openings
Solution Approach 1:
The solder resist opening is designed to cover only the peripheral portion of the connection pad rather than the entire pad area. This localized coverage provides sufficient insulation protection at the edges where short circuits are most likely to occur, while leaving the central area of the pad exposed to enable higher wiring density in the outermost layer.
2Productivity
If connection pads are miniaturized to increase wiring density, then wiring density is improved, but positional accuracy between connection pads and solder resist openings becomes more difficult to control
Solution Approach 1:
The connection pad structure is segmented into a peripheral portion covered by solder resist opening and a central portion exposed on the surface. This segmentation allows the pad to maintain smaller overall dimensions for high density while the peripheral coverage provides robust positional reference for accurate alignment during manufacturing processes.
Solution Approach 2:
The solder resist opening is formed in advance to cover the peripheral portion of the connection pad, establishing a predetermined positional relationship that serves as a reference for subsequent wiring formation processes. This preliminary positioning action ensures accurate alignment even when pads are miniaturized.
3Productivity
If wiring width is reduced to maximize wiring density, then wiring density is improved, but conduction reliability deteriorates due to increased risk of conduction failures
Solution Approach 1:
The connection pad extends in the vertical dimension by projecting from the surface of the wiring board. This vertical extension provides additional conduction pathways and increases the effective cross-sectional area for current flow, compensating for the reduced horizontal wiring width and maintaining conduction reliability despite miniaturization.
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 design achieves a higher wiring density in the outermost layer while maintaining reliability, allowing for more efficient and reliable connections in high-density semiconductor mounting applications.
Implementation Method 1
using techniques such as electroless copper plating and laser processing to enhance positional accuracy
Implementation Method 2
the laser technique is used
Data Source
AI summary
In a wiring board, a plurality of wiring layers and a plurality of insulating layers are alternately stacked. The wiring layers are electrically connected to one another through via holes formed in the insulating layers. The wiring board includes: a connection pad which is disposed on one of the wiring layers that is on the inner side of an outermost wiring layer; and an external connection terminal which is disposed on the connection pad, and which is projected from the surface of the wiring board. The external connection terminal is passed through the outermost wiring layer.