Circuit Board Build-Up Structure for Fine-Pitch De-Flux Clearance
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Solution Overview
Problem
Existing semiconductor packages face challenges in maintaining a fine pitch of pads while ensuring sufficient vertical distance for de-flux penetration, leading to issues like electrical short-circuits and surface contamination due to residual flux, especially as packages become thinner and more complex.
Innovation Solution
A circuit board design with a build-up structure featuring insulating layers and protective layers, where insulating members are spaced apart to increase the vertical distance between the pad and the semiconductor device, allowing for effective de-flux penetration and preventing flux residue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the vertical distance between the pad and the terminal of the semiconductor device is increased to allow sufficient de-flux solution penetration, then the de-flux process effectiveness is improved, but the pitch of pads on the circuit board increases and the semiconductor package cannot be miniaturized
Solution Approach 1:
The patent introduces a vertical dimension solution by forming a protrusion on the circuit board surface at the pad location. This protrusion increases the vertical distance between the pad and the semiconductor device terminal, creating sufficient space for de-flux solution penetration without increasing the horizontal pad pitch. The protrusion effectively adds height (Z-axis) to the mounting structure while maintaining the same footprint area.
Solution Approach 2:
The protrusion is formed on the circuit board before the semiconductor device is mounted. This preliminary structural preparation ensures that when the device is attached, the vertical distance for de-flux penetration is already established. The protrusion pre-creates the necessary clearance space, allowing the de-flux process to be effective without requiring larger pad spacing.
2Length of stationary object
If the thickness of the semiconductor package is decreased for miniaturization, then the package size is reduced, but the vertical distance between the pad and terminal decreases making de-flux penetration insufficient
Solution Approach 1:
The patent resolves this contradiction by utilizing the vertical dimension through the protrusion structure. Even though the overall package thickness is reduced for miniaturization, the protrusion locally increases the height at the pad area, creating sufficient vertical clearance for de-flux solution to penetrate between the circuit board and the semiconductor device terminal.
Solution Approach 2:
The protrusion provides a localized increase in vertical distance only at the pad mounting areas where de-flux penetration is needed, rather than increasing the thickness of the entire package. This local structural modification maintains the overall thin package profile while ensuring sufficient clearance at critical locations for effective flux removal.
Data Source
AI summary
A circuit board according to an embodiment comprises a build-up structure including a plurality of insulating layers stacked along a vertical direction; a protective layer disposed on the build-up structure; and a plurality of insulating members disposed on the protective layer and spaced apart from each other.