Through-Electrode Void Structure for Flat Circuit Board Pads
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Solution Overview
Problem
The increasing thickness of insulating layers in circuit boards leads to deeper through holes, resulting in concave-shaped pad parts that reduce the overall flatness and alignment accuracy of the circuit board, causing reliability issues and misalignment between through electrodes and pad parts.
Innovation Solution
A circuit board design featuring a through electrode with a void portion having specific inclinations and shapes, including a first region with a second inclination in the same direction as the electrode and a second region with a third inclination in a different direction, maintaining a flat pad surface and improving elasticity and strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the thickness of the insulating layer is increased to improve thermal shock and heat dissipation characteristics, then thermal performance is improved, but the depth of the through hole becomes deeper, resulting in a concave shape of the pad part surface and reduced flatness
Solution Approach 1:
The through electrode is designed with different cross-sectional shapes in different regions: an upper portion with a first cross-sectional shape and a lower portion with a second cross-sectional shape. This local variation allows the pad part surface to remain flat while the through electrode extends deeply into the thicker insulating layer, thus maintaining both thermal performance and surface flatness.
2Temperature
If the thickness of the insulating layer is increased, then thermal shock and heat dissipation characteristics are improved, but the alignment between the through electrode and pad part is reduced
Solution Approach 1:
The through electrode has a varying cross-sectional shape along its length, with the upper portion having a first cross-sectional shape that aligns with the pad part and the lower portion having a second cross-sectional shape that facilitates precise positioning. This local differentiation maintains alignment accuracy despite the increased insulating layer thickness.
3Reliability
If the through hole is filled completely to form the through electrode, then electrical conduction is achieved, but the pad part surface becomes concave, reducing overall circuit board flatness
Solution Approach 1:
The through electrode is formed with a non-uniform cross-sectional shape where the upper portion has a different shape than the lower portion. This allows the electrode to maintain good electrical contact with the pad part while keeping the pad part surface flat, eliminating the need for additional filling or leveling processes.
Data Source
AI summary
A circuit board according to an embodiment includes an insulating layer including an upper and lower surface; and a through electrode passing through the upper and lower surfaces of the insulating layer and having a first inclination whose width gradually decreases toward the lower surface of the insulating layer, and wherein the through electrode includes a void portion having an inclination different from the first inclination.