Curved Depression in PCB Through Hole for Adhesion
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Solution Overview
Problem
Existing circuit board mounting structures face electrical reliability issues due to ion migration caused by moisture and thermal stress, leading to conductor layer short-circuits, especially when insulating aggregates project from through hole inner walls.
Innovation Solution
A circuit board design featuring a substrate with a first and second fiber layer and a resin layer, where the through hole conductor is anchored in a curved depression within the resin layer, reducing separation and ion migration risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If insulating aggregate projects from the inner wall of the through hole, then the insulating aggregate and resin composition are easily separated by thermal stress, but moisture accumulates in the separated portion leading to ion migration and short-circuit
Solution Approach 1:
The invention introduces a curved depression in the inner wall of the through hole instead of a flat surface. This curved structure prevents the formation of separated portions between the insulating aggregate and resin composition, eliminating the accumulation of moisture that would lead to ion migration. The curvature design directly addresses the problem by modifying the geometry to avoid crevices where moisture could collect.
Solution Approach 2:
The invention applies a plating layer specifically to the curved depression portion of the through hole inner wall. This localized treatment enhances the adhesive strength and electrical conductivity in the critical area where moisture accumulation would most likely occur, without requiring changes to the entire through hole structure.
2Ease of manufacture
If conventional through hole structure is used, then manufacturing is simple, but thermal stress causes separation and ion migration between through holes
Solution Approach 1:
The curved depression is formed in the through hole inner wall during the manufacturing process, creating a structure that naturally prevents separation between insulating aggregate and resin. This geometric modification can be integrated into existing manufacturing processes while significantly improving resistance to thermal stress and preventing ion migration pathways.
Solution Approach 2:
The invention uses a combination of plating layer and curved depression structure to create a composite solution that addresses both mechanical adhesion and electrical insulation requirements. The plating layer provides enhanced bonding and conductivity, while the curved geometry prevents moisture accumulation, together creating a more reliable through hole structure.
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
The design enhances electrical reliability by increasing adhesive strength between the through hole conductor and the substrate, suppressing conductor layer short-circuits and improving thermal stress resistance.
Implementation Method 1
A portion of the through hole conductor is arranged in the curved depression... increasing adhesive strength between the through hole conductor and the substrate
Implementation Method 2
suppressing conductor layer short-circuits... suppressing ion migration risks
Data Source
AI summary
A circuit board comprises a substrate; a through hole penetrating the substrate along with a direction of a thickness thereof; and a through hole conductor covering an inner wall of the through hole. The substrate comprises a first fiber layer, a second fiber layer, and a resin layer arranged between the first fiber layer and the second fiber layer. Each of the first fiber layer and the second fiber layer has a plurality of fibers and a resin arranged among the plurality of the fibers. The resin layer contains a resin and doesn't contain a fiber. The inner wall of the through hole, in a cross-section view along with the direction of the thickness of the substrate, comprises a curved depression in the resin layer.