PCB Penetrating Hole Asymmetric Drum Shape Void Prevention
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Solution Overview
Problem
Existing methods for forming through-holes in printed circuit boards often result in voids and surface irregularities due to concentrated plating currents, which can lead to adhesion issues when additional layers are applied.
Innovation Solution
A printed circuit board design featuring a penetrating hole with a monotonically decreasing inner diameter from the top to the back surface, where the inner diameter at the center is smaller than the average of the opening diameters on both sides, allowing for sequential filling from the back side and minimizing voids and surface irregularities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the through-hole diameter is decreased to achieve thinner printed circuit boards and smaller interconnections, then the miniaturization requirement is satisfied, but the opening of the penetrating hole closes with metal plating before the inside is sufficiently filled, causing void formation
Solution Approach 1:
The penetrating hole is designed with an asymmetric drum shape where the diameter varies along the thickness direction - smaller at the center and larger at the top and back surfaces. This asymmetric geometry prevents plating current concentration at corners while ensuring the opening remains open during filling, eliminating void formation in miniaturized through-holes
Solution Approach 2:
The invention changes the geometric parameters of the penetrating hole by forming it with a drum shape that has different diameters at different positions along the thickness direction. This parameter modification allows the hole to maintain adequate opening size while accommodating smaller overall dimensions, preventing void formation during electroplating
2Manufacturing precision
If the penetrating hole is formed with a drum shape to prevent void formation, then the metal filling completeness is improved, but the inner diameter at the center becomes smaller than the average of opening diameters, requiring precise dimensional control
Solution Approach 1:
The drum shape of the penetrating hole is formed in advance during the hole formation process (e.g., drilling or laser machining) before electroplating. This preliminary geometric preparation ensures that during subsequent electroplating, the plating current distributes evenly and the opening remains open, automatically preventing void formation without requiring complex real-time control during plating
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 approach prevents void formation and reduces surface irregularities, ensuring efficient metal filling and reliable adhesion of additional layers without air pockets that can expand and prevent adhesion.
Implementation Method 1
a metal plating layer layered on both surfaces of the insulating material and an inner peripheral surface of the penetrating hole
Implementation Method 2
a through-hole is formed by performing electroless plating on the inner peripheral surface of a penetrating hole formed in an insulating material to become a substrate and performing electroplating on a metal layer layered by the electroless plating
Data Source
AI summary
A printed circuit board according to one embodiment of the present invention is a printed circuit board including a plate-shaped or a sheet-shaped insulating material having a penetrating hole, and a metal plating layer layered on both surfaces of the insulating material and an inner peripheral surface of the insulating material, wherein an inner diameter of the penetrating hole monotonically decreases from a top surface of the insulating material toward a back surface, and wherein the inner diameter of the penetrating hole at a center in a thickness direction of the insulating material is smaller than an average of an opening diameter on the top side and an opening diameter on the back side.