PCB Penetrating Hole Tapered Geometry for Void-Free Plating
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Solution Overview
Problem
Existing printed wiring boards face challenges in forming reliable through-hole conductors due to voids and cracks in the plating process, particularly in the filling of penetrating holes with conductive material, which affects the connection reliability between circuits.
Innovation Solution
The solution involves creating a penetrating hole with a first opening portion that tapers inward from the first surface toward the second surface and a second opening portion that also tapers inward from the second surface toward the first surface, with the inner walls of these portions bending inward to facilitate even plating and reduce voids, using a method that includes laser irradiation to form these specific opening portions within the core substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a penetrating hole is formed with straight inner walls, then the manufacturing process is simple, but voids and cracks occur in the plating process reducing connection reliability
Solution Approach 1:
The penetrating hole is designed with curved inner walls that bend inward from both surfaces toward the center, creating a tapered configuration. This curvature prevents voids and cracks during plating by ensuring uniform material deposition along the hole walls, thereby improving connection reliability between circuit layers.
Solution Approach 2:
The geometry of the penetrating hole is modified by changing the wall angle parameters. The inner walls are configured to taper inward at specific angles from both surfaces, transforming the hole shape from cylindrical to tapered. This parameter change optimizes plating flow and adhesion, eliminating defects while maintaining manufacturing feasibility.
2Productivity
If the penetrating hole diameter is reduced to increase density, then higher density of through-hole conductors is achieved, but plating quality deteriorates due to voids and cracks
Solution Approach 1:
By curving the inner walls inward in the penetrating hole, the plating process achieves uniform coating even in smaller diameter holes. The curved geometry guides plating material flow and prevents air entrapment, eliminating voids and cracks that typically occur in narrow holes, thus maintaining high plating quality while enabling higher conductor density.
Solution Approach 2:
The penetrating hole is pre-formed with optimized tapered geometry before the plating process. This preliminary shaping of the hole walls ensures that subsequent plating deposition occurs uniformly without defects, allowing small diameter holes to be plated reliably and enabling increased density of through-hole conductors.
3Stability of the object's composition
If conventional plating is used in straight-walled holes, then the manufacturing process is simple, but thermal warping tolerance is reduced
Solution Approach 1:
The curved inward walls of the penetrating hole create a tapered structure that distributes thermal stresses more evenly during plating and subsequent thermal cycles. This geometry reduces stress concentration that causes warping, improving dimensional stability and thermal warping tolerance while accounting for the increased geometric complexity.
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 enhances the reliability of through-hole conductors by reducing voids and cracks, improving the connection between circuits and increasing the tolerance against thermal warping, while allowing for a higher density of through-hole conductors without compromising reliability.
Implementation Method 1
a method that includes laser irradiation to form these specific opening portions within the core substrate
Data Source
AI summary
A printed wiring board includes a core substrate having a penetrating hole, a first circuit on a first surface of the substrate, a second circuit on a second surface of the substrate, and a through-hole conductor in the hole connecting the first and second circuits. The hole has first and second opening portions. The first opening portion becomes thinner toward the second surface. The second opening portion becomes thinner toward the first surface. The first opening portion has first and second portions. The second opening portion has first and second portions. The first and second portions of the first opening portion form inner walls bending inward at the boundary between the first and second portions. The first and second portions of the second opening portion form inner walls bending inward at the boundary between the first and second portions.