PCB Via Taper Angle for Plating Thickness
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Solution Overview
Problem
Conventional methods for forming vias in multilayer printed wiring boards face challenges in securing sufficient thickness of the plated film at the periphery of the via, leading to plating failures and reduced connection reliability, especially with increasing aspect ratios and finer pitches.
Innovation Solution
A printed wiring board design featuring a through hole with a first inner wall part and a second inner wall part, where the taper angle of the second inner wall part contacting the conductor layer is larger than that of the first inner wall part, ensuring a milder gradient and sufficient plated film thickness, and a manufacturing method involving specific hole formation and plating processes to achieve this configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional via forming method with a mask is used, then the via can be formed with precise positioning, but the plated film thickness at the periphery of the via opening becomes insufficient
Solution Approach 1:
The patent applies preliminary action by forming a tapered portion at the opening of the via hole before the plating process. This tapered structure is created in advance through mechanical means (such as blasting or grinding) to prepare the surface geometry that will ensure sufficient plated film thickness during subsequent plating operations, thereby preventing plating failure at the via periphery
Solution Approach 2:
The patent applies local quality by creating a localized tapered structure only at the opening periphery of the via hole, while the rest of the via maintains its original cylindrical shape. This localized geometric modification ensures that the plated film accumulates sufficiently at the critical periphery region without unnecessarily increasing the overall via dimensions or affecting other areas
2Productivity
If the aspect ratio of the via is increased to achieve finer pitch, then the packaging density is improved, but the plated film becomes locally thin and plating failure occurs
Solution Approach 1:
The patent applies local quality by creating a localized tapered structure only at the opening periphery of the via hole, while the rest of the via maintains its original cylindrical shape. This localized geometric modification ensures that the plated film accumulates sufficiently at the critical periphery region without unnecessarily increasing the overall via dimensions or affecting other areas
Solution Approach 2:
The patent applies preliminary action by forming a tapered portion at the opening of the via hole before the plating process. This tapered structure is created in advance through mechanical means (such as blasting or grinding) to prepare the surface geometry that will ensure sufficient plated film thickness during subsequent plating operations, thereby preventing plating failure at the via periphery
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 solution enhances connection reliability by preventing plating failures and ensuring sufficient plated film thickness, even at higher aspect ratios, effectively addressing the trend of finer pitches and higher packaging density.
Implementation Method 1
irradiating the insulation layer with the laser beam by using an aperture pattern of the upper conductor layer as a mask (conformal mask); piercing a via so as to expose the lower conductor layer to be a wiring body from the insulation layer
Data Source
AI summary
The present invention provides a printed wiring board which can prevent a plating failure in a connection hole such as a via to be formed in the printed wiring board, thereby can enhance the connection reliability and a manufacturing method therefor. The printed wiring board 100 includes a thermosetting resin sheet 16 (insulation layer) having a via hole 20 (through hole) constituted by inner wall parts having different taper angles from each other, a copper foil 17 (conductor layer) provided on the thermosetting resin sheet 16, and a wiring pattern 13 (wiring layer) which is provided so as to be exposed from the via hole 20 and is electrically connected with the copper foil 17 through the via hole 20.