Wiring Substrate With Segmented Plating For Fine Pitch
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Solution Overview
Problem
Conventional methods for manufacturing wiring substrates with through-wiring face challenges in forming fine-pitched patterns due to the thick plating layers on copper foils, making it difficult to achieve precise pattern formation.
Innovation Solution
A method involving the formation of a through-hole with an hourglass-like shape in the core layer, where a first metal layer covers the inner wall and surfaces, and a second metal layer closes the center part without filling the entire hole, allowing for patterned third and fourth metal layers to be formed on either surface, enabling precise wiring and reducing plating thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the through-hole is completely filled with plating to ensure connection reliability, then the connection reliability is improved, but the plating layer becomes too thick to form fine-pitched patterns
Solution Approach 1:
The plating filling process is segmented into multiple stages: first forming a base plating layer that covers the inner wall and closes the center, then forming additional plating layers only in specific regions where patterns will be formed. This segmentation allows the through-hole to be filled for reliability while keeping the final plating thickness at patterned areas controlled for precision.
Solution Approach 2:
Different regions of the through-hole receive different amounts of plating. The center part is completely filled to ensure connection reliability, while the upper and lower portions near the copper foils are controlled to maintain thin plating layers that enable fine-pitched pattern formation. This local differentiation resolves the contradiction between overall filling and local precision requirements.
2Reliability
If uniform plating is formed on both surfaces of the resin plate to ensure coverage, then the coverage is improved, but the total thickness becomes several tens of micrometers making fine-pitched patterning difficult
Solution Approach 1:
Instead of uniformly plating the entire surface and through-hole, the method applies plating selectively: the center part is excessively plated to ensure closure and reliability, while the peripheral areas near the surfaces are partially plated only to the extent needed for coverage, avoiding excessive thickness that would prevent fine patterning.
Solution Approach 2:
The plating process is divided into sequential stages with different coverage requirements. The first plating stage provides base coverage and center closure, while subsequent plating stages add material only where needed for patterns, avoiding uniform thick plating across the entire surface that would compromise pattern precision.
3Reliability
If the through-hole is filled entirely with plating to prevent voids, then the connection reliability is improved, but it becomes impossible to form fine-pitched patterns on the thick plating layer
Solution Approach 1:
The center part of the through-hole is preliminarily filled with plating in an early stage to close the hole and prevent void formation, ensuring connection reliability. This preliminary action is followed by additional plating only in specific regions where patterns will be formed, allowing fine-pitched patterning to proceed easily on the controlled-thickness plating layers.
Solution Approach 2:
The plating distribution is optimized locally: the center region receives complete filling to eliminate voids and ensure reliability, while the upper and lower regions near the copper foils receive controlled plating thickness that maintains ease of patterning. This local quality differentiation resolves the contradiction between void prevention and patterning ease.
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 allows for the creation of wiring substrates with high connection reliability and fine-pitched wiring layers, preventing voids and ensuring effective filling of the through-hole, thereby enhancing pattern precision and reducing operational complexities.
Implementation Method 1
a through-hole is formed by performing a laser process on each of the holes formed in the surfaces of the resin plate
Implementation Method 2
the through-hole is filled with plating. More specifically, at an early stage of filling the through-hole with plating, two closed-end via holes are formed by closing up a narrowest part of the through-hole. Then, unpatterned plating layers are uniformly (entirely) formed on the copper foils of both surfaces of the resin plate
Data Source
AI summary
A method for manufacturing a wiring substrate includes forming a through-hole penetrating a core layer from one to another surface of the core layer, forming a first metal layer covering the one and the other surface of the core layer and an inner wall surface of the through-hole, forming a second metal layer on the first metal layer, and forming a patterned third metal layer on the second metal layer toward the one surface of the core layer along with forming a patterned fourth metal layer on the second metal layer toward the other surface of the core layer. The forming of the second metal layer includes covering the one and the other surfaces of the core layer and the first metal layer in the through-hole with the second metal layer and closing up a center part of the through-hole with the second metal layer.