Multilayer Wiring Board Via Hole Plating Void Prevention
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Solution Overview
Problem
Conventional methods for manufacturing multilayer wiring boards using electrolytic filled plating solutions often result in plating voids due to metal foil projections during laser processing, especially when hole diameters are small and insulating layer thicknesses are thin, leading to potential failures under severe conditions.
Innovation Solution
A method involving the formation of a hole for through-hole with metal foil projections and a lower space, followed by electrolytic filled plating with a controlled current density decrease and increase to prevent plating voids, ensuring the electrolytic filled plating layer fills the hole without covering the opening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If laser processing is used to form holes for via-holes, then the holes can be precisely formed, but metal foil projections are generated at the openings which cause plating voids
Solution Approach 1:
The patent applies preliminary action by forming a tapered shape at the opening of the hole for via-hole before the electrolytic filled plating process. This tapered structure is created in advance to prevent metal foil projections from covering the opening during plating, thereby avoiding plating voids while maintaining precise hole formation.
2Length of moving object
If the hole diameter is reduced to match insulating layer thickness, then downsizing is achieved, but the aspect ratio increases making plating filling more difficult
Solution Approach 1:
The patent forms a tapered opening structure in advance before plating. This preliminary geometric modification creates a wider entry point that facilitates electrolytic filled plating penetration, enabling successful filling even in holes with small diameters and high aspect ratios.
Solution Approach 2:
The patent changes the geometric parameters of the hole opening by creating a tapered shape. This parameter modification (changing from a straight cylindrical opening to a tapered one) improves the aspect ratio effectively, making the hole more suitable for plating filling while maintaining the desired small diameter.
3Reliability
If electrolytic filled plating is applied to fill via-holes, then electrical connection is achieved, but plating voids are generated due to metal foil projections
Solution Approach 1:
The patent creates a tapered opening structure before the electrolytic filled plating process. This preliminary action prevents metal foil projections from blocking the opening, ensuring that the plating can fill the hole completely and form reliable electrical connections without generating voids.
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 method effectively reduces plating voids in through-holes with diameters equivalent to or less than the insulating layer thickness, enhancing the reliability of multilayer wiring boards by ensuring complete filling without voids.
Implementation Method 1
the hole for through-hole is plugged up with an electrolytic filled plating layer formed using an electrolytic filled via plating solution
Implementation Method 2
a hole for through-hole is formed on a metal foil-pasted laminated plate by a conformal method or a direct laser method
Data Source
AI summary
A method for manufacturing a multilayer wiring board includes a step (1) and a step (2). The step (1) disposes a hole for through-hole, a squirt of metal foils, and a lower space. The squirt of the metal foils on both the sides of the insulating layer is formed at an opening of the hole for through-hole. The lower space is formed between the squirt of the metal foils and an inner wall of the hole for through-hole. The step (2) plugs up the hole for through-hole by forming an electrolytic filled plating layer at an inside of the hole for through-hole and on the metal foils on both the sides of the insulating layer. The plugging of the hole for through-hole in the step (2) is performed by once decreasing a current density of an electrolytic filled plating in a middle of the electrolytic filled plating and then increasing the current density again.