Wiring Substrate Ni/Au Plating Over-Etching Prevention
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Solution Overview
Problem
Conventional methods for forming a Ni/Au plating film on wiring substrates often result in over-etching of copper patterns, leading to hollow end portions and potential breakage, which can cause short circuits due to the fragility of the Ni/Au alloy and the thickness of the Ni plating film.
Innovation Solution
A method involving the formation of a conductor circuit with a solder resist layer, a plating resist layer, and an etching resist layer to control the deposition and removal of the Ni/Au metal film, ensuring it is only on the necessary portions and preventing over-etching by exposing copper under the Ni/Au film, thereby reducing the risk of film drop-off and short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the Ni/Au plating film is formed on the lead pattern using electrolytic plating, then connection reliability is improved, but over-etching of copper patterns occurs leading to hollow end portions and potential breakage
Solution Approach 1:
The patent applies preliminary action by forming the Ni/Au plating film on the lead pattern before the etching process. The plating film serves as a protective layer that prevents over-etching of the copper patterns during subsequent etching steps. This preliminary protective measure ensures that the copper patterns are not excessively removed, avoiding hollow end portions and potential breakage while maintaining connection reliability.
Solution Approach 2:
The Ni/Au plating film acts as an intermediary protective layer between the copper patterns and the etching solution. During the etching process, the plating film mediates by preventing direct contact between the etching solution and the copper patterns, thereby controlling the etching depth and preventing over-etching. This intermediary function maintains the integrity of the copper patterns while allowing the etching process to proceed.
2Reliability
If the Ni/Au plating film is made thicker to improve connection reliability, then connection reliability is improved, but the risk of film drop-off and short circuits increases
Solution Approach 1:
The patent applies parameter changes by optimizing the thickness of the Ni plating film to a specific range (0.5-3 μm) that balances connection reliability with the risk of film drop-off. By controlling the Ni plating thickness within this optimized range, the patent achieves sufficient connection reliability while minimizing the harmful effects of excessive thickness, such as film drop-off and short circuits between independent wirings.
3Ease of manufacture
If electrolytic plating is used instead of electroless plating, then manufacturing cost is reduced, but process complexity increases due to lead pattern removal requirements
Solution Approach 1:
The patent applies preliminary action by forming the Ni/Au plating film on the lead pattern before the etching process. This preliminary plating step simplifies the subsequent etching process by providing a protective layer that prevents over-etching, thereby reducing the complexity of the overall process. The preliminary action of plating first allows for more controlled and simpler etching operations.
Solution Approach 2:
The Ni/Au plating film serves as an intermediary that simplifies the etching process by acting as a protective barrier. During the etching process, the plating film mediates by preventing direct etching of the copper patterns, thereby reducing the complexity of controlling etching depths and preventing over-etching. This intermediary function makes the overall manufacturing process more manageable despite using electrolytic 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 the Ni/Au plating film from dropping off and reduces the risk of short circuits between independent wirings, allowing for a thinner Ni film and improved connection reliability between electronic parts and the wiring substrate.
Implementation Method 1
The Ni/Au plating film is formed using electrolytic plating in place of electroless plating
Implementation Method 2
removing a portion of the lead pattern not covered with the Ni/Au plating film by etching
Data Source
AI summary
A method for manufacturing a wiring substrate includes forming a conductor circuit on an insulating layer, the conductor circuit including a pad, a circuit pattern connected to the pad, and a lead pattern connected to the pad. A solder resist layer is formed on the circuit pattern and on the insulating layer, and a plating resist layer is formed on the lead pattern and on the insulating layer and forming a metal film on a first portion of the conductor circuit not covered by the solder resist layer and not covered by the plating resist layer. The plating resist layer is removed to expose a second portion of the conductor circuit adjacent to the first portion of the conductor circuit and not covered with the metal film, and an etching resist layer is formed on the metal film and on the second portion of the conductor circuit. A third portion of the conductor circuit not covered by the etching resist layer is removed by etching, and the etching resist is removed. The conductor circuit covered with the etching resist layer is a part of the second portion of the conductor circuit exposed by removing the plating resist.