Packaging Board Stepped Boundary Moisture Infiltration
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Solution Overview
Problem
Conventional semiconductor packaging boards are prone to moisture infiltration, leading to ion migration and reliability issues due to the flat and smooth gold plating layer interface with the solder resist, which allows moisture to reach the wiring pattern, causing shorting and dielectric breakdown.
Innovation Solution
A packaging board design featuring a copper wiring layer with a stepped portion in the boundary region, a gold plating layer on the electrode region, and an insulating layer that covers the gold plating and boundary regions, with predetermined openings, restricting moisture spread and improving adhesion, thereby preventing ion migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a flat and smooth gold plating layer is used on the wiring pattern, then the manufacturing process is simple and adhesion is adequate, but moisture can easily infiltrate along the interface between the gold plating layer and solder resist, causing ion migration and reliability issues
Solution Approach 1:
The invention introduces a stepped portion with a curved profile on the gold plating layer surface, replacing the conventional flat surface. This curved structure increases the path length for moisture infiltration and creates capillary barriers, effectively preventing moisture from reaching the wiring pattern while maintaining manufacturing feasibility through standard plating processes
Solution Approach 2:
The invention transitions from a two-dimensional flat gold plating surface to a three-dimensional stepped structure by adding vertical height variation. This dimensional change creates multiple interfaces and longer moisture diffusion paths, significantly improving moisture resistance without substantially increasing manufacturing complexity
2Reliability
If the gold plating layer surface is made rough to prevent moisture infiltration, then moisture resistance improves, but manufacturing precision and surface uniformity deteriorate
Solution Approach 1:
The stepped portion introduces controlled curvature to the gold plating surface, creating a systematic non-uniform profile rather than random roughness. This curved structure provides predictable moisture barriers while maintaining manufacturing precision through controlled plating parameters and standardized design dimensions
3Reliability
If a stepped portion is added to the wiring layer to restrict moisture spread, then moisture resistance improves, but manufacturing process complexity increases
Solution Approach 1:
The stepped portion is formed on the gold plating layer before final assembly, pre-establishing moisture barriers that passively protect the wiring pattern throughout the product lifecycle. This preliminary structural modification eliminates the need for additional active moisture protection steps during manufacturing and assembly
Solution Approach 2:
The invention modifies the surface topology parameter of the gold plating layer by introducing controlled height variations through the stepped portion. This parameter change achieves moisture resistance through geometric design rather than material changes or complex process modifications, maintaining ease of manufacture
Data Source
AI summary
An advantage of the present invention is to suppress moisture infiltrating from a pad electrode portion from spreading over the surface of a wiring pattern and improve the reliability of a packaging board. The wiring pattern of the packaging board is formed on an insulating substrate and includes a wiring region, an electrode region (pad electrode) connected with a semiconductor device, and a boundary region provided between the wiring region and the electrode region. A gold plating layer is provided on the surface of the electrode region of the wiring pattern. The top surface of the boundary region of the wiring pattern is so formed as to be dented from the top surface of the wiring region of the wiring pattern, and there is provided a stepped portion in the boundary region. A solder resist is formed in such a manner as to cover part of the gold plating layer and the wiring pattern corresponding to the boundary region and the wiring region, and the solder resist has a predetermined opening through which to connect to the semiconductor device. A conductive member is connected to the gold plating layer in the electrode region, and a molded resin layer seals the entire semiconductor module.