PCB Cavity Dam and Sputtered Barrier for Pad Exposure
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Solution Overview
Problem
Conventional printed circuit board manufacturing methods face challenges in accurately exposing bonding pads for electronic components due to the use of thick dry films, leading to adhesion issues with etching resist, stepped structures, and dimensional faults in cavities.
Innovation Solution
A method involving the formation of a thin barrier on the bonding pad using a sputtering process, which is reactive to different etching solutions than the bonding pad and circuit layers, allowing for precise exposure and preventing the second insulation layer from covering the bonding pad, along with a protection layer and surface treatment to prevent corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick dry film is used to cover the bonding pad, then the bonding pad is protected during manufacturing, but adhesion issues with etching resist occur and dimensional accuracy of the cavity is compromised
Solution Approach 1:
The patent changes the thickness parameter of the protective film from thick (conventional dry film) to thin (few micrometers), fundamentally altering the film's properties to eliminate adhesion issues and dimensional inaccuracies while maintaining protective function during etching
Solution Approach 2:
The patent introduces a barrier layer as an intermediary between the bonding pad and the etching process. This barrier layer, being thin and properly adhered, serves as a mediator that protects the bonding pad without causing the adhesion failures or dimensional errors that occur with thick dry films
2Reliability
If a thick dry film is used to protect the bonding pad, then protection during etching is provided, but stepped structures and residue are created causing manufacturing defects
Solution Approach 1:
The patent changes the thickness parameter of the protective film from thick to thin (few micrometers), which eliminates the formation of stepped structures and residue while maintaining adequate protection during the etching process
Solution Approach 2:
The thin protective film serves as a disposable protective layer that performs its function during etching and is then completely removed without leaving residue, unlike thick dry films that create persistent manufacturing defects
3Manufacturing precision
If the bonding pad is exposed directly without a protective layer, then manufacturing precision is improved, but the bonding pad is vulnerable to corrosion and damage
Solution Approach 1:
The patent introduces a thin barrier layer as an intermediary protective film between the bonding pad and the corrosive etching environment. This thin film provides corrosion protection while being thin enough to avoid the adhesion and dimensional accuracy problems of thick films
Solution Approach 2:
The patent changes the protective film thickness to a thin configuration (few micrometers), which provides sufficient corrosion protection during manufacturing while allowing precise exposure of the bonding pad without creating stepped structures or adhesion failures
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 resolves reliability issues and dimensional inaccuracies by eliminating residue from improper dry film removal and ensures proper adhesion of etching resist, maintaining designed cavity dimensions and enhancing the manufacturing process's precision and reliability.
Implementation Method 1
forming a barrier on the dam and the bonding pad that is exposed to an outside
Data Source
AI summary
A printed circuit board includes a first substrate including a first insulation layer and a first circuit layer including a bonding pad, the bonding pad disposed on the first insulation layer, a second substrate disposed on the first substrate and having a cavity exposing the bonding pad to an outside, and a dam disposed between the bonding pad and an inner wall of the cavity.