Wiring Board Thick Conductive Layer via Screen Printing
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Solution Overview
Problem
Existing wiring boards with thick wiring for carrying large currents face challenges in manufacturing time and cost due to the need for repeated exposure, development, and sintering processes, and in achieving high-density wiring due to lateral erosion of copper plates during etching.
Innovation Solution
A wiring board with a layered structure comprising a titanium layer, a nickel alloy layer, a copper plating layer, and a metal-paste sintered layer, where the metal-paste sintered layer is formed by sintering a metal paste applied in a wiring pattern using screen printing, allowing for thick wiring without the need for repeated etching processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If repeated exposure, development, and sintering of photosensitive conductive material is performed to increase wiring thickness, then the wiring can carry larger currents, but the number of manufacturing steps increases and manufacturing time and costs increase
Solution Approach 1:
The wiring structure is segmented into multiple functional layers: a base conductive layer formed by conventional photo lithography, and a thick metal paste sintered layer formed by screen printing. This segmentation allows each layer to be optimized independently - the base layer provides adhesion and pattern definition, while the paste layer provides the thick conductive path for high current carrying capacity, eliminating the need for repeated sintering cycles
Solution Approach 2:
A nickel alloy intermediate layer is introduced between the base conductive layer and the metal paste sintered layer. This intermediate layer serves as a mediator that ensures strong adhesion between the organic-based paste layer and the substrate, while also providing a suitable surface for sintering. This allows the use of thick paste layers without compromising bonding strength, resolving the contradiction between thickness and manufacturing efficiency
2Quantity of substance
If a thick copper plate is used to provide sufficient wiring thickness for large currents, then the wiring can carry large currents, but lateral erosion during etching increases and the distance between adjacent wiring sections increases, preventing high-density wiring
Solution Approach 1:
The conventional mechanical etching process is replaced with a screen printing process for forming the thick conductive layer. Instead of etching away material to create patterns, the metal paste is directly deposited in the desired wiring pattern through screen printing and then sintered. This substitution eliminates lateral erosion entirely, as the paste is applied only where wiring is needed, allowing thick wiring to be formed with precise pattern definition and minimal spacing between adjacent sections
Solution Approach 2:
The method changes the formation parameter of the thick conductive layer from etching (removal-based) to screen printing and sintering (additive-based). By controlling the paste application thickness and sintering parameters, precise wiring patterns with controlled thickness can be achieved without the lateral erosion that plagues thick copper plate etching, thereby maintaining high wiring density
3Length of stationary object
If thicker copper plate is etched to form wiring patterns, then sufficient wiring thickness is achieved, but deeper etching is required and lateral erosion increases, leading to increased distance between adjacent wiring sections
Solution Approach 1:
Instead of starting with a thick copper plate and removing material through etching, the invention inverts the approach by applying metal paste directly in the desired wiring pattern through screen printing and then sintering it. This inversion eliminates the fundamental problem of lateral erosion during etching, as the paste is deposited only where wiring is required, maintaining precise pattern definition regardless of wiring thickness or spacing
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 enables the efficient manufacturing of thick wiring capable of carrying large currents while reducing manufacturing time and costs, and allows for high-density wiring by minimizing lateral erosion and maintaining adhesion to the insulating layer.
Implementation Method 1
a plating layer that is formed on the nickel alloy layer by plating
Implementation Method 2
a metal-paste sintered layer that is formed on the plating layer
Data Source
AI summary
A wiring board includes an insulating layer and a wiring layer that is patterned, wherein the wiring layer includes: a titanium layer that is formed on the insulating layer and is mainly composed of titanium; a nickel alloy layer that is formed on the titanium layer and is mainly composed of nickel and a metal other than nickel; a plating layer that is formed on the nickel alloy layer by plating; and a metal-paste sintered layer that is formed on the plating layer.