Printed Wiring Board Silver-Particle Seeding for Fine-Pitch Circuits
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Solution Overview
Problem
Existing methods for producing printed wiring boards face challenges such as poor adhesion between the substrate and conductor circuit, undercuts, and non-rectangular cross-sectional shapes, often requiring surface roughening, alkali treatment, or expensive vacuum equipment.
Innovation Solution
A method involving the formation of a silver-particle layer on an insulating substrate, followed by electroless or electrolytic plating to create a conductor circuit, and subsequent removal of the silver-particle layer using a carboxylic acid and hydrogen peroxide etchant, ensuring strong adhesion and a rectangular cross-section without surface roughening or vacuum equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If surface roughening is performed to ensure adhesion between substrate and plating film, then adhesion strength is improved, but fine-pitch wiring formation becomes difficult and transmission characteristics deteriorate
Solution Approach 1:
The invention changes the surface treatment parameters from strong chemical roughening (chromic acid, permanganic acid) to mild plasma treatment, and introduces a primer layer with specific composition and thickness parameters to ensure adhesion without surface roughening
Solution Approach 2:
The invention introduces a primer layer as an intermediary between the substrate and plating film. This primer layer contains specific compounds that promote adhesion while maintaining a smooth surface, thus mediating between the conflicting requirements of strong adhesion and fine-pitch wiring formation
2Strength
If surface roughening is performed to ensure adhesion, then adhesion strength is improved, but transmission characteristics for radiofrequency waves are degraded
Solution Approach 1:
The invention changes the surface treatment from strong chemical roughening to mild plasma treatment, and uses a primer layer with controlled composition and thickness, thereby maintaining smooth surface characteristics that preserve radiofrequency wave transmission while ensuring adequate adhesion
3Strength
If electroless nickel plating with palladium catalyst is used to form seed layer, then adhesion is ensured, but surface roughening is still required which causes difficulty in forming fine-pitch wiring
Solution Approach 1:
The invention replaces the electroless nickel plating with palladium catalyst approach with a direct plasma treatment and primer layer system. The primer layer acts as an intermediary that provides adhesion promotion without requiring surface roughening, thus enabling fine-pitch wiring formation
Solution Approach 2:
The invention changes the seed layer formation method from electroless plating requiring surface roughening to plasma treatment followed by primer layer application, fundamentally altering the surface preparation parameters to eliminate the need for roughening while maintaining adhesion
4Manufacturing precision
If sputtering is used to form seed layer without surface roughening, then fine-pitch wiring can be formed, but expensive vacuum equipment and complex process are required
Solution Approach 1:
The invention replaces expensive, complex sputtering equipment with a simpler, more cost-effective plasma treatment system. The plasma process uses readily available equipment and eliminates the need for expensive vacuum systems, while still achieving the required fine-pitch wiring formation
Solution Approach 2:
The invention replaces the mechanical/vacuum-based sputtering process with a plasma-based chemical process. This substitution eliminates the need for expensive vacuum equipment and complex mechanical systems, using plasma chemistry to achieve seed layer formation and adhesion promotion
5Reliability
If strong chemical etching is used to remove copper residue, then insulation reliability is improved, but wiring width thins and side etching increases
Solution Approach 1:
The invention performs preliminary action by forming a resist pattern before plating, which defines the exact wiring boundaries. This prevents copper residue in the skirting area from the outset, eliminating the need for strong chemical etching to remove such residue and thereby preventing wiring width thinning and side etching
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 produces high-density, high-performance printed wiring boards with strong adhesion and rectangular cross-sections, suitable for various substrates and sizes, at a lower cost, and can be applied to connectors, electromagnetic wave shields, RFID antennas, and decorative plating.
Implementation Method 1
forming a silver-particle layer on an electrically insulating substrate
Implementation Method 2
followed by electroless or electrolytic plating to create a conductor circuit
Implementation Method 3
subsequent removal of the silver-particle layer using a carboxylic acid and hydrogen peroxide etchant
Data Source
AI summary
The present invention provides a method for producing a printed wiring board having a circuit pattern on an electrically insulating substrate. The method includes step 1, forming a silver-particle layer (M1) in a range of 0.01 to 0.5 g/m2 on an electrically insulating substrate (A); step 2, forming a patterned resist on the silver-particle layer (M1), the patterned resist being a resist patterned by removing the portion thereof in the area in which the circuit is to be formed; step 3, forming a conductor-circuit layer (M2) by plating; and step 4, peeling away the patterned resist and removing, using an etchant, the silver-particle layer (M1) in the area in which no circuit has been formed. This production method allows the manufacturer to produce a printed wiring board requiring no treatment such as surface roughening with chromic acid or permanganic acid or the formation of a surface modified layer with an alkali and without using vacuum equipment. The resulting printed wiring board has high adhesiveness between its substrate and conductor circuit, few undercuts, and a rectangular cross-sectional shape good for use as circuit wiring.