Printed Wiring Board Smoothing Without Polishing
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Solution Overview
Problem
Conventional methods for producing printed wiring boards result in surface depression between circuit traces and can damage the circuit during surface polishing, reducing productivity.
Innovation Solution
A method involving the application of a photo- and heat-curable resin composition onto a printed wiring substrate, followed by thinning with a hard roller, exposure through a negative-image mask, and development to produce a smoothed printed wiring board without the need for surface polishing, using a solvent-free resin composition and an alkali-developable resin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If surface polishing is performed to smooth the printed wiring board, then surface depression is eliminated, but circuit damage and wear occur and productivity decreases
Solution Approach 1:
The resin composition is applied in advance to fill surface depressions before the actual production process. This preliminary filling action prevents the need for subsequent polishing operations, thereby eliminating circuit damage risks while maintaining productivity.
Solution Approach 2:
A resin composition serves as an intermediary material that fills surface depressions between circuit traces. This intermediary layer smooths the surface without requiring mechanical contact or polishing, thus preventing circuit wear and maintaining high productivity.
2Shape
If surface polishing is performed to smooth the printed wiring board, then surface depression is eliminated, but circuit damage occurs
Solution Approach 1:
The resin composition acts as a non-contact intermediary that fills surface depressions. This eliminates the need for mechanical polishing that would otherwise cause circuit wear and damage, thereby maintaining circuit integrity while achieving surface smoothness.
Solution Approach 2:
The mechanical polishing process is replaced by a chemical/material-based approach where resin composition fills surface irregularities. This substitution eliminates mechanical contact with the circuit, preventing circuit damage while achieving the desired surface smoothness.
3Productivity
If conventional production method is used, then productivity is maintained, but surface depression between circuit traces occurs
Solution Approach 1:
The resin composition is applied preliminarily to fill surface depressions before subsequent production steps. This preliminary action corrects surface flatness issues without adding time-consuming polishing steps, thereby maintaining productivity while improving surface flatness.
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
The method achieves a smoothed printed wiring board with no depression between circuit traces and no damage to the circuit, enhancing productivity by eliminating the polishing step.
Implementation Method 1
a photoreaction initiator, wherein the photo- and heat-curable resin composition comprises an alkali-developable resin having an unsaturated group, an acrylic monomer and/or a methacrylic monomer, the photoreaction initiator, an epoxy compound, and a heat-curing agent
Implementation Method 2
completely heat-curing the cured light-exposed portion
Data Source
AI summary
A method produces an undercoat-covered smoothed printed wiring board, requiring no step of polishing the surface of the printed wiring board. A method for producing a solder-resist-covered printed wiring board causes no depression in an area between circuit traces. A printed wiring board so produced is also described. The method for producing a printed wiring board includes applying a photo- and heat-curable resin composition onto at least a part of a surface of a printed wiring substrate; placing an optically transparent smoothing member on the resin layer; moving a hard roller on the smoothing member to thin the applied resin layer to a thickness of interest; placing a negative-image mask on the smoothing member; exposing the applied resin layer to light via the negative-image mask; removing the optically transparent smoothing member; removing a light-unexposed portion of the applied resin layer through development; and completely heat-curing the cured light-exposed portion.