Printed Wiring Board Uneven Conductor Surfaces for Resin Adhesion
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Solution Overview
Problem
Existing printed wiring boards face challenges in filling narrow spaces between conductor circuits with resin insulating layers due to the difficulty in accessing and adhering to smooth conductor surfaces, which can lead to incomplete filling, peeling, and potential short circuits or cracks during heat cycles.
Innovation Solution
A printed wiring board design featuring a first resin insulating layer, a conductor layer with specific width and positioning of conductor circuits, and a second resin insulating layer that fills spaces between these circuits, where the second resin insulating layer can easily enter and adhere to the conductor circuits without forming unevenness on all side walls, allowing for smooth filling even in narrow spaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a roughened layer is formed on entire surfaces of conductor circuits, then adhesion between resin insulating layer and conductor circuits is improved, but filling of narrow spaces between conductor circuits becomes difficult and incomplete filling occurs
Solution Approach 1:
The invention applies different surface treatments to different parts of the conductor circuits: the upper surfaces have unevenness for adhesion, while the side walls remain smooth to facilitate resin filling. This local differentiation resolves the contradiction between achieving good adhesion and enabling complete filling of narrow spaces.
Solution Approach 2:
The invention forms unevenness only on the upper surfaces of conductor circuits before applying the resin insulating layer. This preliminary action ensures that adhesion is optimized at the interface where it is most needed, while leaving side walls smooth for subsequent complete resin penetration.
2Ease of manufacture
If resin insulating layer is pressed to fill narrow spaces between conductor circuits, then filling completeness is improved, but roughened layer on side walls causes filling difficulty and potential short circuits
Solution Approach 1:
The invention creates smooth side walls on conductor circuits, eliminating the roughened layer that would obstruct resin filling. This allows the resin to completely fill narrow spaces without encountering resistance, preventing voids and potential short circuits while maintaining adhesion through unevenness on upper surfaces only.
3Reliability
If unevenness is formed on all side walls of conductor circuits, then adhesion is improved, but resin filling of narrow spaces becomes difficult
Solution Approach 1:
The invention selectively forms unevenness only on the upper surfaces of conductor circuits that contact the resin insulating layer, while keeping side walls smooth. This local differentiation optimizes adhesion where needed without impeding resin flow and filling in narrow spaces.
Solution Approach 2:
The invention segments the conductor circuit surface into two functional zones: upper surfaces with unevenness for adhesion, and side walls without unevenness for easy resin filling. This segmentation allows each zone to perform its specific function optimally.
Data Source
AI summary
A printed wiring board includes a first resin insulating layer, a second resin insulating layer formed on a surface of the first layer, and a conductor layer formed on the surface of the first layer such that the second layer is covering the conductor layer and that the conductor layer includes first, second, third, fourth, fifth, and sixth circuits such that the third and fourth circuits are sandwiching the first circuit and that the fifth and sixth circuits are sandwiching the second circuit. Widths between the first and third circuits and between the first and fourth circuits are 5 μm to 14 μm, and when a width between the second and fifth circuits and a width between the second and sixth circuits is 20 μm or more, the upper surface of the first circuit, and the upper surface and side walls of the second circuit are formed to have unevenness.