Embedded Pads in Printed Wiring Boards to Suppress Warping
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Solution Overview
Problem
Existing multilayer wiring boards without core substrates face issues with warping and short-circuit defects due to exposed connection pads at fine pitches, leading to unreliable connections and mounting challenges.
Innovation Solution
A printed wiring board design featuring a laminate structure with alternately layered conductor and resin insulating layers, where first conductor pads are exposed on one surface and second conductor pads are embedded in the resin, supported by a solder resist layer and a removable support plate, which suppresses warping and short-circuit defects by embedding pads and facilitating stable electronic component mounting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If connection pads are exposed on the surface at fine pitches, then electrical connectivity is achieved, but warping and short-circuit defects occur
Solution Approach 1:
The patent introduces a solder resist layer as an intermediary substance between the exposed connection pads and the external environment. This layer selectively covers areas around the pads while leaving pad surfaces exposed, thereby preventing short-circuit defects between adjacent pads at fine pitches while maintaining electrical connectivity. The solder resist acts as a mediator that resolves the conflict between achieving fine-pitch connectivity and preventing harmful short-circuits.
Solution Approach 2:
The connection pads are segmented into two distinct regions: exposed pad surfaces that provide electrical connectivity and covered surrounding areas that prevent short-circuits. The solder resist layer applies this segmentation by selectively coating only certain regions, creating a patterned structure where conductivity and insulation coexist at the micro-level, enabling reliable fine-pitch connections without warping or short-circuit defects.
2Object-affected harmful factors
If conductor pads are embedded in the resin insulating layer, then short-circuit defects are prevented, but mounting stability deteriorates
Solution Approach 1:
The patent applies local quality by creating different structural conditions in different regions of the connection pad system. The pad surfaces remain exposed with high conductivity and mechanical accessibility for mounting, while the surrounding regions are covered by solder resist providing insulation. This localized differentiation allows the structure to simultaneously achieve short-circuit prevention through coverage and mounting stability through exposed pad surfaces.
Data Source
AI summary
A printed wiring board includes a laminate including first conductor pads on first surface side of the laminate and second conductor pads on second surface side of the laminate, and a solder resist layer formed on the first surface side of the laminate and having openings formed such that the openings are exposing the first conductor pads respectively. The laminate includes a resin insulating layer and has first surface on the first surface side and second surface on the second surface side on the opposite side with respect to the first surface of the laminate, and the second conductor pads are embedded in the second surface of the laminate such that the second conductor pads have surfaces exposed from the second surfaces of the laminate respectively and that the surfaces of the second conductor pads are protruding from the second surface of the laminate.