Printed Wiring Board Insulation Layer Flatness
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Solution Overview
Problem
Conventional printed wiring boards often experience connection failures due to insufficient flatness of the insulation layer surface on the outermost conductive-circuit layer, which is affected by the concavo-convex patterns of the inner conductive-circuit layer, leading to incomplete solder connections.
Innovation Solution
A printed wiring board structure with a double-layer insulation system, where a thinner second insulation layer is laminated between the first insulation layer and the outermost conductive-circuit layer, ensuring a flatter surface on the outermost conductive-circuit layer side, and a manufacturing method involving specific lamination and curing processes to achieve this flatness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single insulation layer is used, then the structure is simple, but the surface flatness is insufficient leading to connection failures
Solution Approach 1:
The insulation layer is divided into two separate layers: a first insulation layer and a second insulation layer. The first insulation layer provides the base insulation, while the second insulation layer specifically addresses surface flatness requirements. This segmentation allows each layer to be optimized for its specific function, with the second layer being thinner and having better flatness characteristics to ensure proper soldering of connection portions.
Solution Approach 2:
The solution transitions from a single-layer insulation structure to a multi-layer insulation structure, adding a dimensional aspect to the design. By stacking the first and second insulation layers with different thicknesses and flatness characteristics, the patent achieves both structural simplicity and surface flatness requirements through vertical layering rather than modifying a single layer.
2Manufacturing precision
If the insulation layer is made thinner to improve flatness, then surface flatness improves, but insulation performance may deteriorate
Solution Approach 1:
The insulation function is segmented between two layers: the first insulation layer maintains adequate thickness to ensure proper insulation performance and electrical isolation, while the second insulation layer is made thinner to provide the necessary surface flatness. This segmentation allows both insulation reliability and surface flatness to be optimized independently without compromising either requirement.
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 solution enhances the surface flatness of the insulation layer, reducing the likelihood of connection failures and improving the mounting of components by ensuring a more even and stable surface for solder bumps, thereby increasing the reliability of component attachment.
Implementation Method 1
an insulation layer may be formed by providing a thermosetting resin sheet on an inner conductive-circuit layer and applying pressure and heat thereon
Implementation Method 2
The outermost conductive-circuit layer is formed on the flat surface by plating or the like
Data Source
AI summary
A printed wiring board includes an inner conductive-circuit layer, an insulation layer structure including a first insulation layer laminated on inner conductive-circuit layer and a second insulation layer laminated on the first insulation layer, and an outermost conductive-circuit layer laminated on the insulation layer structure and including connection portions such that the connection portions are positioned to mount a component on the insulation layer structure. The second insulation layer is interposed between the first insulation layer and the outermost conductive-circuit layer and has a thickness which is smaller than a thickness of the first insulation layer such that an outer surface of the second insulation layer on an outermost conductive-circuit-layer side is flatter than an inner surface of the second insulation layer on a first insulation-layer side.