Printed Wiring Board Build-Up Layers for Warpage and Reliability
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Solution Overview
Problem
Existing multilayer printed wiring boards face challenges in connection reliability and warpage due to stress on through-hole conductors, particularly when subjected to thermal cycles, and have limitations in wiring density and flatness of mounting surfaces.
Innovation Solution
The printed wiring board design includes a core substrate with alternating conductor and resin insulating layers, where conductor layers have specific thickness ratios and electrolytic plating films, and through-hole conductors are formed with seed layers and electrolytic plating films to enhance connection reliability and reduce warpage, while inner side conductor layers with varying thicknesses increase wiring density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If through-hole conductors are formed to connect conductor layers, then electrical connection between layers is achieved, but connection reliability deteriorates under thermal cycles due to stress on through-hole conductors
Solution Approach 1:
The patent changes the structural parameters of conductor layers by forming build-up layers with alternating resin insulating layers and conductor layers on both surfaces of the core substrate. This creates a more robust layered structure that distributes stress more effectively compared to traditional through-hole only designs, improving connection reliability under thermal cycling conditions.
Solution Approach 2:
The patent uses composite material structures where each conductor layer consists of multiple materials: resin insulating layers (such as epoxy resin), metal foils (copper or aluminum), seed layers, and electrolytic plating films. This composite structure provides both electrical conductivity and mechanical strength, enhancing the overall reliability of connections under thermal stress.
2Strength
If conductor layers are made thicker to improve connection reliability, then strength increases, but warpage of the printed wiring board increases
Solution Approach 1:
The patent applies local quality by making conductor layers with different thicknesses at different locations. The build-up layers on the surfaces allow for localized thickening of conductor layers where high current carrying capacity or connection strength is needed, while keeping other areas thinner to minimize overall warpage. This selective thickness variation optimizes both strength and shape stability.
3Adaptability or versatility
If wiring density is increased by adding more conductor layers, then functionality improves, but flatness of mounting surfaces deteriorates
Solution Approach 1:
The patent segments the conductor layers into multiple thin layers within the build-up structure, with resin insulating layers separating them. This segmentation allows for better distribution of material stresses and improved flatness control compared to a single thick conductor layer, while still achieving high wiring density through the multi-layer configuration.
4Reliability
If electrolytic plating films are made thicker to improve connection reliability, then strength increases, but manufacturing complexity increases
Solution Approach 1:
The patent optimizes the thickness parameter of electrolytic plating films to achieve the minimum required connection reliability without excessive thickness. By carefully controlling plating thickness within specific ranges, the patent balances connection strength requirements with manufacturing simplicity and cost-effectiveness.
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 design improves connection reliability between conductor layers and electronic components, reduces warpage, and enhances the flatness of mounting surfaces, leading to increased reliability and density in printed wiring boards.
Implementation Method 1
each of the first and second conductor layers, the inner side first and second conductor layers, and the outermost first and second conductor layers includes a metal foil, a seed layer formed on the metal foil, and an electrolytic plating film formed on the seed layer
Data Source
AI summary
A printed wiring board includes: a core substrate having a core layer and first and second conductor layers; a first build-up layer including a first insulating layer, an inner first conductor layer, an outermost first insulating layer, and an outermost first conductor layer; and a second build-up layer including a second insulating layer, an inner second conductor layer, an outermost second insulating layer, and an outermost second conductor layer. Each conductor layer includes metal foil, seed layer, and electrolytic plating film, t1/T1, t2/T2, u1/U1 and u2/U2 are smaller than 1, and s1/S1 and s2/S2 are larger than 1, where t1, t2, u1, u2, s1 and s2 are electrolytic plating film thicknesses of the first and second and outermost and inner first and second conductor layers, T1, T2, U1, U2, S1 and S2 are metal foil thicknesses of the first and second and outermost and inner first and second conductor layers.