Multilayer Wiring Board Conductive Bonding Layer Design
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Solution Overview
Problem
Multilayer wiring boards face challenges with material flow between via conductors and conductive wiring layers, leading to increased resistance and cracking due to the absence of adhesive layers, which are necessary for height reduction.
Innovation Solution
A multilayer wiring board design that includes a conductive bonding layer with specific diameter and thickness relationships to via conductors, made of intermetallic compounds or sintered metals, directly bonding insulating layers without adhesive layers, ensuring effective interfacial bonding and preventing material flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If adhesive layers are used to bond insulating layers, then bonding reliability is improved, but height of the multilayer wiring board increases
Solution Approach 1:
The patent removes adhesive layers from the multilayer wiring board structure entirely. Instead, insulating layers are directly bonded to each other through direct contact interfaces, eliminating the additional height while maintaining bonding reliability through proper surface preparation and bonding process control.
Solution Approach 2:
The bonding function previously performed by separate adhesive layers is merged into the direct interface between insulating layers. This integration eliminates the adhesive layer as a distinct component, reducing overall height while achieving bonding through the bonding interface itself.
2Length of stationary object
If adhesive layers are removed to reduce height, then height is reduced, but material flow occurs between via conductors and conductive wiring layers
Solution Approach 1:
The insulating layers perform their own bonding function through direct contact without requiring external adhesive materials. The bonding interface itself provides the necessary adhesion, and the structure self-prevents material flow through proper interface design and control of processing conditions.
Solution Approach 2:
The patent controls bonding parameters such as temperature, pressure, and time to prevent material flow while achieving reliable bonding. By optimizing these parameters, the direct bonding interface maintains structural integrity without allowing insulating layer material to flow into spaces between via conductors or wiring layers.
3Length of stationary object
If adhesive layers are removed to reduce height, then height is reduced, but resistance increases due to material flow
Solution Approach 1:
The patent optimizes bonding parameters including temperature, pressure, and time to prevent insulating layer material from flowing into conductive paths. This control maintains low resistance by ensuring clean interfaces between via conductors and conductive wiring layers, preventing material contamination that would increase conductor loss.
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 reduces conductor loss and enhances bonding reliability, allowing for reduced resistance and improved structural integrity in multilayer wiring boards, enabling efficient high-frequency signal transmission.
Implementation Method 1
a conductive bonding layer to bond the via conductors to each other... the bonding layer includes an intermetallic compound layer M including a Cu component and a Sn component
Implementation Method 2
the bonding layer includes a sintered metal layer including at least one of Cu or Ag
Implementation Method 3
collectively compressing the stacked insulating sheets by heat treatment
Data Source
AI summary
A multilayer wiring board includes a first insulating layer, a second insulating layer stacked on the first insulating layer, a via conductor inside each of the first insulating layer and the second insulating layer, and a conductive bonding layer that bonds the via conductors to each other. The first insulating layer is directly bonded to the second insulating layer, and a relationship a1>b1 is satisfied, where a1 is a maximum diameter of the bonding layer and b1 is a maximum diameter of the via conductor at an interface with the bonding layer.