Constricted Via Conductors for Wiring Substrate Reliability
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Solution Overview
Problem
Existing multilayer wiring boards face issues with via connection reliability due to tapered hole shapes formed by laser beam irradiation, leading to reduced bottom surface area and potential peeling and increased electrical resistance.
Innovation Solution
A wiring substrate design featuring a core layer with multiple conductor layers and interlayer insulating layers, where at least one inner and outer conductor layer includes a metal foil and plating film, and intermediate layers with thinner metal foil, incorporating constricted via conductors that maintain larger connection areas and reduce breakage risk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser beam irradiation is used to form via holes, then via holes can be efficiently formed through the board, but the holes become tapered with reduced bottom surface area
Solution Approach 1:
The patent changes the geometric parameters of the via hole from a standard cylindrical shape to a constricted shape with a narrower bottom portion. This parameter change allows the via hole to maintain structural integrity and electrical connectivity while compensating for the tapered effect caused by laser beam irradiation, thus resolving the contradiction between formation efficiency and shape control.
2Ease of manufacture
If conventional via holes are used, then manufacturing is simpler, but peeling and increased electrical resistance occur
Solution Approach 1:
The patent applies local quality by creating a via hole with a constricted bottom portion that has different geometric properties than the upper portion. This localized structural modification enhances connection reliability at the critical via hole bottom interface without complicating the overall manufacturing process, as the constricted shape is formed through controlled laser irradiation parameters.
3Reliability
If via holes with large bottom surface area are used, then electrical resistance is reduced, but the structure becomes more prone to breakage
Solution Approach 1:
The patent employs a curved, constricted geometry at the via hole bottom rather than a flat or wide opening. This curved, narrowed structure concentrates the metal deposition to form a stronger, more compact electrical connection path that maintains low electrical resistance while inherently resisting mechanical breakage through its geometric reinforcement.
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 enhances via connection reliability by minimizing peeling and electrical resistance while preventing breakage within via conductors, thereby improving overall connection reliability.
Implementation Method 1
tapered hole shapes formed by laser beam irradiation
Implementation Method 2
The wiring pattern layers are formed together with the via holes by electroless plating and electrolytic plating
Implementation Method 3
The wiring pattern layers are formed together with the via holes by electroless plating and electrolytic plating
Data Source
AI summary
A wiring substrate includes a core layer, first conductor layers including first inner, outer and intermediate layers, second conductor layers including second inner, outer and intermediate layers, interlayer insulating layers interposed between the first conductor layers and between the second conductor layers, and via conductors formed in the insulating layers such that each via conductor connects two conductor layers and is integrally formed with one of the conductor layers on side away from the core layer. The first and/or second inner conductor layers has a first conductor layer structure including metal foil and plating film layers, the first and/or second outer conductor layers has the first structure, the first and/or second intermediate conductor layers has a second conductor layer structure including metal foil and plating film layers, and the via conductors include a group integrally formed with the first structure and including constricted via conductors each having a constricted portion.