Printed Wiring Board Via Formation Using Thickened Second Metal Foil
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Solution Overview
Problem
Existing printed wiring boards face issues with reliable connection between via conductors and metal foils due to incomplete exposure of the second metal foil during laser drilling, leading to potential cracks and increased electrical resistance under thermal stress.
Innovation Solution
A method involving the formation of a laminate structure with a second metal foil thicker than the first, where laser irradiation is controlled to prevent penetration of the second foil, ensuring complete exposure and reliable connection through the resin insulating layer, and subsequent electroplating to form a via conductor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser irradiation is used to form openings through the metal foil and resin insulating layer, then openings can be efficiently formed, but the second metal foil may be incompletely exposed leading to connection reliability issues
Solution Approach 1:
The patent applies local quality by differentiating the thickness of metal foils at different locations. The second metal foil is made thicker specifically at the region where opening formation occurs, while other regions maintain standard thickness. This localized thickness variation ensures complete exposure at the opening bottom without compromising overall structural integrity or requiring excessive laser energy that could damage surrounding areas.
Solution Approach 2:
The patent implements preliminary action by pre-forming the thicker second metal foil before the opening formation process. This preliminary structural preparation ensures that when laser irradiation occurs, the opening can be completely formed through the resin insulating layer and expose the metal foil surface, eliminating the need for subsequent corrective operations and ensuring reliable via conductor connection from the outset.
2Reliability
If the second metal foil is made thicker to ensure complete exposure, then connection reliability improves, but material consumption and manufacturing cost increase
Solution Approach 1:
The patent resolves this contradiction by applying local quality - the second metal foil is thickened only at the specific region where openings are formed and via conductors are located, rather than increasing the thickness of the entire metal foil layer. This localized approach ensures reliable connection where needed while minimizing overall material consumption and maintaining cost-effectiveness.
Solution Approach 2:
The patent employs parameter changes by modifying the thickness parameter of the second metal foil selectively. Instead of uniformly increasing thickness across the entire foil, the thickness parameter is changed only in the regions requiring opening formation, optimizing the balance between connection reliability and material efficiency.
3Manufacturing precision
If laser irradiation energy is increased to ensure complete exposure of the second metal foil, then opening formation is more effective, but the risk of damaging surrounding structures increases
Solution Approach 1:
The patent applies preliminary action by pre-configuring the second metal foil with increased thickness before opening formation. This preliminary structural preparation allows the laser to efficiently form complete openings without requiring excessive energy, as the thicker foil provides a defined boundary that facilitates clean opening formation through the resin insulating layer while protecting surrounding areas from damage.
Solution Approach 2:
The patent resolves this contradiction through local quality by concentrating the thickness enhancement only where openings are formed. This localized thickening creates natural boundaries that guide laser energy concentration, improving opening precision while the surrounding thinner regions remain protected from excessive laser exposure and potential damage.
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 approach results in a highly reliable printed wiring board with improved connection integrity and reduced risk of cracks between the via conductor and the second metal foil, maintaining electrical performance under thermal stress.
Implementation Method 1
irradiating laser upon the first metal foil such that an opening is formed through the first metal foil and the resin insulating layer
Implementation Method 2
plating the first metal foil such that a via conductor is formed in the opening and a first conductor layer including the first metal foil and an electroplating film on the first metal foil is formed
Data Source
AI summary
A method for manufacturing a printed wiring board includes forming on carrier a laminate including a second metal foil, a resin layer laminated on the second foil and a first metal foil laminated on the resin layer, irradiating laser upon the first foil such that opening is formed through the first foil and resin layer and exposes surface of the second foil at bottom, plating the first foil such that a via conductor is formed in the opening and a first conductor layer including the first foil and an electroplating film is formed on surface of the resin layer, removing the carrier from the laminate, patterning the first conductor layer on the resin layer, and patterning the second foil such that a second conductor layer including the second foil is formed on opposite surface of the resin layer. The second foil has thickness greater than thickness of the first foil.