Printed Wiring Board Cavity Formation via Laser Ablation
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Solution Overview
Problem
Conventional methods for forming cavities in printed wiring boards using release layers or dummy patterns are costly, difficult to adjust, and can lead to defects such as increased plate thickness and disconnected wiring, while drilling processes require precise depth adjustment to avoid over- or under-cutting.
Innovation Solution
A printed wiring board with a cavity formed by drilling through a multilayer substrate with an insulating resin layer and an electrical conductor layer, where the conductor layer is embedded in the resin and exposed at the cavity bottom, allowing for improved connection to circuit wiring and enhanced peel strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a release layer is provided inside the printed wiring board to form a cavity, then the cavity formation is enabled, but the member cost and the cost of forming the release layer increase
Solution Approach 1:
The invention extracts and removes the release layer after the cavity is formed. The release layer is used temporarily during the cavity formation process and then completely removed, eliminating the need to retain it in the final product. This reduces material cost while maintaining the cavity formation capability.
Solution Approach 2:
The release layer is provided in advance before cavity formation, enabling the drilling process to proceed smoothly. The release layer serves as a temporary aid during manufacturing and is subsequently removed, allowing cavity formation without permanent addition of costly materials.
2Ease of manufacture
If a release layer is provided inside the printed wiring board, then the cavity can be formed, but the layer configuration adjustment becomes difficult and the plate thickness of the periphery may increase
Solution Approach 1:
The release layer is completely removed after serving its temporary purpose during cavity formation. This extraction eliminates the interference of the release layer with subsequent layer configuration adjustments and prevents any increase in peripheral plate thickness that would result from retaining the release layer.
3Ease of manufacture
If a dummy pattern is provided inside the printed wiring board to form a cavity, then the cavity can be formed, but the wiring connected to the pad cannot be formed and the electronic component cannot be connected to the circuit wiring
Solution Approach 1:
The release layer is removed after cavity formation, leaving no obstruction for wiring connections. Unlike a dummy pattern that would remain and block wiring, the release layer is completely extracted, allowing wiring patterns to be formed and electronic components to be connected to the circuit wiring without interruption.
4Device complexity
If the cavity is formed by drilling without using the dummy pattern or the release layer, then the manufacturing process is simplified, but fine accuracy is required for depth adjustment which may result in over-cutting or under-cutting
Solution Approach 1:
The release layer acts as an intermediary that facilitates precise depth control during drilling. The drill stops when it reaches the release layer, providing a natural depth reference that eliminates the need for complex depth adjustment mechanisms. This intermediary layer simplifies the manufacturing process while ensuring accurate cavity depth without over-cutting or under-cutting.
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
Enables effective connection of electronic components to circuit wiring at the cavity bottom with improved peel strength of the wiring pattern, reducing costs and manufacturing complexities.
Implementation Method 1
removing, by laser machining, the portion of the substrate that remains in the cavity by using the partial region of the seed layer as a shielding member of a laser beam
Data Source
AI summary
To improve the peel strength of a wiring pattern formed at a cavity bottom portion while enabling connection between an electronic component inside a cavity and a circuit outside the cavity to be performed at the cavity bottom portion. A method of manufacturing a printed wiring board according to the present disclosure includes performing pattern plating on a substrate made of insulating resin. Forming an electrical conductor layer on a seed layer of a second face, forming a first insulating resin layer on a first face and forming a second insulating resin layer. Drilling in and removing the insulating resin to form a cavity. Removing, by laser machining, a remaining portion of the substrate in the cavity and exposing a surface position of the second insulating resin layer to be equivalent to a surface position of the electrical conductor layer embedded in the second insulating resin layer.