PCB Cavity Structure Without Stop Layers for Pad Reliability
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Solution Overview
Problem
Conventional embedded printed circuit boards face challenges in achieving high-density integration due to large tolerances in processing, difficulty in forming cavities to desired depths, and increased manufacturing costs, particularly when using sand blasting or protective layers, which also complicate the process and lead to reliability issues.
Innovation Solution
A printed circuit board structure that forms a cavity through sand blasting without a stop layer, allowing a portion of the insulating layer to remain on the surface with roughness, enabling improved adhesion with a molding layer and reducing the need for additional layers, thereby simplifying the manufacturing process and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a protective layer or stop layer is formed to enable sand blasting or laser process, then the cavity can be formed to desired depth, but the process becomes more complex and additional etching is required to remove the protective layer
Solution Approach 1:
The patent removes the protective layer and stop layer from the conventional process. By directly sand blasting the insulating layer without forming these additional layers, the process is simplified while still achieving precise cavity formation. The insulating layer itself serves as the cavity wall material, eliminating the need for separate protective and stop layers.
Solution Approach 2:
Instead of forming a protective layer to protect during processing and then removing it, the patent inverts the approach by directly processing the insulating layer to form the cavity. The insulating layer is selectively removed to create the cavity, and the remaining insulating layer portions naturally provide the necessary structural boundaries without requiring additional protective layers.
2Manufacturing precision
If a protective layer of thickness 3 to 10 μm is formed for sand blast process, then the cavity can be formed, but a part of the pad exposed through the cavity is also removed during etching process
Solution Approach 1:
The patent extracts the protective layer from the process entirely. By directly sand blasting the insulating layer without forming a protective layer, there is no need for subsequent etching to remove the protective layer, thereby preventing any damage to the pad that would occur during such etching processes.
Solution Approach 2:
The patent uses the insulating layer itself as the intermediary material for cavity formation. Instead of using a separate protective layer that requires removal, the insulating layer is selectively removed to form the cavity, and the remaining insulating layer portions naturally protect and define the cavity boundaries without requiring additional protective layers that could damage the pad.
3Ease of operation
If manual work is required to use subsidiary materials such as a release film, then the device can be assembled, but the size of the cavity cannot be reduced and manufacturing cost increases
Solution Approach 1:
The patent enables the insulating layer to serve multiple functions automatically. The insulating layer provides both the structural substrate and the cavity wall material, eliminating the need for separate release films or subsidiary materials. The sand blasting process automatically forms the cavity to the desired size and shape, with the remaining insulating layer naturally providing the necessary boundaries, all without manual intervention.
Solution Approach 2:
The patent merges the functions of the insulating layer and the cavity wall into a single integrated structure. Instead of using separate insulating layer and cavity-forming materials, the insulating layer itself is selectively removed to form the cavity, combining multiple functions into one material and process step, thereby reducing cavity size and eliminating manual assembly requirements.
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 allows for the formation of cavities without additional layers, reducing process complexity and improving product reliability by maintaining the shape and adhesion of the pad, while also increasing bonding strength with the molding layer.
Implementation Method 1
forming a cavity through a sand blasting process
Data Source
AI summary
A printed circuit board according to an embodiment includes a first insulating layer; a second insulating layer disposed on the first insulating layer and including a cavity; and a pad disposed on the first insulating layer and exposed through the cavity; wherein the second insulating layer includes a first portion disposed on an upper surface of the first insulating layer in a region where the cavity is formed; and a second portion other than the first portion, and wherein a thickness of the first portion is smaller than a thickness of the second portion.