PCB Cavity Structure for Precise Pad Exposure Without Stop Layers
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Solution Overview
Problem
Conventional embedded printed circuit boards face challenges in achieving high-density integration due to large tolerances in position and depth during processing, and require protective or stop layers that complicate the manufacturing process and can lead to signal loss in high-frequency applications.
Innovation Solution
The proposed solution involves a printed circuit board structure with a second insulating layer that includes a cavity formed without a protective or stop layer, using a sandblasting process with controlled conditions to achieve the desired depth, and a pad exposed through the cavity, allowing for stable mounting of electronic devices without additional layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a protective layer or stop layer is formed during cavity formation, then the cavity can be formed to the desired depth, but the manufacturing process becomes more complex and additional removal processes are required
Solution Approach 1:
The patent removes the protective layer and stop layer from the manufacturing process entirely. Instead of forming these layers and then removing them, the invention uses direct sandblasting or laser processing to form the cavity to the desired depth without any protective or stop layers, thereby eliminating the complexity of forming and removing these additional layers
Solution Approach 2:
The insulating layer itself serves as the limiting structure for cavity depth through its inherent thickness, eliminating the need for separate stop layers. The cavity formation process directly utilizes the insulating layer's properties to define the cavity boundaries without requiring additional protective or stop layers
2Manufacturing precision
If a protective layer or stop layer with thickness of 3 to 10 μm is formed, then the cavity can be formed by sand blast or laser process, but the pad exposed through the cavity is also removed during etching process
Solution Approach 1:
The patent extracts the protective layer and stop layer from the process to eliminate the harmful side effect of pad removal. By using direct sandblasting or laser processing without these layers, the invention prevents the etching process from removing portions of the pad that would otherwise be lost when removing the protective or stop layer
Solution Approach 2:
The invention converts the potential harm of direct cavity formation (which could expose and damage the pad) into a benefit by using sandblasting or laser processing methods that precisely form the cavity to the desired depth without requiring protective layers, thereby protecting the pad from etching damage while still achieving accurate cavity formation
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 easily reduced and manufacturing cost increases
Solution Approach 1:
The invention uses sandblasting or laser processing to form the cavity directly through the insulating layer without requiring manual placement of release films or other subsidiary materials. This automated process eliminates manual operations and enables precise control of cavity dimensions, facilitating miniaturization while reducing manufacturing cost
Solution Approach 2:
The patent replaces manual mechanical operations (placing and removing release films) with automated sandblasting or laser processing. This substitution eliminates the need for subsidiary materials and manual work, enables precise cavity size control for miniaturization, and reduces manufacturing complexity and cost
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 reduces the number of manufacturing processes, improves product reliability by avoiding changes in the pad's thickness or shape, and enhances signal integrity in high-frequency applications by minimizing signal loss.
Implementation Method 1
forming a cavity exposing an upper surface of the pad by performing a cavity forming process of opening a part of the second insulating layer
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.