Circuit Board Cavity Structure for Flat-Bottom Laser Formation
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Solution Overview
Problem
Conventional circuit boards for 5G communication systems face challenges in maintaining a compact size due to cavity expansion during the de-smear process, leading to increased dead regions and reduced circuit integration, and the roughness of the cavity's lower surface affects device mountability and reliability.
Innovation Solution
A circuit board design featuring a top-hat distributed laser beam to form cavities with a flat lower surface and controlled inclination angles, eliminating the need for stop layers and masks, which minimizes dead regions and enhances physical reliability by maintaining uniform power distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the de-smear process is performed to remove debris from the cavity sidewall, then the cavity is cleaned, but the cavity size expands beyond the target size
Solution Approach 1:
A stop layer is formed at the target cavity depth position before cavity formation, serving as a pre-established boundary that prevents the de-smear process from removing sidewall material beyond the intended cavity size, thus cleaning the cavity without expanding it
Solution Approach 2:
The stop layer acts as an intermediary protective layer between the laser/sandblast process and the cavity sidewall, allowing the de-smear process to occur without directly removing the cavity boundary material
2Productivity
If the cavity size is reduced to minimize dead regions, then circuit integration is improved, but the cavity formation process becomes more difficult to control
Solution Approach 1:
The mechanical de-smear process is replaced with a chemical etching process using an inductive coupling plasma reactor, which provides more precise control over material removal and cavity size, enabling smaller cavities with minimal dead regions
Solution Approach 2:
The cavity formation method is changed from laser/sandblast to inductive coupling plasma etching, altering the physical and chemical parameters of the process to achieve better size control and reduced dead regions
3Volume of moving object
If the insulating layer thickness is reduced to decrease overall board thickness, then the device becomes more compact, but the circuit pattern protection becomes unstable
Solution Approach 1:
The cavity is formed as a three-dimensional structure with depth rather than simply reducing the insulating layer thickness, allowing compactness to be achieved through vertical space utilization while maintaining adequate insulating layer thickness for circuit protection
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
The solution improves device mountability, reduces the overall volume of the circuit board, and lowers production costs by minimizing cavity roughness and dead regions, while maintaining high circuit integration and reliability.
Implementation Method 1
forming a cavity in a circuit board using a laser or sand blast
Implementation Method 2
a de-smear process for removing debris from a sidewall of the cavity after forming the cavity using a laser or sandblast
Data Source
AI summary
A circuit board according to an embodiment includes a first insulating layer; and a second insulating layer disposed on the first insulating layer and including a cavity; wherein the second insulating layer includes a lower surface of the cavity positioned higher than an upper surface of the first insulating layer, wherein the lower surface of the cavity includes: a plurality of first portions, and a plurality of second portions provided between the plurality of first portions and having a height different from that of the plurality of first portions, and wherein a height difference between a portion having a highest height and a portion having a lowest height of the plurality of first portions is 1 μm or less.