PCB Cavity Structure Without Stop Layers for Dense Package Substrates
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Solution Overview
Problem
Conventional printed circuit boards face challenges in achieving high-density integration due to large tolerances in cavity formation using drill bits or sandblasting, which require additional layers like protective or stop layers that complicate the process and lead to reliability issues.
Innovation Solution
A printed circuit board structure is developed without a stop layer, using a sandblasting process to form cavities, where the second insulating layer has a first portion with a smaller thickness on the surface and a second portion with a larger thickness, allowing the cavity to be formed without passing through the second-first insulating layer, thus maintaining the pad's shape and reducing process complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a drill bit is used to form a cavity for embedding a device, then the cavity can be formed, but the position and depth tolerances are large making high density integration difficult
Solution Approach 1:
The patent replaces the mechanical drill bit system with a sandblasting system that uses kinetic energy of abrasive particles to erode the insulating layer. This substitution enables precise cavity formation by controlling sandblasting parameters (particle size, velocity, duration) rather than mechanical drilling tolerances, achieving the required precision for high-density integration without compromising productivity
2Manufacturing precision
If sand blasting is used to form a cavity, then the cavity can be formed, but it is difficult to form the cavity to the desired depth without a stop layer
Solution Approach 1:
The patent controls cavity depth by adjusting sandblasting parameters including abrasive particle size,喷射 velocity, treatment duration, and incident angle. By optimizing these parameters, the cavity can be formed to the desired depth (exposing the pad while leaving the first insulating layer intact) without requiring additional stop layers, thus reducing process complexity while maintaining precise depth control
3Manufacturing precision
If a protective layer or stop layer is formed, then the cavity can be formed to desired depth, but the process becomes complicated and additional removal steps are required
Solution Approach 1:
The patent extracts and eliminates the protective layer and stop layer from the manufacturing process. By directly forming the cavity to the required depth through controlled sandblasting that exposes the pad while preserving the first insulating layer, the need for additional protective layers and their subsequent removal is eliminated, simplifying the overall manufacturing process while maintaining precise cavity depth control
4Ease of manufacture
If the protective layer or stop layer is removed by etching, then the layer can be removed, but part of the pad exposed through the cavity is also removed
Solution Approach 1:
The patent prevents pad damage by designing the cavity formation process to expose only the necessary portion of the pad while leaving a protective margin. The sandblasting parameters are controlled to create a cavity that exposes the pad surface for electrical connection but does not compromise the pad's structural integrity, eliminating the need for subsequent etching removal that would risk pad damage
5Ease of operation
If manual work is required to use subsidiary materials such as a release film, then the device can be seated, but the cavity size cannot be reduced and manufacturing cost increases
Solution Approach 1:
The patent enables the cavity to serve its own function as the seating structure for the device. By forming the cavity with precise dimensions through sandblasting that exposes the pad while maintaining appropriate walls, the cavity itself provides the necessary support and positioning for the device without requiring additional release films or subsidiary materials, reducing cavity size and eliminating manual operations
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 pad's shape and enhancing adhesion with a molding layer through surface roughness.
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.