PCB Cavity Design for Pad Protection and Adhesion
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Solution Overview
Problem
Conventional embedded printed circuit boards face challenges in achieving high-density integration due to processing tolerances, difficulty in forming cavities of desired depth, and increased manufacturing costs associated with manual use of auxiliary materials like release films.
Innovation Solution
A printed circuit board design featuring a cavity with a non-penetrating structure through the second insulating layer, where the cavity exposes a pad on the first insulating layer and has a bottom surface positioned lower than the pad's upper surface, allowing for reduced process complexity and improved adhesion with a molding layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a protective layer or stop layer is formed to enable cavity formation through sand blasting or laser process, then the cavity can be formed to desired depth, but the etching process to remove the protective layer or stop layer causes removal of part of the pad exposed through the cavity
Solution Approach 1:
The patent introduces a release film as an intermediary layer during the cavity formation process. This release film serves as a temporary protective layer that enables precise cavity depth control through sand blasting or laser processes, while being designed to be easily removable without requiring aggressive etching that would damage the pad structure
Solution Approach 2:
The patent extracts the protective function from permanent layers (protective layer or stop layer requiring etching) and transitions to using a temporary release film that can be removed without etching, thereby separating the cavity formation process from the pad protection requirement
2Ease of manufacture
If manual work is performed to use subsidiary materials such as release film, then cavity formation is enabled, but manufacturing cost increases and cavity size reduction becomes difficult
Solution Approach 1:
The patent merges the release film application process with existing manufacturing workflows and integrates it into automated processing sequences, reducing the need for separate manual operations and thereby lowering labor costs while maintaining cavity formation capability
3Device complexity
If the insulating layer is completely removed to form the cavity, then the cavity structure is simplified, but adhesion with the molding layer deteriorates
Solution Approach 1:
The patent applies local quality by selectively removing the insulating layer only in the specific cavity region while preserving the insulating layer in surrounding areas. This creates a localized cavity structure that maintains overall adhesion integrity, as the preserved insulating layer continues to provide bonding surfaces for the molding layer in non-cavity regions
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 having an upper surface exposed through the cavity; wherein the cavity includes a first part including a first inner wall; and a second part including a second inner wall under the first part; and wherein an inclination angle of the first inner wall is different from an inclination angle of the second inner wall.