PCB Bump-and-Wall Structure for Fine-Pitch Deep Cavities
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Solution Overview
Problem
The increasing trend towards thinner package structures in high-performance mobile application processor packages poses challenges in handling interposer substrates during manufacturing and assembly, and finer pitches of solder balls become difficult to achieve due to the increased distance between substrates.
Innovation Solution
A printed circuit board design that includes a substrate with a plurality of bumps and insulating walls on its uppermost or lowermost side, allowing for a deeper cavity while maintaining a consistent pitch of connection conductors, reducing the risk of warpage, and improving flowability of molding materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the cavity depth is increased to reduce the pitch of connection conductors, then the pitch of connection conductors is reduced, but the risk of warpage increases
Solution Approach 1:
The insulating member is divided into multiple layers (first insulating layer, second insulating layer, third insulating layer) with the cavity formed through specific layers. This segmentation allows the cavity depth to be controlled without compromising the overall structural integrity of the insulating member, thereby reducing warpage risk while maintaining fine pitch capability
Solution Approach 2:
The cavity is positioned locally in the center region of the insulating member rather than uniformly distributed. This localized cavity design concentrates the depth increase in a specific area, allowing pitch reduction at connection points while maintaining structural stability in other regions
2Length of stationary object
If the thickness of mounted electronic component is increased, then the component can accommodate deeper cavity, but the pitch of connection conductors cannot be maintained
Solution Approach 1:
The cavity extends in the thickness direction (vertical dimension) of the insulating member rather than only in the planar dimensions. This vertical extension allows the electronic component thickness to be increased to accommodate the cavity while the horizontal pitch of connection conductors remains unchanged, resolving the contradiction between component thickness and pitch maintenance
3Manufacturing precision
If the depth of cavity is increased, then the pitch of connection conductors is reduced, but the flowability of molding material deteriorates
Solution Approach 1:
The insulating member is segmented into multiple layers with the cavity formed through specific layers (first and second insulating layers) while leaving the third insulating layer intact. This segmentation creates a structured cavity that guides molding material flow, preventing complete blockage and maintaining manufacturability despite increased cavity depth
Solution Approach 2:
The third insulating layer acts as an intermediary structure that spans across the cavity opening. This intermediary layer provides a surface for molding material to flow over and into the cavity, facilitating material injection while maintaining the deep cavity structure needed for fine pitch connections
Data Source
AI summary
A printed circuit board includes: an insulating member; a first bump disposed on the insulating member; a second bump disposed adjacently to but spaced apart from the first bump on the insulating member; a first insulating wall covering at least a portion of the first bump; and a second insulating wall covering at least a portion of the second bump and disposed adjacently to but spaced apart from the first insulating wall.