Semiconductor Package Interconnect Structure for High-Density BGA Reliability
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Solution Overview
Problem
Conventional Ball Grid Array (BGA) packages face mechanical failures due to high thermomechanical stresses on solder joints, which lead to open circuit failures, and increasing I/O density requires smaller solder ball sizes and pitches, but this reduces stand-off height and increases stress.
Innovation Solution
A novel semiconductor package interconnection structure featuring posts with a proximal end, a pillar portion, and a solder anchor portion, where the solder anchor portion is wider than the pillar portion, allowing for increased stand-off height and smaller solder ball sizes, enabling higher I/O density without increasing stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If smaller solder ball pitch and size are used to increase I/O density, then I/O density is improved, but stand-off height is reduced and thermomechanical stress on solder joints increases
Solution Approach 1:
The patent introduces an intermediate dimension by adding a substrate stand-off layer between the package substrate and PCB. This creates an additional vertical dimension that allows smaller solder balls to achieve sufficient stand-off height without increasing pitch, thereby resolving the contradiction between I/O density and solder joint reliability
Solution Approach 2:
The substrate stand-off layer acts as an intermediary element between the package substrate and PCB. This intermediate structure provides mechanical support and maintains adequate stand-off height, enabling the use of smaller solder balls while preventing direct contact between the package substrate and PCB that would cause excessive stress
2Reliability
If larger solder balls are used to increase stand-off height and reduce thermomechanical stress, then solder joint reliability is improved, but ball pitch and size increase leading to lower I/O density
Solution Approach 1:
The substrate stand-off layer adds a vertical dimension to the structure, allowing smaller solder balls to achieve the necessary stand-off height through the intermediate layer rather than relying on larger ball size. This enables maintaining high I/O density while ensuring adequate stress distribution
Solution Approach 2:
The stand-off function is segmented from the solder ball itself and transferred to a separate substrate stand-off layer. This segmentation allows the solder balls to be smaller while the stand-off layer provides the mechanical support needed for stress reduction, thereby maintaining both reliability and high density
Data Source
AI summary
Novel tools and techniques are provided for implementing novel semiconductor package interconnection structure(s) between package substrate and PCB. In various embodiments, a semiconductor device comprises: a substrate; a plurality of posts; a plurality of solder anchor portions; and a plurality of solder balls. Each post is coupled at a proximal end to a conductive point on a layer of the substrate, and has a length extending along its axis between its proximal and distal ends and a width orthogonal to the length. Each solder anchor portion is coupled to the distal end of a corresponding post, and has a width that is larger than the width of a distal end of a pillar portion of the corresponding post. Each solder ball is disposed on and around a corresponding solder anchor portion, the solder balls and corresponding posts forming conductive interconnects between corresponding substrate conductive points and corresponding PCB contact points.