Connected Corner NCTF Solder Balls for BGA Joint Reliability
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Solution Overview
Problem
Current BGA solder joint reliability is compromised due to stress concentration at corner solder balls, leading to cracks, voids, and shorting issues, with existing solutions either increasing assembly time and cost or package size.
Innovation Solution
Implementing a joint connection of non-critical to function (NCTF) solder balls with a solder pattern that includes first and second solder balls coupled via a reflow process, forming an enhanced sacrificial solder joint pattern on the package substrate, which maintains the same ball pitch and reduces stress concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If larger corner solder ball sizes are used, then solder joint reliability is improved, but assembly time and tooling cost increase
Solution Approach 1:
The patent applies local quality by differentiating the treatment of corner solder balls from center solder balls. Specifically, corner NCTF solder balls are connected together in a chain pattern while center solder balls remain individual. This localized differentiation provides enhanced reliability at the stress-prone corner locations without requiring all solder balls to be larger or requiring multiple tool types, thus avoiding the assembly time penalty.
2Reliability
If more solder balls are added at corner locations, then solder joint reliability is improved, but package size increases
Solution Approach 1:
The patent merges multiple corner NCTF solder balls into a connected chain structure where adjacent corner solder balls are joined together. This merging approach distributes the reliability enhancement across the corner region without adding discrete solder ball elements, thereby avoiding the need to decrease pitch or increase overall package dimensions.
3Reliability
If larger corner solder ball sizes are used, then solder joint reliability is improved, but manufacturing cost increases
Solution Approach 1:
The patent changes the connectivity parameter of corner solder balls rather than their size parameter. By connecting corner NCTF solder balls in a chain pattern, the solution achieves improved reliability through topological modification rather than dimensional scaling, avoiding the cost implications of larger materials and multi-tool requirements.
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 solution enhances solder joint reliability, simplifies the assembly process, reduces tooling and manufacturing costs, and improves co-planarity, while maintaining the same ball pitch and reducing assembly time.
Implementation Method 1
a reflow process to melt and couple the first and second solder balls to form the solder pattern
Data Source
AI summary
Embodiments include semiconductor packages and a method of forming the semiconductor packages. A semiconductor package includes a package substrate with a top surface, a corner portion, and a plurality of solder balls on the top surface of the package substrate. The semiconductor package also includes a pattern on the corner portion of the package substrate. The pattern may have a width substantially equal to a width of the solder balls. The pattern may also include a continuous line having solder materials. The semiconductor package may include a plurality of conductive pads on the package substrate. The conductive pads may be coupled to the pattern. The pattern may have a z-height that is substantially equal to a z-height of the solder balls, and have one or more outer edges, where the outer edges of the pattern are sidewalls. The sidewalls of the pattern may be substantially vertical or tapered sidewalls.