Underbump Metallization Dimension Variation for Solder Reliability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Packaged semiconductor devices face reliability and lifespan issues due to thermal and mechanical stresses caused by differing coefficients of thermal expansion (CTE) between materials, leading to potential damage to solder connections and underlying circuitry.
Innovation Solution
Implementing underbump metallization (UBM) structures with varying dimensions to match stress levels in different areas of the package, using wider center portions outside the die footprint for reinforcement and narrower center portions within the die footprint to minimize additional stress, and incorporating oblong-shaped UBM structures perpendicular to stress propagation directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If wider center portion UBM structures are used outside the die footprint, then mechanical strength of solder connections is improved, but device complexity increases
Solution Approach 1:
The patent applies local quality by implementing different UBM structure configurations in different spatial locations: wider center portion UBM structures are used outside the die footprint where stress is higher, while narrower center portion UBM structures are used within the die footprint where stress is lower. This location-dependent differentiation optimizes mechanical strength where needed without unnecessarily increasing complexity elsewhere.
Solution Approach 2:
The patent segments the UBM structures into two distinct types based on their center portion widths: first UBM structures with wider center portions for areas outside the die footprint, and second UBM structures with narrower center portions for areas within the die footprint. This segmentation allows each type to be optimized for its specific stress environment, resolving the contradiction between strength and complexity.
2Stress or pressure
If narrower center portion UBM structures are used within the die footprint, then stress on package substrate is reduced, but solder connection reinforcement is decreased
Solution Approach 1:
The patent applies local quality by matching UBM structure characteristics to local stress conditions: narrower center portion UBM structures are placed within the die footprint where stress propagation is a concern, while wider center portion structures are placed outside the die footprint where reinforcement is more critical. This localized adaptation resolves the contradiction by optimizing each location for its specific 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
Enhances the mechanical strength and reliability of solder connections by accommodating different stress levels, reducing the risk of damage to the package substrate and underlying die circuitry, thereby improving the overall lifespan and reliability of the packaged semiconductor device.
Implementation Method 1
Due to various thermal and mechanical forces, solder connections can suffer various mechanical failures... materials used in a package often have different coefficients of thermal expansion (CTE), which is a measurement that indicates a rate of expansion of a material as temperature of the ambient environment of the package changes
Implementation Method 2
A first type of UBM structure is implemented in the area outside of the footprint, which has a center portion with a first lateral width. A second type of UBM structure is implemented in the area within the footprint, which has a center portion with a second lateral width that is smaller than the first lateral width
Data Source
AI summary
One embodiment of a packaged semiconductor device includes: a redistributed layer (RDL) structure formed over an active side of a semiconductor die embedded in mold compound, the RDL structure includes a plurality of solder ball pads that in turn includes: a set of first solder ball pads located on a front side of the packaged semiconductor device within a footprint of the semiconductor die, and a set of second solder ball pads located on the front side of the packaged semiconductor device outside of the footprint of the semiconductor die, each first solder ball pad includes a first center portion having a first diameter measured between opposite outer edges of the first center portion, each second solder ball pad includes a second center portion having a second diameter measured between opposite outer edges of the second center portion, and the first diameter is smaller than the second diameter.