Dummy Chips Mitigate Thermal Stress in Semiconductor Bump Electrodes
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Solution Overview
Problem
Semiconductor devices face fractures in bump electrodes near the corners of semiconductor chips due to stress caused by differences in thermal expansion coefficients between the chip and the package substrate, leading to unreliable connections.
Innovation Solution
The introduction of dummy chips with a similar thermal expansion coefficient to the semiconductor chip, mounted near the chip's corners on the package substrate, reduces stress-induced damage to bump electrodes by mitigating the expansion and contraction differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bump electrodes are formed on the back surface of the package substrate, then electrical connection is achieved, but fracture occurs due to stress concentration at corner portions
Solution Approach 1:
The patent applies local quality by forming a through-hole specifically at the corner portion of the package substrate, rather than uniformly across the entire substrate. This localized structural modification targets the specific stress concentration problem at corner regions while maintaining the integrity of other areas. The through-hole creates a stress relief zone precisely where needed, preventing fracture without affecting the overall connection structure.
Solution Approach 2:
The through-hole acts as a pre-formed stress relief structure that cushions against thermal expansion stress before it can cause fracture. By anticipating the stress concentration problem at corner portions during the manufacturing stage, the design incorporates a protective feature (the through-hole) that absorbs or redistributes the stress, preventing damage before it occurs during thermal cycling.
2Ease of manufacture
If the package substrate uses material with different thermal expansion coefficient, then manufacturing is easier, but stress-induced damage increases during temperature fluctuation
Solution Approach 1:
Rather than changing the material properties of the entire package substrate, the patent applies a localized structural modification (through-hole) at the corner portions. This allows the substrate to maintain its original material composition and manufacturing process while introducing a specific geometric feature that addresses the thermal stress problem only where needed.
Solution Approach 2:
The patent changes the geometric parameter of the substrate by introducing a through-hole, which alters the stress distribution characteristics locally. This structural parameter change compensates for the material property mismatch (thermal expansion coefficient difference) between the substrate and mounted components, reducing stress concentration without requiring material substitution.
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 approach effectively prevents fractures in bump electrodes, enhancing connection reliability while allowing for high-density arrangements without hindering the number of pins or pitch in semiconductor devices.
Implementation Method 1
a difference between coefficients of thermal expansion is larger than that of the package substrate or resin, and therefore some of the bump electrodes are prone to damage due to stress induced at a boundary portion of the semiconductor chip
Data Source
AI summary
A semiconductor device comprises a package substrate, a semiconductor chip, a plurality of bump electrodes and one or more dummy chips. The semiconductor chip is mounted on one surface of the package substrate. The bump electrodes are the other surface of the package substrate and electrically connected to the semiconductor chip through a wiring structure. Each of the dummy chips is mounted on a predetermined region close to a corner portion of the semiconductor chip on the one surface of the package substrate.In the semiconductor chip, the dummy chips are formed of material having the same or similar coefficient of thermal expansion as that of the semiconductor chip. Therefore the stress caused by a difference between coefficients of thermal expansion is suppressed so as to improve connection reliability.