Underfill Material Viscosity Stability for Flip-Chip Bonding
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Solution Overview
Problem
In semiconductor device manufacturing, the thermal history differences between initial and final stages of the flip-chip bonding process lead to viscosity changes in underfill materials, causing cracks in connection members and unreliable electrical connections, while reducing reactivity to mitigate this slows down the process efficiency.
Innovation Solution
An underfill material with specific viscosity and reaction rate characteristics, including a melt viscosity of 50-3000 Pa·s at 150°C and a viscosity change rate of ≤500%, and a reaction rate of ≥90% after heating, combined with a latent curing accelerator and acrylic resin, to maintain electrical connectivity and process efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the reactivity of the underfill material is decreased to reduce the influence of thermal history, then the viscosity change is reduced, but the curing reaction requires a long period of time or high temperature, reducing process efficiency
Solution Approach 1:
The patent applies parameter changes by carefully controlling the reactivity of the underfill material and the heating conditions. Specifically, the heating temperature is maintained at 130°C or lower and the heating time is controlled to be 1 hour or less, while the reactivity of the underfill material is adjusted to achieve a viscosity change rate of 500% or less. This combination of parameters enables both viscosity stability and efficient curing without requiring prolonged high-temperature treatment.
2Productivity
If the underfill material is used in chip-on-wafer or TSV lamination process with collective bonding, then process efficiency is improved, but difference in thermal history causes drastic viscosity change and cracks in connection members
Solution Approach 1:
The patent applies beforehand cushioning by pre-adjusting the reactivity of the underfill material to minimize viscosity changes during the bonding process. The underfill material is formulated to have a viscosity change rate of 500% or less when heated at 130°C for 1 hour, which cushions against the adverse effects of thermal history differences. This pre-adjustment ensures that even when multiple chips are bonded collectively with different thermal histories, the underfill material maintains stable viscosity, preventing cracks in connection members and ensuring reliable electrical connections.
3Productivity
If heating treatment is applied to collectively bond semiconductor chips, then process efficiency is improved, but thermal history differences cause cracks in bump electrodes
Solution Approach 1:
The patent applies parameter changes by controlling the heating temperature to 130°C or lower and the heating time to 1 hour or less. These parameter adjustments ensure that the underfill material's viscosity change remains within acceptable limits (500% or less), which prevents excessive stress on the bump electrodes during collective bonding. This maintains the strength of connection members while achieving efficient batch processing.
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
The underfill material ensures reliable electrical connections and improved process efficiency by minimizing viscosity changes and accelerating curing reactions, even under varying thermal histories, without requiring prolonged high-temperature curing.
Implementation Method 1
a reaction rate represented by {(Qt−Qh)/Qt}×100 % is 90% or more, where Qt is the total calorific value in a process of temperature rise from −50° C. to 300° C. and Qh is the total calorific value in a process of temperature rise from −50° C. to 300° C. after heating at 175° C. for 2 hours in a DSC measurement
Data Source
AI summary
An underfill material having sufficient curing reactivity, and capable of achieving a small change in viscosity and good electrical connection even when loaded with thermal history, a laminated sheet including the underfill material, and a method for manufacturing a semiconductor device. The underfill material has a melt viscosity at 150° C. before heating treatment of 50 Pa·s or more and 3,000 Pa·s or less, a viscosity change rate of 500% or less, at 150° C. as a result of the heating treatment, and a reaction rate represented by {(Qt−Qh)/Qt}×100% of 90% or more, where Qt is a total calorific value in a process of temperature rise from −50° C. to 300° C. and Qh is a total calorific value in a process of temperature rise from −50° C. to 300° C. after heating at 175° C. for 2 hours in a DSC measurement.