Underfill Material Viscosity Control for Voidless Flip-Chip Mounting
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Solution Overview
Problem
Conventional underfill films used in semiconductor chip mounting face challenges in controlling their behavior from a molten state to a cured state, leading to void generation and bonding defects such as resin entering between solder bumps, due to their single curing agent composition, which makes it difficult to adapt to the conditions of flip-chip bonding.
Innovation Solution
An underfill material comprising epoxy resin, acid anhydride, acrylic resin, and organic peroxide, with a minimum melt viscosity ranging from 1000 Pa*s to 2000 Pa*s and a viscosity gradient from 10° C. higher than the minimum melt viscosity attainment temperature to a further 10° C. higher temperature ranging from 900 Pa*s/° C. to 3100 Pa*s/° C., is used under specific temperature increase conditions to facilitate voidless mounting and excellent solder bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional underfill films use a single curing agent, then the formulation is simple, but fine control of behavior from molten state to cured state is difficult
Solution Approach 1:
The patent divides the curing system into two separate curing agents with different curing mechanisms and activation conditions. The first curing agent operates at lower temperatures to provide initial bonding, while the second curing agent activates at higher temperatures to complete the curing process. This segmentation allows precise control over the underfill material's behavior during different stages of the mounting process.
Solution Approach 2:
The patent utilizes changes in temperature parameters to control the activation of different curing agents. By carefully selecting curing agents with different activation temperatures and controlling the heating rate, the patent achieves precise control over the viscosity changes and curing progression of the underfill material during thermocompression bonding.
2Device complexity
If conventional underfill films lack controlled viscosity behavior, then the material composition is simple, but voids are generated and bonding defects occur
Solution Approach 1:
The patent creates a dynamic viscosity profile by selecting two curing agents with different temperature-dependent behaviors. The underfill material's viscosity changes dynamically during the heating process, transitioning from a low-viscosity state that allows good wetting and void elimination to a high-viscosity state that prevents resin overflow and maintains bonding integrity.
Solution Approach 2:
The patent formulates a composite underfill material containing two different curing agents with complementary properties. This composite formulation combines the advantages of each curing agent to achieve the desired viscosity behavior and bonding characteristics, eliminating the drawbacks of single-curing-agent systems.
3Productivity
If temperature is increased rapidly during bonding, then the process time is short, but voids are generated due to uncontrolled material behavior
Solution Approach 1:
The patent implements a staged heating approach where the temperature is increased in controlled increments rather than uniformly. The heating process is synchronized with the curing progression, allowing the underfill material to adapt its viscosity behavior at each temperature stage, thereby preventing void formation while maintaining efficient 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 achieves voidless mounting and excellent solder bonding properties by controlling the viscosity behavior during thermocompression bonding, suppressing void generation and ensuring reliable connections between the semiconductor chip and the substrate.
Implementation Method 1
an underfill film is applied to a wafer and the wafer is diced to obtain a semiconductor chip(s)... The semiconductor chip and substrate are crimped together by using a high temperature and a high pressure, electrical conduction is ensured using metallic bonding of solder bumps, and the semiconductor chip is bonded to the substrate by curing of the underfill film
Implementation Method 2
the underfill material contains an epoxy resin, an acid anhydride, an acrylic resin and an organic peroxide
Data Source
AI summary
An underfill material enabling voidless packaging and excellent solder bonding properties, and a method for manufacturing a semiconductor device using the same are provided. An underfill material, including an epoxy resin, an acid anhydride, an acrylic resin, and an organic peroxide, the minimum melt viscosity being between 1000 Pa*s and 2000 Pa*s, and gradient of melt viscosity between 10° C. higher than the minimum melt viscosity attainment temperature and a temperature 10° C. higher being between 900 Pa*s/° C. and 3100 Pa*s/° C., is applied to a semiconductor chip having a solder-tipped electrode formed thereon, and the semiconductor chip is mounted onto a circuit substrate having a counter electrode opposing the solder-tipped electrode, and the semiconductor chip and the circuit substrate are thermocompressed under bonding conditions of raising the temperature from a first temperature to a second temperature at a predetermined rate.