Underfill Material Viscosity Control for Voidless Mounting
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Solution Overview
Problem
Existing underfill materials for semiconductor chip mounting face challenges in achieving voidless mounting and good solder bonding due to variations in temperature profiles and heat conduction, leading to a narrow margin for mounting and difficulty in determining suitable conditions for voidless assembly.
Innovation Solution
An underfill material containing epoxy resin, acid anhydride, acrylic resin, and organic peroxide is applied to semiconductor chips, with a minimum melt viscosity attainment temperature and viscosity range optimized between 100°C to 150°C and 100 to 5000 Pa·s, allowing for voidless mounting and good solder bonding without strict temperature control during thermocompression bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an underfill material is used with predetermined mounting profile, then good mounting can be achieved, but the margin for mounting becomes narrow
Solution Approach 1:
The invention changes the physical parameters of the underfill material by controlling the molecular weight distribution of the epoxy resin and the characteristics of the curing agent. Specifically, using epoxy resin with a specific number-average molecular weight (3000-7000) and combining it with a curing agent having a glass transition temperature of -50°C to -100°C creates a material whose viscosity changes more gradually with temperature, providing a wider processing window and larger mounting margin while maintaining good bonding quality.
2Productivity
If temperature increase rate in rheometer measurement is greatly different from actual mounting, then it is difficult to determine suitable mounting conditions from rheometer data
Solution Approach 1:
The invention establishes a feedback relationship between rheometer measurement conditions and actual mounting conditions by specifying that the temperature increase rate during rheometer measurement should be controlled within 5-50°C/min. This creates a measurable correlation between the laboratory test data and actual mounting performance, allowing engineers to predict mounting outcomes from rheometer data and adjust formulations accordingly, thereby improving both measurement precision and productivity.
3Reliability
If pressure is applied at wrong timings during mounting, then voids are likely to remain in the assembly
Solution Approach 1:
The invention changes the viscosity-temperature characteristics of the underfill material by selecting specific epoxy resin molecular weights (3000-7000) and curing agents with low glass transition temperatures (-50°C to -100°C). This creates a material that maintains suitable viscosity over a broader temperature range, providing a more extended window of opportunity for pressure application during mounting. The material's gradual viscosity change allows operators to apply pressure at less critical timing points while still achieving voidless assembly, thereby improving ease of operation without sacrificing reliability.
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 provides a wide margin for mounting and ensures voidless assembly with good solder bonding properties, reducing the generation of voids and improving reliability by minimizing variations in melt viscosity with temperature changes.
Implementation Method 1
the underfill material containing an epoxy resin, an acid anhydride, an acrylic resin, and an organic peroxide
Implementation Method 2
an organic peroxide
Implementation Method 3
an epoxy resin, an acid anhydride
Data Source
AI summary
An underfill material achieving a wide margin for mounting and a method for manufacturing a semiconductor device using the same are provided. The underfill material contains an epoxy resin, an acid anhydride, an acrylic resin, and an organic peroxide, wherein a minimum melt viscosity attainment temperature and a minimum melt viscosity obtained when melt viscosity of the underfill material is measured under a temperature increase rate condition in a range of 5 to 50° C./min are in a range of 100° C. to 150° C. and in a range of 100 to 5000 Pa·s, respectively. Since variation in the minimum melt viscosity attainment temperature measured under different temperature increase conditions is small, voidless mounting and good solder bonding properties can be achieved without strict control on the temperature profile during thermocompression bonding, and a wide margin for mounting can be achieved.