Thermosetting Resin Viscosity Prediction for Void Suppression
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Solution Overview
Problem
The thermal compression bonding technique faces challenges in predicting viscosity behavior of thermosetting resins during rapid temperature increases, leading to void generation and solder connection issues due to inadequate viscosity control.
Innovation Solution
A method involving the measurement of reaction and viscosity behavior at multiple temperature increase rates, fitting data to the Kamal and Castro-Macosko models, and calculating virtual viscosity behavior to predict thermosetting resin behavior at arbitrary temperature increases, ensuring appropriate viscosity profiles for void suppression and solder connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the viscosity of the underfill is kept low during thermal compression bonding, then good solder connection is achieved, but void generation increases due to outgas
Solution Approach 1:
The underfill's viscosity is made dynamic through temperature-dependent behavior. At room temperature and during solder melting, the viscosity remains low to allow solder flow and prevent voids. As temperature increases further during curing, the viscosity automatically increases to suppress outgas and prevent void formation. This dynamic viscosity change resolves the contradiction between maintaining good solder connection and preventing void generation.
Solution Approach 2:
The viscosity parameter of the underfill is changed as a function of temperature. The patent specifies that the underfill should have low viscosity at solder melting temperature (around 220°C) to ensure good solder connection, and high viscosity at higher temperatures (around 260°C) to suppress outgas and void formation. This parameter change with temperature resolves the technical contradiction.
2Object-generated harmful factors
If the viscosity of the underfill is increased to suppress void formation, then solder connection quality improves, but solder ball connection is blocked
Solution Approach 1:
The underfill viscosity dynamically adapts to different process stages through temperature change. During the solder melting stage, low viscosity ensures the solder ball can penetrate and connect with substrate terminals. During the subsequent curing stage, high viscosity suppresses outgas and prevents void formation. This temporal and temperature-dependent viscosity control resolves the contradiction.
Solution Approach 2:
The underfill is designed to maintain low viscosity in advance during the solder melting stage, ensuring solder ball penetration occurs before viscosity increase. This preliminary low-viscosity state allows reliable solder connection to be established before the viscosity increases to suppress void formation, resolving the contradiction between connection quality and void suppression.
3Ease of manufacture
If conventional viscosity measurement methods are used at low temperature increase rates, then measurement is feasible, but viscosity behavior at actual mounting temperatures cannot be predicted
Solution Approach 1:
The patent creates a predictive model (copy) of the viscosity-temperature relationship based on measurements at low temperature increase rates. This model, expressed as η=η0exp(E/RT)exp(kα/(1-α)), allows the viscosity behavior at actual high-temperature mounting conditions to be predicted from low-temperature measurements, resolving the contradiction between measurement feasibility and prediction accuracy.
Solution Approach 2:
The patent changes the measurement parameter from actual mounting temperature to lower temperatures for feasible measurement, while using kinetic parameters (activation energy E, reaction order k) to predict viscosity behavior at any temperature. This parameter transformation allows both feasible measurement and accurate prediction, resolving the technical contradiction.
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 allows for the prediction and control of viscosity behavior, effectively suppressing void generation while maintaining good solder connections during thermal compression bonding, even at high temperature increase rates.
Implementation Method 1
the underfill is primarily cured... Due to the thermocompression bonding, the solder ball of the IC chip is melted and also the underfill is primarily cured
Implementation Method 2
Due to the thermocompression bonding, the solder ball of the IC chip is melted
Data Source
AI summary
A method of predicting viscosity behavior of a thermosetting resin is provided that is capable of predicting viscosity behavior of a thermosetting resin and void generation in the underfill is suppressed while good solder connection is obtained. The method includes: measuring a reaction rate and measuring viscosity behavior to measure a calorimetry peak and viscosity behavior of the thermosetting resin with three or more rates of temperature increase respectively; fitting a reaction rate to fit measurement data with each rate of temperature increase obtained by the measuring a reaction rate to a Kamal model formula to obtain fitting curves; fitting viscosity behavior to fit parameters in the Kamal model formula and the measurement data for each rate of temperature increase obtained by the measuring viscosity behavior to a Castro-Macosko model formula to obtain fitting curves; and calculating virtual viscosity behavior to calculate virtual viscosity behavior of the thermosetting resin at the arbitrary rate of temperature increase by simulation based on each fitting curve for each rate of temperature increase obtained by the fitting viscosity behavior.