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B-staging of toughened epoxy composites
by Fred Arnold and Steve Thoman
Elgin BravoFebruary 09, 2001
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Overview of B-stage process for LLP
• Reduce package size by wirebonding close to the edge of the die.
• Backcoat wafers with a B-stage epoxy.
• Delamination of die from DAP due to high humidity and temperature.
• Understand structure and properties of epoxy.
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About the authors
• Fred Arnold and Steve Thoman affiliated with Naval Air Warfare Center
• Polymers and Composite branch.
• 28th International SAMPE conference Seattle WA, 1996
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Objectives
• Characterize cure behavior and glass transition temperature of Hercules 8552 sulfone toughened B-stagable epoxy.
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Definition of B-staging
• To cure an epoxy to a pre-determined degree of chemical conversion.
• Stage o Chemical conversion
• Green 0• B-stage <0.29• C-stage <0.90
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Equipment• Dynamic Mechanical Analyzer (DMA)
– glass transition– secondary transitions– gelation– vitrification
• Differential Scanning Calorimeter (DSC) equipped w/ modulated DSC cell (MDSC)– specific heat capacity – heats of transition – temperature of phase change
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Experimental
• Sample size:• 3-5 mg for resin• 25-35 mg for B-staged
• Heating rate• 3oC/min
• Modulation frequency• 0.5oC
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Glass transition temperature
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MDSC results compared to DSC
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Tg of green epoxy at 23oC
T(t) = To + Bt dQ/dt = CpB + f(t,T)
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Tg as a function of conversion
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Conversion and Isothermal cure
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Results
• MDSC produces more accurate results
• Reversing component eliminates effect of residual heat release near Tg
• Optimum B-stage temperature obtained to ensure mechanical strength at RT
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Research comparison
• Understand Tg using DSC• Degree of chemical rxn for B & C stage• Die delamination
• MDSC not available