1. B-staging of toughened epoxy composites by Fred Arnold and Steve Thoman Elgin Bravo February 09, 2001

2. 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.

3. About the authors Fred Arnold and Steve Thoman affiliated with Naval Air Warfare Center Polymers and Composite branch. 28 th International SAMPE conference Seattle WA, 1996

4. Objectives Characterize cure behavior and glass transition temperature of Hercules 8552 sulfone toughened B-stagable epoxy.

5. Definition of B-staging To cure an epoxy to a pre-determined degree of chemical conversion. Stage o Chemical conversion Green0 B-stage <0.29 C-stage <0.90

6. 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

7. Experimental Sample size: 3-5 mg for resin 25-35 mg for B-staged Heating rate 3 o C/min Modulation frequency 0.5 o C

8. Glass transition temperature

9. MDSC results compared to DSC

10. Tg of green epoxy at 23 o C T(t) = T o + Bt dQ/dt = C p B + f(t,T)

11. Tg as a function of conversion

12. Conversion and Isothermal cure

13. 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

14. Research comparison Understand Tg using DSC Degree of chemical rxn for B & C stage Die delamination MDSC not available