1. B-Stage Process For Leadless Leadframe Package (LLP) ELGIN F BRAVO December 1, 2000 Advisors Dr. Richard Chung Randall Walberg SJSU National Semiconductor

2. Leadless Leadframe Package MDIPLLP

3. Project Objective To reduce current LLP size from 3.0mm x 3.0mm to 2.0mm x 2.0mm in order to stay completive in the small appliance market.

4. Proposed Solution 0.5 mm 0.3 mm

5. Epoxy Bleeding 0.3mm

6. Proposed Solution To Epoxy Bleeding Stencil coat back of wafers with a thin layer of B-stage epoxy.

7. Properties Of B-stage Epoxy Stencil or screen printable. B-stageable or semicures at low temp (~100  C), which removes tackiness. Shelf life of 6 months @ 25  C after semicuring. Becomes tacky again at a 150  C. Completely cures or C-stageable at 180  C.

8. Objectives Of 1 st Experiment Determine if a 0.5mm layer of epoxy can be successfully applied onto wafer. Determine if backcoated die can be successfully die attach onto leadframe. Determine epoxy bond strength by conducting die shear test.

9. Stencil Coating Of Wafers

10. Results From B-Stage Process B-Stage process Regular process

11. Die Shear Shear (B-Stage epoxy) Shear (Standard epoxy) F F

12. Future Experiments Wirebonding process Board level reliability – Electrical testing – Moisture sensitivity level – Thermal cycling

13. Conclusion Backcoated die with B-Stage epoxy was successfully die attached. Die shear test will be done by end of December. Wirebonding is scheduled to begin in early January. Board level reliability tests will start in early April.