Codification of Flip Chip Knowledge

1. Codification of Flip Chip Knowledge Antonio Prats March 2002

2. Objective • Facilitate practical applications of research results • Design optimization • Specs • Materials selection • Product specific process development • Trouble shooting

3. Two Parts • Yield Prediction Software • “Placement Yield” – in-plane variations • “Assembly Yield” – out-of-plane variations • Codification Documents • “Underfill Codification” – Materials evaluation and underfill process design • “Reflow Encapsulant Codification” – Materials evaluation and reflow encapsulant process design

4. Placement Yield Software • Goal • Conservative estimate of defect levels associated with in-plane (primarily substrate) tolerances • Defect • A solder bump not in contact with its pad • User Input • Substrate layout, pad shapes and sizes, variations in size and location, mask thickness, bump dimensions, machine accuracy

5. Example Pad Design Screen

6. Example Thickness Consideration Screen

7. Assembly Yield Software • Goal • Conservative estimate of defect levels associated with warpage, bump height variations, and solder collapse • Defect • A solder bump not in contact with its pad/paste • Solder Bridging (New for 2001) • User Input • Bump locations and variations in bump height, pad diameters and thicknesses, paste volume, component and board warpage

8. Assembly Yield Software Screen

9. Underfill Codification Manual • Discussion of issues important to the underfill process • Establishment of a materials knowledge base to save time during process development • Procedures for process development • Troubleshooting (to be expanded in 2002)

10. 1 INTRODUCTION • 2 DISPENSER EVALUATION • 2.1 Specific Flip Chip Issues • 3 MATERIALS SELECTION • 4 DATA BASE • 4.1 Thaw • 4.2 Flow & 'Gel' Times • 4.3 Life • 4.4 Flow Time Optimization • 4.5 Fillet Thickness Dependence • 4.6 Cure • 4.7 Automatic Fillet Formation • 4.8 Proximity Test • 4.9 Bakeout Requirements • 4.10 Diagnostic Tests (Reference Performance) • 5 MATERIALS SPECIFIC EQUIPMENT CHARACTERIZATION • 6 MATERIALS HANDLING • 6.1 Substrates • 6.2 Chips • 6.3 Underfill Materials • PRODUCT SPECIFIC PROCESS • 7.1 Underfill Process • 7.2 Bake • 7.3 Standoff • 7.4 Substrate Temperature • 7.5 Preferred Fillet Thickness • 7.6 Volumes • 7.7 Dispensing • 7.8 Final Flow Optimization • 7.9 Footprint & Keep Out • 7.10 Curing • 7.11 Wetting & Voiding • 7.12 SMT Process Integration • 8 TROUBLESHOOTING • 9 REFERENCES Table of Contents

11. Typical Correlation Between Nominal Dispensed Volume and Fillet Thickness

12. Clamp Clamp 5 mil 0 mil Taper Flow Experimental Setup

13. Different Dispense Patterns

14. Reflow Encapsulant Codification Manual • Discussion of issues important to assembly with reflow encapsulants, with emphasis on differences from underfill process • Establishment of a materials knowledge base to save time during process development • Procedures for process development

15. INTRODUCTION • DISPENSER EVALUATION • Board Handling • Ease of programming, calibration (offsets) • Vision System • Pump Type • Dispense Volume Control • Uniformity and Precision • Heating • Cleaning • Technical support • Potential Alternatives: Stencil Printing • MATERIAL EVALUATION • Life • Bakeout • Dispensing • Needle Size and Type • Volume • Dispense Voids • Due to Substrate Features • From High Shear Rate • Absorption of Voids • Placement • Wetting • Placement Force and Hold Time • Placement Voiding • Reflow Soldering Window • Post Curing • Statistics • PROCESS DEVELOPMENT • Dispensing • Repeatability of Volume/Fillet Thickness • Dispense Pattern • Bakeout • Placement • Reflow Soldering Window • Post Curing Table of Contents

16. Reflow Profiles for Testing Reflow Process Window

17. Some Possible Dispense Patterns

18. Summary • Defect Prediction Programs • Design optimization • Specs • Codification Documents • Equipment and materials evaluation • Rapid product specific process design • Troubleshooting