1. Codification of Flip Chip Knowledge
Good afternoon.
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 Codification Documents
“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. Table of Contents Largest sections are 4 and 7 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
Largest sections are 4 and 7

11. Typical Correlation Between Nominal Dispensed Volume and Fillet Thickness

12. Taper Flow Experimental Setup
Clamp
0 mil
5 mil

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. Table of Contents 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
Repeatability of Volume/Fillet Thickness
Dispense Pattern

16. Reflow Profiles for Testing Reflow Process Window

17. Some Possible Dispense Patterns

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