Image of epoxy underfill beneath flip
chip, showing void in center
Adhesive bonds have broad applications
Automotive: body panel assembly
Semiconductor packaging: flip chip and die attach
underfill
Performance requirements
High strength
High thermal conductivity
High electrical conductivity
Manufacturing challenges
Stabilize spread of adhesive
Maintain thickness value
Insure good adhesion
Solution: laser ultrasonics
Noncontact
Fast areal scanning
Small laser spots yield high spatial resolution
High bandwidth enables measurement of bond
strength
Replaces slow water-based ultrasonic systems
Image of adhesive distribution underneath sheet metal
Laser Ultrasonics