Integrated temperature microsensors for characterization and optimization of thermosonic ball bonding process

A novel ball bond process optimization method based on the thermal response of an integrated aluminum microsensor is reported. The in situ temperature during ball bonding is measured and analyzed. The ultrasonic period shows distinct stages corresponding to scrubbing of the ball on the pad, intermetallic bond growth, and ball deformation by ultrasonic softening. A peak of the signal indicates the end of interconnection growth. This can be used for bond time optimization. When optimizing bonding force, the sensor signal correlates with ball shear strength. Using this method, bonding force process windows can be determined by on-line measurements. A test measurement shows that at a chip temperature of 34/spl deg/C, the bonding force optimized by the microsensor method is 260 mN whereas it is 252 mN when using conventional shear testing for optimization. In summary, the method produces a wealth of new insights in transient thermal phenomena of the ball bonding process and promises to simplify the evaluation of process windows.

[1]  O. Brand,et al.  Micromachined thermally based CMOS microsensors , 1998, Proc. IEEE.

[2]  Richard C. Jaeger,et al.  Piezoresistive Stress Sensors for Structural Analysis of Electronic Packages , 1991 .

[3]  B. Shu.  Fine pitch wire bonding development using a new multipurpose, multi-pad pitch test die , 1991, 1991 Proceedings 41st Electronic Components & Technology Conference.

[4]  W. K. Shu,et al.  Fine pitch wire bonding development using statistical design of experiment , 1995, 1995 Proceedings. 45th Electronic Components and Technology Conference.

[5]  Ma.M.T. Aguila,et al.  Ball bond characterization: an intensive analysis on ball size and shear test results and applicability to existing standards , 1997, Proceedings of the 1997 1st Electronic Packaging Technology Conference (Cat. No.97TH8307).

[6]  Oliver Paul,et al.  In-situ calibration of wire bonder ultrasonic system using integrated microsensor , 1998, Proceedings of 2nd Electronics Packaging Technology Conference (Cat. No.98EX235).

[7]  Oliver Paul,et al.  In-situ Measurement of Stress and Temperature under Bonding Pads During Wire Bonding Using Integrated Microsensors , 1999 .