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In the past ten years, the increasing price of gold has motivated the wire bonding industry to lo... more In the past ten years, the increasing price of gold has motivated the wire bonding industry to look for alternative bonding wire materials in the field of microelectronics packaging. A new candidate wire to replace gold is palladium coated silver wire. In this thesis, the effect of the two specific process parameters “bond stress” and “process temperature” on the ball bonds made with the new candidate wire are investigated. Using 20 μm diameter wire and various level-combinations of these process parameter, ball bonds are produced according to a special accelerated optimization method to result in a target diameter of 46 ± 0.5 μm and target height of 16 ± 0.5 μm. Three different levels are used for each of the specific process parameters. After pre-selecting a few process parameters, the accelerated method determines the levels for the process parameters “impact force” and “electric flame-off current” with a 2×2 design of experiments. Then, the ultrasound parameter is maximized up t...
International Symposium on Microelectronics, 2015
The high price of Au has motivated many to look for alternative bonding wire materials in the fie... more The high price of Au has motivated many to look for alternative bonding wire materials in the field of microelectronics packaging. In the present study, the reliability performance of palladium coated silver (PCS) wire in high temperature storage test (HTST) is carried out using 18 μm diameter fine pitch PCS wire. Fine pitch ball bonds are made on Al metallization, with bonded ball diameter (BBD) of 32 ± 0.5 μm and ball height (BH) of 8 ± 0.5 μm. The aging temperature used in HTST is 170 °C and both shear and pull test are used to evaluate the aged ball bonds at regular time intervals. The shear force increases from 9.9 gf at 96 h to 12.5 gf at 192 h, and remains almost constant until 1344 h, and starts dropping gradually until 10.9 gf at 1848 h. The pad lift percentage recorded in pull test gradually drops from 90 % at 96 h to 20 % at 1008 h, and increases to 90 % at 1848 h. The chip side fractography after shear test indicates that the main failure modes are through pad at 96 h, t...
Microelectronics Reliability, 2015
ABSTRACT An accelerated optimization method is developed to minimize required time and resources,... more ABSTRACT An accelerated optimization method is developed to minimize required time and resources, and demonstrated for a 25 μm diameter Au ball bonding process. After a preparation phase to pre-set many parameters based on literature values, the values for more significant process parameters, impact force (IF) and EFO time (tEFO) for a given target bond geometry are optimized in a second phase, utilizing a 32 full factorial experiment and the response surface method (RSM). The target bond strength of 120 ± 2 MPa is achieved in a third phase by optimizing the ultrasonic energy (US) parameter using an iterative method. For an example process with a target geometry of 58 μm for the bonded ball diameter measured at the capillary imprint (BDC) and 16 μm for the height of the bonded ball (BH), the optimized process parameters (phases 2 & 3) can be found in less than 4 h. The values for IF and tEFO are found to be 424 mN and 0.474 ms, respectively. The bond is strengthened with incrementing US until additional ball deformation occurs. The bond strength achieved is >120 MPa with 48.6% US. Other bonding parameters include EFO current (IEFO) = 50 mA, temperature (T) = 158 °C, bond time (Bt) = 20 ms, and bond force (BF) = 185 mN.
In the past ten years, the increasing price of gold has motivated the wire bonding industry to lo... more In the past ten years, the increasing price of gold has motivated the wire bonding industry to look for alternative bonding wire materials in the field of microelectronics packaging. A new candidate wire to replace gold is palladium coated silver wire. In this thesis, the effect of the two specific process parameters “bond stress” and “process temperature” on the ball bonds made with the new candidate wire are investigated. Using 20 μm diameter wire and various level-combinations of these process parameter, ball bonds are produced according to a special accelerated optimization method to result in a target diameter of 46 ± 0.5 μm and target height of 16 ± 0.5 μm. Three different levels are used for each of the specific process parameters. After pre-selecting a few process parameters, the accelerated method determines the levels for the process parameters “impact force” and “electric flame-off current” with a 2×2 design of experiments. Then, the ultrasound parameter is maximized up t...
International Symposium on Microelectronics, 2015
The high price of Au has motivated many to look for alternative bonding wire materials in the fie... more The high price of Au has motivated many to look for alternative bonding wire materials in the field of microelectronics packaging. In the present study, the reliability performance of palladium coated silver (PCS) wire in high temperature storage test (HTST) is carried out using 18 μm diameter fine pitch PCS wire. Fine pitch ball bonds are made on Al metallization, with bonded ball diameter (BBD) of 32 ± 0.5 μm and ball height (BH) of 8 ± 0.5 μm. The aging temperature used in HTST is 170 °C and both shear and pull test are used to evaluate the aged ball bonds at regular time intervals. The shear force increases from 9.9 gf at 96 h to 12.5 gf at 192 h, and remains almost constant until 1344 h, and starts dropping gradually until 10.9 gf at 1848 h. The pad lift percentage recorded in pull test gradually drops from 90 % at 96 h to 20 % at 1008 h, and increases to 90 % at 1848 h. The chip side fractography after shear test indicates that the main failure modes are through pad at 96 h, t...
Microelectronics Reliability, 2015
ABSTRACT An accelerated optimization method is developed to minimize required time and resources,... more ABSTRACT An accelerated optimization method is developed to minimize required time and resources, and demonstrated for a 25 μm diameter Au ball bonding process. After a preparation phase to pre-set many parameters based on literature values, the values for more significant process parameters, impact force (IF) and EFO time (tEFO) for a given target bond geometry are optimized in a second phase, utilizing a 32 full factorial experiment and the response surface method (RSM). The target bond strength of 120 ± 2 MPa is achieved in a third phase by optimizing the ultrasonic energy (US) parameter using an iterative method. For an example process with a target geometry of 58 μm for the bonded ball diameter measured at the capillary imprint (BDC) and 16 μm for the height of the bonded ball (BH), the optimized process parameters (phases 2 & 3) can be found in less than 4 h. The values for IF and tEFO are found to be 424 mN and 0.474 ms, respectively. The bond is strengthened with incrementing US until additional ball deformation occurs. The bond strength achieved is >120 MPa with 48.6% US. Other bonding parameters include EFO current (IEFO) = 50 mA, temperature (T) = 158 °C, bond time (Bt) = 20 ms, and bond force (BF) = 185 mN.