Browsing by Author "Chiu, SH"

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Electromigration failure mechanisms for SnAg3.5 solder bumps on Ti/Cr-Cu/Cu and Ni(P)/Au metallization pads
(2004-10-15)
Shao, TL
;
Chen, YH
;
Chiu, SH
;
Chen, C
;
材料科學與工程學系
The electromigration behavior of SnAg3.5 solder bumps is investigated under the current densities of 1x10(4) A/cm(2) and 5x10(3) A/cm(2) at 150degreesC. Different failure modes were observed for the two stressing conditions. When stressed at 1x10(4) A/cm(2), damage occurred in both the anode/chip side and the cathode/chip side. However, failure happened only in the cathode/chip side under the stressing of 5x10(3)A/cm(2). A three-dimensional simulation of the current-density distribution was performed to provide a better understanding of the current-crowding behavior in the solder bump. The current-crowding effect was found to account for the failure in the cathode/chip side. In addition, both the temperature increase and the thermal gradients were measured during the two stressing conditions. The measured temperature increase due to Joule heating was as high as 54.5degreesC, and the thermal gradient reached 365degreesC/cm when stressed by 1x10(4)A/cm(2). This induced thermal gradient may cause atoms to migrate from the chip side to the substrate side, contributing to the failure in the anode/chip side. Moreover, the formation of intermetallic compounds in the anode/chip side may also be responsible for the failure in the anode/chip side. (C) 2004 American Institute of Physics.
Electromigration in eutectic SnPb solder bumps with Ni/Cu UBM
(2005)
Chiu, SH
;
Liang, SW
;
Chen, C
;
Lin, SS
;
Chou, CM
This study investigates the electromigration behavior of eutectic SnPb solder bumps with Ni/Cu UBM, in which the thickness of the Ni and Cu layer is 3 pm and 5 pm, respectively. It was found that the SnPb solderjoints have better electromigration resistance than that of SnAg bumps with thin film UBM. The thermal characteristic of SnPb solder joints under current stressing was measured by infrared technique. The Joule heating effect was less serious due to the wide Al trace of 100 mu m. Besides, a three-dimensional simulation on current density distribution was performed to examine the current crowding behavior in the joint. The results show that the current crowding occurs at the entrance point of the Al trace, which caused higher formation rate of intermetallic compounds there, and thus open failure occurred.
Infrared microscopy of hot spots induced by Joule heating in flip-chip SnAg solder joints under accelerated electromigration
(2006-01-09)
Chiu, SH
;
Shao, TL
;
Chen, C
;
Yao, DJ
;
Hsu, CY
Joule heating effect in solder joints was investigated using thermal infrared microscopy and modeling in this study. With the increase of applied current, the temperature increased rapidly due to Joule heating. Furthermore, modeling results indicated that a hot spot existed in the solder near the entrance point of the Al trace, and it became more pronounced as the applied current increased. The temperature difference between the hot spot and the solder was as large as 9.4 degrees C when the solder joint was powered by 0.8 A. This hot spot may play an important role in the initial void formation during electromigration.
Thermal gradient in solder joints under electrical-current stressing
(2004-11-01)
Shao, TL
;
Chiu, SH
;
Chen, C
;
Yao, DJ
;
Hsu, CY
The thermal gradient and temperature increase in SnAg3.5 solder joints under electrical-current stressing have been investigated by thermal infrared microscopy. Both positive and negative thermal gradients were observed under different stressing conditions. The magnitude of the thermal gradient increases with the applied current. The measured thermal gradients reached 365degreesC/cm as powered by 0.59 A, yet no obvious thermal gradient was observed when the joints were powered less than 0.25 A. The temperature increase caused by joule heating was as high as 54.5degreesC when powered by 0.59 A, yet only 3.7degreesC when stressed by 0.19 A. The location of heat generation and path of heat dissipation are believed to play crucial roles in the thermal gradient. When the major heat source is the Al trace, the thermal gradient in the solder bumps is positive; but it may become negative because the heat generated in the solder itself is more prominent.