Effects of Cu contents in flux on microstructure and joint strength of Sn–3.5Ag soldering with electroless Ni–P/Au surface finish

Hitoshi Sakurai; Keun-Soo Kim; Kiju Lee; Chang-Jae Kim; Youichi Kukimoto; Katsuaki Suganuma

doi:10.1016/j.microrel.2012.05.005

Effects of Cu contents in flux on microstructure and joint strength of Sn–3.5Ag soldering with electroless Ni–P/Au surface finish

Microelectronics Reliability ◽

10.1016/j.microrel.2012.05.005 ◽

2012 ◽

Vol 52 (11) ◽

pp. 2716-2722 ◽

Cited By ~ 3

Author(s):

Hitoshi Sakurai ◽

Keun-Soo Kim ◽

Kiju Lee ◽

Chang-Jae Kim ◽

Youichi Kukimoto ◽

...

Keyword(s):

Surface Finish ◽

Joint Strength ◽

Electroless Ni

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Evaluation of Surface Finish on Build Up Substrate

2003 International Electronic Packaging Technical Conference and Exhibition, Volume 2 ◽

10.1115/ipack2003-35153 ◽

2003 ◽

Cited By ~ 1

Author(s):

L. Y. Hung ◽

Y. P. Wang ◽

C. S. Hsiao

Keyword(s):

Solder Joint ◽

Surface Finish ◽

Joint Strength ◽

Failure Modes ◽

Electroless Nickel ◽

Deposition Process ◽

Sodium Hypophosphite ◽

Ball Shear ◽

Phosphorous Content ◽

Electroless Ni

In recent years, the most explosive technologies in electronic systems have demanded ever-higher functionality, ever-faster circuit speeds, and always increasing interconnection density. Electrolytic and electroless nickel/gold (Ni/Au) deposition process are used commonly to provide flat, solderable pad surface finish on area array (BGA or CSP) packages and printed wiring boards (PWB). The electroless nickel/immersion gold (ENIG) process is widely used which do not requires plating lines for electrolytic plating, better meets the fine pitch wiring requirements. However, ENIG deposition process may cause or contribute to catastrophic, brittle, interfacial solder joint fractures. ENIG plating has previously shown lower reliability at solder joints. This is because Phosphorous segregation at the interface Sn-Ni intermetallic and Ni layer caused poor adhesion at that interface, especially high phosphorous content (10∼15%) of the electroless Ni. There have been many studies verified that Ni3P formation is a major factor, which causes weaker joint strength and flat fracture surface. Owing to sodium hypophosphite (NaH2PO2) was used to provide electron and return Ni ion to deposit on Cu pad for ENIG plating, it is not dodge that phosphorous element exist at the Ni layer. Hence, ph value, temperature and loading factor (plating area/ plating tank volume) in the plating path are controlled to reduce phosphorous content (less than 10%) to avoid Ni3P formation. Furthermore, ENIG has a potential risk of black pad, because Porous Au plating layer caused the oxidation of Ni layer underneath the Au plating to occur solder joint failure and low shear forces after assembly. In order to overcome foregoing problem, a flip chip ball grid array (FCBGA) test vehicle is used to compare three kinds surface finish electroless Ni/Au, direct gold and solder on Cu pad in this study 63Sn/37Pb solder bump is reflowed onto these substrates. High temperature storage test (HTS) is used to evaluate thickness and structure of IMC to affect solder joint attachment reliability. Ball shear test is used to measurement joint strength at various HTS time. Optical microscopy (OM) and scanning electron mcroscopy (SEM) are used to observe failure modes after ball shear.

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Joint Strength and Microstructure for Sn-Ag-(Cu) Soldering on an Electroless Ni-Au Surface Finish by Using a Flux Containing a Cu Compound

Journal of Electronic Materials ◽

10.1007/s11664-008-0408-5 ◽

2008 ◽

Vol 37 (6) ◽

pp. 806-814 ◽

Cited By ~ 6

Author(s):

Seishi Kumamoto ◽

Hitoshi Sakurai ◽

Youichi Kukimoto ◽

Katsuaki Suganuma

Keyword(s):

Surface Finish ◽

Joint Strength ◽

Electroless Ni

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Interfacial Reaction of Electroless Ni-P Plating with Sn-3.5Ag (-Co) Solder

Materials Science Forum ◽

10.4028/www.scientific.net/msf.580-582.243 ◽

2008 ◽

Vol 580-582 ◽

pp. 243-246 ◽

Cited By ~ 1

Author(s):

Hiroshi Nishikawa ◽

Akira Komatsu ◽

Tadashi Takemoto

Keyword(s):

Intermetallic Compound ◽

Interfacial Reaction ◽

Fracture Mode ◽

Joint Strength ◽

Solder Bump ◽

Solder Joints ◽

Pull Strength ◽

Electroless Ni

The reaction between Sn-Ag (-Co) solder and electroless Ni-P plating was investigated in order to clarify the effect of the addition of Co to Sn-Ag solder on the formation of intermetallic compound (IMC) at the interface and the joint strength at the interface. Sn-Ag-Co solder was specially prepared. The results show that there is little effect of the addition of Co to the Sn-Ag solder on the IMC formation and the thickness of the IMC at the interface. For the pull strength of the solder bump joint, the addition of Co to the solder didn’t strongly affect the pull strength of the solder joints, but it affected the fracture mode of the solder joints.

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