FCPBGA with SOP Pad Finishing A Study of Lead-Free Solder Ball Attach Improvement

Author(s):  
Eu Poh Leng ◽  
Wong Tzu Ling ◽  
Nowshad Amin ◽  
Ibrahim Ahmad
Author(s):  
Vithyacharan Retnasamy ◽  
Zaliman Sauli ◽  
Phaklen Ehkan ◽  
Steven Taniselass

Author(s):  
Takahiro Kano ◽  
Ikuo Shohji ◽  
Tetsuyuki Tsuchida ◽  
Toshikazu Ookubo

An electroless Ni/Pd/Au plated electrode is expected to be used as an electrode material for lead-free solder to improve joint reliability. The aim of this study is to investigate the effect of the thickness of the Pd layer on joint properties of the lead-free solder joint with the electroless Ni/Pd/Au plated electrode. Solder ball joints were fabricated with Sn-3Ag-0.5Cu (mass%) lead-free solder balls and electroless Ni/Pd/Au and Ni/Au plated electrodes. Ball shear force and microstructure of the joint were investigated. The (Cu,Ni)6Sn5 reaction layer formed in the joint interface in all specimens. The thickness of the reaction layer decreased with increasing the thickness of the Pd layer. In the joint with a Pd layer 0.36 μm thick, the remained Pd layer was observed in the joint interface. In the joint, impact shear force decreased compared with that of the joint without the remained Pd layer. On the contrary, when the thickness of the Pd layer was less than 0.36 μm, the Pd layer was not remained in the joint interface and impact shear force improved. Impact shear force of the joint with the electroless Ni/Pd/Au plated electrode was higher than that with the electroless Ni/Au one.


Author(s):  
Bankeem V. Chheda ◽  
Sathishkumar Sakthivelan ◽  
S. Manian Ramkumar ◽  
Reza Ghaffarian

With lead-free implementation it is important to examine the behaviour of the solder joint at the component level and at the board level. Assembly related issues along with component reliability are the main focus of this experimental research. This experimental study aims to evaluate the mechanical integrity of solder joints comprising of both lead-free and SnPb alloys. Lead-free and SnPb solder pastes were used to assemble the components. This will allow us to check the forward and the backward compatibility of the solder alloys. The test vehicle considered for this study contained a variety of components such as ultra chip scale package (UCSP192), package on package (PoP), plastic ball grid array (PBGA-676 & 1156), very thin chip array BGA (CVBGA432), thin small outline package (TSOP-40 & 48), dual row micro-lead frame (DRMLF), micro-lead frame (MLF-36 & 72), and chip resistors (0201, 0402, 0603). The scope of this paper is limited to the performance evaluation for area array packages only. Solder ball alloy for the area array packages included SAC 305, SAC405, SAC105, SnAg and SnPb. Three different PCB surface finishes, electroless nickel immersion gold (ENIG), SnPb hot air solder level (HASL), and immersion silver (ImAg) were used. Different solder ball alloys and surface finish combinations provided good comparison data for investigating the assembly performance. The PCB assemblies were subjected to mechanical shock test in the as-soldered condition and also after 200 and 500 thermal shock cycles at −55 to 125°C. For the mechanical shock test, the assemblies were subjected to 30 drops from a height of 3 ft, generating an average G force of 485N. After each drop the components were checked for the continuity of the total daisy chain. The number of drops for the first failure was used in analyzing the performance of the components for various combinations. Since each component had many independent daisy chains, the failure of the individual daisy chains was later used in determining the location of the failure and how it progressed. Two sets of test vehicles were assembled. One set comprised of components with lead-free solder balls of different composition (SAC305, SAC405, SAC105, SnAg) and the other set comprised of components with lead-free solder balls and SnPb solder balls (SAC305, SAC405, SnPb). This mix of alloy composition provided adequate data for comparison. It was critical to optimize the process in order to enable the melting of the mix of alloys. The area array package performance was evaluated when assembled with lead-free and SnPb solder paste. Some of the assemblies were cross-sectioned after the tests and the microstructure of the solder joint was analyzed to study the possible cause for assembly failure.


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