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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.

It indicated that soft polymer cored could reduce the impact The reliability life of solderjointsisawell-knoduring drop test. The failure mode of polymer-cored solder topicforthe relabiltyolifecofindusole joi sard weell-peyu ball was different from SnlAgO.5Cu solder ball. The major crack of polymer-cored solder went into the bulk solder cycling test is most common test method and provide an initially and along the copper layer. approximate means of relating the results from these performance tests to the reliability solder attachments for the Introduction use environments and conditions of electronic assemblies.Board level drop test in commonly used for the evaluation of Recently, due to environmental debates, SnPb solder has solder joint performance, including eutectic and Sn-Ag-Cu solder replaced by lead free materials. The two most common alloys. It is founded by increasing the sensitivity to high strain compositions are Sn3.OAgO.5Cu and Sn4.OAgO.5Cu, failure for the usage during handheld, automotive, and respectively. Since small and thin package is the future communication productions [1][2][3]. The common Sn3 4AgO.5Cu tendency, the structure of shorter interconnection of chip scale of lead free solder is poor drop performance due to higher package (CSP) with ball grid array (BGA) is customarily Young's modulus by high volume of Ag3Sn. Lower silver occupied for handheld products. In virtue of recognizing content solder, Sn-l.OCu-0.5Cu, was introduced to replace package quality for actual status, board level drop impact is a Sn3 -4AgO.5Cu solder to satisfy trend requirement [4]. But, great concern to simulate mishandling during usage. As well the drop performance of Sn-l.OCu-0.5Cu is not still enough to known, the common Sn3-4AgO.5Cu of lead free solder is satisfy the end user demand. Polymer cored solder ball can poor drop performance due to higher Young's modulus by enhance board level TCT and drop test performance at the high volume of Ag3Sn. Lower silver content solder was same time. Up to now, some core materials of solder ball introduced to replace Sn3 4AgO.5Cu solder to satisfy trend were investigated for board level TCT test, such as cupper requirement. But, the drop performance is not still enough to and polymer cored solder balls. The cored solder ball has the satisfy the end user demand.better characteristic life of TCT due to the higher standoff In this study, two kinds of the solder ball were height. Optimum interconnection material should be had investigated, as the pure solder ball -SnlAgO.5Cu and better modulus property for higher drop performance polymer cored solder ball. There are three major layers for application. The Young modulus (115GPa) of Copper is polymer cored solder ball. The cored material is polymer, and higher than lead free solder (40-60GPa). The Cu cored then lum thickness of Cu was coated on the surface of solder ball did not fit this requirement. In this study we focus then lum thickness of Cu was coated on the surface Of q y,p olymer cored, final, the outer layer is 10 um ...

reasonable electrical conductibility. The Sn-Pb solder is a The solder bump interconnection is originated by IBM in 2-phase system. It represents typical phase diagram for binary the early 1960s and Flip chip technology became popular in eutectic systems, as the figure 1. The eutectic represents the packaging. Comparing with conventional wire bonding point where that composition goes directly from solid to interconnection package method, flip chip interconnection can liquid, i.e. without partially melting to a solid-liquid offer excellent electrical performance, very small chip size combination. The major characteristic is that a mixture of packages and high input/output handling capability. Recently, substance having a minimum melting point. Hence, organic substrates have replaced conventional ceramic 63Sn/37Pb of the eutectic composition is most commonly substrate. It is due to that the organic substrate can provide a used joint material for Integrated Circuit (IC) due to 1830C of minimal board area requirement, such as a reduction in weight the minimum melting point [1]. and height profile. Therefore, the interconnection of flip chip capability of the bumping process and the capability of the target substrate technology to route the die pitch. The Key~~~~~~wod:ftge'lpCi,9P/5 up connection of high Pb bump to ceramic iS accomplished by high temperature reflow, typically at temperature of 350°C or

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As the semiconductor technology advancing, the component size is gradual miniaturizing, so either busless design or electroless plating process should be used to meet the requirement of high routing density. Between these two solutions, electroless plating process has another advantage-lower cost. In electroless plating process, ENIG is popular in the industries, but it easily causes solder joint problems due to potential black pad issue. Therefore, a new surface finish-E'less nickel E'less Palladium immersion Gold (ENEPIG) is developed to overcome this problem by introducing a Pd layer between Ni and Au.In this paper, we studied the solder joint reliability for ENEPIG after multiple reflow times ( 1x, 3x, 6x ) by using conventional ball shear test, cold-ball pull test. High speed ball shear test was also applied to simulate high strain rate loading, such as drop test. Failure mode and micro analysis were carried out by the analytical tools, including SEM and EDX.From the SEM imagines, it is founded that the IMC thickness of electrolytic Ni/Au was thicker than ENEPIG under identical reflow times. From the ball shear test results, it seems no obvious difference between different reflow times for Electrolytic Ni/Au and ENEPIG. The failure mode of Electrolytic Ni/Au and ENEPIG were both broken at solder. Cold-ball pull test showed Electrolytic Ni/Au and ENEPIG have same failure mode distribution. In the high speed ball shear test, the behavior of broken interface was quite different between Electrolytic Ni/Au and ENEPIG. The broken interface of electrolytic Ni/Au ususlly happened at IMC phase, but the ENEPIG usually happened at solder phase. It could be deduced that ENEPIG has better solder joint quality.