Many governments, particularly in Japan and Europe, have proposedlaws reducing or eliminating the use of lead (Pb) and other toxicsubstances in products in an effort to decrease landfill pollution andground water contamination. Thus, there exists a need for lead-freecomponents in order to comply with government standards and to meetmarket demands for “green” products. As the semiconductorindustry moves towards environmentally friendly components, it isimportant that their assembly and reliability be well characterized.This paper will describe experiments performed to determine theinterconnect reliability of a peripherally leaded 1.0 mm pitch, 324 PBGAwith lead-free (tin-silver) versus conventional (tin-lead-silver) solderballs. Assembly was performed with lead-free versus eutectic solderpaste. Two different PBGA substrate manufacturers were evaluated and thetest boards used had an immersion gold over electroless nickel surfacefinish. The assembled boards were thermal cycled in both -40 to 125 and-50 to 150° C until >50% failure to compare lifetime of thelead-based and lead-free material. Solder joint failures were detectedwith continuous in-situ electrical monitoring and most were thenverified with dye penetrant. Additionally, solder ball shear testingversus 125 and 150° C bake out to 1,008 hrs was performed on lead andno-lead parts using one of the two substrate suppliers. Ball shear as afunction of number of reflows was also performed. Scanning electronmicroscopy (SEM) was used to analyze the elemental content andintermetallic thickness of both ball sheared and board-level cycledparts. The data from the aforementioned experiments suggests that thelead-free 324 PBGA packages are at least as reliable as the leadcontaining ones
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