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Future applications will require higher I/O counts, more densification, and greater performance. CBGA(Ceramic Ball Grid Arry) packages are appropriate to this demand. As it is well known, the distribution of I/O contacts in CBGA is made on the surface of the ceramic substrate, following a matric group geometry. The connections have a ball shape and are made with a Snl0Pb90 alloy characterized by an high fusion temperature; this balls are attached on the package metallization using the classical Sn63Pb37 alloy. After assembling, the connection appears as a SnlOPb90 ball embedded in a Sn63Pb37 joint linking the package metallization and the PCB pads. The attach strength of the balls influence a lot on assembling reliability. In this paper, the higher leaded balls attach strength of CBGA packages are studied through experimental programs. The factors include: ceramic pads geometry, stencil thickness, plated metals, reflow process, high temperature storage time, etc. |
