EXPERIENCES WITH MONOTONIC BEND TEST OF ELECTRONIC PACKAGES
Author: Thomas Koschmieder Company: Freescale Semiconductor, Inc. Date Published: 10/11/2007
Abstract: Monotonic bend as a mechanical test for mounted electronic packages has an industry standard, IPC-9702 (Monotonic Bend Characterization of Board-Level Interconnects.) The test is a single bend to failure of electronic packages mounted to a specialized test board. Freescale Semiconductor has used the test for a variety of ball grid array (BGA) package styles. Experiences with the monotonic bend test for PBGA (plastic BGA), TBGA (tape BGA), FC-PBGA (flip-chip plastic BGA) and FC-CBGA (flip-chip ceramic BGA) packages will be presented. Classic eutectic SnPb solder-joints, high-Pb solder-joints and also Pb-free solder-joint results will be shown. Lidded packages for flip-chip packages will be compared to non-lidded versions. The bend to failure where the failure is the electrical open of a packages solder-joint, changes by package style. For instance, FC-CBGA packages tend to fail by catastrophic cracking of the substrate and not by solderjoint separation. In contrast PBGA and TBGA packages will fail in the solder-joint or by test board pad rip out. The shift from failure at the package side to a failure at the printed circuit board side will also be discussed including mechanical limitations when this occurs. In effect, the test is limited in range of applicability to only when the solderjoint fails. From IPC-9702, the standard test board design has 4 sites for mounted packages. An experimental comparison of only one site or of two sites being populated will be provided. The results will provide an indication of whether multiple packages on a board mechanically assist each other during monotonic bend. Experimental results from general monotonic bend testing crosshead speed will be compared to Annex A in IPC-9702.