ENHANCED PROCESS FOR HIGH I/O EDGE STRADDLING CONNECTOR ATTACH

摘要

Long surface mount edge connectors, Grad and 1.5D connectors, have been used effectively in the IBM ES 9000 main frame systems. With traditional through-hole assembly, the connectors were attached to the raw cards prior to card assembly. However, with the introduction of surface mount processing, this method has been changed. They must be attached after assembly. Any defect caused by this connector attach operation could result in high manufacturing value add cost. These connectors are large components in SMT process. They are over six inches long, half inch wide. They consist of four rows of 268 and three rows of 144 pins on both sides of the card respectively as high density I/O interface. These features make the connector attach process complex and could cause damage to the assembled cards. Based on the study of the soldering stress, solder joint quality and reliability of the connector attach operation, a robust attach process was developed. With respect to this process, a set of machine tools were designed and built. This paper summarizes a series of studies on Grad connector attach process and the introduction of the implementation of the new process.During the transition of the whole card assembly process to a water soluble process, non CFC process, the use of water soluble flux and deionized water in the original process led to connector failure. The failure was analyzed and the result showed that the edge of the defective card was delaminated. Further experiments determined that the delamination was caused during the initial mounting of the connector to the card, the subsequent lead soldering sequence and the warpage of the incoming parts.To address these problems, a new process was developed to accommodate the large tolerance of the parts. In addition, the lead soldering sequence was optimized and floating support technique was used. Since the new process was implemented, this failure mechanism has been eliminated.