Solderability Characteristics of Palladium , Palladium Nickel , Hard and Soft
Palladium and palladium alloys are the only serious ahematives to gold as an "electronic finish". In the past, the major impetus for such a substitution has been economic; however, today palladium's technological advantages are generally recognized. This is especially true in the connector markets where the material properties (e.g. hardness, ductility, thermal stability, etc.) of palladium are in many instances superior to hard gold. Recent advances in plating technologies coupled with a m r e thorough understanding of the materials properties have expanded the use of electroplated palladium and palladium alloys in the PCB, semiconductor and optoelectronic packaging markets. To assess the suitability for such applications, the wire bondability and solderability of these finishes need to be investigated.
Contact resistance characteristics of noble metal alloys for connector contacts
Contact resistance characteristics, corrosion characteristics, and the degradation mechanism for several binary and ternary alloys are investigated to evaluate the applicability of lower-cost noble metal alloys to connector contacts. These alloys include Pd, Ag, low-content Au, and Ni. The test connector contacts are clad inlays mated with each other, clad inlays mated with hard gold plating, and clad inlays with hard gold flash mated with inlays of the same material. The atmospheric conditions are air mixed with one or more of the following gases: SO/sub 2/. NO/sub 2/, Cl/sub 2/, or H/sub 2/S. The following alloys, used in inlays of the same alloy that are mated with each other, are listed in order of increasing contact resistance: Au-Ag, Ag-Pd, Au-Ag-Pd, Au-Pd, and Pd-Ni. The contact resistance characteristics of inlays mated with hard gold plating and those of inlays with hard gold flash mated with inlays of the same material are as stable as those of hard gold plating mated with hard gold plating The dominant degradation mechanism affecting the inlay contacts of these alloys is the formation of a corrosion product on the surface area of the contact material. The dominant corrosion products causing an increase in contact resistance are the chlorides in Pd alloys. >
Dimensional Errors of Fixtures, Locating and Measurement Datum Features in the Stream of Variation Modeling in Machining
Machining processes are usually multi-station processes involving a large number of operations and several locating datum changes. Machining errors are thus introduced, transformed and accumulated as the workpiece is being machined. This paper introduces procedures for expressing the influence of errors in fixtures, locating datum features and measurement datum features on dimensional errors in machining. These procedures are essential in the derivation of the Stream of Variation model of dimensional machining errors using the CAD/CAPP parameters of the machining process. The linear state space form of the Stream of Variation model allows for advanced control theory achievements to be employed in formal solutions to problems in multi-station machining. Modeling procedures presented in this paper were experimentally verified in machining of an automotive cylinder head.