John Joseph Mottine

New, Z‐direction anisotropically conductive composites

This paper reports the development of a new class of anisotropically conductive materials based on magnetic alignment of conductive particles in nonconductive matrix materials such as elastomeric or adhesive polymers. These composites contain many vertically aligned but laterally isolated chains of ferromagnetic metal spheres, the ends of which protrude from the surfaces for better electrical contact. These novel composite structures exhibit Z‐direction‐only electrical conduction (>1012 to 1 anisotropy ratio), which, in combination with the compliant nature of the materials, can be exploited advantageously for a variety of electronic applications including fine‐pitch, area‐array, circuit interconnections, circuit‐testing, heat sink interfacing, and sensor devices. The movement and alignment of magnetic particles in a viscous medium, and the stability of configurations in a magnetic field will be discussed. The properties of the composite materials as well as potential circuit and device applications will ...

Investigation of Fretting Corrosion at Dissimilar Metal Interfaces in Socketed IC Device Applications

Gold has traditionally been the material of choice for separable connector contact surfaces in high reliability applications. With the rising cost of gold, major efforts have been focused on finding ways of reducing or altogether eliminating its use while still maintaining low and stable values of contact resistance. Currently in commercial semiconductor devices, gold-plated device leads are often not available. Tin and solder finishes are common. Recently early intermittent contact resistance failures were found when dissimilar metal (Au/Sn and Au/solder) interfaces were used in conjunction with socketed integrated circuit (IC) devices. Analysis of these failures indicated that fretting corrosion of tin had occurred. To better understand the phenomena of fretting corrosion in such applications, a laboratory study was conducted on a variety of dissimilar metal (socketed device) interfaces under conditions of mild vibration. The static resistance behavior of the samples was studied for a ten month period. The samples were then disassembled and the contact surfaces were examined using scanning electron microscope (SEM) and scanning Auger microprobe (SAM) techniques. The resistance data obtained indicated that, without lubrication, all metal interfaces except Au/ Au failed repeatedly. Subsequent SEM and SAM investigations showed that all interfaces of Sn and SnPb (solder) mated to themselves or to Au failed by tin fretting corrosion, resulting in high contact resistances (>100 \Omega .

The Effect of Lubrication on Fretting Corrosion at Dissimilar Metal Interfaces in Socketed IC Device Applications

The early failure rate of socketed dual in-line package (DIP) devices that used dissimilar metal interfaces (Sn/Au and SnPb-solder/ Au) have been previously reported by the authors. These high resistance failures (both in field systems and in the laboratory) were attributed to the formation of tin oxide fretting corrosion at the device/socket interface. Lubrication of metal contacts has been shown to reduce or eliminate fretting corrosion in various contact configurations. In this study, the effect of a thixotropic synthetic lubricant, composed of a mixture of an oil and a wax, on the production of fretting corrosion at dissimilar metal interfaces under conditions of very mild vibration is evaluated. The static resistance behavior of these samples was studied for 18 months. The samples were then disassembled and the contact surfaces examined using scanning electron microscopic (SEM) and scanning Auger microprobe (SAM) techniques. The resistance data obtained indicated that all dissimilar metal interfaces failed repeatedly. Only the SnPb/SnPb and Au/Au interfaces showed no significant increases in resistance over the test period. Subsequent SEM and SAM investigations showed that all of the dissimilar interfaces failed due to build-up of tin oxide fretting corrosion resulting in high contact resistances (> 100 \Omega ). It was observed that lubrication was effective in reducing both the amount of and the rate of fretting corrosion, as well as dispersing the corrosion that formed. The greatest reduction of fretting corrosion occurred in the SnPb/SnPb systems such that no resistance failures occurred during the 18 month study.