Shigeru Umemura

Degradation Mechanisms in Tin- and Gold-Plated Connector Contacts

Degradation mechanisms in tin-plated contacts (Sn contacts) and gold-plated contacts (Au contacts) are clarified. Contact resistance and corrosion characteristics for both types of contacts are investigated and compared. Contact resistance is more stable for Sn contacts than for Au contacts in a SO 2 + NO 2 + C1 2 atmosphere. This is because relatively few corrosion products are formed on Sn contacts. Also, the surface films formed on Sn contacts shatters more easily upon plastic deformation. Corrosion experiments in atmospheres containing different combinations of SO 2 , NO 2 , and Cl 2 demonstrate that two types of corrosion processes take place in plated contacts. One is surface corrosion which occurs when the surface finish is severely attacked by a corrosive atmosphere. The other is pore corrosion which occurs when the underplating materials are attacked to a greater extent than surface corrosion. Both processes occur in Sn contacts and the former is dominant in atmospheres containing Ci 2 . On the other hand, only pore corrosion occurs in Au contacts. Furthermore, galvanic corrosion either enhances or inhibits the formation of outcroppings in the pore corrosion process, depending on the electrode potential of the surface finish and underplating materials.

High density pin board matrix switches for automated MDF systems

High-density, low-cost pin board matrix switches for automated main distributing frame (MDF) systems are described. The MDF system has two basic functions, cross connection and route setting for line test functions. These two functions can be performed automatically using a robot hand to insert a connecting pin into a crosspoint hole on the matrix board. Each crosspoint hole has four isolated cylindrical contacts that are connected to X/sub A/, Y/sub A/, X/sub B/, and Y/sub B/ conductive patterns, which represent the A and B wires of a telephone set circuit. Corresponding to the four contacts of a crosspoint hole, a connecting pin has two spring contacts, one spring contact to connect X/sub A/ and Y/sub A/ conductive patterns, and the other for connecting X/sub B/ and Y/sub B/ conductive patterns. In addition, arrangements have been made to perform the route setting for line testing. A matrix board with crosspoint holes on a 1.5-mm grid has been attained using the low-contact-force design and minimum insulation spacing between the neighboring conductive patterns. The design also considers requirements for the robot hand interface. These pin board matrix switches allow the MDF system to be automated. >

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. >

Design of high density pin board matrix switches for automated main distributing frame systems

High-density pin board matrix switches composed of matrix boards and connecting pins are designed to provide the cross connection function of an automated main distributing frame (AMDF) system. The cross connection is performed by inserting a connecting pin into a through hole on the matrix board. A small economic AMDF system is made possible by using a laminated matrix board structure based on mass production technology for printed circuit boards and the simultaneous connection of a paired line by inserting a single connecting pin. The low normal contact force design and small insulation spacing between the neighboring conductor patterns give a through-hole pitch of 1.5 mm and a connecting pin diameter of about 1 mm. The layer design of the matrix boards based on the high insulation resistance and high withstanding voltage characteristics allows a matrix board thickness of about 4.2 mm and a connecting pin length of about 8.7 mm. Evaluations of the electrical and contact characteristics of the matrix boards and connecting pins satisfy the design requirements. >

Effects of CO/sub 2/ atmosphere on contact resistance characteristics of noble metal contacts

Mixed atmospheres of N/sub 2/ and an active gas such as H/sub 2/ or O/sub 2/ are used in sealed enclosures to assure stable contact resistance and to prevent failures due to adhesion in sealed contacts. The effects of a CO/sub 2/ atmosphere on contact resistance and adhesion characteristics are investigated to determine if CO/sub 2/ could be an alternative atmosphere, because it is considered to be stable and nonreactive with contact materials. The test contact materials are Ag, Au, Pd, Ag-Pd alloy, and Au-Pd alloy. For Ag, Au, Ag-Pd alloy, and Au-Pd alloy contacts, the contact resistance increases with the number of operations, but for Pd contacts it remains low and stable. The increase in contact resistance in Ag and Au contacts is caused by film formation on the contact areas. Most of the films are amorphous carbon, and the film formation is restricted to the contact area. These results indicate that the carbon films are formed by the reduction of CO/sub 2/ on the contact area and that this reaction is accelerated by the opening and closing contact operations. >