Connector contacts, gold-plated

A solution for these drawbacks was found in using commercially available New Objective Picospray emitters with distal coating, mounted onto the chip with Upchurch Nanoport connectors. To facilitate mounting of the needles and to connect the chip with capillary fibers to the mass spectrometer, a holder was designed as shown in Figure 9.4. The electrical connection to the liquid was realized by using a metal-coated needle, electrically contacted via a gold-plated... 

A problem discovered by an air force corrosion engineer was the corrosion of tin-plated electrical connector pins mated with gold-plated sockets. Fretting corrosion between these very small contacts appears to have been implicated in as many as six F-16 fighter aircraft crashes when their main fuel shutoff valves closed uncommanded (17). 

High Contact Resistance on Gold-Plated Connector Contacts Caused... 

In modem times, starting from the second half of the 1940s, the birth and rapid development of the electronic industry totally changed the scenario that had determined the development of gold plating up to that time. The use of gold layers as a contact surface in connectors, switches, and... 

Corrosion inhibition and wear protection of gold plated connector contacts, S. J. Krumbein and M. Antler, IEEE Trans. Parts Mater. Packag., 1968, PMP-4, 3. 

Fretting corrosion (36,37) can lead to high contact resistance of base metal contacts, such as tin plate in electronic connectors. Small cycHcal displacements of the connector halves occur because of external vibration or differential thermal expansion and contraction of the mating contacts. The wear debris that is formed remains in the contact zone. The accumulation of oxide debris in the contact region leads to increased contact resistance. Solutions to this problem are stmctures that do not permit movement of contact surfaces with respect to one another, the use of gold as a contact finish, and the appHcation of thick coatings of contact lubricants and greases, which reduce the rate of wear and restrict access of air to the contact surfaces. 

Integrated electrodes are another option available for microchips in which the electrodes are fabricated into the microchip itself. Thin strips of metal, usually gold, are deposited on either the substrate containing the channels or the cover plate. Methods for this type of metal deposition and micropatterning are well established in the semiconductor industry. The interface connection then resembles a computer board in which the microchip plugs into a connector to make contact with the power supply. Although useful for disposable... 

Deposits from the sulfate or phosphate are hard (900 to 1000 Knoop), highly reflective, extremely corrosion-resistant, and highly conductive (resistivity is 4.51 pi/cm). Rhodium plate is used where a low-resistance, long-wear, oxide-free contact is required. In addition, rhodium as a deposit on nickel for edge connectors has been replaced by gold.This is due to difficulty in bath control problems with organic and metallic contaminants, as weU as cost. Table 29.12 shows details of rhodium plating. 

Low-force, low-voltage separable cormectors and contacts also have wide use in electronic systems [11,12], A variety of different configurations exist, but the substrate of most is made from copper, brass, bronze, or copper-beryllium. The use of copper alloys ensures some susceptibility to environmental degradation. To reduce interfacial resistance and corrosion, the substrate is plated with a nickel diffusion barrier and then with a precious metal (e.g., gold, palladium) [11,13], However, a trade-off exists between plating cost (thickness) and reliability [14]. Hence, physical defects (pores and cracks) are usually present. In the past, connectors and contacts could not be coated because of interference with their function, although some new coating inhibition formulations have been developed for this purpose [11,12]. 

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