EFFECT OF POTASSIUM GOLD CYANIDE ADDITION INTO Ni-W BATH ON COMPOSITION, HARDNESS AND DEPOSIT STRUCTURE

• Main Author: FATRA (NIM 23105020), WARMAN
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/11574
• Institution: Institut Teknologi Bandung

Gold is used as coating element for electronic devices such as electrical contactor and connector because of its low electrical resistivity, chemically stable and good corrosion resistance. Soft gold plating has low wear resistance since gold is a soft metal. Some elements are added as hardeners to gold coating to increasing deposit hardness. Cobalt-Hardened Gold (CoHG) and Nickel-Hardened Gold (NiHG) can increase deposit hardness up to around 187 VHN, meanwhile it was reported from previous research that deposit hardness up to around 400 VHN has been obtained by underlayer nickel.<p>In this experiment, Potassium Gold Cyanide was added into Nickel-Tungsten bath by electrodeposition. The result showed that deposit hardness obtained is higher than CoHG and NiHG. Increasing current density increase deposit hardness. The hardness of deposit on current density of 150 mA/cm2 and with the addition of potassium gold cyanide of 2.5, 5, and 7.5 g/L was 476 VHN, 451 VHN and 353 VHN, respectively. On current density of 200 mA/cm2 the deposit hardness achieved 533 VHN, 507 VHN and 386 VHN, respectively.<p>The deposit composition (wt%) on coating surface were determined by EDS. The result showed that the deposit composition on current density of 200 mA/cm2 were (38% Au -59% Ni -3% W), (59% Au -37% Ni -5% W) and (67% Au -27% Ni -6% W), respectively. Deposit composition on current density of 150 mA/cm2 were (53% Au -42% Ni -6% W), (65% Au -29% Ni -6% W) and (67% Au -27% Ni -6% W), respectively. Deposit hardness was influenced by nickel but not by tungsten content. The increase of deposit hardness was possibly caused by the formation of nickel hydride. XRD pattern showed that by the addition of 2.5 and 5 g/L KAu(CN)2 into the Ni-W bath the deposit has a crystalline type structure. While the addition of 7.5 g/L KAu(CN)2 showed towards an amorphous structure. <br />