R. Weeks

Publications (2)0 Total impact

• Article: Plated copper on ceramic substrates for power hybrid circuits

  R.W. Johnson, R. Weeks, D.C. Hopkins, J. Muir, J.R. Williams
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  ABSTRACT: Plated copper on ceramic has been evaluated for fabrication of power hybrid circuits. The copper is plated using a semiadditive process that yields rectangular conductor cross sections. Copper thicknesses can be varied from 12 to 150 μm depending on electrical current requirements. Typically, a 2.5-μm nickel barrier layer and a 1.25-μm gold layer are plated onto the copper metallization. The soldered adhesion (62Sn/36Pb/2Ag) of the metallization has been studied. No adhesion degradation was observed after storage for 1000 h at 150°C or after 118 thermal cycles between -65°C and 125°C. The bonding of small-diameter gold-wire bonding to the Au/Ni/Cu metallization was evaluated. No reduction in bond strength (≈7.5 gf) was observed after 1000 h of storage at 150°C. The bonding of large-diameter aluminium wire to the Au/Ni/Cu metallization was also studied. The average initial pull strength was 560 gf. After 2050 h at 150°C, the average pull strength was 499 gf, while the average after 2050 h at 200°C was 438 gf. Screen printable polyimide encapsulants were used for solder masking and high voltage insulation. Electrical properties were measured. To demonstrate the use of plated copper on ceramic, the power section of a 100-W DC-DC converter was fabricated
  IEEE Transactions on Components Hybrids and Manufacturing Technology 01/1990;
• Conference Proceeding: Plated copper on ceramic for power hybrid applications

  R. Weeks, R.W. Johnson, D. Hopkins, J. Muir, J.R. Williams
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  ABSTRACT: A technique for plating copper onto ceramic with top layers of nickel, gold, and/or solder is described. The adhesion mechanism of the copper is an interlocking of the film and ceramic surface to form a mechanical bond. Soldered adhesion of the copper did not degrade during high-temperature storage or thermal cycling. A nickel barrier between the plated copper and solder inhibits diffusion and intermetallic formation. Testing of small-diameter gold and large-diameter aluminum wire bonds after high-temperature storage demonstrated the reliability of wire bonding to the Cu/Ni/Au metallization. While a small percentage of bond lifts occurred among the aluminum-wire-bond samples stored at 200°C, the bond strengths were high and there was no increase in series bond resistance. Preliminary evaluation of a screen-printable polyimide encapsulant revealed pinholes in the cured film. Alternate polyimide formulations are being evaluated. A 2-MHz, 100-W DC-DC converter was fabricated to demonstrate the use of plated copper on ceramic substrate technology
  Electronic Components Conference, 1989. Proceedings., 39th; 06/1989