Patents Assigned to Imasa Limited
  • Method of removing deposits of tin, lead or tin/lead alloys from copper substrates and compositions for use therein
    Patent number: 4964920
    Abstract: A composition for removing a layer of tin, lead or tin/lead alloy from a copper substrate such as a printed circuit board comprises an aqueous solution of nitric acid and ferric acid and also contains anthranilic acid to inhibit the degree of attack on the copper substrate. A surfactant, such as a mixture of cocoamine and an ethoxylated fatty alcohol or a mixture of a phosphate ester and an ethylene oxide/propylene oxide copolymer, may also be present to improve the brightness of the remaining copper.
    Type: Grant
    Filed: December 15, 1989
    Date of Patent: October 23, 1990
    Assignee: Imasa Limited
    Inventors: Brian Jackson, Gary Barnett
  • Black chromate coatings
    Patent number: 4065327
    Abstract: The properties of black chromate coatings on zinc and cadmium metal substrates are improved by treating the coating with an aqueous solution of sodium thiosulphate, sodium thioglycolate or thio urea. Treatment of the black chromate coating ensures that light fastness and corrosion resistance are reliably obtained.
    Type: Grant
    Filed: November 15, 1976
    Date of Patent: December 27, 1977
    Assignee: Imasa Limited
    Inventor: John Russell House