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Process for bonding metals to electrophoretically deposited resin coatings

  • US 4,601,916 A
  • Filed: 07/18/1984
  • Issued: 07/22/1986
  • Est. Priority Date: 07/18/1984
  • Status: Expired due to Fees
First Claim
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1. In a process for producing a printed circuit on an insulated metal substrate, which process includes providing one or more insulating layers on surfaces of a metal sheet to form the insulated metal substrate;

  • providing one or more holes through the insulated substrate for through connections;

    etching the hole walls defined by the metal sheet to enlarge by a predetermined amount only the portion of the holes extending through the metal sheet, electrophoretically depositing a resinous coating comprising a cathodic or anodic electrophoretic thermosetting resin from a solution thereof on the etched portion of the hole walls;

    curing the resinous coating; and

    forming the printed circuit on the surface of the insulating layers and on the walls of the holes;

    the improvement comprising;

    incorporating in the resin solution a solid filler in finely divided form and having an average particle size of about 1 micron or less, the filler being non-resinous, inorganic, non-reactive with the solution and uniformly dispersed therethrough, the filler being capable of improving the adhesion of a metal layer to the electrophoretically deposited resinous coating after the coating is adhesion promoted, the resinous coating containing the filler having a volume resistivity greater than 104 megohm-cm between the printed circuit conductor and the metal sheet;

    electrophoretically depositing the resinous coating and the filler from the solution onto the metal wall portions of the holes, the deposited coating having fillers dispersed therethrough;

    curing the resinous coating, the thickness of the cured resinous coating being between about 0.025 mm and about 0.055 mm, the cured resinous coating being comprised of (a) 1% to 25% by weight of said filler, and (b) the balance being said thermosetting resin;

    adhesion promoting the surface of the resinous coating containing the filler to create a hydrophilic, microetched surface on the coating;

    depositing a metal layer on the surface of the resinous coating on the hole walls, and on the insulating layers, the metal layer deposited on the microetched surface of the resinous coating being continuous and free of blisters, andforming said printed circuit on the insulated metal substrate.

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