Original Publication Date: 1972-Jul-01
Included in the Prior Art Database: 2005-Feb-25
AbstractElectrophoresis enables construction of an intermediate connector for chip attachment to a substrate.
Electrophoresis enables construction of an intermediate connector for chip attachment to a substrate.
In Fig. 1, connector 1 for circuit chip attachment is formed by electrophoretic deposition of an insulator 2 and subsequent plating of solder through-pins 3.
In Fig. 2, a polished steel mandrel 4 is given a flash coat of electroless copper 5 and then coated completely with a positive photoresist. The photoresist is exposed in the desired attachment pattern and developed to leave a covering 6 over the through-pin locations. Thereafter, this remaining resist 6 is exposed but not developed to leave a latent image. A suitable insulative polymer 7 such as one of the polyamides is then electrophoretically deposited on the exposed mandrel surface to a desired thickness, rinsed and baked at a moderate temperature to produce a homogeneously fused film.
Through-pins are next formed by developing out the remaining exposed photoresist and electroplating solder in the pin openings 8. Pin height is optional. After plating is concluded, the layer is separated from the steel at the copper interface by peeling. The copper flash is removed by a brief immersion in an etchant. Further. fusion of the insulation, if required, can be done by baking. The completed interconnection layer can then be attached by the usual solder reflow techniques.
After solder joining, the film may be removed chemically by dissolving the polyamide in methylene chloride-methanol solven...