Abstract: Method of fabricating high density multilayer interconnect structures or flexible HDMI decals. The methods secure a top surface of an HDMI decal fabricated on a rigid substrate to a protective film layer which is in turn adhesively secured to a flat carrier. This structure is then demounted or delaminated from the rigid substrate. The bottom of the HDMI decal, with the protective film layer and flat carrier attached thereto, is secured to a mounting substrate using a relatively thick adhesive layer. After the HDMI decal is adhesively secured to the mounting substrate, the carrier and protective film layer are removed. The top surface of the HDMI decal thus remains flat after it is secured to the mounting substrate, and therefore connection of integrated circuit chips to contact pads on the top surface of the decal is ensured because this surface is flat. The carrier and protective film layer also protects the top surface of the decal while it is secured to the mounting substrate.

Abstract: Methods of forming two-sided high density multilayer interconnect (HDMI) structures on a relatively large carrier and subsequently releasing and removing one or more structures to provide useable flexible interconnects or decals. In general, a carrier is provided and a release layer is formed on the carrier. Flexible high density multilayer interconnect structures are fabricated on the release layer. The release layer is processed to release and remove one or more flexible HDMI structures from the carrier. The carrier may be an ultraviolet transparent substrate, such as quartz, for example, and the release layer may be a polyimide layer. The HDMI structures are released by irradiating the release layer through the transparent carrier using ultraviolet radiation from an ultraviolet radiation source. Alternatively, a silicon carrier may be used that has a metal or silicon dioxide release layer formed thereon.

Abstract: Interconnection of densely populated multiple chip integrated hybrid circuits (12) in a manner such that heat can be efficiently extracted therefrom. An integrated circuit die (31) is attached to a flip chip interconnect layer by soldering the connection pads thereto. The interconnect layer is slid off its substrate (11) in the manner of a decal. After the circuit has been tested and found acceptable, the other side of the die (31) is permanently bonded to a thermal conduction plate or heat sink (32). The decal interconnect (33) is made of alternating layers of an insulator (41) and a conductor (42) built on top of an erodible sacrifical layer (48) applied to a substrate. The sacrificial layer (48) is dissolved by a suitable solvent to float the multilayer interconnect off the substrate (11).

Abstract: A via (26) is formed through a dielectric layer (8) separating two conductive layers (16,28) by establishing a laterally erodible mask (18) over the dielectric (8), with a window (24) over the desired via location. The mask (18) and exposed dielectric material (8) are eroded simultaneously, preferably by reactive ion etching, producing a via (26) through the dielectric (8) which expands laterally as vertical erosion proceeds. The erosion conditions, the materials for the mask (18) and dielectric (8), and the initial window (24) taper are selected so that the final via (26) is tapered at an angle of less than about 45.degree. to the lower metal layer (6), and preferably about 30.degree.-45.degree., to enable a generally uniform width for the upper metallization (28) in the via (26).

Abstract: An adhesive mixture reworkably adheres electronic integrated circuit dies to hybrid microcircuit substrates, and includes a thermosetting epoxy resin. A thermoplastic resin additive allows the mixture to retain the high adhesive strength of the epoxy resin up to approximately 150.degree. C., or the upper limit of the operating and testing temperature range of the dies, and then soften sufficiently to enable defective dies to be removed at a temperature of preferably between 150.degree. C. and 200.degree. C. without damage to the substrate or adjacent dies.