Hughes Aircraft Company

Harold C Bowers

Haim Feigenbaum

William R Crumly

Christopher M Schreiber

Dennis F Elwell

An inexpensive arrangement for mounting multiple, closely spaced integrated circuit chips (18, 20, 22, 24) on a low temperature co-fired ceramic (LTCC) substrate (10) uses a mandrel-produced thin film decal (26) having patterns of interconnecting conductive traces (34, 46, 47) that connect to the fine pitch connecting pads (60) of the integrated circuit chips at one end and connect to the relatively coarse pitch connecting pads (50) of the low temperature co-fired ceramic substrate at the other end. The interconnect decal is formed independently of the LTCC substrate and is provided with chip connections at a pitch of about 0.004 inches. The interconnect pads of the decal are connected by conductive traces on the decal to the LTCC pads which have a pitch in the order of about 0.01 inches or greater. The decal, which is formed independently of the LTCC substrate, is connected to the substrate pads by one of several different electrically conductive adhesives, including silver loaded epoxy, Z-axis conductive epoxy and anisotropically and isotropically conductive epoxy or low melting temperature solder. The decal enables use of a 'fan-out' arrangement in which connections are routed under the chip.

Multichip module with a mandrel-produced interconnecting decal

A multi-level substrate (24) for mounting and interconnecting a number of integrated circuit chips (10) is formed of a stack of laminated sheets each comprising a conductive circuit layer (30,34,38,42,46) is laminated to a dielectric film (32,36,40,44,48). The sheets are formed by fully additive or semi-additive processes on a reusable mandrel and are interconnected to one another by raised features (78) on the circuit layer of one sheet that project through a hole (86) in the dielectric film of an adjacent sheet to contact a receiving area (88) of the circuit layer of the adjacent sheet. Integrated circuit chips (10) and other electrical components are mounted to the uppermost sheet and electrically connected thereto by means of wiring bonding (16) or a f lip-chip arrangement (150) in which chip pads (148) rest upon and contact raised features (146) of the circuit layer (140) of the uppermost sheet.

Multi chip module substrate

The helix (10) of the slow wave structure of a travelling wave tube is formed on a steel mandrel (12) by depositing the metal (44) of the helix on the mandrel and then coating the deposited metal with a photo resist (46). A laser light beam (24,26), having a cross section in the form of a short line, is focused upon the resist and moved linearly along the axis of the mandrel while the mandrel is rotated. The resulting helical exposure pattern on the photo resist is developed and the remainder of the undeveloped resist is then removed to expose a helical pattern (50,52) of deposited helix metal (44). The latter is subjected to etching processes so as to remove the deposited metal between the turns of the helical resist pattern (54,56), leaving a helix (44) of deposited metal on the mandrel underneath the resist. The resist is then removed and the mandrel etched away to leave the completed helix.

Growing community of inventors

Rancho Palos Verdes, CA, United States of America

Harold C Bowers