Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Patent
1991-05-16
1993-10-19
Picard, Leo P.
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
361398, 361751, H05K 100
Patent
active
052548112
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
This invention relates to a hybrid bonding article which can be provided in arrangements suitable for use in tape-automated bonding (TAB) of semiconductor microcircuits (microchips).
INTRODUCTION TO INVENTION
Known TAB devices have a structure akin to that shown schematically in the accompanying sketch A. A polymer tape A1 having edge sprocket holes A2 for feeding the tape in automated bonding equipment carries a series of arrays (one shown) of conductive tracks A3 arranged in a pattern suitable for bonding their inner ends A4 to the bonding sites of a microchip (not shown). The tape A1 is cut away under the ends A4 of the tracks so that the ends project as unsupported "flangers" over the cut-away space A5. Bonding is effected by bending the flangers into the space A5 to make contact with the chip positioned against the opposite side of the tape from that carrying the tracks. This is followed by bonding by known techniques which often require the chip bonding sites to "bumped" with bonding material, e.g. solder.
The present invention can avoid such disadvantageous "bumping" processes.
Another form of TAB device known as "area TAB" is described in U.S. Pat. Nos. 3,832,769, 3,868,724 and 4,472,876, in which the conductive tracks do not project as "fingers", but instead are connected to solid metal terminals formed in holes passing through the tape material. The terminals project from the surface of the tape remote from the tracks and can therefore make electrical contact with bonding sites on micro chips or other devices brought into contact therewith. The reliability of the electrical contacts thus established may be limited by the relative rigidity of the terminals hindering their ability to conform to variations in height of the bonding sites on the chip, especially as increasing miniaturization and complexity of microchips requires bonding sites in central areas of the chip as well as around its edges.
SUMMARY OF THE INVENTION
The present invention alleviates these problems by means of an ingenious hybrid form of TAB article, and accordingly provides in one of its aspects a tape-automated bonding article comprising a carrier sheet carrying at least one array of electrically conductive tracks having ends arranged for bonding to a microcircuit device, each such bondable track end being supported by the carrier sheet material and being electrically connected to a surface region of the carrier material not carrying that track end by a tubular formation of electrically conductive material within, preferably plated within, at least one connecting hole of diameter less than 200 micrometers, preferably less than 100 micrometers, more preferably less than 50 micrometers. The holes will usually pass more or less straight through the sheet to its opposite surface (i.e., the "surface region not carrying the track end"), but may be sloping or indirect (e.g. curved) if desired. Preferably, the tubular conductive material in the connecting hole or holes projects beyond the said surface region so as to facilitate bonding to the microcircuit, and this may be achieved by removing one or more layers from the carrier sheet after plating (or other provision) of the conductive material in the connecting hole.
The use of a tubular formation of conductive material (preferably metal) in the connecting holes has considerable advantages over the known solid metal terminals. The tubes may crumple when compressed longitudinally against a microchip or other device, thus taking up irregularities without the major deviation from the longitudinal axis which normally results when solid columns or wires are so compressed. Also, solder or other fusible material may be provided at or within the ends (at least) of the tubes to facilitate thermal bonding and electrical connection.
This hybrid TAB article according to the invention may be constructed with cut-away "fingers" of the carrier sheet material supporting the conductive track ends to be bonded, thus providing a "fingered" construction corresponding to, but wi
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patent: 4949158 (1990-08-01), Ueda
Ludden Michael J.
Nyholm Peter
Burkard Herbert G.
Korka Trinidad
Novack Sheri M.
Picard Leo P.
Raychem Limited
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