| abstract |
A bonded structure comprising the physical and electrical connections between an integrated circuit element and substrate using a composite bump comprised of a single polymer body of low Young's Modulus and a conductive metal coating. When the bonded structure is formed the composite bump is deformed and the low Young's Modulus of the polymer body allows a very reliable bonded structure with very low bonding force. Due to the low Young's Modulus there is little tendency to separate the connections after the bonded structure is formed. The bond can be formed using thermocompression bonding, ultrasonic bonding, application of heat or application of light. The bond can also be formed using a non conductive adhesive between the integrated circuit element and the substrate. The bond can also be formed with a conductive adhesive coating on the composite bump. The polymer body may be covered by a conductive metal coating formed at the input/output pads of an integrated circuit element or substrate. The composite bump is formed using material deposition, lithography, and etching techniques. A layer of soldering metal can be formed on the composite bumps if this is desired for subsepuent processing. n It is possible to use a conductive barrier metal coating covering the polymer body and a soldering metal coating covering the conductive barrier metal coating. When the bonded structure is formed the composite bump is deformed and the low Young's Modulus of the polymer body allows a very reliable bonded structure with very low bonding force. Due to the low Young's Modulus there is little stress tending to break the solder joint after the bonded structure is formed. The bond is formed using a soldering process so that the soldering metal forms a conductive adhesive between the composite bumps and either the substrate input/output pads or the integrated circuit element input/output pads. |