Bonding electrical conductors

Abstract

Abstract A METHOD OF BONDING IS DESCRIBED, PARTICULARLY SUITABLE FOR BONDING THE CONDUCTORS OF AN INTEGRATED CIRCUIT MODULE, FOR EXAMPLE, TO A SET OF CONDUCTORS SUPPORTED ON A SUBSTRATE. IN CONVENTIONAL TECHNIQUES A MODULE IS COMPRESSION WELDED TO A PATTERN OF PROTUBERANCES FORMED ON A SET OF CONDUCTORS, AND IT IS FREQUENTLY FOUND THAT UNDER NORMAL MANUFACTURING TOLERANCES A HIGH PROPORTION OF WELD FAILURES MAY BE EXPECTED. THE PRESENT DISCLOSURE ENVISAGES THE FORMATION OF PILLARS OF A SOFT, READILY DEFORMABLE MATERIAL, SUCH AS A TIN/LEAD EUTECTIC, BETWEEN THE CONDUCTORS SO THAT DURING COMPRESSION WELDING THE PILLARS ARE DEFORMED UNDER THE WELDING PRESSURE, THUS ENABLING ALL THE CONDUCTORS TO MAKE GOOD ELECTRICAL CONTACT WITH THEIR RESPECTIVE PILLARS, DESPITE ANY DISCREPANCIES IN HEIGHT THAT MAY EXIT AS BETWEEN THE PILLARS. THE USE OF AN OXIDIZABLE MATERIAL, SUCH AS THE TIN/LEAD EUTECTIC AS NOTED ABOVE, COULD RESULT IN THE FORMATION OF AN OXIDE LAYER WHICH WOULD PREVENT A GOOD ELECTRICALLY CONDUCTIVE BONDING BEING ESTABLISHED, AND IN THIS CASE IT IS PROPOSED TO FORM A LAYER OF AN OXIDATION-RESISTANT MATERIAL, SUCH AS GOLD, OVER ANY EXPOSED CONTACTING SURFACE OF A PILLAR. THIS LAYER, BESIDES BEING ITSELF RESISTANT TO OXIDATION PREFERABLY ALSO PRESENTS A HARD SURFACE TO THE CONDUCTOR TO WHICH IT IS TO BE BONDED AND THE WELDING PRESSUR IS SUFFICIENT TO ENSURE THAT THIS SURFACE BREAKS THROUGH ANY OXIDE LAYER PRESENT ON THE SURFACE OF THE CONDUCTOR, A FEATURE OF IMPORTANCE WHERE THE CONDUCTOR IS, FOR EXAMPLE, OF ALUMINUM.

Inventors

• 👤 Kenneth Charles Arthur Bingham
• 👤 Alan George Albert Gillingham

Bibliographic Details