| 摘要 |
PURPOSE:To prevent the unsatisfactory bonding caused by an oxide film present on the part where the bonding work will be performed by a method wherein an ethcing process is performed on the surface layer part of a lead using an acid solution or a basic solution. CONSTITUTION:After a degreasing process has been performed on a lead frame, composed of a heat discharging plate consisting of oxygen free high conductivity copper of 1.5mm. in thickness and a lead consisting of oxygen free high conductive copper which are formed in one body, the lead frame is soaked in an acid solution which is the mixture of ammon hydrofluoric acid (acidic activator) of 50g/l and concentrated sulfuric acid of 30ml/l for 40 seconds. Then, after the above has been picked up, it is washed clean and dried up. As a result, the surface of the lead is removed by approximately 3mum by etching. Then, a semiconductor element is fixed on a heat radiating plate using silver paste. Said lead frame is controlled at 300 deg.C, placed in a heating furnace which is maintained in a nitrogen atmosphere, and a gold wire of 25mumphi (metal thin wire) is bonded and the electrode of semiconductor element and the end part of the lead by performing a supersonic thermo-press welding bonding method. Besides, a very thin oxide film is formed on the surface of the lead when a bonding is performed, but a bonding can be performed completely on the gold wire lead and unsatisfactory strength is not generated at all. |
