| 摘要 |
1,185,347. Making lead frames for semiconductor devices. ADVALLOY Inc. 23 Oct., 1967 [9 Nov., 1966], No. 48061/67. Heading B3A. [Also in Division H1] A method of making a multiplicity of lead frames for semi-conductor devices comprises providing a flexible strip of metal, vapour depositing a narrower strip of conductive material along one surface thereof, and removing portions of the flexible strip at intervals to produce a repetitious lead frame pattern having integral frame sections with spaced apart lead portions extending within each frame section. Ferrous strip for the frames is checked for correct dimensions and physical properties, degreased and coiled on a steel core, on which the coil sides are straightened. The strip is electron beam heated to facilitate the vapour deposition of a layer of aluminium (38), Fig. 6 (not shown), which has a thickness of 100-300 micro inches. The clad strip 40 is passed through a stamping die, where it is perforated to the frame pattern. The strip of lead frames is checked with an optical comparator, any faulty frames are cut out and the cut ends of the strip spot welded together. The strip is again degreased, liquid vinyl masking 42 is sprayed on and cured in an infra red oven. It is then etched in a sodium hydroxide solution at 160-180‹ F while preferably subjected to ultrasonic vibrations to remove the unmasked aluminium. The etched strip is rinsed in tap water followed by deionized water and then passed through baths of diluted sulphuric acid, tap water, de-ionized water, alcohol and a drying oven before it is recoiled. The frame is next gold plated, preferably after the application of a layer of nickel plating. The vinyl masking is removed in an acetone tank and samples may be taken as it emerges therefrom for quality control purposes. Any remaining traces of vinyl are removed in a solution of five parts of water to one of sulphuric acid. Substrate units may be secured to the frames while they are still in strip form. The units are of ceramic, e.g. aluminium oxide, and are provided with a thin layer 34 of glass frit, which is heated until it becomes viscous and the leads 26 are pressed into it and become bonded thereto. |
