Image Number 3 for United States Patent #4906314.
A process for simultaneously applying precut protective swatches of precured polymer film to each semiconductor die on a wafer, whereby an indexed greater-than wafer-width strip of precured polyimide film having a heat-attach adhesive on its lower surface is die punched to remove essentially half of the scrap film, material between each of the individual portions on the film which dimensionally correspond to the areas of individual dies on a silicon wafer requiring protection. Each punched area corresponds to areas on the wafer die matrix that are to remain unprotected. Following this first punching, a strip of dimensionally-stable backing paper coated with heat-release adhesive is bonded to the upper surface of the polyimide strip in the region which will become matrices of swatches. The double layer strip is then subjected to second die-punch process which removes the remaining scrap film material between the individual swatches. Since the paper has been punched only once, the individual swatches--which are no longer continuously joined--are held in proper position by the paper backing strip. The double-layer strip is then wound onto a supply reel. The strip is then fed, on indexed rollers through an optically-aligning wafer positioning machine. When an entire wafer-size matrix arrives at the attachment location, the strip stops moving, at which point the machine optically positions a wafer immediately below the matrix, using the fiduciary marks on the wafer as reference points. A heated roller or pad presses the strip against the wafer, attaching the swatches comprising the matrix to each of the dies on the wafer and releasing the backing strip. The bare backing strip is wound up on a take-up reel as subsequent matrices move sequentially to the attachment position.