Development of very thin (0.5 mmt) transfer-molded TAB packages

In the development of the new packages with 0.5 mm thickness, two-layer tapes with transferred gold bumps are used. Important factors which govern the assembly process stability and the package reliability, are elimination of die-tilting during transfer molding, reduction of warpage depending on the properties of molding compounds, and the structure and design of TAB tapes. Various molding compounds and tapes are tried. The viscosity is controlled by the content and shape of fillers. For TAB tapes, different copper layer thicknesses, and different locations of polyimide supporting bars are tried. For stable assembly processes, molding compounds with low viscosity (about 50 poise), and tapes with 44 μm thick copper layer produce a good balance between the top half and the bottom half of the package, and the least amount of warpage after molding. Package reliability is evaluated. The preconditioning tests, consisting of 20 cycles of temperature cycling, storage at 85°C/85% RH for 168 hours, and three amounts of IR reflow, result in no delaminations and no popcorn cracks. The new packages pass internal reliability guidelines of temperature cycle tests and pressure cooker tests