STUDY OF FLIP-CHIP BUMP INTERCONNECTION IN MM-WAVE GAAS MMIC

The flip-chip bump interconnection structure has become popular for pa ckaging of microwave and Millimeter (MM)-wave applications. The struct ure is expected to provide a higher-performance and lower-cost packagi ng method. This paper presents the results of an evaluation of flip-ch ip assembled RF devices. A co-planer line type GaAs MMIC (Monolithic M icrowave IC) was mounted on an Al2O3 substrate using the flip-chip bum p interconnection method, and the electrical performance (S-parameter) was measured and the reliability of the interconnection was tested. T he DC characteristics of a 30 GHz and 76 GHz band LNA (Low Noise Ampli fier) were the same between before and after mounting the MMIC. The RF performance of the device assembled MMIC was the same as that of the bare chip only without packaging; however, the influence of resin unde rfilling was confirmed. When epoxy resin was injected into the gap bet ween the bare chip and the substrate, the frequency band of the MMIC s hifted to the lower side. The reliability of the bump interconnection was excellent. The interconnection resistance did not change in a temp erature cycle (-55 degrees C to +125 degrees C, 1,500 cycle) test.