HIGH-FREQUENCY MEASUREMENTS AND SIMULATIONS ON WIRE-BONDED MODULES ONTHE SEQUENTIAL BUILDUP BOARDS (SBUS)

This paper presents the results from high-frequency measurements and s imulations on sequential build-up boards (SBU's), A high-frequency tes t pattern was designed in order to investigate the high-frequency prop erties of SBU's, The SBU boards were supplied by four different manufa cturers. The test boards contained patterns for cross talk, impedance matching, stray capacitance, and wire-bonding. The test boards consist ed of doublesided FR-4 core with two built-up layers on each side. How ever, the high-frequency test board was only on one side of the core. The test patterns were located in layer five and layer six. Two differ ent line spacings between signal track and victim track, 50 and 100 mu m, were considered, The S-parameters were measured on a network analy zer in the frequency range 45 MHz-10 GHz, In the time domain experimen t, the near-end and the far-end response in the victim track was measu red. All the simulations were carried out, using the simulation progra ms P-Spice, HP MDS, and a two-dimensional (2-D) finite difference prog ram. Impedance measurements and simulations were performed in layer fi ve and six with conductor widths corresponding to characteristic imped ances of 50 and 55 Omega. The line widths ranged from 40 to 65 mu m in layer five and 150 to 200 mu m in layer six, Reference tracks were de signed in order to estimate conductor and dielectric losses. In the wi re-bonding test, an isotropically conductive adhesive joint (TCA) was investigated. A silicon test chip was mounted on the SBU-board. The re sults show that cross talk measurements and simulations agreed closely in the frequency range 45 MHz-10 GHz, Small differences between the t hree Investigated dielectrics were obtained. The results show that die lectric loss is a limiting factor in the high-frequency range. For a t est-pattern length of 30 mm, the high-frequency limit (based on -3 dB transmission losses), was 2-3 GHz in layer six and 3-4 GHz In layer fi ve, The measured characteristic impedances ranged from 44-63 Omega, de pending on the manufacturer of the SBU-board.