Advanced Bond-Wire Interconnect Solution for Ultra-Broadband Applications Covering DC to 210 GHz

This article presents an advanced bond wire interconnect solution to enable heterogeneous system designs from dc up to and exceeding 210 GHz. A wideband transition is realized by tailoring the impedance of the bond wire transition to the feeding transmission lines. A novel adhesive film component combined with an aluminum sheet encapsulates the bond wires as part of the impedance tailoring. Furthermore, a 3-D-printed microstructure tool controls and fine-tunes the distance between the individual bond wires, improving impedance tailoring and achieving repeatable interconnects. To our knowledge, this is the first time a 3-D-printed structure has been employed to fabricate such transitions. The novel encapsulation method is demonstrated within two printed circuit board (PCB)-to-PCB interconnects with a length of 280 and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$380~\mu $ </tex-math></inline-formula>m, showing an insertion loss of less than 0.7 and 0.85 dB from dc to 170 GHz. A chip-to-chip interconnect using two alumina dummy substrates demonstrates the combination of the encapsulation with the fine-tuning of the bond wire distance. Integrating both methods, results in an insertion loss of less than 1 dB up to 211 GHz, while the return loss remains better than 15 dB up to 217 GHz. The proposed combination of fine-tuning and encapsulating bond wire interconnects enables high-density, low-loss, ultra-broadband packages with improved mechanical stability, thanks to the protection provided by the encapsulation. Furthermore, it ensures greater consistency during fabrication, improving efficiency and enabling ultra-broadband bond wire interconnects in mass production.