Interior of ALMA Band 5 DSB SIS mixer. The mixer uses the end-piece configuration (Billade et al. 2013). The Nb-AlOx-Nb SIS junctions have a nominal area of 3 μm², a normal state resistance of R_n = 5 Ω (for twin-junction configuration Belitsky & Tarasov 1991), a quality factor R_j ∕R_n ≥ 20, and employ crystal quartz substrates of 90 μm thick. The insert on top shows the details of the Band 5 SIS mixer chip layout to scale. The SIS mixer chips were fabricated by GARD (Pavolotsky et al. 2011) using the Nanofabrication Laboratory Clean room facility at Chalmers University.