We present a new image of the 5.5 GHz radio emission from the extended Chandra Deep Field South .
Deep radio observations at 5.5 GHz were obtained in 2010 and presented in the first data release .
A further 76 hours of integration has since been obtained , nearly doubling the integration time .
This paper presents a new analysis of all the data .
The new image reaches 8.6 \mu Jy rms , an improvement of about 40 % in sensitivity .
We present a new catalogue of 5.5 GHz sources , identifying 212 source components , roughly 50 % more than were detected in the first data release .
Source counts derived from this sample are consistent with those reported in the literature for S _ { 5.5 GHz } > 0.1 mJy but significantly lower than published values in the lowest flux density bins ( S _ { 5.5 GHz } < 0.1 mJy ) , where we have more detected sources and improved statistical reliability .
The 5.5 GHz radio sources were matched to 1.4 GHz sources in the literature and we find a mean spectral index of -0.35 \pm 0.10 for S _ { 5.5 GHz } > 0.5 mJy , consistent with the flattening of the spectral index observed in 5 GHz sub-mJy samples .
The median spectral index of the whole sample is \alpha _ { med } = -0.58 , indicating that these observations may be starting to probe the star forming population .
However , even at the faintest levels ( 0.05 < S _ { 5.5 GHz } < 0.1 mJy ) , 39 % of the 5.5 GHz sources have flat or inverted radio spectra .
Four flux density measurements from our data , across the full 4.5 to 6.5 GHz bandwidth , are combined with those from literature and we find 10 % of sources ( S _ { 5.5 GHz } \gtrsim 0.1 mJy ) show significant curvature in their radio spectral energy distribution spanning 1.4 to 9 GHz .