Does credit spread = liquidity risk premium + default risk premium

My understanding of credit spread is that it is the extra yield on backing assets (say corporate bonds) that is in excess of risk-free rates.

The SII matching adjustment = credit spread on matching assets - fundamental spread
The SII volatility adjustment = credit spread on a representative portfolio of assets.

In each case is the credit spread composed of a a liquidity risk premium + a default risk premium? Are there any other components to the credit spread?

 

Pretty much. Downgrade risk is another that is usually used. The FS is equal to portion of spread relating to expected defaults and downgrades. There could be other ways of breaking it down (which may include more risks), but illiquidity, defaults, and downgrades is how SII thinks about it.