Their specialists look into a company's situation and identify a bond ranking for the company. Every ranking service has its own formula for determining threat and its own type of rating scale. Usually, rating scales are spelled out in letter grades, where an AAA score designates a safe, low-risk bond, and a D ranking designates a high-risk bond.federal government bonds, are generally low-yield bonds. You can depend upon getting a payout but that payment will be small. what is a bond finance. On the other side of the spectrum, you have what's not-so-affectionately called, which are low-rated, high-risk bonds. In order to entice financiers into purchasing these dangerous junk bonds, the providing companies promise high yields.