This followed the surprise announcement of new stimulus measures in April. These included an increase in the ECB's monthly asset purchases and an extension in the program to include corporate bonds from June.
From next month, UBS estimates 1,289 corporate bonds with an outstanding value of 756 billion euros will be eligible for purchase. In a report on Friday, the bank suggested 12 billion euros or 15 percent of the ECB's total monthly purchases would be corporate bonds, with a split of around 30:70 between the primary and the secondary market.
UBS said the impact on corporate bond pricing would be "negligible."
The purchases will be carried out on the ECB's behalf by the national banks of Belgium, Germany, Spain, France, Italy and Finland. They will take place in both the primary and secondary markets. To be eligible, instruments must be denominated in euros and have a credit rating of at least "BBB-" or equivalent; they must also have a remaining maturity of between six months and 30 years at the time of purchase.