Many, if not most, banks have eliminated the "certificate of deposit" for IRAs. They give the participant a receipt for the deposit, nothing more. These are referred to as "book entry" deposits. (The "certificate" was a bank invention from the 1930's, it serves no purpose whether or not the account is an IRA.)
There never was a legal requirement that the customer sign a certificate of deposit, hence osucpa's question.
In this world you must be oh so smart or oh so pleasant. Well, for years I was smart. I recommend pleasant.