If it's a purchase, WI law provides that the spouse does not have to sign at all even if the purchase is of a homestead.
At refinance, both spouses must sign.
We use the following language on page one of a refinance of homestead property:
(Spouse’s Name) is a “cosigner” under Section 13, but notwithstanding anything else in this Mortgage, did not execute the Note.
Then the spouse signs on the last page of the mortgage and is notarized as doing so too.
Don't forget under WI law the legal must identify the property as homestead property.