All states are required to have child support enforcement procedures in place in order to get federal money. That being said, the stringency of enforcement varies. If you’re a deadbeat dad, you’re better off in Florida than Pennsylvania, for example.
As far as the legal standard, in Pennsylvania, contempt proceedings are (usually) automatically generated by the Commonwealth after 60 days of nonpayment. So, there’s a hearing scheduled, and if you don’t show up, the Sheriff comes and gets you. At the hearing, you are found in contempt if the contempt was “wilful”, that is, if you intentionally did not pay and you had the ability to do so.
If you are found in contempt, the hearing officer or judge will set “purge conditions”. If you fulfill these conditions you are “purged” of contempt. If not, you face further sanctions at a contempt review hearing.
It depends on the judge or hearing officer, but if you’ve been found in contempt and haven’t purged, or have been found in contempt more than once, you could be looking at jail.
Now, we don’t have “debtor’s prisons”. Child support delinquency, being civil, rather than criminal contempt, must allow for the prisoner to hold the key to the jail cell, so to speak. That is to say, the purge conditions for contempt must be such that the contemnor (guy in contempt) can meet them. So, for example, a purge condition might be “6 months in county jail or payment of $1,000 towards arrears, whichever comes first, then wage-attachable employment, regular monthly payments, etc.”
Another remedy, for the guy who is too good for employment, is sentencing him to work-release, where he’s confined except that he can leave to look for a job, and is released once he’s found one. Unfortunately, there’s quite a bit of backlog for these facilities, at least in PA.