I had a similar problem with my 5 month old pup Max. He was okay when we were around but if we left him to go out for a couple of hours in his exercise pen we would come back to a mess. There would be pieces of his pee pad torn to bits and thrown all over his pen. I was upset but at the same time I couldn't stop laughing because he had bits of pee pad hanging off his mouth, chin & ears. However it became less funny after 8 times of trying to clean it up.
I started to look up dog litter boxes. The two that caught my attention was Pet Loo and Ugodog. The problem I found with the Pet Loo was it was very expensive and they used artificial turf which can get messy and difficult to clean up after they poo. I settled on the Ugodog when was cheap and easy to clean. The good things is you can use newspaper to line the tray then it is covered by two plastic racks with holes. This allows the dog pee to drain to the newspapers and prevent the dog from tearing up the newspaper. So far it has been very good. Plus I save from not having to purchase anymore pee pads.
The Dogs Obedience Training Blog