I have never broken a seam ripper. Maybe it's the type you are using. (?) The best seam ripper I have ever used is one by Clover with a large, smooth white handle. The second best is the one that came with my Bernina sewing machine. (you can buy one withOUT the machine lol) Both of these have sharp points that are thin enough to get under the stitches.
If I am frog-stitching (unsewing) a short area, I slip the tip of the seam ripper under every third stitch. Then I can pull a long thread from the opposite side. If I am unsewing a large area, I do as ponyriver does and use my rotary blade. It goes much faster.