Typically the incline bench can have variable positions between 30 and 45 degrees. As the angle increases the more activation of the upper pectoralis major with assistance from anterior deltoid and triceps brachii. The NCSA recommends a 90 degree flexion at the elbow when performing bench press. However, some people may not have the shoulder mobility to achieve this. In this case you would want to modify the depth of the action.
I would also suggest doing some progressive shoulder function exercises. Lee Burton, ATC, CSCS is a good source. Also you may want to refer to an article by Louver titled Influence of bench angle on upper extremity muscular activation during bench press exercise.