Robot manipulators perform various tasks such as assembly, material handling, welding, painting. In recent years collaborative robots have drawn much attention because they share working area with humans. Such robots require reliable joint brakes that works in an emergency situation. However, conventional joint brakes, which are mostly electromagnetic clutch brakes, are heavy, bulky and expensive, and thus are not appropriate for collaborative robots. To cope with this problem, we propose a joint brake which has stable braking performance based on a disk module with coil springs and a small-capacity solenoid. The joint brake has advantages in price and weight, so it can be widely applied to various types of robots. In this study, we designed and manufactured the proposed joint brake, and also verified the performance and durability through emergency stop experiments.