Abstract: Device for thermal joining of a heat exchanger for a motor vehicle. The device has a first and a second locating elements and at least one heat source. The locating elements are designed with at least one thermal insulation and with mutually aligned contact surfaces for joining an object between them. At least one locating element is designed movably in relation to the other locating element. At least the first locating element has at least one thermal mass, which is heatable by means of the heat source. The second locating element has a support element with a contact surface for the object, while at least a first thermal mass of the first locating element has a contact surface for heating the object via heat conduction. Method for thermal joining with the device. The use of the method for manufacturing a heat exchanger of plate elements for a motor vehicle.