In many mechatronic systems, e.g. in automotive sensorics, there is a requirement to integrate printed circuit boards into a housing. Since the electronics have to interface via connectors or other sensoric interfaces with the system periphery, the printed circuit board has to be fixated in the surrounding housing in a defined position. For accomplishing this object, a multitude of solutions is available in the state of the art.
A possibility to establish disengageable connections is using threaded connections. The disadvantage of this process is that the housing then has to be provided with a thread. When using plastic housings, a threaded metal insert is therefore often integrated during the injection molding process in order to obtain a load bearing thread. Consequently, manufacturing a respective connection is very expensive.
Among the non disengageable connection techniques, e.g. encasing the printed circuit board in the housing or so-called hot caulking are being used. During hot caulking, a rod shaped component, briefly also called pin, is run through a hole in the printed circuit board, so that it rests on a shoulder. Subsequently, the pin protruding beyond the thickness of the printed circuit board is deformed under thermal energy, so that the pin forms a rivet head for form locked fixation of the printed circuit board. A respective process using ultrasound energy for generating the necessary heat is described in DE 4215041 C3 (Siemens AG). A similar process is disclosed in JP 62064528 A (Toyota Motor Corp.), in which radiation energy is used to achieve the plastic state of one of the joining partners. The hot caulking processes according to the state of the art, however, have the disadvantage that forming the rivet head is being performed through a contact tool. When using such processes for hot caulking of plastic housings or printed circuit boards, this bears the risk of material sticking to the shaping tool.
Besides mounting the printed circuit board in the housing, also the media tight closing of the housing is an important part of the value creation process of mechatronic systems. As a process which creates particularly high quality welded connections, laser through transmission welding is industrially established. In this process, two joining partners, which can be welded through melting, are being combined, one of which has a high degree of optical transmission for the wavelength of the welding laser that has been used, and however, the other joining partner strongly absorbs this wavelength. In an overlapping assembly of both joining partners, the welding radiation can transmit through the joining partner facing it and is subsequently absorbed at the contact surface of the two components. The absorbing joining partner is being heated until both joining partners are melted in their contact area through heat conduction. In order to facilitate heat conduction between the joining partners, these are loaded with a compressing force. Since the widely used plastic materials have low heat conductivity, the induced welding energy remains in the joining zone for a certain period of time, depending on how the process is performed, so that material, which is still soft, mostly from the absorbing joining partner can be displaced out of the joining plane under the influence of the compression force. Under continued application of a compression force, the joining partners thus can perform a relative motion towards each other, in order to compensate for possible gaps in the weld. A respective process is disclosed e.g. in DE 102004004985 A1 (Laserquipment AG). The process described therein, like other current processes for closing housings, does not provide for a possibility to mount the enclosed printed circuit board, so that separate precursory process steps are necessary, which is disadvantageous.