Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Patent
1997-03-10
1998-12-08
Sparks, Donald
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
29839, 361807, 439 762, H05K 702
Patent
active
058479376
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a method for making contact from high-current connecting elements of an electrical component to connecting conductors of an insulating mount, the connecting conductors, which are formed from sheet metal, being embedded in the plastic of the mount and projecting with connecting tabs from the surface of the mount, and flat connecting tongues of the component, resting parallel on the connecting tabs, being welded to them. In addition, the invention relates to an electrical assembly produced using this method.
In automobile technology and in other fields, it is common to combine one or more relays together with other components, such as diodes and resistors, on a small printed circuit board to form an assembly, a so-called module, which is provided with blade terminals to facilitate easy replacement. If the components in such a module, in particular relays, have to switch heavy currents, the etched and printed conductor tracks of conventional printed circuit boards are not sufficient to carry such high currents. In an attempt to solve this problem, it is known to produce the connecting conductors in the form of stamped sheet metal grids and to embed these grids in a printed circuit board which is produced as a molding, for example by injection molding. The connections between the components and the connecting conductors can in this case be produced via connecting tabs which are bent outward from the plane in which they are embedded in the injection-molded printed circuit board on a connection side. These tabs project a few millimetres from the printed circuit board. Since soft-solder joints between these connecting tabs and the component connections are not feasible because of the high current load and because the flux which is required in this case and damages contacts, attempts have been made to produce the contact via welded joints. However, since there is frequently little space available, the projecting connecting tabs can be only very small, i.e., around 2 to 3 mm. This means that the welding must take place in the immediate vicinity of the mount plastic. If, on the other hand, for environmental protection and cost reasons, a temperature-resistant plastic is not used for the mount, the previous welding methods produce a severe thermal load not only at the welding point but, because of the high conductivity, a severe thermal load on the adjacent mount plastic as well. This heating leads to thermal damage in the plastic, to undesirable formation of coatings on the contacts and, under some circumstances, to explosion of the melt at the welding point, if the liquefied plastic reaches this point.
Accordingly, the object of the present invention is to provide a method for making welded contact with heavy-current connecting elements of an electrical component, as well as an assembly produced using this method, the joint sections of the connecting conductors of the assembly mount and the connecting tongues of the component are designed such that the welded joint can be produced in the immediate vicinity of the plastic mount in a satisfactory manner while avoiding excessive thermal loading of the adjacent plastic mount.
SUMMARY OF THE INVENTION
The aforementioned object is achieved according to the an embodiment invention by a method of the type mentioned initially, where, in addition a tooth contour having one or more teeth is formed on the connecting tabs and the connecting tongues by means of material apertures. The cross section of these teeth is dimensioned such that, although a predetermined amount of welding energy which acts for a specific time duration admittedly welds the teeth which lie on one another of the welding tabs and of the connecting tongues, the thermal conduction via the teeth to the mount does not melt the mount plastic.
The welding energy is applied expediently by laser welding, plasma welding or, preferably, by protected arc welding. In the case of arc welding, it is especially expedient for thermal dissipation to take place at the
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patent: 3868770 (1975-03-01), Davis et al.
patent: 5023752 (1991-06-01), Detter et al.
patent: 5057026 (1991-10-01), Sawai et al.
patent: 5067905 (1991-11-01), Matsumoto et al.
patent: 5446626 (1995-08-01), Dittmann et al.
Cepa Frank
Vojta Erich
Siemens Aktiengesellschaft
Sparks Donald
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