Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
1999-12-22
2001-03-20
Gandhi, Jayprakash N. (Department: 2841)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S633000, C361S640000, C361S765000, C361S785000, C439S065000, C439S069000, C257S723000, C257S724000, C174S524000, C174S1170FF, C174S260000, C174S261000
Reexamination Certificate
active
06205031
ABSTRACT:
German Patent No. 36 24 845 describes, a control unit for an electronic ignition system which has a device plug fastened on the housing of the control unit, the device plug being provided with a multiplicity of contact elements. Routed in an insulated manner through the housing, the contact elements of the device plug are connected within the housing to a control circuit arranged on a hybrid plate via bonding wires and are configured outside the housing in the shape of connector lugs that can be coupled with suitably formed counter-contact elements of a cable harness plug. A control unit of this type is normally installed in the engine compartment of a motor vehicle. The electrical connection to the engine components, e.g., the ignition coils, sensors arranged on the engine or adjustment elements or the connection to components arranged elsewhere in the motor vehicle is established via the cable harness plug.
The disadvantage with the conventional control unit describe above is that all components needed for the different functions of the control unit and the associated connecting printed circuit traces are arranged on the hybrid arranged in the control unit. Since some of these components, particularly power components or capacitors, are relatively large, they require much space on the top side of the hybrid. Moreover, for example, power output stages require low-resistance connection lines, the printed circuit traces being routed to these large components to some extent in an inconvenient manner, which degrades the electromagnetic compatibility, makes the printed circuit trace routing (layout) more difficult and results in an undesired enlargement of the hybrid. Components such as ignition transistors are soldered on to carrier modules which in turn are mounted and contacted on the substrate, thereby further increasing the space requirement. Now, however, there is an increasing demand for ever smaller control units which require little space in the engine compartment. Another difficulty is that the device plugs of the control units have more and more contact elements which must be contacted with connections of the circuit on the hybrid, so that it becomes more difficult, if the hybrid is reduced in size, to place all connections in the direct vicinity of the device plug on the hybrid. It is particularly disadvantageous that the connecting printed circuit traces of the power components must be designed to conduct higher power currents compared to the signal currents and thus have a larger cross-section so that the space requirement on the hybrid increases even further with the number of connecting printed circuit traces for power components.
Moreover, the heat generated by the power components on the housing of the control unit must be dissipated to prevent overheating. Since ceramic multilayer substrates such as LTCC substrates have poor thermal conductivity, this is generally achieved by providing thermal plated-through holes, known as vias, in the substrate. However, as the number of vias increases, the disentanglement of the printed circuit trace layout of the multilayer substrate becomes increasingly expensive.
SUMMARY OF THE INVENTION
A control unit according to the present invention generally avoids the disadvantages described above. With a second substrate arranged in the control unit housing on which power components are arranged having their connecting printed circuit traces, it is advantageously achieved that for device plugs having many pins with a large number of contact elements, a connection of the contact elements to the electronic circuit is simplified by a more flexible printed circuit trace layout. Large components such as tantalum capacitors, power components such as ignition transistors can be accommodated directly on the second substrate without an additional carrier module. The first substrate can thus be specified (made) smaller, which is desirable particularly with expensive LTCC (low temperature cofired ceramic) substrates. The possibility to manufacture the second substrate from a different material than the first substrate is particularly advantageous. For example, an LTCC substrate provided with a hybrid circuit can be used as the first substrate and a cost-effective DBC (direct bonded copper) substrate as the second substrate. Since manufacture of large-area, metallic printed circuit traces on the DBC substrate entails no difficulties, the power currents can be advantageously connected via the low-resistance connecting printed circuit traces of the DBC substrate to the power components accommodated there. This simplifies not only the printed circuit trace layout but also achieves an improvement in the electromagnetic compatibility (EMC protection). Moreover, there is also the possibility of manufacturing the second substrate from a material such as AlO
2
with good thermal conductivity, thereby achieving an improved heat dissipation of the heat produced by the power components without having to provide thermal vias for this purpose.
It is also advantageous, in an electronic control unit in which two device plugs are arranged having contact elements, some of which are designed to conduct power currents and which must be looped through the control unit without interconnecting components, to additionally provide on the second substrate lead-through printed circuit traces which directly connect the contact elements of the two plugs to one another. It is advantageously achieved in this manner that, for example, no electrical bus bars or cable connections that are expensive to connect are required to carry the power currents through the control unit.
Since the second substrate is arranged spatially separated from the first substrate in the control unit housing and the contact elements of the at least one device plug must be connected to both substrates, it is advantageous for bridging smaller distances to connect the connecting printed circuit traces and the lead-through printed circuit traces of the second substrate via bonding wires to the contact elements. The second substrate is arranged for this purpose in the vicinity of the power-current-carrying high-current contact elements of the at least one device plug.
Additionally, lines carrying power currents can also be provided advantageously on the second substrate, which, for example, are connected via bonding wires to contact surfaces on the first substrate, which contact surfaces are connected conductively in turn via a short path to a power component on the first substrate.
In addition, to simplify the printed circuit trace layout on the first substrate, it is advantageous to also arrange, besides the printed circuit traces conducting power currents, some printed circuit traces carrying signal currents on the second substrate. It can be achieved advantageously in this manner, for example, that the signal currents can be led from the contact elements of a device plug via the second substrate in a simple manner to further, remotely lying circuit parts of the first substrate.
It is also advantageous that large components such as tantalum capacitors can be accommodated directly on the second substrate and connected there to the ends of the printed circuit traces since such components would require too much space on the first substrate.
In addition, it is advantageous to provide as the second substrate a DBC (direct bonded copper) substrate which is economical and simple to manufacture and exhibits good thermal conductivity properties. Such substrates are especially well suited to heat dissipation of extreme loading peaks. Individual components such as chip diodes having the anode optionally on the back side or the front side can be accommodated with the aid of a bond option on the DBC substrate and can thus be used flexibly.
REFERENCES:
patent: 4074342 (1978-02-01), Honn et al.
patent: 4518211 (1985-05-01), Stepan et al.
patent: 5159532 (1992-10-01), Kilian et al.
patent: 5319243 (1994-06-01), Leicht et al.
patent: 5488256 (1996-01-01), Tsunoda
patent: 5581130 (1996-12-01), Boucheron
patent: 56103
Herzog Achim
Raica Thomas
Spachmann Jürgen
Wagner Uwe
Foster David
Gandhi Jayprakash N.
Kenyon & Kenyon
Robert & Bosch GmbH
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