Housing for an electronic circuit.

State of the art

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a housing for an electronic circuit provided with a connector, in particular for a control device electronics of an internal combustion engine of a vehicle, comprising a frame to which a printed circuit board having the electronic circuit is attached and a heat sink which is power components of the electronic circuit , And with a cover which surrounds the printed circuit board. Such a housing is known from EP-A-0 335 783.

Enclosures for electronic circuits exposed to environmental influences must close tightly. Known are complex constructions with seal inserts. German Patent Specification No. 25 46 334 discloses an electronic control unit with a housing which has a cooling frame. The cooling frame has a floor on which heating elements of a power stage are located. The cooling frame requires a relatively complicated metal profile. The known version is therefore quite cost-intensive. Since the cooling frame is covered by a hood-like cover, care must be taken during the design to ensure that the heat loss produced by the power stage is dissipated to such an extent that no unacceptable heating takes place.

Advantages of the invention

The object of the invention with the features mentioned in the main claim, on the other hand, has the advantage that, in a very simple, cost-effective design, a tightly closing housing is present which exhibits excellent heat dissipating properties for heat-generating components. It has an injection-molded plastic frame, into which at least one heat conducting web of at least one cooling body is formed. During manufacture, the heat conducting web is embedded in the plastic injection process, so that a gap-free and dense construction is ensured. One end of the heat conducting strip passes into a component mounting surface located inside the housing and the other end of the heat conducting strip is designed as a heat dissipation element lying outside the housing. The heat generated by components located on the component mounting surface is thus conducted directly out of the housing interior via the embedded heat conductor, so that excellent cooling properties are present. Outside the housing, a heat dissipation takes place through the heat dissipation element, preferably one-piece between the component mounting surface, the heat conducting element and the heat dissipation element, so that extremely small heat transfer resistances are present. Despite a tightly closing housing, a particularly effective heat dissipation is ensured in the manner mentioned. The plastic frame is a particularly simple and cost-effective solution. The heat sink preferably consists of metal.

A double function is adopted by the heat dissipating element when this is designed simultaneously as a housing fastening connection. In addition, the heat-dissipating properties are further improved since the heat which is transported by the heat-conducting web is absorbed or passed on via the fastening so that heat accumulation is avoided.

In particular, the housing mounting port is a flange provided with a bore for a mounting member. The heat supplied to the flange can therefore be transmitted to the support structure or the like via the fastening element. If the housing accommodates control electronics for an internal combustion engine, the heat generated by corresponding power semiconductors is derived, for example, from fastening elements, which are designed as threaded screws, to the chassis or body of the motor vehicle. This leads to excellent cooling properties. Since the electronic circuit must be connected to supply and data lines, a connector is provided. This can be fixed to the housing in a particularly simple manner if it is molded into the plastic frame. Therefore, not only the heat conducting bar of the cooler, but also the connector is encapsulated with plastic during the frame production. This also guarantees a gap-free transition to the plastic frame.

According to a preferred embodiment of the invention, the plastic frame has injection-molded projections which can be engaged in bores of the printed circuit board. The circuit board can thus be fixed to the plastic frame by means of a simple latching connection. The printed circuit board is assigned, during assembly, the snap projections integrally formed with the plastic frame in such a way that the latter are aligned with the bores. The latching is then performed. It is also conceivable for correspondingly designed snap projections to engage behind the peripheral edge edge of the printed circuit board.

In addition or alternatively, the printed circuit board can also be held by metal pins which are formed in the plastic frame and which engage in bores in the printed circuit board. The metal pins are preferably bent in such a way that slipping out of the bores is prevented. A particularly durable connection results when the metal pins preferably hold the printed circuit board up to the circuit board soldering process due to their deflections, and a bracing connection between the pins and the printed circuit board is then produced by the soldering process. For this purpose, the bores of the printed circuit board preferably have metallic or metallized regions, in particular conductor tracks, so that a highly loadable soldered connection can be formed.

The cover is preferably formed by two housing plastic shells, which are connected, preferably welded, to the upper and lower side of the plastic frame. A tightly closing housing is realized by the welding in a particularly simple manner. In one operation, for example, a welding can be performed in the plister process, wherein the two housing plastic shells are connected to the plastic frame by closing corresponding tools and heating the tool plungers.

In order to achieve a high electromagnetic compatibility (EMC), so that no radiation from the electronic circuit can be emitted from the electronic circuit, or interference to the interior, the housing plastic shells are preferably metallized.

drawing

The invention is explained in more detail below with reference to the figures. Show it:<ul><li>FIG. 1 is a perspective view of a housing frame made of plastic, to which a circuit board is attached and which has a molded-in heat sink and a molded-in connector,</li><li>FIG. 2 is a side view of a housing according to the invention with a cover consisting of two plastic shells,</li><li>FIG. 3 is a detail sectional view of the fastening zone of the housing plastic shells on the plastic frame and FIG</li><li>FIG. 4 shows a plastic frame section designed with a snap projection for fastening the printed circuit board.</li></ul>

DESCRIPTION OF EXEMPLARY EMBODIMENTS

According to FIGS. 1 and 2, the housing 1 according to the invention has a closed plastic frame 2 produced in injection molding. Two housing plastic shells 5 and 6 are fastened on the upper side 3 as well as the lower side 4 of the plastic frame 2. The housing plastic shell 5 forms a tub-shaped, relatively deep upper shell 7, and the housing plastic shell 6 is designed as likewise tub-shaped, but flatter, lower shells 8.

In the following, the plastic frame 2 will first be discussed. 1, four frame limbs 9, 10, 11 and 12, which are integrally connected to one another, are embedded in the frame limbs 10, a heat conducting web 13 of a cooling body 14 being embedded. The heat conducting web 13 is thus encapsulated with plastic during the production of the plastic frame 2. In the interior of the frame, the heat-conducting cross-piece 13 transitions at its one end 15 into an angled component mounting surface 16. The other end 17 of the heat conducting strip 13 is integrally connected to a heat dissipation element 18 located outside the plastic frame 12. The cooling element 14 shown in the exemplary embodiment of FIG. 1 has two heat conducting webs 13 leading in each case to the component mounting surface 16, both of which are shaped into the frame limbs 10 and each have a heat dissipation element 18 at their ends 17. The heat dissipation elements 18 each have a bore 19 for fastening elements so that they form fastening connections 20 for the plastic frame 2 and thus for the housing 1. By means of suitable fastening elements, which engage in the bores 19, a fixing can be made at a suitable mounting location.

For an attachment, flared tabs 21 which are provided with fastening bores 22 (see frame limbs 12 in FIG. 1) can also be formed on the plastic frame 2. Since the fastening connections 20 as well as the tabs 21 protrude beyond the frame periphery, these elements form flanges 23 ', which permit particularly simple assembly of the housing 1.

A printed circuit board 23 is attached to the frame legs 9, 10, 11 and 12 and has an electronic circuit, preferably electronic control electronics (not shown). The printed circuit board 23 is located either in the interior of the frame or is arranged on the lower side 4 of the plastic frame 2 in such a way that no frame parts project beyond the underside of the printed circuit board 23. For fastening, metal pins 24, which are shaped into the plastic frame 2, are provided, which engage in bores 25 of the printed circuit board 23 and hold the latter by bending on the underside of the printed circuit board. Metal / metallized areas, in particular conductor tracks, are assigned to the holes 25, so that the printed circuit board is retained by the bent metal pins 24 until a soldering process, and a fixed connection between the metal pins 24 and the printed circuit board 23 is established after the soldering.

Alternatively, however, it is also possible for the printed circuit board 23 to be held on the plastic frame 2 by means of screws.

Since the electronic circuit of the printed circuit board 23 has to be connected to supply lines and data lines, a connecting plug 26 is provided, which is embedded in the frame leg 11 of the plastic frame 2. In the production of the plastic frame 2, it is injection-molded with plastic, so that a gap-free seal is ensured. The contact lugs 27 of the contacts 28 of the connector 26 are suitably connected to the electronic circuit arranged on the printed circuit board 23, the latter having heat-generating power components (not shown) mounted on the component mounting surface 16 of the cooling body 14 with the lowest possible heat transfer resistance Are arranged.

2, it is alternatively also possible for the connector plug 26 to be arranged on the upper side 3 of the plastic frame 2, the upper shell 7 of the housing 1 having a shape-adapted edge contour 29, which sealingly engages the upper side of the connector plug 26.

Upper shell 7 and lower shell 8 have angled edge webs 30 and 31, respectively, which are circumferentially welded to the upper side 3 and the lower side 4 of the plastic frame 2, respectively. This is preferably carried out in one operation, in the so-called plister process, wherein the two housing plastic shells 5 and 6 are tightly welded to the plastic frame 2 by closing a suitable tool with a heated tool die.

In order to achieve high electromagnetic compatibility, the housing plastic shells 5 and 6 are provided with a metallization. For this purpose, they are either steamed with metal or equipped with a metal insert. They can be produced by injection molding or by thermoforming.

During the assembly, the subassemblies 8 are first inserted into a tool, then the plastic frame 2 with the printed circuit board 23 fixed to it is applied to the sub-bases 8 by means of suitable joining aids, and finally the housing is completed by applying the upper shell 7.

In the production of the frame / circuit board unit, so-called printed circuit boards are preferably used, on which several plastic frames 2 are accommodated so that several circuit boards can simultaneously be driven simultaneously via a soldering bath by means of the previously described metal pins. After the soldering, the individual printed circuit boards 23 with the plastic frames 2 fastened thereto are broken out or punched out of the circuit board slots. This makes the production particularly economical.

FIG. 3 shows that the plastic frame 2 can be designed in a step-like manner in the fastening region with the housing plastic shells 5 and 6. The upper shell 7 engages in one step 32 and the lower part 8 engages the other step 33. The connecting area between the shells and the frame is thereby formed in a particularly large area so that an absolutely tight connection is produced during welding. Welding can also be carried out instead of the welding.

4, it is also possible for the plastic frame 2 to have integrally molded-on snap-on projections 34. Each snap projection 34 has a web 35, which has a cop-shaped end region 36. Head region 36 and web 35 are provided with a slot 37. The printed circuit board 23 has bores 38 adapted to the diameter of the web 35. For fastening the printed circuit board 23, the printed circuit board 23 is pressed with its bores 38 onto the snap projections 34, the end 37 of the head 36 being reduced in diameter due to the slot 37 so that the web 35 can engage the bore 38. In the plugged-on state, the end region 36 springs apart again so that an obtuse to the printed circuit board 23 is produced.