Diode array and method for producing a diode array

A diode arrangement includes a diode and two electrodes. Each electrode is connected to the diode in an electrically conductive manner via a soldered connection on one of two oppositely arranged contact surfaces of the diode. The contact surfaces of the diode are formed substantially by the surfaces of a lower side and an upper side of the diode and are contacted with the contact extensions of the electrodes via the soldered connection. The contact extensions forming counter contact surfaces are substantially congruent with the contact surfaces of the diode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application represents the national stage entry of PCT International Application No. PCT/DE2010/001082 filed on Sep. 15, 2010 and claims the benefit of German Patent Application No. DE 10 2009 041 641.2 filed Sep. 17, 2009. The contents of both of these applications are hereby incorporated by reference as if set forth in their entirety herein

Not applicable.

FIELD OF THE INVENTION

The present invention relates to a diode arrangement comprising a diode and two electrodes which are each connected to the diode in an electrically conductive manner via a soldered connection on one of two oppositely arranged contact surfaces of said diode, wherein the contact surfaces of the diode are formed substantially by the surfaces of a lower side and an upper side of the diode and are contacted with contact extensions of the electrodes via the soldered connection, said contact extensions forming counter contact surfaces being substantially congruent with the contact surfaces of the diode. Moreover, the present invention relates to a method for the production of such a diode arrangement.

BACKGROUND OF THE INVENTION

Diode arrangements of the type cited at the beginning are employed for instance as components of solar cells and as so-called “power diodes” are exposed to high electric currents. Basically, such diode arrangements are suitable for all fields of application where high output powers are to be rendered by the diode, so that corresponding cooling measures are to be taken to ensure trouble-free operation of the diodes.

BRIEF SUMMARY OF THE INVENTION

Thus, it is an object of the present invention to suggest a diode arrangement which is characterized by a particularly high operating reliability even in the case of a high power density. It is another object of the invention to suggest a method which makes it possible to efficiently produce such diode arrangements which ensure operational reliability also when subjected to higher temperatures.

In the inventive diode arrangement, the contact surfaces of the diode are formed substantially by the surfaces of a lower side and an upper side of the diode and are contacted with contact extensions of the electrodes via the soldered connection, said contact extensions forming counter contact surfaces being substantially congruent with the contact surfaces of the diode.

Hence, in the diode arrangement according to the invention, the entire surface of a lower side or an upper side of the diode is available for contacting with the electrodes. Thus it is possible to configure the transition resistance between the diode and the electrodes so as to be as low as possible. Due to the contacting of the contact surfaces of the diode with contact extensions of the electrodes, which form substantially congruent counter contact surfaces, it is ensured that the surface area of the soldered connection does not extend beyond the contact surfaces of the diode, such that, as a result, the risk of short-circuits occurring between the lower side and the upper side of the electrode is largely minimized. Due to the aspect that contact extensions are provided at the electrodes for contacting with the diode, it is possible to form the electrodes in any optional manner in those areas which extend beyond the contact extensions, and to thereby form in particular electrodes with a large surface area, which enable a particularly good heat dissipation from the diode, respectively from the soldered connections between the diode and the electrodes.

It proves to be particularly advantageous in the production of the diode arrangement if the electrodes are formed by segments of an electrode substrate made of a conductor material, the contact side of said electrode substrate being furnished with a coating of a solder material barrier having a solder material contact layer applied thereon.

To produce the electrodes it is thus possible to provide a semi-finished product having coatings which are applied for instance by means of a plating process and which simplify the production of a soldered connection with defined properties. In particular, the formation of a solder material barrier provides for a diffusion barrier, which on the one hand enables the production of a soldered connection of a defined composition and on the other hand enhances the production of a soldered connection with a defined height, in order to thereby enable reproducible connecting dimensions of the diode arrangement, which is defined for instance by the distance a between the electrodes being disposed on different surfaces of the diode.

It has proven to be particularly advantageous if the electrode substrate is formed of copper or a copper alloy, if the solder material barrier comprises nickel or a nickel alloy and if the solder material contact layer comprises tin or a tin alloy.

In the inventive method, contact extensions formed at the electrodes and forming counter contact surfaces, the surface area of which substantially conforms to a lower side and an upper side of the diode, are furnished with a solder material coating, and in order to from a soldered connection the diode is subsequently disposed in a sandwich arrangement between the electrodes in such a manner that the counter contact surfaces of the contact extensions are disposed so as to overlap with the contact surfaces being formed by the lower side or the upper side of the diode.

It is particularly advantageous if a reflow of the solder material coating applied onto the contact extensions of the electrodes is performed already prior to the production of the sandwich arrangement and the formation of the soldered connection, particularly in order to be able to largely preclude the occurring of short-circuits between the lower side and the upper side of the diode during the subsequent formation of the soldered connection.

It is particularly advantageous for an automated production of the diode arrangement if the production of the sandwich arrangement is performed in two phases in such a manner that in a first phase, a first overlapping arrangement is produced between the counter contact surface of the first electrode and the first contact surface of the diode, and subsequently in a second phase, a second overlapping arrangement is produced between the counter contact surface of the second electrode and the second contact surface of the diode.

In this context, it has proven to be advantageous, in particular in terms of handling the elements in the production of the sandwich arrangement, if the first overlapping arrangement is produced by applying the diode with the first contact surface thereof onto the counter contact surface of the first electrode, and if the second overlapping arrangement is subsequently produced by applying the second electrode with the counter contact surface thereof onto the second contact surface of the diode.

In a possible alternative of the method, the soldered connection is formed subsequent to the production of the sandwich arrangement.

It is particularly advantageous if the formation of the soldered connection is performed in two phases such that a first soldered connection is produced subsequent to the production of the first overlapping arrangement, and a second soldered connection is produced subsequent to the production of the second overlapping arrangement.

If a rear side of the contact extension of at least one electrode is subjected to the action of laser energy in order to form the soldered connection, the relative arrangement of the diode and of the electrode-preserving sandwich arrangement thus defined can be maintained unchanged during the formation of the soldered connection.

If, in order to provide the electrodes for a subsequent formation of the sandwich arrangement, the electrodes are formed by removing segments of a strip-shaped electrode substrate such that subsequent to the removal of the segments the strip-shaped configuration of the electrode substrate is maintained, a semi-finished product can be used for the production, respectively provision of the electrodes, which is formed so as to be continuous and in particular is not required to have a structuring for producing the electrodes.

DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS

Hereinafter, a preferred embodiment of the diode arrangement as well as a method for producing a diode arrangement are described in greater detail by way of example with reference to the drawings.

FIG. 1shows a diode arrangement10being formed in a stacked arrangement or sandwich arrangement44, comprising a diode11being disposed between two contact extensions12,13, which are each formed at a free contact end of strip-shaped electrodes14,15.

As can be seen in particular fromFIG. 2, the electrodes14,15at their ends being diametrically opposed to the contact extensions12,13have further contact extensions16,17serving for the electrically conductive connection of the diode arrangement10with further terminal devices.

As can also be seen fromFIG. 1, the stacked arrangement having a height a produces a contact structure between the contact extensions12,13of the electrodes14,15, said contact structure having a diode contact surface20,21on an upper side18and a lower side19of the diode11, respectively, which diode contact surface can be configured as a metallic terminal face of a blank diode, so that the diode11illustrated inFIG. 1for instance may be a diode which has been separated from a waver assembly by means of sawing directly before being disposed in the stacked arrangement illustrated inFIG. 1, wherein in particular the diode contact surfaces20,21have not been prepared yet, i.e. they are still in an unprocessed state.

On each of the diode contact surfaces20,21provision is made for a soldered connection22,23formed by a molten solder material which forms an electrically conductive and mechanically resistant connection between the diode contact surfaces20,21and the counter contact surfaces24,25of the contact extensions12,13.

As is apparent from a combined view ofFIGS. 1 and 2, the dimensions of the contact extensions12,13and the diode11are adjusted to each other such that, as can be seen in particular fromFIG. 2, a congruent arrangement is realized resulting in a substantially flush arrangement of the contact structure in the stacking direction26illustrated inFIG. 1.

Moreover,FIGS. 1 and 2clearly show that both the diode contact surfaces20,21and the counter contact surfaces24,25formed by the contact extensions12,13have a congruent surface area or dimension.

Said adjusted surface area in combination with the capillary forces arising in the region of the soldered connections22,23in response to a remelting process of the solder material for forming the soldered connections22,23prevents the formation of solder material bridges between the upper side18and the lower side19of the diode11during the formation of the soldered connection.

As can be seen fromFIG. 2, the electrodes14,15between their contact extensions12and16, respectively13and17, starting from the contact extensions12,13serving for contacting with the diode11have an increasing width b, wherein the contact extensions16,17are of a smaller configuration. As a result, on the one hand it is ensured, as already previously described in extenso, that a formation of soldered connections22,23in the region of the diode11is enabled without the risk of short-circuits. On the other hand, it is still possible to form a large cooling surface by the incidentally wide dimensioning of the electrodes14,15, which during power operation of the diode11counteracts thermal overstressing of the diode11or of the soldered connections22,23.

Hereinafter, a possible method for producing the diode arrangement shown inFIGS. 1 and 2will be explained in greater detail with reference toFIG. 3. For this purpose,FIG. 3inter alia shows a device for the production of diode arrangements10, comprising a supply device27that serves for supplying a strip-shaped electrode substrate and by means of which two electrode substrate strips28,29are continuously supplied via a winding device30and an unwinding device31in the supply direction32.

The electrode substrate strips28,29in the present case have a multilayered structure having a copper strip which is furnished with a solder material barrier acting as a diffusion barrier and having a solder material contact layer applied thereon. Preferably, the afore-described structure comprising a solder material barrier having a solder material contact layer formed thereon is disposed both on the lower side and on the upper side of the electrode substrate strips.

As is also apparent fromFIG. 3, a rotary indexing table34is a component of the device for producing the diode arrangements10, wherein in the indexing mode said indexing table34is advanced in the direction of rotation33and by means of a transfer device35transfers electrodes14,15taken over from the supply device27to different devices to be explained hereinafter.

The transfer device35is furnished with a punching device (not shown here in greater detail), which separates electrodes14,15from the continuously uniformly configured electrode substrate strips28,29by means of punching and transfers the electrodes to a respective electrode receptacle36,37formed on the rotary indexing table34. In detail, in the method exemplarily illustrated inFIG. 3, for this purpose a plurality of electrodes14are firstly removed from the electrode substrate strip28and are transferred into the electrode receptacle36being assigned to the periphery of the rotary indexing table34, which in the case at hand results in that four electrodes14are disposed in a row in the electrode receptacle36.

Subsequently, electrodes15are separated from the electrode substrate strip29by means of punching and are transferred into the electrode receptacle37which is disposed adjacent to the electrode receptacle36, in such a manner that four electrodes15are disposed in a row in the electrode receptacle37. Subsequently, the electrodes14and15received in the electrode receptacles36,37are transferred to a solder material application device38by executing a rotary indexing movement in the direction of rotation33. In the solder material application device38, solder material is applied onto the contact extensions12,13of the electrodes14,15, which are not shown in detail inFIG. 3, wherein said application can be performed for instance by applying a solder material deposit in the form of a solder paste. By the same token, solder material deposits can be applied in an at least partially molten state onto the contact extensions12,13of the electrodes14,15.

Subsequently, in response to the execution of another rotary indexing movement in the direction of rotation33, the electrodes14,15are transferred to a remelting device39which can be composed for instance of a laser arrangement, in particular a laser diode arrangement, wherein four laser diodes40are disposed in a row corresponding to the electrodes14,15received in the electrode receptacles36,37. By means of a radial advance movement41of the laser diodes40, said laser diodes can be positioned so as to overlap with the solder material deposits disposed on the electrodes14, such that a rear side of the solder material deposits can be subjected to the action of laser energy from below the rotary indexing table34through the electrodes14.

Subsequent to the melting of the solder material deposits on the electrodes14, four diodes11disposed in a row are applied onto the molten solder material deposits of the electrodes14with the aid of a supply device48.

Subsequent to another rotary indexing movement, the electrodes14being furnished with the diodes11are transferred to another remelting device42which is essentially formed like the previously described remelting device39and makes it possible to subject a rear side of the electrodes14to the action of laser energy from a position below the rotary indexing table34, resulting in the formation of a first soldered connection22between the electrodes14and the diodes11(FIG. 1).

Subsequent to the transfer of the electrodes14and15to a stacking device43, the electrodes15are transferred into a stacked arrangement with the electrodes14by performing a change of direction such that the relative arrangement of the electrodes14and15as illustrated inFIG. 1is realized. For the purpose of fixing the stacked arrangement44and producing the diode arrangement10illustrated inFIG. 1, subsequent to the execution of another rotary indexing movement into the direction of rotation33, the stacked arrangement44is transferred to another remelting device45which forms the further soldered connection23(FIG. 1) by means of remelting the solder material deposits disposed on the electrodes15. In this process, a corresponding impingement with laser energy can be performed optionally from below the rotary indexing table34or also from above of the rotary indexing table34, wherein in the first case, the production of the soldered connection23is performed with the aid of an energy flux via the electrodes14, the soldered connections22and the diodes11, and in the second case, a comparatively more direct energy impingement is performed via the electrodes15. However, irrespective of the direction of impingement, in any case an energy impingement is performed from a rear side via the respective electrodes14or15.

Subsequent to the transfer of the completed diode arrangements10, the diode arrangements can be removed from the electrode receptacle37by means of a removal device46and can be transferred to a storage arrangement47which can serve as a removal reservoir for further processing of the diode arrangements10.