Carrier for an LED

Abstract

A carrier for an LED is disclosed. In an embodiment, the carrier includes a main body, wherein the carrier has an upper side on which a first contact area for attaching an LED is arranged, and wherein a protective device for protecting the LED from electrostatic discharges is integrated in the main body.

Claims

1-16. (canceled)

17. A carrier comprising: a main body, wherein the carrier has an upper side on which a first contact area for attaching an LED is arranged, and wherein a protective device for protecting the LED from electrostatic discharges is integrated in the main body.

18. The carrier according to claim 17, further comprising a second contact area being arranged on the upper side of the carrier, wherein the first and second contact areas are arranged in such a way that a central region that is free from contact areas is located between the first and second contact areas on the upper side of the carrier, and wherein at least one thermal via is located in the main body that connects the central region of the upper side of the carrier to an underside of the carrier.

19. The carrier according to claim 18, wherein regions of the upper side in which the first and second contact areas are arranged are free from vias.

20. The carrier according to claim 17, wherein the first contact area has a coplanarity of less than 3 m.

21. The carrier according to claim 17, wherein the first contact area has a surface roughness of less than 1 m.

22. The carrier according to claim 17, wherein the first contact area has a coplanarity of less than 3 m and a surface roughness of less than 1 m.

23. The carrier according to claim 17, wherein the main body comprises a ceramic material.

24. The carrier according to claim 17, wherein the protective device has internal electrodes integrated in the main body, and wherein the internal electrodes are aligned parallel to the upper side of the carrier.

25. The carrier according to claim 24, wherein the protective device is designed in such a way that a current flows through the protective device when a voltage between the internal electrodes exceeds a predetermined value.

26. The carrier according to claim 17, wherein the carrier has metallic areas for electrical contacting of the LED, which are arranged on the main body and extend from an upper side of the main body to an underside of the main body, which is arranged opposite from the upper side.

27. The carrier according to claim 26, wherein the metallic areas have a layered structure comprising silver, nickel and gold or silver, nickel and tin.

28. The carrier according to claim 17, further comprising a heat spreader having metallic plates is integrated in the main body.

29. The carrier according to claim 28, wherein the metallic plates of the heat spreader are aligned parallel to the upper side of the carrier.

30. The carrier according to claim 28, wherein the carrier has metallic areas for electrical contacting of the LED, which are arranged on the main body and extend from an upper side of the main body to an underside of the main body, which is arranged opposite from the upper side, and wherein the metallic plates of the heat spreader are in contact with the metallic areas.

31. The carrier according to claim 28, wherein the protective device has internal electrodes integrated in the main body, and wherein the heat spreader is arranged closer to an upper side of the carrier than the integrated internal electrodes are.

32. The carrier according to claim 17, wherein the carrier is a surface mounted device, which is suitable for being soldered on a printed circuit board.

33. The carrier according to claim 17, wherein the carrier has contact areas for attaching multiple LEDs.

34. The carrier according to claim 17, wherein the first contact area has a stacked structure comprising at least one gold layer and at least one tin layer, wherein heights of the at least one gold layer and the at least one tin layer are chosen such that in the stacked structure comprises a ratio of gold to tin of between 75:25 and 85:15.

35. A carrier comprising: a main body, wherein the carrier has an upper side, on which at least one contact area for attaching an LED is arranged, wherein a protective device for protecting the LED from electrostatic discharges is integrated in the main body, and wherein the at least one contact area has a coplanarity of less than 3 m or wherein the at least one contact area has a surface roughness of less than 1 m.

36. A carrier comprising: a main body, wherein the carrier has an upper side, on which at least one contact area for attaching an LED is arranged, wherein a protective device for protecting the LED from electrostatic discharges is integrated in the main body, and wherein the at least one contact area has a stacked structure, which has at least one gold layer and at least one tin layer, wherein heights of the at least one gold layer and the at least one tin layer is chosen such that in the stacked structure comprises a ratio of gold to tin of between 75:25 and 85:15.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The invention is explained in more detail below on the basis of the figures.

[0039] FIG. 1 shows a cross section through a carrier according to a first exemplary embodiment.

[0040] FIG. 2 shows a plan view of an upper side of the carrier according to the first exemplary embodiment.

[0041] FIG. 3 shows a plan view of an underside of the carrier according to the first exemplary embodiment.

[0042] FIG. 4 shows a side view of the carrier according to the first exemplary embodiment.

[0043] FIG. 5 shows a carrier according to a second exemplary embodiment.

[0044] FIGS. 6 to 8 show the attachment of an LED on the carrier.

[0045] FIG. 9 shows a third exemplary embodiment of the carrier.

[0046] FIG. 10 shows a fourth exemplary embodiment of the carrier.

[0047] FIGS. 11 and 12 show a fifth exemplary embodiment of the carrier.

[0048] FIGS. 13 and 14 show a sixth exemplary embodiment of the carrier.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0049] FIGS. 1 to 4 show a first exemplary embodiment of a carrier 1 for an LED 2. FIG. 1 shows a cross section through the carrier 1. FIG. 2 shows a plan view of an upper side 3 of the carrier 1. FIG. 3 shows a plan view of an underside 4 of the carrier. Figure 4 shows a side view of the carrier 1. In FIG. 4, an LED 2 mounted on the carrier 1 is also indicated by a dashed line.

[0050] The carrier 1 is a surface mounted device (SMD). Accordingly, the carrier 1 is suitable for being attached on a surface of a printed circuit board (not shown) by means of solder.

[0051] The carrier 1 is also designed to have an LED 2 mounted on it. In particular, the carrier 1 is designed to have an LED 2 attached on it by means of soldering.

[0052] The carrier 1 has a main body 5. The main body 5 is substantially cuboidal. The main body 5 comprises a ceramic material. In particular, the main body 5 consists of the ceramic material. The ceramic material may be zinc oxide-praseodymium or zinc oxide-bismuth.

[0053] A protective device 6 for protecting an LED 2 mounted on the carrier 1 from electrostatic discharges (ESD) is integrated in the main body 5. The protective device 6 has internal electrodes 7 integrated in the main body 5.

[0054] Each of the internal electrodes 7 extends in a plane parallel to the upper side 3 of the carrier 1, the upper side 3 of the carrier 1 being the side on which the LED 2 can be attached. The internal electrodes 7 are therefore aligned parallel to the upper side 3 of the carrier 1. This alignment is also referred to as vertical alignment of the internal electrodes 7.

[0055] In a direction from the upper side 3 of the carrier 1 to the underside 4 of the carrier 1, which lies opposite from the upper side 3, the internal electrodes 7 alternately extend either up to a first end face 8 of the carrier i or up to a second end face 9 of the carrier 1. On the first end face 8 of the carrier 1, a first metallic area 10 has been applied. The first metallic area 10 extends over the entire length of the first end face 8 and reaches both onto the upper side 3 and onto the underside 4 of the main body 5. On the second end face 9 of the carrier 1, a second metallic area 11 has been applied. The second metallic area 11 extends over the entire length of the second end face 9 and reaches both onto the upper side 3 and onto the underside 4 of the main body 5. In the direction from the upper side 3 to the underside 4, the internal electrodes 7 are alternately in contact with the first metallic area 10o and the second metallic area 11.

[0056] The first and second metallic areas 10, 11 comprise Ag, Ni and/or Au. In particular, the metallic areas 10, 11 may have a stacked structure comprising Ag, Ni and Au, with Ag forming the lowermost layer. Instead of Au, Sn may also be used.

[0057] The first and second metallic areas 10, 11 provide electrical contact with an LED 2 mounted on the carrier 1. The protective device is consequently designed in such a way that a voltage that is applied to the LED 2 from the two metallic areas 10, 11 also lies between the internal electrodes 7.

[0058] The protective device forms a varistor. With customary voltages between the internal electrodes 7, no current can flow through the ceramic material of the main body 5, since the ceramic material has too high a resistance. However, this resistance is voltage-dependent. If the voltage between two adjacent internal electrodes exceeds a predetermined threshold value, the resistance of the ceramic material suddenly falls. Then a current can flow between the adjacent internal electrodes 7 and the voltage present can be reduced. In this way it is provided that, when high voltages occur, such as for instance due to an electrostatic discharge, this voltage is prevented from causing damage to the LED 2. The protective device 6 ensures that the voltage is reduced by way of the protective device 6 without subjecting the LED 2 to any load.

[0059] The internal electrodes 7 comprise silver-palladium (AgPd) or consist of silver-palladium.

[0060] Furthermore, the main body 5 is enclosed by a glass passivation 12. The first and second metallic areas 10, 11 are arranged outside on the glass passivation 12. Internal electrodes 7 reach through the glass passivation 12, and are consequently in electrical contact with the first and second metallic areas 10, 11.

[0061] Two contact areas 13 are arranged on the upper side 3 of the carrier 1. The contact areas 13 comprise Ag, Ni and/or Au. In particular, the contact area may have a stacked structure comprising Ag, Ni and Au, with Ag forming the lowermost layer. Instead of Au, Sn may also be used. As indicated in FIG. 4, an LED 2 may be attached on the contact areas 13 of the carrier 1. The contact areas 13 are designed such that the LED 2 can be soldered onto the contact areas 13 in a eutectic soldering process. This may be, for example, a eutectic silver-lead soldering process. Alternatively or in addition, the contact areas 13 may be designed such that the LED 2 can be attached on the contact areas 13 in a gold-gold interconnect (GGI) bonding process. A eutectic soldering process makes it possible to lower the melting point of a solder.

[0062] The carrier 1 may have still further contact areas 13 for the mounting of further LEDs 2.

[0063] The first and second metallic areas 10, 11 have a greater thickness than the contact areas 13.

[0064] Alternatively, the contact areas 13 may have a stacked structure, which has at least one layer comprising gold and a layer comprising tin. Preferably, at least one layer of the stacked structure consists of gold and at least one layer consists of tin.

[0065] The stacked structure may, for example, have a titanium base layer arranged directly on the upper side 3. A nickel layer may be arranged over the titanium base layer. A first gold layer, a first tin layer, a second gold layer and a second tin layer may be arrangedin this sequenceover the nickel layer. The titanium base layer may be created by means of sputtering and have, for example, a height of 0.1 m. The further layers of the stacked structure may be created galvanically. The nickel layer may have a height of 2 m. The gold layers may have a height of 0.8 m. The tin layers may have a height of 0.2 m.

[0066] The heights of the gold and tin layers may be made to match one another so as to obtain in the stacked structure of the contact areas 13 a ratio of gold to tin of between 75:25 and 85:15, preferably of 80:20. This ratio leads to a lowering of the melting temperature of the contact areas. In this way, a melting temperature of between 300 C. and 320 C. can be achieved. In this way, eutectic soldering can be made possible.

[0067] The sputtering on of a base layer and the subsequent galvanic creation of further layers of the contact areas 13 lying thereover allow contact areas 13 that have a particularly low coplanarity and a particularly low surface roughness to be produced. For example, the contact areas 13 may have a coplanarity of less than 3 m. Furthermore, the contact areas 13 may have a surface roughness of less than 1 m.

[0068] The carrier 1 has a height of between 100 m and 500 m, preferably between 150 m and 350 m. The height indicates here the distance from the upper side 3 to the underside 4 of the carrier 1. The carrier 1 also has a width of between 200 m and 2000 m, preferably between 350 m and 1600 m. The carrier 1 also has a length of between 100 m and 1500 m, preferably between 150 m and 100 m. The width indicates here the extent of the carrier 1 in the direction of the normal to the surface of the end faces 8, 9. The length indicates the extent of the carrier 1 in a direction along the end faces 8, 9 and perpendicular to the direction of the connection of the upper side 3 and the underside 4.

[0069] Furthermore, the carrier 1 may have on its underside 4 at least one thermal contact area (not shown). The thermal contact area can improve thermal contact of the carrier 1 with a printed circuit board on which the carrier 1 is mounted. The thermal contact area may comprise Ag, Ni and/or Au. In particular, the thermal contact area may have a stacked structure comprising Ag, Ni and Au, it being possible for Ag to be arranged directly on the main body 5. Instead of Au, Sn may also be used.

[0070] FIG. 5 shows a second exemplary embodiment of the carrier 1. The carrier 1 according to the second exemplary embodiment additionally has a heat spreader 14, which is integrated in the main body 5 of the carrier 1. The heat spreader 14 has metallic plates 15. The metallic plates 15 of the heat spreader 14 are subdivided into two groups. The metallic plates 15 of the first group are connected to the first metallic area 10 on the first end face 8. The metallic plates 15 of the second group are connected to the second metallic area 11 on the second end face 9.

[0071] During operation, an LED 2 mounted on the carrier 1 may radiate a great amount of heat. The heat is thereby also radiated into the carrier 1. The metallic plates 15 of the heat spreader 14 serve the purpose of quickly removing heat produced. They thereby assist the removal of heat by way of the metallic areas 10, 11, and consequently provide an even better removal of heat.

[0072] In this way, overheating of an LED 2 mounted on the carrier 1 and of the main body 5 of the carrier 1 can be avoided. The heat is removed from the metallic plates 15 to the respective metallic area 10, 11, from where the heat can be radiated more easily. The metallic plates 15 of the heat spreader 14 comprise silver-palladium or consist of silver-palladium.

[0073] FIGS. 6, 7 and 8 show how an LED 2 is mounted on the carrier 1. In FIG. 6, the carrier 1 is first depicted without an LED 2. FIG. 7 shows the carrier 1 after a first mounting step, in which solder 16 has been applied to the contact areas 13 of the carrier 1. FIG. 8 shows the carrier 1 after the LED 2 has been attached on the carrier 1. The LED 2 is placed onto the contact areas 13, the solder 16 providing a mechanical connection of the carrier 1 to the LED 2. The solder 16 is subsequently hardened.

[0074] FIG. 9 shows a third exemplary embodiment of a carrier 1. In FIG. 9, a plan view of the upper side 3 of the carrier 1 is represented. A total of four contact areas 13 are arranged on the upper side 3. Each of the contact areas 13 is in electrical contact by way of in each case a metallic area 10, 11, 19. Apart from the first and second metallic areas 10, 11, the carrier has for this purpose further metallic areas 19. In this case, each of the metallic areas 10, 11, 19 extends from the upper side 3 of the carrier 1 over one of the end faces 8, 9 or one of the outer sides 17, 18 to the underside 4 of the carrier 1. The outer sides 17, 18 respectively connect the upper side 3 and the underside 4 and are perpendicular to the end faces 8, 9. The carrier 1 shown in Figure 9 is designed for the attachment of two LEDs.

[0075] FIG. 10 shows a fourth exemplary embodiment of a carrier 1. Also in FIG. 10, a plan view of the upper side 3 of the carrier 1 is represented. A total of eight contact areas 13 are arranged on the upper side 3, so that the carrier is suitable for being loaded with four LEDs. Each of the contact areas 13 is in electrical contact by way of in each case a metallic area 10, 11, 19. In this case, each of the metallic areas 10, 11, 19 extends from the upper side 3 of the carrier 1 over one of the end faces 8, 9 or one of the outer sides to the underside 4 of the carrier 1.

[0076] FIGS. 11 and 12 show a fifth exemplary embodiment of the carrier 1. FIG. 11 shows a cross section and FIG. 12 shows a plan view.

[0077] Two contact areas 13, on which an LED can be soldered, are arranged on the upper side 3 of the carrier 1. Between the contact areas there is a central region 20 of the upper side 3. Once the LED 2 is attached on the contact areas 13, a gap between the LED 2 and the carrier 1 forms in the central region.

[0078] The carrier also has at least one thermal via 21, which connects the central region of the upper side 3 to the underside 4 of the carrier. Here, the carrier 1 has three thermal vias. The thermal vias make it possible to dissipate heat radiated into the gap from the LED 2 to the underside. In this way, the thermal vias make a thermal improvement of the structure possible.

[0079] FIGS. 13 and 14 show a sixth exemplary embodiment of the carrier.

[0080] The carrier has no metallic areas 10, 11. Instead, the carrier has further vias 22, which serve for the contacting of the contact areas 13 and the contacting of the internal electrodes integrated in the main body. The further vias 22 lie against the contact areas 13 in the regions on which the LED 2 does not directly lie. Consequently, they do not disturb the coplanarity and the surface roughness of the contact areas 13 in the regions in which the LED 2 lies on the contact areas 13.

[0081] The contact areas 13 have the stacked structure described above, which has a ratio of gold to tin of 80:20.