EP4074146A1

EP4074146A1 - Led chip insert, illumination device, lighting module and method for producing the illumination device

Info

Publication number: EP4074146A1
Application number: EP21702595.6A
Authority: EP
Inventors: Michael Beck; Sebastian Jooss; Gerhard Behr
Original assignee: Osram GmbH
Current assignee: Osram GmbH
Priority date: 2020-01-24
Filing date: 2021-01-20
Publication date: 2022-10-19
Also published as: WO2021148484A1; US11716815B2; US20230059982A1; CN115004865A

Abstract

An LED chip insert for a circuit board comprises: a leadframe, in which punching is used to form a number of electrically conductive strands having respective ends having bearing surfaces that are designed for attachment to a circuit board and that form a common plane; wherein the leadframe has a region in the form of a depression in relation to the ends, an injection-moulded frame that is formed from an electrically insulating material and annularly surrounds a surface of the leadframe, which surface is exposed within the region of the depression and faces the ends of the strands, and consequently achieves a trough-shaped overall structure, at least one LED chip that is placed in the region in the form of a depression and has a first electrical contact connection and a second electrical contact connection, wherein the first electrical contact connection is electrically conductively connected to a first of the strands and the second electrical contact connection is electrically conductively connected to a second of the strands. The region of the leadframe in the form of a depression in relation to the ends may be inserted into a cutout in the circuit board such that the back faces thereof terminate flush with one another. In the lighting module, the back face of the depressed region of the circuit board may be in contact with an end cooling surface of a heat sink and dissipate heat there.

Description

LED CHIP INSERT, LIGHTING DEVICE, LIGHTING MODULE AND PROCESS FOR MANUFACTURING THE LIGHTING DEVICE

DESCRIPTION

Technical area

The present invention relates to an LED chip insert for a circuit board, a lighting device with an LED chip insert and circuit board, a lighting module using the lighting device, which can also be used in particular in vehicle lights or headlights, and a method for producing the lighting device .

State of the art

In the prior art, vehicle lights and headlights are known in which LED modules are being used to an increasing extent. Depending on the application, high-performance LEDs are also used here. A recently introduced platform that can also comply with the standards provided by the International Technical Commission (IEC) is the eXchangeable LED Signal lamp, or XLS for short. This standard allows uniform designs with the possible variation of lighting equipment, i.e. different combinations and arrangements of LEDs in the module depending on the use and application. Such different applications can be, for example, daytime running lights, indicators, brake lights or additional functions such as fog lights, high beam etc.

A particularly relevant point when using high-performance LEDs in such LED modules relates to thermal management. Conventionally, the LEDs are attached to printed circuit boards (PCBs) directly or by means of lead frames. Depending on the circumstances, the circuit boards essentially consist of flame-retardant FR-4, which, however, does not itself offer sufficient heat conduction. In order to efficiently dissipate the heat, holes, so-called vias, can be provided in the circuit board, which can be filled with copper from the inside. are layered and are connected via superficial copper tracks with the individual or meh eral LEDs having LED chip. The heat can be transported via such vias to the rear surface of the circuit board, where in the case of the XLS modules it is connected to a heat sink via an adhesive layer. Due to the design and thermal stress, however, it has proven to be unfavorable to place LED chips directly on vias. In special cases, individual LED chips may be inclined, so that the result may be that the emitted light is not radiated in the headlight in accordance with the standards.

Alternatively, very thin circuit boards or PCBs with microvias (m-vias) can be used, but such a structure has proven to be partly unstable and therefore unreliable. Furthermore, metal core plates or thermally conductive ceramics were and are still used. However, such solutions are extremely complex and therefore too expensive in the volume market for replaceable light modules considered here.

Presentation of the invention

It is therefore an object of the invention to provide a lighting device or components thereof, a lighting module using the lighting device and a corresponding method for producing the lighting device, with which heat dissipation is improved and / or the costs associated with thermal management in the case of lighting modules are reduced .

The object is achieved by an LED chip insert for a circuit board with the features of claim 1, a lighting device with the LED chip insert and a circuit board with the features according to claim 10, a light module with the features according to claim 14 and a Method for producing the lighting device having the features according to patent claim 15. Advantageous developments of the circuit arrangement according to the invention are the subject matter of the dependent claims. The core of one aspect of the invention is an LED chip insert for a printed circuit board. This comprises a lead frame, an injection molding frame and at least one LED chip provided in use.

In the lead frame, a number of electrically conductive strands are formed with respective ends by punching them, which have bearing surfaces which are intended for attachment to a printed circuit board and which build a common plane. The bearing surfaces can at least partially form contact surfaces. The En can be designed like tabs. However, the contact surfaces do not have to lie flat on the circuit board when the LED chip insert is attached to it.

The strands are formed or structured by die cutting, that is, by removing material from the lead frame blank. They can therefore be (electrically) separated from one another in accordance with the exemplary embodiments described here below. But it is just as possible that these are wholly or partially connected to one another. It can also be that there are only two ends in total, which, for example, form contact surfaces on opposite sides of the leadframe. The support surfaces can, but do not have to form electrical connections of the conductor frame for supplying the LED chip with power in individual cases. If they form electrical connections, they are preferably soldered to the circuit board, preferably with conductor tracks, e.g. made of copper, which are formed on the circuit board. The strings are designed according to the desired number, arrangement and function of the LED chips and have corresponding electrical properties. Not every strand has to be assigned an LED chip. Preferably at least two strands are required.

The lead frame also has an area formed as a recess opposite the ends. The term "recess" already indicates that the material of the leadframe is formed or shifted out of the reference plane of the ends or their support surface, specifically in a direction in which the support surface of the ends of the strands faces, in the case the assembly of the LED chip insert on a circuit board consequently into the circuit board level. Furthermore, the LED chip insert has an injection molding frame which is formed from an electrically insulating material and surrounds a surface of the lead frame which is exposed within the region of the recess and which faces the ends of the strands (ie, the bearing surfaces) in a ring-like manner and as a result causes an overall trough-like structure. The injection molding frame can be manufactured by injection molding processes known in the technical field. It preferably pours the structure of the lead frame and thus forms the trough, which can be used with particular advantage, for example, for filling with a titanium oxide-based reflective layer around the LED chip, so that this alone saves effort. Conventionally, a wall is to be formed around the LED chip or chips around in an additional step, which is then ver afterwards. The injection-molded frame also has the particular advantage that it mechanically connects the components of the lead frame, ie the strands with one another, and at the same time electrically insulates them, but gives the entire insert mechanical cohesion.

Furthermore, at least one LED chip (preferably several LED chips) is provided, which is placed on one or more of the strands in the area of the lead frame designed as a recess and has a first electrical contact connection and a second electrical contact connection, the The first electrical contact connection is connected to a first of the strands and the second electrical contact connection to a second of the strands in an electrically conductive manner. In the assembled state, the strings supply the LED chip with the electrical (voltage or current) signals required for operation.

As a result of the structure according to the invention, the at least one LED chip is connected to the leadframe in the region of the recess directly or at least via an adhesion promoter. He can directly dissipate heat via the strand or strands in question. Since the recess is oriented in the direction of the support surface, the lead frame structure or strand in question extends in the area of the recess through the circuit board in which the LED chip insert is inserted - which is of course only possible if this is a corresponding one Recess in front sees how an aspect of the invention to be described below with regard to a lighting device with circuit board and LED chip insert also provides.

Since the area of the recess extends through the circuit board level, the thermally conductive leadframe structure can also contact a cooling body surface arranged below, as is provided in particular in the case of XLS modules (but also other light modules), and to which, for example, the circuit board in the vicinity the recess is glued. In other words, through the LED chip insert according to the invention, the heat from the LED chip can be given off with high efficiency via the strand in the region of the depression directly to a cooling surface in the light module that may be located below. Preferably, the contact surface, i.e. the rear surface of the lead frame and of the injection molding frame, for example, which encapsulates the space between the strands of the lead frame in the region of the recess, is glued to the cooling surface in the light module.

In this way, it is possible with the help of the invention without the use of cost-intensive components such as metal core PCBs (MCPCB: metal core PCBs) or additional copper tracks to carry out an effective thermal management and at the same time, as described, the process of dispensing a dam to provide a tank for filling with a titanium oxide containing silicone casting compound with reflective properties for the blue primary radiation makes superfluous.

In the prior art (see, for example, DE102017213269 A1), an encircling structure (wall, dam) made of silicone that surrounds the conversion light sources (LED) and is raised in relation to the base area is formed for this purpose. The dam is applied by dispensing. The space enclosed by this dam, including the spaces between the individual copper strands, is filled with a light-reflecting, Ti02-containing silicone potting compound to such an extent that the ( blue) primary radiation is reflected back to the LED or onto the conversion layer of the LEDs and is thus again available for a conversion of blue radiation into yellow conversion light. By providing For a tub, the formation of an external dam is no longer necessary, since the outer boundary of the tub fulfills the function of a wall.

The formation of this reflective layer comprising titanium oxide is also simplified as a result.

The invention enables a spatially very short, direct passage of the heat through pure copper to the heat sink of the light module.

According to an advantageous embodiment, the area of the leadframe designed as a recess is formed by stamping of an originally planar leadframe blank that has been stamped out in advance to form the strands. Such a process is particularly simple and therefore inexpensive and at the same time allows a degree of deepening that can be precisely adjusted.

According to a further advantageous embodiment, the injection molding frame encapsulates a section of the lead frame that adjoins the ends of the strands and extends into the recess between and around the strands. As a result, it causes the ring-like enclosure around the exposed (front-side) surface of the lead frame within the recess. The section of the lead frame extending into the recess is preferably essentially perpendicular to the plane of the support surfaces in order to save space. If the strands are parallel to each other and only form ends on two opposite sides with contact surfaces for attachment to the (front) upper main surface of the circuit board, it may be that there are no ends on the front sides of the lead frame and the area of the recess in directions perpendicular to the Strand direction (within the plane of the plate) is open. This section is then preferably also covered by the injection molding frame, so that the trough is formed, ie the open end (s) of the recess are closed by the injection molding frame, so that the trough shape is advantageously retained and on to form a reflective layer he required dam can be dispensed with. As already mentioned, in a further, correspondingly advantageous embodiment, the trough-like structure within the injection molding frame enclosing the recess in a ring-like manner is filled with a silicone potting compound preferably containing titanium oxide, the upper surface of the layer being at the same level or below an upper light exit surface (Converter layer) of the LED chip is so that it is not wetted by the layer. In this way, the light generated by the LED or LEDs is not impaired. The blue light component emerging from the side and therefore hardly usable due to the geometry can be at least partially reflected back onto the conversion layer of the LEDs in the reflective layer and, if necessary, converted into yellow light and emitted from there in the desired direction of radiation, so that efficiency is further increased will.

The side surfaces of the tub in the area of the injection molding frame can additionally be coated in order to improve the reflection. For this purpose, they can also have an inclination with respect to the surface normal, i.e. not be perpendicular to the support surface. The injection-molded frame can be designed in such a way that only a minimally necessary area around the LEDs remains free for the reflective layer and the electrical contacting of the individual copper strands. The volume required for the reflective layer can thus be reduced.

According to a further advantageous embodiment, the area of the lead frame designed as a depression extends essentially along a plane parallel to the support surface. As a result, the contact area with an underlying cooling surface of a heat sink is enlarged and the heat conduction is improved.

According to a further advantageous embodiment, the lead frame in the region of the recess has a flat back surface facing away from the ends of the strands. The rear surface is essentially flush with the lower main surface of the circuit board. As a result, the relevant Lei terplatte can be glued to the heat sink or its flat heat sink surface with a flat rear side including the LED CHIP insert inserted therein. This increases the contact area even further and improves heat conduction.

There is preferably a tolerance of up to 20 μm, preferably up to 5 μm, with regard to a difference in a direction perpendicular to the lower main surface. This can be easily compensated for by the adhesive between the cooling surface and the back of the circuit board. It is important that the connection between the ends of the lead frame and the soldering pads on the circuit board (if, for example, soldering) is not under mechanical tension. This could be the case if the area of the lead frame containing the recess protrudes beyond the back of the circuit board when these are assembled and the circuit board is glued onto the cooling surface. Therefore, taking into account the manufacturing tolerances, the recess is formed in practice rather cautiously by a small margin compared to the printed circuit board thickness.

According to a further advantageous embodiment, the leadframe is made of copper, preferably has a thickness of 100 μm to 150 μm, and is further preferably coated with a protective film against oxidation that forms an end surface, in particular a film made of ENEPIG (Electroless Nickel Electroless Palladium Immersion gold). This protective layer is extremely planar and has very good oxidation properties. It is also particularly suitable for gold wire bonding, which is used very advantageously in LEDs.

According to a further advantageous embodiment, the injection molding frame on the leadframe is made from a plastic, in particular from a thermoplastic such as polyphthalamide (PPA) or polycyclohexylene dimethylene terephthalate (PCT), or from WEMC (White Epoxy Molding Compound).

According to a further advantageous embodiment, the at least one LED chip is placed on a first of the strands in the region of the recess and is preferably bonded to this first strand by means of an adhesion promoter with its base area forming the first electrical contact connection. Starting from the second electrical contact connection, the at least one LED chip is connected via a bond Wire bonded to a second of the strands. This attachment, implemented using chip-on-board (COB) technology, proves to be particularly suitable for the application. However, according to the invention, the LED chip can also be placed in SMD technology.

According to the invention, as described, a lighting device with the Lei terplatte and the LED chip insert is also provided therein. The circuit board is formed from an electrically insulating material and has an upper main surface with conductor tracks (e.g. made of copper) and a lower main surface opposite to this. A recess extending through the printed circuit board is formed between the main surfaces, as has already been exemplified above. An LED chip insert set up in accordance with one of the above-mentioned aspects and exemplary embodiments is provided, i.e. inserted, therein.

The lead frame is attached to the circuit board by resting the ends of the strands of the lead frame forming the bearing surface with this bearing surface on an upper main surface of the circuit board and being attached to it, for example by soldering, such as reflow soldering, or by laser, which is still offers advantages to be described. The formed as a recess opposite the plane of the ladder frame mens is now fitted into the recess in the circuit board, it should be noted that at least one tolerance distance between the side walls of the recess, ie the injection molding frame, and the inner edge of the recess of the circuit board is provided is. A contact between the two is not excluded, but also not necessary. Rather, the geometry - viewed in the plane of the printed circuit board or the support surfaces of the leadframe - of the recess can also deviate considerably from that of the area of the recess in the leadframe or in the LED chip insert. The term "fitting in" is therefore to be interpreted broadly and relates more to "leading in".

The advantages of this lighting device emerge from the preceding description. According to a further advantageous embodiment, the printed circuit board is made of a poorly thermally conductive material, preferably FR4. Additionally or alternatively, the printed circuit board can be cut in a substantially circular shape. In the latter case, it is particularly suitable for the exchangeable XLS modules, the housing of which is hollow-cylinder-shaped and in which correspondingly circular printed circuit boards are provided on the front side, on which the LED chips are mounted directly or indirectly.

According to a further advantageous embodiment, several LED chips are provided, with one LED chip each placed on one of the strands in the area of the recess and connected via its contact terminals to one and another strand on which an adjacent LED chip is connected is placed in the same way, so that at least a subset of the LED chips are electrically connected in series with one another.

According to a further advantageous embodiment, the strands in the conductor frame are arranged parallel to one another and the LED chips are arranged in a row along a line or at an alternately offset position on the upper surfaces of the strands. Alternatively or additionally, the LED chips are arranged in two parallel rows on the upper surfaces of the strings.

An LED or some of the LEDs or all of the LEDs can have an area of approximately 1 mm ² , for example. An area of 2 mm ² is also conceivable. Other geometries are also conceivable. For example, the LEDs are UX3 chips from Osram. The LED can be in the form of at least one individually housed LED or in the form of at least one LED chip that has one or more light-emitting diodes. The LED can be in the form of a micro-LED.

The arrangement of the LEDs or a part of the LEDs can be matrix-shaped or zel len-shaped or round. Other designs are also conceivable.

According to aspects of the invention, a light module is also provided, preferably for use in a light in a motor vehicle, comprising the previously described level lighting device, wherein the light module is preferably replaceable and designed as an eXchangeable LED signal lamp (XLS). Such a light module can have a housing with mechanical locking elements, a heat sink with cooling fins, an electrical connection element, the lighting device with circuit board and LED chip insert according to the invention and possibly a sealing direction as main components. The end face of the heat sink can have a cooling surface, perpendicular to the axis of the cylindrical housing, on which the printed circuit board is glued in order to dissipate heat and feed it to the cooling fins. Together with the circuit board, the recessed area of the lead frame of the LED chip insert also makes contact with this cooling surface (possibly via an adhesive or bonding agent), so that here too heat is dissipated from the LED chip with high efficiency.

A further aspect of the invention also provides a method for producing a lighting device as described above. The process can include the following steps:

Providing a circuit board which is formed from an electrically insulating material and has an upper main surface with conductor tracks and a lower main surface lying opposite this, and wherein a recess is formed between the main surfaces through the circuit board extending through;

Punching out a lead frame having a number of electrically conductive strands with respective ends;

Stamping of the lead frame to form a joint on a supporting surface forming plane through the ends of the strands and an area formed as a recess opposite the plane;

Fitting the area of the lead frame forming the recess opposite the plane into the recess of the circuit board and fastening the ends of the strands forming the support surface on the circuit board;

Placing the at least one LED chip on one of the strands in the region of the depression and bonding with its base area forming a first electrical contact, preferably by means of an adhesion promoter to the strand,

Bonding of the at least one LED chip starting from a connection point forming a second electrical contact via a bonding wire to another of the strands. The same or similar advantages as described above result.

According to further advantageous refinements, further steps can be provided, for example the formation of an injection molding frame from an electrically insulating material on the lead frame so that the injection molding frame surrounds an upper surface of the lead frame exposed within the region of the recess in a ring-like manner, around a trough-like structure with the at least one LED chip present in effect.

Furthermore, a filling of the tub-like structure within the ring-like to closing injection molding frame with the exposed upper surface of the conductor frame therein and the at least one LED chip on it with a reflective layer preferably comprising titanium oxide can be provided, the upper surface of the layer at the same level or lies below an upper light exit surface of the LED chip, so that it is not wetted by the layer. The advantages described above also result here.

Further advantages, features and details of the invention emerge from the claims, the following description of preferred embodiments and with reference to the drawings. In the figures, the same reference symbols denote the same features and functions.

Brief description of the drawings)

Show it:

1 shows a perspective view of a light module according to an embodiment example of the invention, electronics arranged on the circuit board and optional optics being omitted and conductor tracks not being shown;

FIG. 2 shows an enlarged detail of the view of the light module from FIG. 1; FIG. 3 shows a schematic representation of a longitudinal section through the light module shown in FIG. 1;

4 shows a flow chart for a method for producing a lighting device according to an exemplary embodiment of the invention;

FIG. 5 shows a perspective illustration of a lead frame blank punched in accordance with the method sequence according to FIG. 4; FIG.

FIG. 6 shows a perspective illustration of a lead frame blank provided with an injection molding frame in accordance with the method sequence according to FIG. 4; FIG.

FIG. 7 shows a perspective illustration of a leadframe insert punched out according to the method sequence according to FIG. 4; FIG.

FIG. 8 shows a perspective illustration of a leadframe insert inserted into the recess of a printed circuit board in accordance with the process sequence according to FIG. 4; FIG.

9 shows a perspective illustration of a according to the method sequence according to

Fig. 4 in the recess of a printed circuit board inserted leadframe inserts with LED chips mounted thereon ("LED chip insert").

Preferred embodiment (s) of the invention

1 to 3 show an overview of a light module according to an exemplary embodiment of the present invention. The light module shown corresponds to and satisfies the specifications of the XLS platform (exchangeable LED signal lamp). Examples of such light modules - but still without implementation of the invention described here - can also be found in the following documents: US 2019063706 A1,

DE 102017214659 A1, US 2019110348 A1, DE 102017217883 A1, DE 102017222649 A1, DE 102018202464 A1, US 2019306939 A1, DE 102018201228 A1, DE 102017213269 A1, DE 102015206471 A1. It should be noted that the use of the lighting device according to the invention in the XLS light modules described by the publications also represent particularly advantageous exemplary embodiments, for example the combination of the LED chip insert provided according to the invention in a recess in the circuit board with the Optics and the LED arrangement according to FIGS. 4 to 7 in DE 102015206471 A1, with the electrical contacts provided in the bayonet lock of the housing according to FIG. 3 of DE 102017214659 A1, with those shown in DE 102017217883 A1 in FIGS. 2 to 11 LED arrangements or with the circuit arrangements shown in DE 102018201228 A1 in FIGS. 1 to 4, to name just a few examples.

The light module according to the first embodiment of the invention has three LED chips 11, 12, 13 arranged on a circuit board 10 (each with, for example, a light emitting diode), a housing 2, a heat sink 3 for cooling the semiconductor light sources and electronics 8 for operating the LED chips 11, 12, 13 and an electrical connection element 4 for supplying energy to the LED chips 11, 12, 13. A lens and / or a light guide attached to the LED chips is not shown, but can be provided.

The LED chips 11, 12, 13 contain three light-emitting diodes which are arranged on the circuit board 10 together with the electronics 8 for operating the light-emitting diodes. The circuit board 10 (including the lead frame set 16 to be described below) serves as a common carrier for the LED chips 11, 12, 13 and the electronics 8. The LED chips 11, 12, 13 are on the lead frame insert 16 and the electronics 8 is mounted on a surface 100 of the circuit board 10 itself, with the Lei terrahmen insert 16 and therein the LED chips 11, 12, 13 mounted on strings and the electronics by means of conductor tracks set up on the circuit board, preferably made of copper, electrically with each other connected. The electronics 8 (only shown in FIG. 3) can be designed, for example, as a driver circuit, in particular as a so-called linear driver, that is, as a linear voltage regulator.

However, a pure resistance circuit is also possible. In addition to the pure operation of the LED chips, the driver can also implement various protective functions, e.g. Pole protection, ESD and protection against positive, negative voltage pulses from the vehicle electrical system. If required, the driver can also implement electronic derating, dimming and switching off individual chips.

The LED chips 11, 12, 13 can be covered by optics (not shown). In the case of an optical lens, liquid silicone can be applied to the surface 100 of the circuit board 10 with the aid of a dispenser, so that the LED chips are embedded in the silicone compound. After cooling, the silicone compound then forms the optical lens. Other optics are also possible.

The housing 2 is ring-shaped and designed as a plastic injection-molded part. The hous se 2 has a first end face with a flat annular disc-shaped end face 20. Along the outer circumference of the annular disc-shaped end face 20, four locking elements 21, 21a, 22, 23 are arranged, which protrude radially from the outer surface of the annular housing 2 and one Form bayonet locking with correspondingly shaped counterparts of a socket of the motor vehicle light. The undersides of the four locking elements 21, 21a, 22, 23 define a plane which serves as a reference plane for the alignment of the LED chips 11, 12, 13 with respect to the housing 2 and with respect to an optical axis of the socket of the motor vehicle light, in which the Light module is used. To activate the bayonet lock, the light module is plugged into the socket of the motor vehicle light and then rotated clockwise about the ring axis of the housing 2. A locking element 23 can have a stop (not shown) in order to limit the aforementioned rotational movement, which stop rests in the socket or assembly opening of the motor vehicle light after the bayonet lock. The bayonet locking can be carried out with a product-specific key, so that each type of light module has its own key, thus avoiding mix-ups. A sealing ring 5 (only shown in Fig. 3) provides the necessary contact pressure of the lighting device to the socket.

On its second end face opposite the first end face, the ring-shaped housing 2 has an annular flange section 24 which protrudes radially outward from the outer circumferential surface of the annular housing 2, a support surface surface 240 for a sealing ring 5 forms and together with the locking elements 21, 21a, 22, 23 forms an annular groove 200 for receiving the sealing ring 5 made of silicone or rubber.

The heat sink 3 has a hollow cylindrical shaped heat sink section 31 which is arranged in the inner ring opening of the housing 2 and on its face 20 of the housing 2 facing side a flat support surface, ie, a cooling surface 30 for the circuit board 10 and in particular for the Lead frame insert 16 forms. The cylinder axis of the hollow-cylindrical heat sink section 31 is identical to the ring axis of the annular housing 2. The cooling surface 30 is perpendicular to the cylinder axis of the hollow-cylindrical heat sink section 31 and with the circuit board 10 and the lead frame insert 16 inserted therein with electrically insulating, thermally conductive Glued together. The cooling surface 30 of the hollow-cylindrical heat sink section 31 has openings 300 through which three electrical contact pins 41, 42 of the electrical connection element 4 are passed. The electrical contact pins 41, 42 can form a press fit with the circuit board 10.

The cooling body 3 also has a second, annular disk-shaped cooling body section 32, which is molded onto the hollow-cylindrical cooling body section 31 and whose ring axis coincides with the cylinder axis of the hollow-cylindrical cooling body section 31. The second, annular disk-shaped heat sink section 32 is arranged between the annular disk-shaped flange section 24 of the housing 2 and a circular disk-shaped flange section 40 of the electrical connection element 4 and connected to both by means of adhesive. Alternatively, the heat sink can be completely encapsulated with plastic so that there is only a single plastic part that surrounds the heat sink.

On the second, annular disk-shaped cooling body section 32, cooling fins 33 arranged along its circumference are integrally formed. The cooling fins 33 are angled from the second, annular disk-shaped cooling body section 32 by an angle of 90 degrees (downward in the figures) and each extend parallel to the ring axis of the second, annular disk-shaped Heat sink section 32. The heat sink 3 consists of metal, for example stainless steel sheet or aluminum, and is in one piece, for example designed as a deep-drawn bent part.

The electrical connection element 4 is designed as a plastic injection-molded part and has electrical contact pins 41, 42, which each consist of metal and are embedded in the plastic material of the electrical connection element 4. The electrical connection element 4 has a circular disk-shaped flange section 40 which rests on the second, annular disk-shaped heat sink section 32 on its side facing away from the housing 2. The flange section 40 of the electrical connection element 4 is connected by adhesive to the second, annular disk-shaped heat sink section 32. The adhesive also serves as a sealant between the flange section 40 of the electrical connection element 4 and the second, annularly designed heat sink section 32 and between the annular disk-shaped flange section 24 of the housing 2 and the second, annular disk-shaped heat sink section 32. For this purpose, the adhesive 6 is applied in a ring shape on both sides of the second, annular disk-shaped cooling body section 32. Alternatively, the adhesive can also be applied at the level of the cooling surface 30 and there, at a small distance from the printed circuit board 10, ensure the sealing function with the housing 2.

The electrical connection element 4 also has a section designed as a socket 44, which extends parallel to the ring axis of the housing 2 and is arranged offset paral lel to this ring axis and is integrally formed on the circular disk-shaped flange section 40. The free ends of the electrical contact pins 41, 42 each extend into the socket 44 and serve there as electrical contacts of the lighting module and are provided for connecting a plug that can be plugged onto the socket 44. After the socket and plug have been joined, this connection is sealed. The other ends of the electrical contact pins 41, 42 each protrude through the opening 300 in the cooling surface 30 of the cooling body 3 and can form a press fit with the circuit board 10 and are each connected to an electrical contact on the circuit board 10. The electrical contact pins 41, 42 are used to supply power to the LED chips 11, 12, 13 on the lead frame insert 16. The lead frame insert 15 forms together with the LED chips 11, 12, 13 and possibly layers formed thereon an LED chip insert 15 according to an exemplary embodiment of the present invention

The light-emitting diodes of the LED chips 11, 12, 13 emit e.g. yellow, red light or white light, or combinations thereof, during operation. The number of LED chips is also not limited to three and the arrangement does not have to be in a row, but can also be star-shaped or square or circular.

The light-emitting diodes of the LED chips 11, 12, 13 have a light-emitting surface with a side length of, for example, in the range from 0.4 mm to 0.6 mm. Alternatively, light-emitting diode chips can also be used whose light-emitting surface has a side length in the range from 0.7 mm to 0.8 mm or 0.9 mm to 1.1 mm. The invention and the exemplary embodiments are not restricted to specific types and combinations of LEDs.

In FIG. 4, a schematic sequence of a method according to the invention for producing a lighting device 50, which is intended to include the circuit board 10 and the LED chip insert 15, is shown in a flowchart. The process steps 100 to 140 detected by block 90 initially relate to the production of the conductor frame insert 16 (still without LED chips 11, 12, 13), while process steps 200 to 220 initially only relate to the circuit board 10 and can be carried out in parallel. Only in process step 300 are both parts - printed circuit board 10 and conductor frame insert 16 - brought together.

In a first process step 100 for producing the leadframe insert 16, a leadframe blank 60 - as shown above in FIG. 5 - is provided and punched. The blank consists of copper (C194) with a thickness of 100 μm to 150 μm, the desired structure for a plurality of leadframes 62 being formed in the first process step 100 by punching out copper material. The lead frame blank 60 stamped in this way then has an outer frame 63 which supports all lead frames 62 with an inner frame 64 which holds the lead frame 62 together. In the particular embodiment, the lead frame 62 consists of four parallel strands that are only held together by inner frame 64, such as can be seen at the bottom in FIG. 5, only a section being shown there. Three strands 66, 67, 68 have the same width and length, while the fourth strand 69 has a ge smaller width than the other strands, but the same length.

In a further process step 110, a second punching is carried out, which is now a punching, with which a recess 71 is embossed in an inner region 70 of the leadframe 62 to be manufactured. The strands 66 - 69 are each pressed out or deepened in a central area from the lead frame level, while their ends 660, 670, 680, 690 still attached to the inner frame 64 remain unaffected. The amount of the executed recess by punching is approximately equal to the thickness of the printed circuit board 10 made of FR-4 material provided in step 200.

In the next process step 120, the punched lead frame 62 (or the punched blank with frame 63 and 64 with an anti-oxidation layer, in particular an ENEPIG layer (Electroless Nickel Electroless Palladium Immersion Gold) is optionally also selectively coated. This is extremely planar and has very good oxidation properties and is suitable for soldering applications as well as bonding aluminum or gold wire, but other anti-oxidation layers are also possible.

Then, in process step 130, the lead frame blanks 60 are injection molded, e.g., with PPA. This material has a high tensile strength and rigidity, a high heat resistance, also a high melting point and a high glass transition temperature, and provides a high creep resistance. Other materials such as PCT or WEMC are also possible.

The resulting shape is shown in FIG. The injection molding frame 80 produced in this process step 130 has a wall 81 that surrounds the recessed area 70 in a ring shape and is formed with greater thickness on the sections 661, 671, 681, 691 of the strands 66-69 that extend down into the recess 71 which adjoin the ends 670 - 690 of the strands that have remained unaffected by the stamping and are inclined to the plane of the circuit board. Greater thickness here means that these strand sections are completely encapsulated, ie not only the intermediate spaces are potted but also the front and rear sides of the strand sections 661, 671, 681, 691.

In contrast, only the space 83 between the strands 66 to 69 is cast in the bottom of the recess, the front and rear surfaces of the conductor frame remain free in this area 70 of the recess 71. Furthermore, the ends 660, 670, 680 and 690 are not encapsulated because they are used to establish contact with the circuit board. The ends 660 - 690 consequently extend upwards (opposite to the direction of the recess) out of the injection molding frame and bend here by approximately 90 degrees into the plane of the lead frame in order to form a support surface 500 for the printed circuit board 10.

On the end faces of the lead frame 62, the area 70 of the recess is open. In order to enclose the area 70 of the depression in a ring-like manner, the injection-molded frame 80 is also guided around as an end wall 82, so that the overall result is a trough-like structure of the injection-molded frame, which is advantageously potted in a subsequent step with additional layers serving e.g. optical functions can.

In a further process step 140, the lead frame 62 processed in this way and provided with injection molding frames 80 is separated from the outer frame 63 and from the inner frame 64 of the blank, so that there is now a lead frame insert 16 that can be inserted into a corresponding circuit board 10, as shown in FIG Sectional drawing is shown in Fig. 7.

In process step 200, a printed circuit board blank 1000 is provided, in which - as shown above in FIG. 8 - each circular individual printed circuit boards 10 are precut. In these circuit boards 10, recesses 1010 are preferably also cut in the same step, the shape of which is adapted to that of the recessed area 70 of the lead frame insert 16 in the exemplary embodiment. Furthermore, the openings 300 for the contact pins 41, 42 as well as individual positioning holes visible in the figures (for an alignment when inserting and when equipping) can be cut out. In this process step 200 of providing the circuit board 10 and forming the recess 1010, the conductor tracks, preferably made of copper, for wiring the electronics 8 on the circuit board 10 can also already be formed (not shown). An anti-oxidation layer can also be formed here, but since the wire bonding will later only take place on the leadframe 62 and not on the printed circuit board 10, this layer can optionally also be omitted or a less costly process can be implemented as ENEPIG.

In process step 210, the soldering pads for the leadframe insert 62 are now prepared, and in a further process step 220, soldering paste is applied to the relevant positions on the circuit board 10.

In process step 300, the printed circuit board 10 and the lead frame insert 62 are now brought together. For this purpose, the leadframe insert 62 with its recessed area 70 is inserted into the recess 1010 of the circuit board 10 in the correct orientation, so that the bearing surfaces 500 or the contact surfaces of the ends 670, 680,

690 of the strands 66 - 69 come to rest on the soldering pads or on the soldering paste applied to them (if assigned: not every strand end has to contact or be soldered to a soldering pad, e.g. if no connection is provided at all). The result can be seen in Fig. 8 below.

In process step 310, reflow soldering is carried out at a maximum of 240 ° C. and a total of approx. 5 minutes in the oven, approx. 1 minute of which over 220 ° C. so that the electrical contact between the leadframe 62 and the conductor track of the printed circuit board 10 is established.

As can be seen in FIG. 8 below, the circuit board 10 and the lead frame insert 16 are now flush with the rear surface because the extent d2 (amount) of the recess in the lead frame 62 is carried out approximately or exactly with the circuit board thickness d1 (see Fig. 8). As a result, the lead frame 62 can contact the front cooling surface 30 of the cooling body 3 shown in FIG. 3 via the thermally conductive adhesive and dissipate heat very efficiently. In the next process step 320, the LED chips 11, 12, 13 with their base area forming a first electrical contact are, preferably by means of a conductive adhesive, in particular a conductive silver adhesive, in the recessed area 70 of the lead frame 62 on the exposed surfaces of the strands 66 to 69 bonded (die-bonding). The process can be carried out at 150 ° C for 2 hours, for example.

In the following process step, the LED chips 11, 12, 13 are attached to a contact point facing the top, which forms a second electrical contact, to an adjacent strand in the recessed area 70 of the lead frame 62 on the respective top by wire bonds 900 (especially gold wire bonding with ball bonder) attached. As can be seen, the LED chips are thereby connected in series in this exemplary embodiment. As mentioned, this means that there is no longer any wire bonding directly on the circuit board, so that no ENEPIG process is required for the anti-oxidation and can therefore be omitted.

REFERENCE CHARACTERISTICS LIST:

Light module housing (light module)

Heat sink electrical connection element

Sealing ring

electronics

PCB, 12, 12 LED chips

LED chip insert

PCB insert

End face, 22, 23 locking elements, annular flange section, cooling surface of the lighting module, hollow-cylindrical cooling body section, annular disk-shaped cooling body section, cooling ribs, circular disk-shaped flange section, 42 contact pins

Lighting device

Lead frame blank

Ladder frame

Outer frame

Inner frame, 67, 68 strands to hold LED chips

Line for electrical connection by punching, recessed area

deepening

Injection molding frame ring-shaped enclosing wall 82 front wall

83 Gaps filled at the bottom (injection molding frame)

90 process steps for manufacturing the ladder frame insert

100 Punching out the lead frame

110 Forming the recessed area by punching

120 Coating of the lead frame with anti-oxidation layer (ENEPIG)

130 Potting the injection molding frame

140 Separating the leadframe from the blank

200 groove for sealing ring

200 Prepare the printed circuit board with conductor tracks and recess

210 Manufacture of the soldering pads

220 Applying the solder paste

240 Support surface for sealing ring

300 breakthrough

300 Inserting the ladder frame insert

310 reflow soldering

320 Die-bonding the LED chips

330 wire bonding the LED chips

500 contact surface on the lead frame for attachment to soldering pads

660, 670, ends of the strands (with contact surface)

680, 690

661, 671, strand sections extending in the direction of the recess

681, 691 900 bond wires 1000 PCB blank 1010 recess

Claims

PATENT CLAIMS

An LED chip insert (15) for a printed circuit board (10), comprising: a lead frame (62), in which a number of electrically conductive strands (66-69) with respective ends (660-690 ) is designed which have support surfaces (500) which are intended for attachment (310) on a circuit board (10) and which build up a common plane; wherein the lead frame (62) has an area (70) formed as a recess (71) opposite the ends, an injection-molded frame (80) made of an electrically insulating material and an exposed surface within the area (70) of the recess Leadframe (62) facing the ends of the strands (66-69), surrounds like a ring and consequently creates a trough-like structure overall, at least one LED chip (11, 12, 13), which is located in the recess (71) formed area (70) is placed and has a first electrical contact connection and a second electrical contact connection, the first electrical contact connection with a first of the strands (66-69) and the second electrical contact connection with a second of the strands (66-69) 69) is connected in an electrically conductive manner.

2. LED chip insert (16) according to claim 1, wherein: the area (70) of the lead frame (62) formed as a recess (71) by punching (110) of an originally planar, for forming the strands (66-69) pre-punched (100) leadframe blank (60) is formed.

3. LED chip insert (16) according to claim 1 or 2, wherein the injection molding frame (80) has a section which adjoins the ends (660-690) of the strands (66-69) and extends into the recess (71) (661, 671, 681, 691) of the lead frame (62) each between the strands (66-69) and around them, thereby causing the ring-like enclosure.

4. LED chip insert (16) according to one of claims 1 to 3, wherein: the trough-like structure within the recess (71) ring-like umschlie ßenden injection molding frame (80) with a preferably comprising titanium oxide reflective xionsschicht is filled, wherein the upper surface of the layer is at the same level or below an upper light exit surface of the LED chip, so that this is not wetted by the layer.

5. LED chip insert (16) according to one of claims 1 to 4, wherein the region (70) of the leadframe (62) formed as a recess (71) extends essentially along a plane parallel to the support surface (500).

6. LED chip insert (16) according to one of claims 1 to 5, wherein the lead frame (62) is formed from copper, preferably has a thickness of 100 pm to 150 pm, and more preferably with a protective film bil Denden an end surface is coated against oxidation, in particular a film made of ENEPIG (Electroless Nickel Electroless Pallladium Immersion Gold).

7. LED chip insert (16) according to one of claims 1 to 6, wherein the injection-molded frame (8) on the lead frame (62) is formed from a plastic, in particular from a thermoplastic such as a polyphthalamide (PPA) or polycyclohexylene dimethylene terephthalate (PCT) , or from WEMC (White Epoxy Mol ding Compound).

8. LED chip insert (16) according to one of claims 1 to 7, wherein the at least one LED chip (11, 12, 13) on a first of the strands (66, - 69) in the area (70) of the Placed recess (71) and with its the first electrical contact terminal forming base surface is preferably bonded to this first strand by an adhesion promoter, and wherein the at least one LED chip (11, 12, 13) starting from the second electrical contact terminal via a Bond wire (900) is bonded to a second of the strands.

9. Lighting device (50), comprising: a printed circuit board (10) which is formed from an electrically insulating material and an upper main surface with conductor tracks and an opposite un- having tere main surface, and wherein a recess (1000) extending through the circuit board is formed between the main surfaces; the LED chip insert (16) according to one of claims 1 to 9, wherein the lead frame (62) is attached to the circuit board (10) by the ends (660, 670, 680, 690 ) the strands (66, 67, 68, 69) of the lead frame (62) rest with this support surface (500) on the upper main surface of the circuit board (10) and are fastened thereto; and the region (70) of the leadframe (62) formed as a recess (71) opposite the plane is fitted into the recess (1000) in the printed circuit board (10).

The lighting device (50) according to claim 9, wherein: the lead frame (62) in the region (70) of the recess (71) one of the ends (660, 670, 680, 690) of the strands (66, 67, 68, 69 ) has averted, flat rear surface, the rear surface being essentially flush with the lower main surface of the circuit board (10), with a tolerance of up to 20 μm, preferably up to 5 μm, with regard to a difference in a direction perpendicular to the lower main surface is permissible.

11. Lighting device (50) according to claim 9 or 10, wherein the circuit board (10) is formed from a thermally conductive material, preferably FR-4; and / or the circuit board (10) is cut in a substantially circular shape.

12. Lighting device (50) according to one of claims 9, 10 or 11, wherein several LED chips (11, 12, 13) are provided, one LED chip each on one of the strands (66, 67, 68, 69) placed in the area (70) of the recess (71) and connected via its contact connections to one and another strand on which an adjacent LED chip is placed in the same way, so that at least a subset of the LED chips (11 , 12, 13) is electrically connected in series with one another. 13. Lighting device (50) according to claim 12, wherein the strands (66, 67, 68, 69) in the lead frame (62) are parallel to each other angeord net and the LED chips (11, 12, 13) in a row along a line or are arranged at alternately offset positions on the upper surfaces of the strands, and / or the LED chips (11, 12,

13) are arranged in two parallel rows on the upper surfaces of the strands (66, 67, 68, 69).

14. Light module (1), preferably for use in a light in a motor vehicle, comprising the lighting device (50) according to one of the preceding claims 9 to 13, wherein the light module (1) is preferably replaceable and as an eXchangeable LED signal lamp (XLS ) is formed, and / or has a heat sink (3) with a cooling surface (30), which is contacted by a rear surface of the conductor frame (62) directly or via an adhesion promoter.

15. A method for producing a lighting device, comprising:

Providing (200) a circuit board which is formed from an electrically insulating Ma material and has an upper main surface with conductor tracks and a lower main surface lying opposite this, and wherein a recess is formed which extends through the circuit board between the main surfaces;

Punching out (100) a lead frame having a number of electrically conductive strands with respective ends;

Stamping forms (110) of the lead frame to form a common egg ne supporting surface forming plane through the ends of the strands and an area formed as a recess opposite the plane;

Fitting (300) the area of the lead frame forming the recess opposite the plane into the recess of the circuit board and fastening the ends of the strands forming the support surface on the circuit board;

Placing the at least one LED chip on one of the strands in the area of the recess and bonding with its base area forming a first electrical contact, preferably by means of an adhesion promoter to the strand, Bonding (320, 330) the at least one LED chip, starting from a connection point forming a second electrical contact, via a bonding wire to another of the strands.

16. The method of claim 15, further comprising:

Forming (130) an injection molding frame from an electrically insulating material on the lead frame, so the injection molding frame surrounds an upper surface of the lead frame exposed within the region of the recess in a ring-like manner in order to effect a trough-like structure with the at least one LED chip therein.

17. The method of claim 16, further comprising:

Filling the tub-like structure within the ring-like enclosing injection molding frame with the exposed upper surface of the lead frame therein and the at least one LED chip on it with a reflective layer preferably comprising titanium oxide, the upper surface of the layer being at the same level or below an upper light exit surface of the LED Chips lies so that it is not wetted by the layer.