Optoelectronic component and method for the production thereof, module and device comprising a module of this type

The invention relates to an optoelectronic component, having a semiconductor chip (1) which is mounted on a flexible chip support (6), in which conductor tracks (3, 5) for electrically connecting the semiconductor chip (1) are embodied on a first main face, and on which a housing frame (7) is disposed that is filled with a radiation-permeable medium, in particular a filler compound. A display device, an illumination or backlighting device, and a method for producing components of the invention are also disclosed.

This is a U.S. national stage of application No. PCT/DE01/03197, filed on 22 Aug. 2001.

FIELD OF THE INVENTION

The invention relates to an optoelectronic component with a semiconductor chip, in particular a surface-mountable optoelectronic component for mounting in openings in printed circuit boards. It also relates to a method for producing a plurality of optoelectronic components of this kind, to a module having a plurality of such optoelectronic components, and to a display device as well as an illumination or backlighting device having such a module.

BACKGROUND OF THE INVENTION

Typically, optoelectronic components such as light emitting diode components are offered in so-called radial designs, which are secured to printed circuit boards by through-mounting, or in surface-mountable designs. For instance, one can refer to F. Möllmer and G. Waitl,SIEMENS SMT-TOPLED für die Oberflächenmontage[SIEMENS SMT-TOPLED for Surface Mounting], Siemens Components 29 (1991), No. 4, pages 147-149. Both types of design can be disposed in printed circuit board recesses or openings only with considerable technological effort.

SUMMARY OF THE INVENTION

One object of the present invention is to develop a design for an optoelectronic component that makes a low structural height possible and that can be positioned in a simple way in recesses or openings of printed circuit boards.

This and other objects are attained in accordance with one aspect of the invention directed to an optoelectronic component, having a semiconductor chip which is mounted on a flexible chip support, in which conductor tracks for electrically connecting the semiconductor chip are embodied on a first main face, and on which a housing frame is disposed that is filled with a radiation-permeable medium, in particular a filler compound.

Because the conductor tracks are embodied on the flexible chip support, the flexible chip support itself becomes an element of the component that can advantageously simultaneously be used for packaging the component.

In a component assembly machine, such components are preferably not lifted from a flexible support, such as a packaging belt; instead, the flexible chip support is cut apart into components in accordance with the subdivision of the flexible chip support, and the components thus obtained are placed on a printed circuit board. In a design according to the invention, separate packaging belts are advantageously not necessary.

In a preferred embodiment, the flexible chip support is a plastic film. Components that are especially low in height are thus obtained.

In a preferred embodiment, the semiconductor chip is a light emitting diode chip, which is disposed in the center of a housing frame embodied on the flexible chip support. The result is light sources of low structural height, which are especially well suited for conductor track openings in mobile radio communication devices, such as cellular phones, for instance for backlighting a keypad or a display.

DETAILED DESCRIPTION OF THE DRAWINGS

In the various exemplary embodiments, elements that are the same or function the same are each provided with the same reference numerals.

The component shown inFIGS. 1,2A and2B is for example a light emitting diode component and has a radiation-emitting semiconductor chip1, which contains a radiation-emitting active layer2. The semiconductor chip1is electrically conductively connected by its underside to a first contact layer3. The top side of the semiconductor chip1is connected via a bond wire4to a second contact layer5. The first contact layer3and the second contact layer5are produced for instance from metal foils, which are laminated onto a flexible chip support film6.

In an alternative semiconductor chip, which has both electrical connection faces on the top, both connection faces are connected to the contact layers3and5, for instance by means of bond wires. Here, the semiconductor chip can once again be secured to one of the contact layers3and5, or between the two contact layers3and5.

The semiconductor chip1is located in the center of an annular reflector frame7, with a funnel-shaped inside8that is preferably embodied reflectively. As a result, the reflector frame7is capable of deflecting radiation, emitted toward the side from the semiconductor chip1, in a projection direction9.

The interior enclosed by the reflector frame7is filled with a transparent filler compound10, in which luminescent pigments may be embedded that at least partly absorb the radiation emitted by the semiconductor chip1and re-emit radiation of a different wavelength from the absorbed radiation.

InFIGS. 3 and 4, a modified exemplary embodiment of the light emitting diode component described in conjunction withFIGS. 1,2A and2B is shown. In this exemplary embodiment, the semiconductor chip1is secured, tipped onto a side face, to the first contact layer3and the second contact layer5. In this case, the active layer2is at a right angle to the chip support film6. This arrangement has the advantage of not requiring any bond wires for securing the semiconductor chip1to the contact layers. However, a disadvantage is that one side of the active layer2is covered by the chip support film6. Moreover, the top and bottom sides of the semiconductor chip1are at least partly covered with material that is used to secure the semiconductor chip1to the first contact layer3and the second contact layer5. In comparison to the exemplary embodiment shownFIGS. 1,2A and2B, the light yield is less in the light emitting diode ofFIGS. 3 and 4.

As a material for the chip support film6, especially temperature-proof and metallizable plastic films can be considered. For instance, the chip support film6can be an epoxy-resin-based chip support film, or it can be made from polyimide or a polyester, such as polyethylene naphthalate. As the material for the reflector frame7, temperature-stable and optically reflective materials such as polyphthalamide (PPA), liquid crystal polymer (LCP), and polyetheretherketone (PEEK) are especially suitable. Other thermoplastics can also be considered, as long as they are temperature-stable and optically reflective. Such thermoplastics can have a very high reflectivity, from embedded pigments, such as TiO2.

The materials are selected such that the reflector frame7sticks to the chip support film6. To improve the strength of the bond between the reflector frame7and the chip support film6, at least one opening or recess in the chip support film6may be provided, which is engaged by a retaining peg11of the reflector frame7.

As the material for the filler compound10, one of the usual reaction resins for producing optoelectronic semiconductor components can be used, such as epoxy resin, silicone resin, or acrylate-like compounds.

As the luminescent material, a pigment based on cerium-doped yttrium-aluminum-garnet (YAG:Ce) is suitable, such as (Y1-x-yGdxTby)3Al5O12:Ce, where 0≦x≦1, 0≦y≦1, and x+y≦1.

In addition to the luminescent material, a diffusor material such as titanium dioxide, barium oxide, zirconium dioxide, or dialuminum trioxide can be included in the filler compound10. This diffusor material advantageously contributes to a more-homogeneous appearance of the projected light. If no beam conversion is to be effected but instead only scattering of the emitted radiation, then to that end the filler compound10can contain only diffusor material but not any luminescent material.

For producing the light emitting diodes, a metal foil is preferably first laminated to a chip support film strip and then coated with a photoresist layer. The photoresist layer is exposed to light, and then the photoresist layer and the metal foil are structured, by-an etching process known per se, so that many pairs of contact layers3and5are removed, and the reflector frame7is applied to the chip support film strip, for instance by means of transfer molding or injection molding. For anchoring the reflector frame7to the chip support film6, openings are made in the film which can be engaged by the pegs11of the reflector frame7.

As an alternative to the injection molding or transfer molding of the reflector frame, it is conceivable to simply place and/or glue prefabricated reflector frames7onto the chip support film6.

Next, each semiconductor chip1is placed on the chip support film strip. After each semiconductor chip1has been bonded and the wire connection4has been made between the top contact of the chip1and the contact layer5, the interior of the associated reflector frame7is filled with the filler compound10. The chip support film6is then folded or rolled up, creating an easily handled packaging unit for the light emitting diodes.

As an alternative to the procedure explained above, the respective reflector frame7can be applied only after the associated semiconductor chip1has been mounted on the chip support film6.

In the exemplary embodiments shown inFIGS. 1-4, the chip support film6is embodied in bandlike form, and the semiconductor chips1are lined up along the chip support film6. In addition, the chip support film6can be selected to be wide enough that there is space for a plurality of rows of light emitting diode chips side by side.

It is also possible to dispose a plurality of

It is also possible to dispose a plurality of semiconductor chips1within a single reflector7and in this way to obtain among other things light emitting diode components that light up in various colors or that emit multicolored light.

Also in the design according to the invention, the back side of the chip support film6can likewise be provided in a simple way with a metallizing layer or metallizing structure12as a shielding layer, in particular over the full surface, which serves to shield against interfering waves in high-frequency applications.

The designs described here are distinguished by requiring comparatively little space and by the possibility of being virtually completely sunk in an opening in a printed circuit board. The flexible chip support film6can furthermore be adapted without difficulty to various spatial conditions. Since furthermore the chip support film6is embodied as generally thin, the light emitting diodes generally have a low structural height. Especially flat components are therefore obtained.

A further advantage is that the chip support film6and the reflector frame7can be made from materials that have identical or at least very similar coefficients of thermal expansion. This makes the reliability of the light emitting diodes in temperature cycles very high.

Finally, it is also advantageous that the light emitting diode components produced by means of the chip support film6no longer require any particular additional packaging belt for packaging and shipping. The elastic chip support film can advantageously fully perform the role of a

The chip support film strip is preferably not cut apart into the desired individual components or groups of components made up of a plurality of components until just before the components are mounted.

If light emitting diode components produced in this way are to be used for backlighting a keypad, for instance in a mobile radio communication device, then the chip support film can be cut apart on the assembly line for the mobile radio set, and the intended groups of light emitting diodes can be inserted jointly into the mobile radio set. In such an application, the circuits required for triggering the light emitting diode chips are expediently already embodied on the chip support film6.

The method has been described above in terms of light emitting diodes. However, other semiconductor chips can be packaged and made easy to handle in the manner described as well.

InFIG. 5, a module with a plurality of components of the invention is shown. A plurality of openings20is made in a substrate element19, such as a printed circuit board. The substrate element19also has a projection side21.

A plurality of radiation-emitting components of the invention are secured to the side of the substrate element19opposite the projection side21; a housing frame7of each radiation-emitting component protrudes into a respective one of the openings20, and the projection direction24extends through the openings20.

Each chip support6rests with its electrical strip conductors3and5of the component on the surface, opposite the projection side21, of the substrate element19. For securing the components, adhesive connections or soldered connections can be employed. Because the chip support6is preferably embodied as flat, the space required horizontally and vertically is markedly less than in components of the prior art. In particular, the invention makes an at least partly sunken mounting of the components possible.

Because the chip support6is embodied flexibly, the component is flexible enough to elastically or optionally plastically absorb warping and deformation, without harmful warping being transmitted to the housing or to a radiation-emitting chip located in it. This mounting arrangement is especially well suited for tightly packed flat display modules.

The substrate, or at least the surface on the projection side, is preferably radiation-absorbent, for instance being blackened, so that the contrast between the individual radiation-emitting components and the environment is enhanced. This is especially advantageous in arrangements intended as a display device.

InFIG. 6, another arrangement of components of the invention is shown. Unlike the arrangement described above, the arrangement shown inFIG. 6is suitable in particular as background lighting, for instance for a liquid crystal display.

As in the previous exemplary embodiment, radiation-sunken fashion on a substrate19. On the projection side, a scattering plate22is downstream of the substrate or components. Also, the substrate19or at least the projection-side surface of the substrate19is preferably uniformly diffusely reflective, for instance being white. This enables largely homogeneous backlighting of extremely flat construction. Downstream of the scattering plate is for instance a liquid crystal display (LCD)23that is to be illuminated.

The substrate19can either be rigid, as described above, or flexible, for instance being embodied as a plastic or ceramic film, so that a backlighting or display module can be adapted in a simple way to various shapes and advantageously can even be mounted on surfaces the shape of which changes with time.

It is understood that the explanation of the invention in terms of the exemplary embodiments shown is not meant to limit the invention. For instance, the chip can be mounted directly on a chip mounting face of the chip support, for instance being glued, and the chip can be electrically connected to the conductor tracks solely by means of wire connections. The chip can equally well be mounted on a separate thermal connection that is embedded in the chip support and that can in turn be connected electrically to the conductor tracks by means of wire connections. Heat is transferred from the through the thermal connection, such as to a heat sink. None of these embodiments are outside the fundamental concept of the present invention.