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1. (WO2019025009) METHOD FOR PRODUCING AN OPTOELECTRONIC SEMICONDUCTOR DEVICE
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Description

Method for producing an optoelectronic semiconductor device

A method for producing an optoelectronic semiconductor device is specified.

In document WO 2011/015449 Al a method for producing an optoelectronic semiconductor device is specified.

One problem to be solved is to specify a method with which optoelectronic semiconductor devices can be produced in a particularly short time and at reduced costs.

According to one aspect of the method, the method comprises a method step wherein a frame part, which comprises a plurality of openings, is provided. The frame part is, for example, formed from a rigid material. For example, the frame part comprises a rigid material like a metal and/or a plastic material. The frame part has the shape of a cuboid, for example. The frame part comprises openings which extend completely through the material of the frame part. For example, the openings are arranged at the nodes of a regular lattice, for example a rectangular lattice. In this case, some or all of the openings have the shape of a rectangle, for example. That is to say, the rim of some or all of the openings is in the shape of a rectangle.

For example, parts of the material of the frame part which abut an opening and which connect the top side of an opening to its underside run crosswise or perpendicular to the plane of main extension of the frame part.

According to one aspect of the method an auxiliary carrier is provided in a further method step. The auxiliary carrier has the shape of a cuboid, for example. The auxiliary carrier can be formed from a rigid or from a flexible material. In the lateral directions, which are the directions which run parallel to the plane of main extension of the frame part, the auxiliary carrier has an extension which is equal to or greater than the extension of the frame part. For example, the area of the auxiliary carrier in a plane parallel to the plane of main extension of the frame part is equal to or greater than the area of the frame part.

According to one method step of the method, the auxiliary carrier is connected to the frame part such that the

auxiliary carrier covers at least some of the openings at an underside of the frame part. Thereby it is possible that the auxiliary carrier covers all openings of the frame part. This means that the auxiliary carrier closes the openings which are covered by the auxiliary carrier on one side, namely the underside of the frame part.

The auxiliary carrier and the frame part are connected with each other. For example, the auxiliary carrier and the frame part are connected by a magnetic force, a mechanical force or a chemical bond. It is, for example, possible that the auxiliary carrier and the frame part are glued to one

another. However, the connection between the auxiliary carrier and the frame part can advantageously be broken at least without destroying the frame part or without destroying the frame part and without destroying the auxiliary carrier.

According to a further aspect of the method, the method comprises a method step in which conversion elements are placed onto the auxiliary carrier in at least some of the openings. The conversion elements comprise at least one luminescence conversion material. The luminescence conversion material is configured to absorb electromagnetic radiation of a first wavelength range and to emit electromagnetic

radiation of a second wavelength range. For example, the second wavelength range comprises wavelengths which are greater than the wavelengths of the first wavelength range. For example, it is possible with the conversion element to convert blue primary radiation to yellow secondary radiation.

The conversion elements are placed onto the auxiliary carrier in at least some of the openings. This means that a

conversion element placed into one opening has an area which is equal to or smaller than the cross-sectional area of the opening. For example, after placing the conversion element into one opening onto the auxiliary carrier, at least 90% of the part of the auxiliary carrier placed in the opening is covered by the conversion element. Further it is possible that the part of the auxiliary carrier in the opening is completely covered by the conversion element placed in this opening. Thereby it is possible that the conversion elements are connected with the auxiliary carrier, for example by the same force by which the frame part is connected to the auxiliary carrier. This means that the conversion elements are glued to the auxiliary carrier, for example. Further, it is possible that the conversion elements are only put on the auxiliary carrier without connecting the conversion elements to the auxiliary carrier.

According to a further aspect of the method, an

optoelectronic semiconductor device is placed onto the conversion element in at least some of the openings. For example in every opening an optoelectronic semiconductor chip is placed onto the conversion element in the opening. The optoelectronic semiconductor chip is, for example, an

optoelectronic semiconductor chip which emits electromagnetic radiation, for example light, during operation. For example, the optoelectronic semiconductor chip is a light-emitting diode or a laser diode. The optoelectronic semiconductor chip can be simply placed on the conversion element without a mechanical connection between the conversion element and the optoelectronic semiconductor chip. Further, it is possible that the optoelectronic semiconductor chip is connected to the conversion element by an adhesive material, for example by a glue .

According to one aspect of the method, a housing is placed onto the conversion elements and around the semiconductor chips and in at least some of the openings, for example in all of the openings. The housing is formed from an

electrically insulating material, for example. For example, the housing is formed from a plastic material, such as for example an epoxy resin and/or a silicone material. The housing can comprise further materials, for example particles which are light-scattering and/or light-reflecting or light-absorbing. This means that the housing can for example be reflective to the radiation produced by the optoelectronic semiconductor chip or the housing has a certain color, like black, red or blue.

According to one aspect of the method for producing an optoelectronic semiconductor device, the frame part and the auxiliary carrier are removed. By removing the frame part and the auxiliary carrier single optoelectronic semiconductor devices, each comprising an optoelectronic semiconductor chip, a conversion element and a housing, remain. In this way, a plurality of optoelectronic semiconductor devices is produced .

According to one aspect of the method for producing an optoelectronic semiconductor device, the method comprises the following steps:

- providing a frame part which comprises a plurality of openings,

- providing an auxiliary carrier,

- connecting the auxiliary carrier to the frame part such that the auxiliary carrier covers at least some of the openings at an underside of the frame part,

- placing conversion elements onto the auxiliary carrier in at least some of the openings,

- placing optoelectronic semiconductor chips onto the

conversion elements in at least some of the openings,

- applying a housing onto the conversion elements and around the semiconductor chips in at least some of the openings,

- removing the frame part and the auxiliary carrier.

These steps can be performed in the given order. In

particular the placing of the conversion elements can be conducted before placing the optoelectronic semiconductor chips in the openings and before applying a housing onto the conversion elements and around the semiconductor chips.

It is possible to dispense a housing material around an optoelectronic semiconductor chip. However, the process of dispensing takes a long time and the curing necessary after dispensing the housing material also takes a long time.

Furthermore, there are other handling and quality issues in connection with a dispensing process, such as panel warping, volume inconsistency, creeping of the housing material to places of the optoelectronic semiconductor chip where no housing material is wanted and the escaping of primary radiation at the rims of the optoelectronic semiconductor chip - so-called blue piping for optoelectronic semiconductor chips which emit blue light as primary radiation. Other techniques for forming a housing material around

optoelectronic semiconductor chips for example require an additional sawing process for singulating the optoelectronic semiconductor devices, which also makes the assembly process lengthy and subject to increased yield loss.

The method described herein inter alia relies on the insight that using a frame part allows for example molding of the housing around the optoelectronic semiconductor chips without the requirement of an additional sawing process. Further, the production of the housing and the connection of the

optoelectronic semiconductor chip to a conversion element can be performed in a single method step, which allows for an accelerated production of optoelectronic semiconductor devices. Due to the fact that fewer processes, for example no sawing, are needed for the production of the optoelectronic semiconductor devices, less yield loss is induced because the risk of mechanically damaging the optoelectronic

semiconductor devices during production is reduced.

Further, the production of single units in each opening of the frame part allows, for example, the production by molding in shorter periods of time as in the case where a housing material is formed around a plurality of semiconductor chips by dispensing or molding. Further, material and process variations in terms of total package thickness are overcome by the described method. This means that the optoelectronic semiconductor devices for example show a well-defined layer thickness which does not fluctuate or hardly fluctuates.

Further, cracks in the housing due to the variation in total thickness of the housing are minimized by minimizing the stress induced otherwise due to warping or sawing. In

conclusion, the described method allows for shorter process times and a cheaper production of the optoelectronic

semiconductor devices.

According to one aspect of the method, the auxiliary carrier comprises an adhesive tape which has heat-releasing

properties. Here it is possible that the adhesive tape is placed on the top side of a base body of the auxiliary carrier which faces away from the frame part. Further, it is possible that the auxiliary carrier consists of an adhesive tape which has heat-releasing properties. Due to the heat-releasing properties, it is possible in a later method step to release the tape from the frame part and from the

conversion element by heating.

According to one aspect of the method, the frame part is a waffle pack. This means that the frame part is formed with a material which has the shape of a cuboid and into which openings which completely penetrate through the material are placed at the knots of a rectangular lattice, and the rims of the openings have the shape of rectangles. Here, each opening has the same shape and the same cross-sectional area. With such a frame part it is possible to produce a large number of optoelectronic semiconductor devices which are similar in shape and size.

According to one aspect of the method, at least one of the conversion elements comprises a B-stage or uncured silicone base material. For example, in this case all conversion elements comprise the B-stage silicone base material. For example particles of a luminescence conversion material are introduced into the base material. The usage of a B-stage silicone base material has the advantage that the thus formed conversion elements are sticky before curing. In this way, the conversion elements adhere to the auxiliary carrier, and the optoelectronic semiconductor chip placed on such a conversion element adheres to the conversion element without the need for a further adhesive material like, for example, a glue .

According to one aspect of the method, the housing is applied by compression molding. For example, the housing comprises a silicone material in the shape of pellets which is applied around the optoelectronic semiconductor chips by compression molding .

According to one aspect of the method, the housing material comprises particles of T1O2 and S1O2 in a silicone base material. For example, pellets which comprise these particles and silicone are provided for applying the housing onto the conversion elements and around the semiconductor chips by compression molding. In this way a housing can be produced which is reflective and, for example, has a white appearance. Radiation produced during operation of the optoelectronic semiconductor chip, which leaves the optoelectronic chips through side faces which abut the housing, is reflected by the housing into the optoelectronic semiconductor chip and, for example, leaves the optoelectronic semiconductor chip through the top surface which abuts the conversion element.

According to one aspect of the method, the combined thickness of one of the conversion elements and one of the

optoelectronic semiconductor chips placed on said conversion element is at least the thickness of the frame part e.g. in a region abutting the opening into which the optoelectronic semiconductor chip and the conversion element are placed. In this way, it is possible that on a side facing away from the conversion element the optoelectronic semiconductor chip is flush with the frame part or the semiconductor chip protrudes over the frame part on a side of the frame part facing away from the auxiliary carrier. In this way it is particularly easy to produce an optoelectronic semiconductor device in which the optoelectronic semiconductor chip has a bottom surface which faces away from the conversion element which is not covered by a material of the housing.

According to one aspect of the method, at least some of the optoelectronic semiconductor chips, for example all of the optoelectronic semiconductor chips, comprise contact

locations for electrically contacting the optoelectronic semiconductor chips which are arranged at a bottom surface facing away from the conversion element. In this way, it is possible that the optoelectronic semiconductor chips are surface-mountable . For example, the optoelectronic

semiconductor chips can be so-called flip-chips.

According to one aspect of the method, the bottom surface of at least some of the optoelectronic semiconductor chips remains free of the housing. This means that the housing is applied around the optoelectronic semiconductor chips in such a way that the bottom surface of the optoelectronic

semiconductor chips, for example of all optoelectronic semiconductor chips, remains free of the housing material. In this way it is not necessary to remove the housing material afterwards, which allows for a particularly fast and cost-saving production of the optoelectronic semiconductor

devices .

According to one aspect of the method, the curing of the housing material, the curing of the conversion element, which comprises for example a B-stage silicone material, and the releasing of the auxiliary carrier are conducted by heating during the same method step. This means that the material of the auxiliary carrier, the material of the housing and the material of the conversion element are chosen in such a way that curing of the conversion element and of the housing and releasing of the auxiliary carrier can be completed by means of heat within the same temperature range. This allows for a particularly easy and fast production of the optoelectronic semiconductor devices as all three method steps can be performed during a single heating of the arrangement

comprising the auxiliary carrier, the frame part, the

conversion element and the housing.

According to one aspect of the method, the conversion element completely covers the auxiliary carrier in the region of the opening into which the conversion element is placed. Due to this fact, the housing material does not cover the side surface or the top surface of the conversion element which faces away from the optoelectronic semiconductor chip, and in the finished optoelectronic semiconductor device only the conversion element, not the housing material, is visible in top view.

In the following the method described herein is further explained with respect to schematic drawings which illustrate method steps of an embodiment of the described method.

Figures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10A, 10B show schematic drawings which illustrate method steps of a method described herein .

In the exemplary embodiments and figures, similar or

similarly acting constituent parts are provided with the same reference symbols. The elements illustrated in the figures and their proportions in relation to one another should not be regarded as true to scale. Rather, individual elements may be represented with an exaggerated size for the sake of better representability and/or for the sake of better

understanding .

In a first method step, shown in Figure 1, a frame part 1 is provided. The frame part 1 comprises a base material into which a plurality of openings 11 are formed. For example the frame part 1 is a waffle pack, which comprises a plurality of openings 11 which are through-holes. The dimension of the openings 11 is customized to the size of the optoelectronic semiconductor device which is to be produced and the area of the frame part 1 is determined according to the molding capacity and capability of the used machines. For example the frame part 1 comprises or consists of a plastic material like Teflon or consist of a metal material like steel. The frame part 1 is recyclable and can be used multiple times for producing optoelectronic semiconductor devices.

In a second method step, shown in Figure 2, an auxiliary carrier 2, for example an adhesive tape, is placed on the underside la of the frame part 1. By this attaching of auxiliary carrier 2 pockets of a cavity are produced. For example, the auxiliary carrier 2 comprises a heat-releasing tape which loses its adhesiveness upon heating.

In a next method step, shown in Figure 3, conversion elements 3 are picked and placed into the openings 11 of the frame part 1 on the top side of the auxiliary carrier 2 which faces the frame part 1. The conversion elements 3 comprise a B-stage silicone material, for example. The size and the shape of the conversion element 3 are, for example, exactly the size and shape of the openings 11 in the frame part 1 and the size and shape of the optoelectronic semiconductor device produced by the described method.

In connection with Figure 4 a further method step is shown, in which optoelectronic semiconductor chips 4 are picked and placed into the openings 11. Each optoelectronic

semiconductor chip is placed with its top surface, through which electromagnetic radiation is emitted during operation, towards the conversion elements 3. At the bottom surface 43 contact locations 41 and 42 for electrically contacting the optoelectronic semiconductor chips are arranged. The size of each optoelectronic semiconductor chip is smaller than the size of the openings 11 and thus there is some empty space surrounding each optoelectronic semiconductor chip.

In the next method step, shown in Figure 5, a housing

material 5 is applied, for example by molding or pellets which comprise T1O2, S1O2 and a silicone material.

After the application of the housing material around each optoelectronic semiconductor chip, degating by the molding machine and then a laser de-flashing for any mold flashes onto the optoelectronic semiconductor chips during molding are performed. This is illustrated in Figure 6.

In the next method step, shown in Figure 7, detaping is performed to release the auxiliary carrier 2. For example in the case that a heat-releasing tape is used as an auxiliary carrier 2, after molding and curing of the housing 5 the auxiliary carrier 2 no longer adheres to the conversion element 3 and the frame part 1, which allows a simple detaping to release the auxiliary carrier 2.

This results in the arrangement of Figure 8, consisting of the frame part 1, the housing 5, the semiconductor chips 4 and the conversion elements 3.

In a next method step, shown in Figure 9, the single

optoelectronic semiconductor devices are released from the frame part 1, for example by using a rubber pin to release the devices from the bottom surface 43 of the optoelectronic semiconductor chips.

The method results in a plurality of optoelectronic

semiconductor devices as shown, for example, in Figure 10A from the bottom surface 43 of the optoelectronic

semiconductor chips 4 or in Figure 10B from the top side, which is completely covered by the conversion element 3.

The invention is not restricted to the exemplary embodiments by the description on the basis of said exemplary

embodiments. Rather, the invention encompasses any new feature and also any combination of features, which in particular comprises any combination of features in the patent claims and any combination of features in the

exemplary embodiments, even if this feature or this

combination itself is not explicitly specified in the patent claims or exemplary embodiments.

Reference Signs

1 frame part

la underside

lb top side

11 opening

2 auxiliary carrier

3 conversion element

4 semiconductor chip

41 contact location

42 contact location

43 bottom surface

5 housing

10 semiconductor device