WO2018219460A1

WO2018219460A1 - Method for producing an optoelectronic device

Info

Publication number: WO2018219460A1
Application number: PCT/EP2017/063294
Authority: WO
Inventors: Geok Ling Adelene NG; Seong Tak KOAY; Chui Wai CHONG; Teng Hai Ocean CHUAH; Choon Kim LIM
Original assignee: Osram Opto Semiconductors Gmbh
Priority date: 2017-06-01
Filing date: 2017-06-01
Publication date: 2018-12-06

Abstract

A method for producing an optoelectronic devicecomprises a step, wherein asheetcomprising a wavelength-converting material is provided. Furthermore, at least one optoelectronic semiconductor chip is provided, wherein the optoelectronic semiconductor chip comprises a bottom side. The optoelectronic semiconductor chip is pressedinto the sheetsuch that the optoelectronic semiconductor chip is at least partially em- bedded into the sheet, wherein at least the bottom side re- mains uncovered by the sheet.

Description

METHOD FOR PRODUCING AN OPTOELECTRONIC DEVICE

DESCRIPTION

The present invention relates to a method for producing an optoelectronic device according to the independent claim.

From the state of art, it is known to embed optoelectronic semiconductor chips into a resin. It is also known to embed an optoelectronic semiconductor chip into blends of a resin together with a wavelength-converting material.

The objective of the invention is to provide a method for producing an optoelectronic device. This objective is solved by a method with the features of claim 1.

A method for producing an optoelectronic device comprises the following steps. A sheet comprising a wavelength-converting material is provided. Furthermore, at least one optoelectron^¬ ic semiconductor chip comprising a bottom-side is provided. The optoelectronic semiconductor chip is pressed into the sheet such that the optoelectronic semiconductor chip is at least partially embedded into the sheet, wherein at least the bottom side remains uncovered by the sheet. Advantageously, an optoelectronic semiconductor chip can be embedded easily into the sheet as the method is simple and does not require specialized equipment.

In one embodiment of the method, the sheet is cured after pressing the optoelectronic semiconductor chip into the sheet. Advantageously, the optoelectronic semiconductor chip is safely embedded into the sheet upon curing. Curing of the sheet can e.g. be enabled by thermal treatment.

In an embodiment, the sheet is heated. Heating of the sheet can be performed before and/ or during the optoelectronic semiconductor chip is pressed into the sheet. Advantageously, the sheet becomes viscous upon heating so that the optoelec^¬ tronic semiconductor chip can be pressed into the sheet.

In another embodiment, a first carrier comprising a first carrier-surface is provided. The optoelectronic semiconductor chip is arranged with its bottom-side onto the first carrier- surface. Advantageously, a first carrier can be intended to press the optoelectronic semiconductor chip into the sheet by its weight. In an embodiment, a spacer is arranged on the first carrier- surface before pressing the optoelectronic semiconductor chip into the sheet. Advantageously, the spacer can be designed such that the bottom-side of the optoelectronic semiconductor chip is not embedded into the sheet after pressing the optoe- lectronic semiconductor chip into the sheet.

In an embodiment, the first carrier is removed after pressing the optoelectronic semiconductor chip into the sheet. In an embodiment, the sheet is cut into individual units, wherein at least one individual unit comprises at least one optoelectronic semiconductor-chip being at least partially embedded into the individual unit. Advantageously, an optoe^¬ lectronic device can comprise a user-defined number of optoe- lectronic semiconductor chips being embedded into the sheet.

In an embodiment, the sheet is provided on a second carrier comprising a second carrier-surface. After pressing the opto^¬ electronic semiconductor chip into the sheet, the second car- rier is removed.

In an embodiment, the optoelectronic semiconductor chip is a volume-emitting LED-chip. One advantage of the method for producing an optoelectronic device is that a volume-emitting LED-chip can be embedded into the sheet without risking the leakage of non-converted electromagnetic radiation emitted by the volume-emitting LED-chip as the LED-chip can be embedded into the sheet such that only a bottom-side of the LED-chip is not covered by the sheet while the most parts are embedded into the sheet thus emitting electromagnetic radiation that becomes converted by the wavelength-converting material with^¬ in the sheet.

In an embodiment, the sheet comprises silicone or an epoxy. Advantageously, the sheet can be obtained in an uncured state which allows pressing the optoelectronic chip into the sheet. The above-described properties, features and advantages of this invention and the way in which they are achieved will become clearer and more clearly understood in association with the following description of the exemplary embodiments explained in greater detail in association with the drawings. Here, in each case in schematic illustration:

Fig. 1 shows a side view of optoelectronic semiconductor chips being arranged with their bottom sides on a first carrier-surface;

Fig. 2 shows a side view of the optoelectronic semiconductor chips being arranged with their upper sides on a sheet;

Fig. 3 shows a side view of the optoelectronic semiconductor chips after pressing them into the sheet;

Fig. 4 shows a side view of a separation step, wherein the sheet with the optoelectronic semiconductor chips embedded therein is cut into individual units;

Fig. 5 shows a side view of an optoelectronic device.

Fig. 1 shows a schematic side view of optoelectronic semicon^¬ ductor chips 30 being arranged on a first carrier-surface 21 of a first carrier 20. The first carrier 20 can comprise any suitable material, e.g., the first carrier 20 can be a metal^¬ lic carrier. In the shown case, three optoelectronic semiconductor chips 30 are arranged on the first carrier-surface 21. The number of optoelectronic semiconductor chips 30 arranged on the first carrier-surface 21 can deviate from the case shown in Fig. 1.

The optoelectronic semiconductor chips 30 comprise upper sides 31, bottom sides 32 and side facets 33. They are ar^¬ ranged with their bottom sides 32 on the first carrier- surface 21. The bottom sides 32 may comprise electric con^¬ tacts 34 of the optoelectronic semiconductor chips 30. A dou^¬ ble-sided adhesive tape or any other common fixation means could be used to arrange the optoelectronic semiconductor chips 30 on the first carrier-surface 21.

The optoelectronic semiconductor chips 30 are designed to emit electromagnetic radiation. The optoelectronic semicon^¬ ductor chips 30 may be any emitting diodes, for example vol^¬ ume-emitting LED-chips. In this case, the optoelectronic sem- iconductor chips 30 are capable of emitting electromagnetic radiation at their upper sides 31 and their side facets 33.

Fig. 2 shows a schematic side view of the carrier 20 and the optoelectronic semiconductor chips 30 being arranged such that the upper sides 31 of the optoelectronic semiconductor chips 30 are in contact with a sheet 60 provided on a second carrier-surface 51 of a second carrier 50. The second carrier 50 can comprise any suitable material. The sheet 60 is pro^¬ vided in order to embed the optoelectronic semiconductor chips 30 into it. The sheet 60 can e.g. comprise a silicone or an epoxy. Furthermore, the sheet 60 is provided to convert electromagnetic radiation emitted by the optoelectronic semi^¬ conductor chips 30 by modifying its wavelength. Therefor the sheet comprises a wavelength-converting material 61. A wave- length-converting material 61 is also called a phosphor. As a typical example, cerium-doped yttrium aluminium garnet (YAG:Ce³⁺) based phosphors can be used as wavelength- converting materials 61. One approach to convert the wave- length of electromagnetic radiation may consist of using a LED and converting a part of the emitted light to longer wavelengths, thus obtaining a mixture of the originally emit^¬ ted and the converted light.

In order to embed the optoelectronic semiconductor chips 30 into the sheet 60, the sheet is provided in an uncured state. Heating such a sheet 60 enables a softening of the sheet 60. In such a viscous state the optoelectronic semiconductor chips 30 can be pressed into the sheet 60.

Apart from the optoelectronic semiconductor chips 30, a spac^¬ er 40 is arranged on the first carrier-surface 21. The spacer can e.g. be a wafer ring or any other suitable means with a defined height. The spacer 40 is intended to define a depth for pressing the optoelectronic semiconductor chips 30 into the sheet 60. This allows to define the parts of the optoe^¬ lectronic semiconductor chips 30 to be embedded into the sheet 60. E.g. if the bottom sides 32 of the optoelectronic semiconductor chips 30 comprise electric contacts 34, it is desirable to embed the optoelectronic semiconductor chips 30 only partially, so that the bottom sides 32 remain uncovered by the sheet 60. In order to ensure that the bottom sides 32 of the optoelectronic semiconductor chips 30 remain uncovered by the sheet 60, the spacer 40 comprises a height 41 such that a gap 70 between the spacer 40 and the second carrier 50 comprises a height 71 which is smaller than a height 35 of the optoelectronic semiconductor chips 30. The spacer 40 can also be omitted. Alternatively, an actuator could be used to press the optoelectronic semiconductor chips 30 into the sheet 60 by applying a defined force onto the first carrier 20 until the desired parts of the optoelectron^¬ ic semiconductor chips 30 are embedded into the sheet 60. However, by using a spacer 40 in combination with a heavy weight metal carrier as the first carrier 20 the optoelec^¬ tronic semiconductor chips 30 will sink into the sheet 60 due to the weight of the first carrier 20. Advantageously, such a method for embedding optoelectronic semiconductor chips 30 into a sheet 60 does not require specialized equipment. The spacer 40 could also be arranged on the second carrier- surface 51.

Fig. 4 shows a schematic side-view of the optoelectronic sem^¬ iconductor chips 30 after pressing them into the sheet 60. Apart from their bottom sides 32, the optoelectronic semicon^¬ ductor chips 30 are embedded into the sheet 60. By further heating of the sheet 60 the sheet 60 can be cured. Typically, a temperature during curing will be higher than a temperature during the pressing of the optoelectronic semiconductor chips 30 into the sheet 60. After curing, the sheet 60 is hardened and the optoelectronic semiconductor chips 30 are safely em- bedded into the sheet 60.

In Fig. 2 and 3 the first carrier 20 is arranged above the second carrier 50 but this has not necessarily to be the case. It is also possible to flip the geometry, such that the second carrier 50 is arranged above the first carrier 20. In this case, the second carrier 50 could be a heavy metal car^¬ rier pressing the sheet 60 by its own weight to embed the op^¬ toelectronic semiconductor chips 30 into the sheet 60. Fig. 4 shows a schematic side view of the optoelectronic sem^¬ iconductor chips 30 being embedded into the cured sheet 60 while the first carrier 20 has been removed. The sheet 60 is further cut along the cutting lines 80 to obtain individual units of the sheet 60, wherein at least one individual unit comprises at least one optoelectronic semiconductor chip 30 being at least partially embedded into the individual unit of the sheet 60. The second carrier 50 can be removed before or after cutting the sheet 60. Fig. 5 shows a schematic side view of an optoelectronic de^¬ vice 10 after fabrication. The optoelectronic device 10 com^¬ prises an optoelectronic semiconductor chip 30 being partial^¬ ly embedded into the sheet 60. The bottom side 32 of the op- toelectronic semiconductor chip 30 comprises electric con^¬ tacts 34 and is not covered by the sheet 60 while the upper side 31 and the side facets 33 are covered by the sheet 60. Such an optoelectronic device 10 advantageously gets rid of a leakage of the light emitted by the optoelectronic semicon^¬ ductor chip 30 without being converted by the wavelength- converting material 61. A further advantage consists in a good heat dissipation as most parts of the optoelectronic semiconductor chip 30 are embedded into the sheet 60 and be- ing in direct contact with the sheet 60 as no interconnect is arranged between them. An optoelectronic device 10 as shown in Fig. 5 is often referred to as a chip scale package (CSP) . The optoelectronic device 10 may e.g. comprise a LED-chip emitting blue light and a phosphor converting the blue light into yellow light resulting in the effective emission of white light.

The invention has been illustrated and described in more spe^¬ cific detail on the basis of the preferred exemplary embodi- ments. Nevertheless, the invention is not restricted to the examples disclosed. Rather, other variations can be derived therefrom by the person skilled in the art, without departing from the scope of protection of the invention.

REFERENCE LIST optoelectronic device first carrier

first carrier-surface

30 optoelectronic semiconductor chip

31 upper side of the optoelectronic semiconductor chip 32 bottom side of the optoelectronic semiconductor chip

33 side faces of the optoelectronic semiconductor chip

34 electric contacts of the optoelectronic semiconductor chip

35 height of the optoelectronic semiconductor chip

40 spacer

41 height of the spacer

50 second carrier

51 second carrier-surface

60 sheet

61 wavelength-converting material 70 gap

71 height of the gap

80 cutting line

Claims

1. A method for producing an optoelectronic device (10) com^¬ prising :

- providing a sheet (60) comprising a wavelength- converting material (61);

- providing at least one optoelectronic semiconductor chip (30), wherein the optoelectronic semiconductor chip (30) comprises a bottom side (32);

- pressing the optoelectronic semiconductor chip (30) into the sheet (60) such that the optoelectronic semicon^¬ ductor chip (30) is at least partially embedded into the sheet (60), wherein at least the bottom side (32) remains uncovered by the sheet (60) .

2. The method as claimed in claim 1, comprising the following step after pressing the optoelectronic semiconductor chip (30) into the sheet (60) :

- curing the sheet (60) .

3. The method as claimed in claim 1 or 2,

wherein the sheet (60) is heated before and/ or during the optoelectronic semiconductor chip (30) is pressed in^¬ to the sheet ( 60 ) .

4. The method as claimed in one of the previous claims, com^¬ prising :

- providing a first carrier (20) comprising a first carrier-surface (21);

- arranging the optoelectronic semiconductor chip (30) with its bottom side (32) onto the first carrier-surface (21) .

5. The method as claimed in claim 4,

wherein the following step is performed before pressing the optoelectronic semiconductor chip (30) into the sheet (60) :

- arranging a spacer (40) on the first carrier-surface (21) .

6. The method as claimed in claim 4 or 5, comprising the

following step after pressing the optoelectronic semicon- ductor chip (30) into the sheet (60) :

- removing the first carrier (20) .

7. The method as claimed in one of the previous claims, com^¬ prising :

- cutting the sheet (60) into individual units, wherein at least one individual unit comprises at least one opto^¬ electronic semiconductor chip (30) being at least partially embedded into the individual unit.

8. The method as claimed in one of the previous claims,

wherein the sheet (60) is provided on a second carrier (50) comprising a second carrier-surface (51), wherein the method comprises the following step after pressing the optoelectronic semiconductor chip (30) into the sheet (60) :

- removing the second carrier (50) .

9. The method as claimed in one of the previous claims,

wherein the optoelectronic semiconductor chip (30) is a volume-emitting LED-chip.

10. The method as claimed in one of the previous claims,

wherein the sheet (60) comprises a silicone or an epoxy.