WO2017182094A1

WO2017182094A1 - Led module and method for producing an led module

Info

Publication number: WO2017182094A1
Application number: PCT/EP2016/058985
Authority: WO
Inventors: Heng Keong Yip
Original assignee: Osram Opto Semiconductors GmbH
Current assignee: Ams Osram International GmbH
Priority date: 2016-04-22
Filing date: 2016-04-22
Publication date: 2017-10-26
Anticipated expiration: 2018-10-22

Abstract

An LED module (10) comprises a glass tube (100) having a cylindrical shape. A filling material (500) is arranged inside the glass tube (100). A plurality of LED chips (200) is arranged on an outer barrel surface (140) of the glass tube (100).

Description

LED MODULE AND METHOD FOR PRODUCING AN LED MODULE DESCRIPTION The present invention relates to an LED module and to a meth^¬ od for producing an LED module according to the independent claims .

LED modules with LED chips (light emitting diode chips) are known in the state of the art for lighting applications. It is known in the state of the art to provide LED modules with a plurality of LED chips for increasing the brightness.

It is an object of the present invention to provide an LED module. It is a further object of the present invention to provide a method for producing an LED module. These objec^¬ tives are achieved by an LED module and by a method for pro^¬ ducing an LED module according to the independent claims. Various embodiments are disclosed in the dependent claims.

An LED module comprises a cylindrical glass tube. A filling material is arranged inside the glass tube. A plurality of LED chips is arranged on a barrel surface of the glass tube. The filling material arranged inside the glass tube of this LED module can advantageously improve dissipation of heat generated in the LED chips and can increase thermal homogene^¬ ity inside the LED module to increase the reliability of the LED module. The arrangement of the LED chips on the barrel surface of the glass tube of the LED module allows the LED module to emit light into a large angle, for example into an angle of up to 360 degrees. Light emitted by this LED module may comprise a high optical homogeneity. In an embodiment of the LED module, the filling material com^¬ prises silicone. Advantageously, this allows for an easy ar^¬ rangement of the filling material inside the glass tube of the LED module. Additionally, the filling material comprising silicone may comprise advantageous thermal properties and may be available at affordable prices.

In an embodiment of the LED module, the filling material com- prises light-reflective particles. Advantageously, the fill^¬ ing material comprising light-reflective particles can re^¬ flect light emitted by the LED chips of the LED module and can thus increase the efficiency of the LED module. In an embodiment of the LED module, the barrel surface and the LED chips are at least partially covered with a covering material. Advantageously, the covering material may protect the LED chips arranged on the barrel surface from damage caused by external impacts. The covering material may for ex- ample protect bond wires for electrically connecting the LED chips from tearing.

In an embodiment of the LED module, the covering material comprises silicone. This allows for an easy and cost- effective production of the LED module. The covering material may for example be applied to the barrel surface of the glass tube of the LED module by dipping the glass tube into the covering material. In an embodiment of the LED module, a phosphor is embedded in the covering material. The phosphor may be designed for con^¬ verting at least parts of light emitted by the LED chips of the LED module into light of a different wavelength. The phosphor may for example be designed for converting light comprising a wavelength in the blue or ultraviolet spectral range into yellow light.

In an embodiment of the LED module, the glass tube and the LED chips are at least partially enclosed in a molding mate- rial. The molding material may serve to protect the glass tube and the LED chips from damage by external impact. The molding material may also serve to provide the LED module with consistent outer dimensions, independently of a thick- ness of a covering material arranged between the glass tube and the molding material.

In an embodiment of the LED module, a phosphor is embedded in the molding material. The phosphor may be designed for con^¬ verting at least parts of light emitted by the LED chips of the LED module into light of a different wavelength. The phosphor may for example be designed to convert light com^¬ prising a wavelength in the blue or ultraviolet spectral range into yellow light. A phosphor embedded in the molding material may be provided instead of or in addition to a phos^¬ phor embedded in the covering material.

In an embodiment of the LED module, the glass tube is closed on one of its longitudinal ends. Advantageously, this simpli^¬ fies filling the filling material into the glass tube.

In an embodiment of the LED module, a metallisation is ar^¬ ranged on the barrel surface of the glass tube. The metalli- sation may serve for electrically connecting the LED chips arranged on the barrel surface of the glass tube of the LED module .

In an embodiment of the LED module, the glass tube comprises at least two electrical contact elements for electrically connecting the LED module. The electrical contact elements may serve as external contact elements and may be electrical^¬ ly connected to the LED chips of the LED module. In an embodiment of the LED module, the arrangement of LED chips comprises at least one strand of LED chips which are arranged one after another along a longitudinal direction of the glass tube. The LED chips of that strand are electrically connected in a serial manner. Advantageously the serial con- nection of the LED chips of the strand ensures that all LED chips of the strand are driven with equal current during op^¬ eration of the LED module. In an embodiment of the LED module, the arrangement of LED chips comprises a plurality of strands of LED chips. The strands are arranged in parallel to each other. The strands are electrically connected in a parallel manner. Advanta- geously, the arrangement of a plurality of strands of LED chips on the barrel surface of the glass tube allows for emitting light into a large angle of up to 360 degrees. The more strands the LED module comprises, the higher an optical homogeneity of the light emitted by the LED module may be. The parallel arrangements of the plurality strands advanta^¬ geously ensures that each strand of the LED module is driven with the same electrical voltage during operation of the LED module . In an embodiment of the LED module, the LED chips are elec^¬ trically connected with bond wires. Advantageously, this al^¬ lows for an easy and reliable electrical connection of the LED chips . A method for producing an LED module comprises steps for providing a cylindrical glass tube, for arranging a plurality of LED chips on a barrel surface of the glass tube, and for arranging a filling material inside the glass tube. Advantageously, this method allows for producing an LED mod^¬ ule capable of emitting light into a large angle of up to 360 degrees. The filling material arranged inside the glass tube of the LED module may serve to improve dissipation of heat generated in the LED chips and may improve thermal homogenei- ty inside the LED module and a reliability of the LED module. Additionally, the filling material may serve to reflect light emitted by the LED chips to increase an efficiency of the LED module . In an embodiment of the method, the LED chips are attached to the barrel surface by means of a silicone die attach adhe^¬ sive. Advantageously, this allows for a simple, reliable and cost-effective attachment of the LED chips. The silicone die attach adhesive may be UV precured. The attachment of the LED chips to the barrel surface may be followed by curing the silicone die attach adhesive in an oven. In an embodiment of the method, the method comprises a step for covering at least parts of the barrel surface and the LED chips with a covering material. The covering material may serve to protect the LED chips from damage caused by external impacts. Covering the barrel surface and the LED chips with the covering material may be carried out by dipping the glass tube carrying the LED chips into the covering material. The covering material may for example comprise a silicone. The step of covering the barrel surface and the LED chips with the covering material may be carried out before arranging the filling material inside the glass tube.

In an embodiment of the method, the method comprises a step for enclosing at least parts of the glass tube and the LED chips by means of a molding process. The molding process may for example be a compression molding process. Enclosing the glass tube and the LED chips by means of the molding process may serve to provide the LED module with consistent outer di^¬ mensions irrespective of outer dimensions of the covering ma^¬ terial that covers at least parts of the barrel surface and the LED chips. The step for enclosing at least parts of the glass tube and the LED chips by means of a molding process may be carried out after covering at least parts of the bar^¬ rel surface and the LED chips with a covering material but before arranging the filling material inside the glass tube.

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 which are explained in greater detail in association with the drawings. Here in schematic illustration in each case: Fig. 1 shows a glass tube provided for producing an LED module ;

Fig. 2 shows a section through the glass tube with LED chips arranged on a barrel surface of the glass tube ;

Fig. 3 shows a section through the glass tube with bond wires arranged between the LED chips;

Fig. 4 shows a section through the glass tube with a

covering material covering the barrel surface of the glass tube and the LED chips arranged on the barrel surface;

Fig. 5 shows a section through the glass tube with a

molding material encapsulating the covering material and the LED chips on the barrel surface of the glass tube; and

Fig. 6 shows a section through an LED module in a finished processing state.

Fig. 1 shows a schematic depiction of a glass tube 100 that may be used for producing an LED module. The glass tube 100 comprises a cylindrical shape and may for example comprise a circular cross section. The glass tube 100 is made of a glass .

The glass tube 100 comprises a hollow interior space 130. The cylindrical glass tube 100 extends along a longitudinal di^¬ rection and comprises a first longitudinal end 110 and a sec^¬ ond longitudinal end 120 that is opposed to the first longi^¬ tudinal end 110. At its first longitudinal end 110, the glass tube 100 is open, providing access to the hollow interior space 130. At its second longitudinal end 120, the glass tube 100 is closed. The cylindrical glass tube 100 comprises an outer barrel sur^¬ face 140. A metallisation 150 is arranged at the barrel sur^¬ face 140. The metallisation 150 comprises a first internal contact ele^¬ ment 151 arranged near the second longitudinal end 120 of the glass tube 100. The first internal contact element 151 may be ring-shaped and may extend circumferentially around the bar^¬ rel surface 140 of the glass tube 100.

The metallisation 150 further comprises a first external con^¬ tact element 153 arranged near the first longitudinal end 110 of the glass tube 100. The first external contact element 153 may for example be of rectangular shape. The first internal contact element 151 and the first external contact element

153 are electrically connected by a section of the metallisa^¬ tion 150 that may for example comprise the shape of a thin strip line. The metallisation 150 further comprises a second internal contact element 152 that is arranged near the first longitu^¬ dinal end 110. The second internal contact element 152 may for example comprise the shape of a slotted ring and extend circumferentially around an angular section of the barrel surface 140 of the glass tube 100. The first external contact element 153 can be arranged in the slot of the second inter^¬ nal contact element 152 such that the second internal contact element 152 and the first external contact element 153 are electrically isolated from one another.

The metallisation 150 further comprises a second external contact element 154 arranged near the first longitudinal end 110 of the glass tube 100. The second external contact ele^¬ ment 154 is arranged closer to the first longitudinal end 110 than the second internal contact element 152. The second ex^¬ ternal contact element 154 and the second internal contact element 152 are electrically connected to each other and may be directly concatenated. Fig. 2 shows a schematic cross section of the glass tube 100 depicted in a processing state that follows the depiction of Fig. 1.

A plurality of LED chips (light emitting diode chips) 200 has been arranged on the barrel surface 140 of the glass

tube 100. The LED chips 200 are designed for emitting elec^¬ tromagnetic radiation, for example visible light. The LED chips 200 may for example be designed to emit light compris^¬ ing a wavelength in the ultraviolet or blue spectral range.

The LED chips 200 are arranged in a plurality of strands 210. Each strand 210 comprises a plurality of LED chips 200. In the exemplary depiction of Fig. 2, each strand 210 comprises nine LED chips 200. The strands 210 may, however, comprise fewer or more than nine LED chips 200 each. Each strand 210 extends in parallel to the longitudinal direction of the glass tube 100 such that the LED chips 200 of each strand 210 are arranged one after another along the longitudinal direc^¬ tion of the glass tube 100. The LED chips 200 of each

strand 210 are arranged between the first internal contact element 151 of the glass tube 100 and the second internal contact element 152 of the glass tube 100.

The individual strands 210 are arranged in parallel to each other and are distributed around the circumference of the barrel surface 140 of the glass tube 100. The LED chips 200 may for example be arranged in three strands 210 which are respectively offset against each other by an angle of

120 degrees. There may, however, be a higher number of strands 210, for example ten or more strands 210. The higher the number of strands 210 is, the better optical homogeneity will be achievable with the LED module produced from the glass tube 100. Optical homogeneity will also be improved if the strands 210 are distributed equally around the circumfer^¬ ence of the barrel surface 140 of the glass tube 100. The LED chips 200 may for example be connected to the barrel surface 140 of the glass tube 100 by means of a silicone die attach adhesive 230. The silicone die attach adhesive 230 may be UV precured. The attachment of the LED chips 200 to the barrel surface 140 of the glass tube 100 may be followed by a process step for oven curing (vertical curing) .

Each LED chip 200 comprises an upper side that faces away from the barrel surface 140 of the glass tube 100. The LED chips 200 are designed for emitting electromagnetic radiation at their upper sides such that electromagnetic radiation is emitted mainly in a radial direction away from the glass tube 100. Each LED chip 200 comprises a first electrical contact pad 201 and a second electrical contact pad 202 arranged on the respective upper side. The first electrical contact pads 201 and the second electrical contact pads 202 are provided for applying an electric voltage and an electric current to the LED chips 200.

Fig. 3 shows a schematic sectional view of the glass tube 100 depicted in a processing state that follows the depiction of Fig. 2.

The LED chips 200 arranged on the barrel surface 140 of the glass tube 100 have been electrically connected with bond wires 220. The bond wires 220 may for example comprise gold. The LED chips 200 of each strand 210 are electrically con- nected in a serial manner. The various strands 210 are elec^¬ trically connected in a parallel manner.

In each strand 210, the first electrical contact pad 201 of the first LED chip 200 that is arranged the closest to the second longitudinal end 120 of the glass tube 100 is electri^¬ cally connected to the first internal contact element 151 of the glass tube 100 with a bond wire 220. The second electri^¬ cal contact pad 202 of this LED chip 200 is electrically con- nected to the first electrical contact pad 201 of the next neighbouring LED chip 200 of that strand 210. The second electrical contact pad 202 of said second LED chip 200 is electrical connected to the first electrical contact pad 201 of the third LED chip 200 of the strand 210 with a bond wire 220. This serial connection extends up to the last LED chip 200 of the strand 210 that is arranged closest to the first longitudinal end 110 of the glass tube 100. The second elec^¬ trical contact pad 202 of said last LED chip 200 is electri- cally connected to the second internal contact element 152 of the glass tube 100.

Fig. 4 shows a schematic sectional view of the glass tube 100 depicted in a processing state that follows the depiction of Fig. 3.

The barrel surface 140 of the glass tube 100 and the LED chips 200 arranged on the barrel surface 140 of the glass tube 100 have at least partially been covered with a covering material 300. The covering material 300 also covers the bond wires 220 that electrically connect the LED chips 200. The covering material 300 may thus serve to protect the LED chips 200 and the bond wires 220 from damage caused by exter^¬ nal influences. In the depiction of Fig. 4, the covering ma- terial 300 also covers the first internal contact element 151 and the second internal contact element 152 of the glass tube 100.

The covering material 300 may comprise a silicone. The cover- ing material 300 may also comprise an embedded phosphor 310. The phosphor 310 may be embedded in the covering material 300 in the form of luminescent particles. The phosphor 310 may serve to convert at least a part of the electromagnetic radi^¬ ation emitted by the LED chips 200 into electromagnetic radi- ation comprising a different wavelength. The phosphor 310 may for example be designed to convert electromagnetic radiation comprising a wavelength in the ultraviolet or blue spectral range into yellow light. The covering material 300 may have been applied to the glass tube 100 by dipping the glass tube 100 into an amount of the covering material 300 provided in liquid state. Afterwards, the covering material 300 may have been hardened using a thermal process or another process. The covering material 300 has been applied to the glass tube 100 such that the covering material 300 has not entered the interior space 130 of the glass tube 100.

The covering material 300 may also have been applied in sev^¬ eral consecutive layers by dipping the glass tube 100 into the amount of liquid covering material 300 several times. In the case that the covering material 300 comprises an embedded phosphor 310, applying the covering material 300 in consecu^¬ tive layers may serve to adjust a colour temperature of a mixture of converted and unconverted light emitted by the LED module to a desired value by adjusting the amount of covering material 300 and phosphor 410 that is being arranged on the barrel surface 140 and the LED chips 200.

Fig. 5 shows a schematic sectional view of the glass tube 100 depicted in a processing state that follows the depiction of Fig. 4.

The covering material 300 covering the barrel surface 140 of the glass tube 100 and the LED chips 200 arranged on the bar^¬ rel surface 140 of the glass tube 100 have been enclosed in a molding material 400. Consequently, also the glass tube 100 and the LED chips 200 are at least partially enclosed in the molding material 400.

The molding material 400 may have been applied by means of a molding process, for example a compression molding process. The molding material 400 has been applied such that no mold^¬ ing material 400 has entered the interior space 130 of the glass tube 100. The molding material 400 serves to provide the assembly of the glass tube 100, the covering material 300 and the molding material 400 with defined and consistent outer dimensions, irrespective of possible variations of the thickness of the layer of covering material 300 arranged on the barrel sur^¬ face 140 of the glass tube 100.

The molding material 400 may for example comprise a silicone. The molding material 400 may also comprise an embedded phos- phor 410. The phosphor 410 may be embedded in the molding ma^¬ terial 400 in the form of luminescent particles. The phos^¬ phor 410 embedded in the molding material 400 may serve to convert at least a part of the electromagnetic radiation emitted by the LED chips 200 into electromagnetic radiation comprising a different wavelength.

In the case that the molding material 400 comprises the em^¬ bedded phosphor 410, the covering material 300 may be chosen as a clear material without the embedded phosphor 310. In the case that the covering material comprises the embedded phos^¬ phor 310, the molding material 400 may be chosen as a clear material without the embedded phosphor 410.

Fig. 6 shows a schematic sectional view of an LED module 10 that has been formed from the arrangement of the glass tube 100, the LED chips 200, the covering material 300 and the molding material 400 depicted in Fig. 5 by performing further processing steps. Fig. 6 depicts a final processing state of the LED module 10.

Following the processing state depicted in Fig. 5, a filling material 500 has been arranged in the interior space 130 in^¬ side the glass tube 100. The filling material 500 may have been filled into the interior space 130 through the open first longitudinal end 110 of the glass tube 100. The open first longitudinal end 110 of the glass tube 100 has after^¬ wards been closed using a plug 600. The plug 600 may, howev^¬ er, be omitted. The filling material 500 may for example comprise a silicone.

The filling material 500 may serve to dissipate heat generat- ed by the LED chips 200 during operation of the LED module 10 and to increase a thermal homogeneity in the LED module 10 during operation of the LED module 10. To this end, the fill^¬ ing material 500 may comprise a high thermal conductivity. The filling material 500 may also comprise embedded light- reflective particles 510. The light-reflective particles 510 may for example comprise silver or Ti02- The light-reflective particles 510 may serve to increase an optical reflectivity of the filling material 500. The filling material 500 ar- ranged in the interior space 130 of the glass tube 100 may serve to reflect light emitted by the LED chips 200 in the direction of the interior space 130 of the glass tube 100 such that this light is reflected into a radial direction away from the LED module 10.

The first external contact element 153 and the second exter^¬ nal contact element 154 arranged at the barrel surface 140 near the first longitudinal end 110 of the glass tube 100 are accessible near the first longitudinal end 110 of the glass tube 100 and may serve to electrically connected the LED mod^¬ ule 10.

The invention has been illustrated and described in detail with the aid of the preferred exemplary embodiments. Never- theless, the invention is not restricted to the examples dis^¬ closed. Rather, other variants may be derived therefrom by a person skilled in the art without departing from the protec^¬ tive scope of the invention. REFERENCE SYMBOLS

10 LED module 100 glass tube

110 first longitudinal end

120 second longitudinal end

130 interior space

140 barrel surface

150 metallisation

151 first internal contact element

152 second internal contact element

153 first external contact element

154 second external contact element

200 LED chip

201 first electrical contact pad

202 second electrical contact pad 210 strand

220 bond wire

230 silicone die attach adhesive

300 covering material

310 phosphor

400 molding material

410 phosphor

500 filling material

510 light-reflective particles

600 plug

Claims

1. An LED module (10)

comprising a cylindrical glass tube (100),

wherein a filling material (500) is arranged inside the glass tube (100) ,

wherein a plurality of LED chips (200) is arranged on a barrel surface (140) of the glass tube (100) .

2. The LED module (10) according to claim 1,

wherein the filling material (500) comprises silicone.

3. The LED module (10) according to one of the previous

claims ,

wherein the filling material (500) comprises light- reflective particles (510).

4. The LED module (10) according to one of the previous

claims ,

wherein the barrel surface (140) and the LED chips (200) are at least partially covered with a covering material (300) .

5. The LED module (10) according to claim 4,

wherein the covering material (300) comprises silicone.

6. The LED module (10) according to one of claims 4 and 5, wherein a phosphor (310) is embedded in the covering material (300) .

7. The LED module (10) according to one of the previous

claims ,

wherein the glass tube (100) and the LED chips (200) are at least partially enclosed in a molding material (400) .

8. The LED module (10) according to claim 7,

wherein a phosphor (410) is embedded in the molding mate^¬ rial (400) .

9. The LED module (10) according to one of the previous claims ,

wherein the glass tube (100) is closed on one of its Ion gitudinal ends (120) .

10. he LED module (10) according to one of the previous

claims ,

wherein a metallisation (150) is arranged on the barrel surface (140) of the glass tube (100) .

11. The LED module (10) according to one of the previous

claims ,

wherein the glass tube (100) comprises at least two elec trical contact elements (153, 154) for electrically con^¬ necting the LED module (10) .

12. The LED module (10) according to one of the previous

claims ,

wherein the arrangement of LED chips (200) comprises at least one strand (210) of LED chips (200) which are ar^¬ ranged one after another along a longitudinal direction of the glass tube (100),

wherein the LED chips (200) of said strand (210) are electrically connected in a serial manner.

13. The LED module (10) according to claim 12,

wherein the arrangement of LED chips (200) comprises a plurality of strands (210) of LED chips (200),

wherein the strands (210) are arranged in parallel to each other,

wherein the strands (210) are electrically connected in a parallel manner.

14. The LED module (10) according to one of the previous

claims ,

wherein the LED chips (200) are electrically connected with bond wires (220) .

15. A method for producing an LED module (10)

comprising the following steps:

- providing a cylindrical glass tube (100);

- arranging a plurality of LED chips (200) on a barrel surface (140) of the glass tube (100);

- arranging a filling material (500) inside the glass tube (100) .

16. he method of claim 15,

wherein the LED chips (200) are attached to the barrel surface (140) by means of a silicone die attach adhesive (230) .

17. he method of one of claims 15 and 16,

wherein the method comprises the following step:

- covering at least parts of the barrel surface (140) and the LED chips (200) with a covering material (300) .

18. The method of one of claims 15 to 17,

wherein the method comprises the following step:

- enclosing at least parts of the glass tube (100) and the LED chips (200) by means of a molding process.