# Patent

## Title
Flip chip type LED lighting device manufacturing method

## Abstract

A flip chip type LED lighting device manufacturing method includes the step of providing a strip, the step of providing a submount, the step of forming a metal bonding layer on the strip or submount, the step of bonding the submount to the strip, and the step of cutting the structure thus obtained into individual flip chip type LED lighting devices.

## Background
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a lighting device manufacturing method and more particularly, to a simple method of making flip chip type LED lighting devices without wire bonding.
2. Description of the Related Art
A lighting device is a requisite in our daily life. It lights up the space when dark. Following fast development of high technology, flip chip LEDs have been intensively used to substitute for conventional incandescent lamps.
FIG. 1 is a schematic sectional view of a flip chip type LED lighting device made according to the prior art. According to this design, the flip chip type LED lighting device 1 comprises a submount 12, bond fingers 16, 18 provided at two sides of the submount 12, and a plurality of flip chip LEDs (light emitting diodes) 10 bonded on the submount 12 and electrically connected to the bond fingers 16, 18 by wire bonding. According to this design, a die bonding and a wire bonding procedures must be employed to have the legs of the LEDs 10 connected to the bond fingers 16, 18. This wire bonding procedure is complicated. During wire bonding, the LEDs 10 or submount 12 may be damaged accidentally.
Therefore, it is desirable to provide a flip chip type LED lighting device manufacturing method, which eliminates the aforesaid problem.
SUMMARY OF THE INVENTION
The present invention has been accomplished under the circumstances in view. It is one object of the present invention to provide a flip chip type LED lighting device manufacturing method, which eliminates the application of wire bonding. It is another object of the present invention to provide a flip chip type LED lighting device manufacturing method, which has the bottom wall of the submount exposed to the outside for the bonding of a heat conducting/dissipating member to improve the heat dissipation effect of the lighting device. To achieve these and other objects of the present invention, the flip chip type LED lighting device manufacturing method comprises the steps of a) providing a strip, the strip comprising a plurality of strip elements, the strip elements having a respective metal lead frame respectively electrically connected to one another; b) providing a submount, the submount comprising a submount and a plurality of flip chip LEDs (light emitting diodes) installed in the submount; c) forming a metal bonding layer between the strip bond pad, that has been pre-fixed in the strip, and the submount to form a lighting structure; and d) cutting the lighting structure thus obtained into individual flip chip type LED lighting devices based on each strip element. The method of the invention further comprises the step of bonding a heat conducting/dissipating member to the submount of each individual flip chip type LED lighting device.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic sectional view of a flip chip type LED lighting device made according to the prior art.
FIG. 2 is a block diagram showing the flow of a flip chip type LED lighting device manufacturing method according to the present invention.
FIG. 3 is a schematic drawing of a strip for the fabrication of a flip chip type LED lighting device according to the present invention.
FIG. 4 is a schematic sectional view of a flip chip type LED lighting device made according to the present invention.
FIG. 5 is a schematic sectional view of a light module based on a flip chip type LED lighting device according to the present invention.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 2, a flip chip type LED lighting device manufacturing method in accordance with the present invention includes the steps of:
S10—providing a strip, as FIG. 3 shown, wherein the strip is prepared having a plurality of strip elements 20, each strip element 20 having a metal lead frame 21, the metal lead frames 21 of the strip elements 20 being respectively electrically connected together;
S12—providing a submount, for example, silicon or low temperature co-firing ceramic(LTCC) submount is provided, and a plurality of light emitting elements, for example, light emitting diodes are installed on the silicon submount by flip chip;
S14—formation of metal bonding layer where a metal bonding layer is formed on the bottom wall of the strip or the top wall of the submount with a low temperature solder material for example, tin base alloy, bismuth base alloy, or indium base alloy, or by means of eutectic bonding, or gold to gold ultrasonic bonding to form a lighting structure;
S16—bonding of sub-mount to strip where the submount is attached to the bottom side of the strip and at the same time the submount is heated to melt the metal bonding layer to fix the submount to the strip and to electrically connect the metal lead frames to the bond pads of the submount, or using a lower bonding temperature by associating with ultrasonic energy; and
S18—cutting where the structure thus obtained is cut into individual flip chip type LED lighting devices each containing one strip element.
After the aforesaid step S18, a heat conducting/dissipating member is provided under and fixedly fastened to each individual flip chip type LED lighting device. The heat conducting/dissipating member could be bonded to the flip chip type LED lighting device by means of the application of a conductive adhesive containing silver or copper filler. Alternatively, a low temperature solder material may be directly applied on the bottom wall of the flip chip type LED lighting device and following treated with thermal process (Ex. reflow) to achieve the bonding. It is also constructive to bond a heat conducting/dissipating member to the bottom wall of each individual flip chip type LED lighting device by means of eutectic bonding.
After bonding of a heat conducting/dissipating member to the bottom wall of each individual flip chip type LED lighting device, a light condensing element, for example, condenser lens or reflector is used to adjust the light path of the lighting device, enhancing the radiation brightness.
FIG. 4 is a sectional view of a flip chip type LED lighting device 2 made according to the present invention. As illustrated, the flip chip type LED lighting device 2 comprises a strip element 20, a metal lead frame 21 embedded in the strip element 20, a flip chip embedded submount 22 bonded to the strip element 20, flip chip LEDs 24 bonded to circuits on the strip element 20, and a metal, for example, conductive or Ag paste bonding layer 26 between the strip element 20 and the sub-mount 22.
FIG. 5 is a light module based on the aforesaid flip chip type LED lighting device. As illustrated, the light module comprises a flip chip type LED lighting device 2, a heat conducting/dissipating member 30 bonded to the bottom wall of the submount 22 by means of a thermal interface material (TIM), for example, silver glue, copper glue, low temperature solder material, and a light condensing element 32 covering the top side of the flip chip type LED lighting device 2 to concentrate the light of the flip chip LEDs 24.
As indicated above, The method of the present invention comprises the step of providing a strip, the step of providing a submount, the step of forming a metal bonding layer on the strip or submount, the step of bonding the submount to the strip, and the step of cutting the structure thus obtained into individual flip chip type LED lighting devices. This method eliminates the procedure of wire bonding as is commonly seen in the prior art designs. Therefore, the invention simplifies the fabrication of flip chip type LED lighting devices.
Although a particular embodiment of the invention has been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention.

## Claims

1. A flip chip type LED lighting device manufacturing method comprising the steps of:
providing a strip, said strip comprising a plurality of strip elements, said strip elements having a respective metal lead frame respectively electrically connected to one another, wherein each strip element comprises a depression on the bottom of each strip element;
providing a submount and a plurality of flip chip LEDs (light emitting diodes) installed on said submount;
forming a metal bonding layer between said strip element and said submount to bond said submount to said strip element to form a lighting structure, wherein the submount is bonded under the strip element and accommodated by the depression of the strip element;
cutting the lighting structure thus obtained into individual flip chip type LED lighting devices based on each said strip element; and
bonding a heat conducting/dissipating member to the submount of each said individual flip chip type LED lighting device, wherein said heat conducting/dissipating member is bonded to the bottom of said submount by means of a thermal interface material.

2. The flip chip type LED lighting device manufacturing method as claimed in claim 1, wherein said submount is a silicon submount having circuits arranged thereon for the bonding of said flip chip LEDs.

3. The flip chip type LED lighting device manufacturing method as claimed in claim 1, wherein said metal bonding layer is formed of a low temperature solder material.

4. The flip chip type LED lighting device manufacturing method as claimed in claim 3, wherein said low temperature solder material is selected from a group of alloys including tin base alloy, bismuth base alloy, and indium base alloy.

5. The flip chip type LED lighting device manufacturing method as claimed in claim 3, wherein said submount is bonded to said strip by said metal bonding layer by means of heating said metal bonding layer to a molten status.

6. The flip chip type LED lighting device manufacturing method as claimed in claim 1, wherein said metal bonding layer is formed of a electric conductive adhesive paste.

7. The flip chip type LED lighting device manufacturing method as claimed in claim 6, wherein said submount is bonded to said strip by said metal bonding layer by means of heating said electric conductive adhesive paste to a hardening status.

8. The flip chip type LED lighting device manufacturing method as claimed in claim 1, wherein said metal bonding layer is bonded to the metal lead frames of said strip elements and said submount by means of eutectic bonding.

9. The flip chip type LED lighting device manufacturing method as claimed in claim 1, wherein said thermal interface material (TIM) is selected from a material group including silver glue, copper glue, and a low temperature solder material.

10. The flip chip type LED lighting device manufacturing method as claimed in claim 1, further comprising the step of bonding a light condensing means to the strip element of each said individual flip chip type LED lighting device after the bonding of heat conducting/dissipating member.

11. The flip chip type LED lighting device manufacturing method as claimed in claim 10, said light condensing means comprises a condenser lens and a reflector.

12. A flip chip type LED lighting device manufacturing method comprising the steps of:
providing a plurality of strip elements, each strip element comprising a metal lead frame and a depression on the bottom of the strip element;
providing a plurality of submounts corresponding to the plurality of strip elements, each submount having a plurality of flip chip LEDs electrically coupled to the submount and having circuits arranged thereon for electrically contacting the plurality of flip chip LEDs; and
bonding each strip element to the corresponding submount to form a lighting structure, wherein the submount is bonded under the strip element and accommodated by the depression of the strip element.

13. The flip chip type LED lighting device manufacturing method as claimed in claim 12, wherein said submount is a silicon submount.

14. The flip chip type LED lighting device manufacturing method as claimed in claim 12, wherein a metal bonding layer is disposed between each strip element to the corresponding submount.

15. The flip chip type LED lighting device manufacturing method as claimed in claim 12, further comprising:
bonding a heat conducting/dissipating member to the bottom of the submount.

16. The flip chip type LED lighting device manufacturing method as claimed in claim 15, wherein said heat conducting/dissipating member is bonded to said submount by means of a thermal interface material.