CIRCUIT BOARD FOR DIRECT FLIP CHIP ATTACHMENT

• US 20090212317A1
• Filed: 02/27/2008
• Published: 08/27/2009
• Est. Priority Date: 02/27/2008
• Status: Active Grant

• Current Assignee: Lumination LLC
• Original Assignee: Lumination LLC
• Inventors: Reginelli, James, Kolodin, Boris
• Granted Patent: US 7,749,813 B2
• Time in Patent Office: Days
• US Class Current: 257/99
• CPC Class Codes: H01L 25/0753 the devices being arranged next to each other
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2924/01019 Potassium [K]
• CPC Class Codes: H01L 2924/01079 Gold [Au]
• CPC Class Codes: H01L 33/62 Arrangements for conducting electric current to or from the semiconductor body, e.g. lead-frames, wire-bonds or solder balls
• CPC Class Codes: H05K 2201/09363 wherein only contours around conductors are removed for insulation
• CPC Class Codes: H05K 2201/10106 Light emitting diode [LED]
• CPC Class Codes: H05K 2203/1476 Same or similar kind of process performed in phases, e.g. coarse patterning followed by fine patterning
• CPC Class Codes: H05K 3/027 the conductive material being removed by irradiation, e.g. by photons, alpha or beta particles
• CPC Class Codes: H05K 3/064 Photoresists
• CPC Class Codes: Y10T 29/49155 Manufacturing circuit on or in base

Abstract

A packaging method comprises: forming a circuit board by forming a substantially continuous conductive layer on an insulating board and removing selected portions of the continuous conductive layer to define an electrically conductive trace; laser cutting the electrically conductive trace to define sub-traces electrically isolated from each other by a laser-cut gap formed by the laser cutting; and bonding a light emitting diode (LED) chip to the circuit board across or adjacent to the laser-cut gap, the bonding including operatively electrically connecting an electrode of the LED chip to one of the sub-traces without using an interposed submount. A semiconductor package comprises an LED chip flip-chip bonded to sub-traces of an electrically conductive trace of a circuit board, the sub-traces being electrically isolated from each other by a narrow gap of less than or about 100 microns.

Claims

1. A packaging method comprising:

forming a circuit board by forming a substantially continuous conductive layer on an insulating board and removing selected portions of the continuous conductive layer to define an electrically conductive trace;

laser cutting the electrically conductive trace to define sub-traces electrically isolated from each other by a laser-cut gap; and

bonding a light emitting diode (LED) chip to the circuit board across or adjacent to the laser-cut gap, the bonding including operatively electrically connecting an electrode of the LED chip to one of the sub-traces without using an interposed submount.

2. The packaging method as set forth in claim 1, wherein the removing of selected portions of the continuous conductive layer to define the electrically conductive trace is performed by a process other than laser cutting.

3. The packaging method as set forth in claim 1, wherein the bonding comprises:

flip-chip bonding the LED chip across the laser-cut gap with anode and cathode electrodes of the LED chip operatively electrically connected to different ones of the sub-traces that are electrically isolated from each other by the laser-cut gap formed by the laser cutting, there being no submount interposed between the LED chip and the circuit board.

4. The packaging method as set forth in claim 3, wherein the removing of selected portions of the continuous conductive layer to define the electrically conductive trace defines one or more gaps of greater than or about 150 microns, and the laser cutting defines sub-traces electrically isolated from each other by the laser-cut gap which is less than or about 100 microns.

5. The packaging method as set forth in claim 4, wherein the laser cutting defines sub-traces electrically isolated from each other by the laser-cut gap which is less than or about 80 microns.

6. The packaging method as set forth in claim 1, wherein the substantially continuous conductive layer formed on the insulating board has a thickness that is greater than or about 30 microns.

7. The packaging method as set forth in claim 6, wherein the removing of selected portions of the continuous conductive layer to define the electrically conductive trace comprises:

removing the selected portions of the continuous conductive layer by a wet chemical etching process.

8. The packaging method as set forth in claim 1, wherein the operative electrically connecting of an electrode of the LED chip to one of the sub-traces without using an interposed submount comprises:

electrically connecting the electrode to the sub-trace via a bonding bump by soldering, thermosonic bonding, or thermocompressive bonding.

9. A method for bonding a semiconductor chip to a circuit board, the method comprising:

laser cutting a conductive trace of the circuit board to define sub-traces electrically isolated from each other by a laser-cut gap formed by the laser cutting; and

bonding the semiconductor chip to the circuit board across or adjacent to the laser-cut gap, the bonding including operatively electrically connecting the semiconductor chip with at least one of the sub-traces.

10. The method as set forth in claim 9, wherein prior to the laser cutting the circuit board includes one or more gaps of greater than or about 150 microns in an electrically conductive layer defining the conductive trace, and the laser-cut gap formed by the laser cutting is less than or about 100 microns.

11. The method as set forth in claim 10, wherein the semiconductor chip is a light emitting diode (LED) chip, and the bonding comprises:

flip-chip bonding the LED chip across the laser-cut gap, the flip-chip bonding including operatively electrically connecting anode and cathode electrodes of the LED chip to respective sub-traces electrically isolated from each other by the laser-cut gap.

12. The method as set forth in claim 11, wherein the anode and cathode electrodes of the LED chip have a minimum spacing of less than or about 100 microns, and the laser-cut gap formed by the laser cutting is less than or about 80 microns.

13. The method as set forth in claim 11, wherein the laser cutting operation is performed on a conductive trace of the circuit board having a thickness that is greater than or about 30 microns.

14. The method as set forth in claim 10, wherein the bonding does not include interposing a submount between the semiconductor chip and the circuit board.

15. The method as set forth in claim 9, wherein the semiconductor chip is a light emitting diode (LED) chip, and the bonding comprises:

flip-chip bonding the LED chip across the laser-cut gap, the flip-chip bonding including operatively electrically connecting p and n electrodes of the LED chip to respective sub-traces electrically isolated from each other by the laser-cut gap.

16. The method as set forth in claim 15, wherein the bonding operation does not include interposing a submount between the LED chip and the sub-traces.

17. The packaging method as set forth in claim 16, wherein the bonding operation comprises:

operatively electrically connecting p and n electrodes of the LED chip to respective sub-traces electrically isolated from each other by the laser-cut gap via bonding bumps by soldering, thermosonic bonding, or thermocompressive bonding.

18. The method as set forth in claim 15, further comprising:

forming the circuit board by a process comprising;

forming a substantially continuous conductive layer on an insulating board, and

removing selected portions of the continuous conductive layer by wet chemical etching to define the conductive trace on which the laser cutting operation is performed.

19. The method as set forth in claim 9, further comprising:

forming the circuit board by a process comprising;

forming a substantially continuous conductive layer on an insulating board, and

removing selected portions of the continuous conductive layer by a process other than laser cutting to define the conductive trace on which the laser cutting operation is performed.

20. A semiconductor package comprising a semiconductor chip and a circuit board, wherein the semiconductor chip is bonded to the circuit board by a process as set forth in claim 9, the semiconductor package not including a submount interposed between the semiconductor chip and the circuit board.

21. A semiconductor package comprising:

a light emitting diode (LED) chip; and

a circuit board on which the LED chip is attached by a flip-chip bond including operative electrical connections of n and p electrodes of the LED chip to respective sub-traces of an electrically conductive trace of the circuit board, the sub-traces being electrically isolated from each other by a narrow gap of less than or about 100 microns.

22. The semiconductor package as set forth in claim 21, wherein the sub-traces are electrically isolated from each other by a narrow gap of less than or about 80 microns.

23. The semiconductor package as set forth in claim 21, wherein the electrically conductive trace of the circuit board has a thickness that is greater than or about 30 microns.

24. The semiconductor package as set forth in claim 21, wherein the semiconductor package does not include a submount interposed between the LED chip and the circuit board.