System and method for mounting electronic components onto flexible substrates

• US 6,642,485 B2
• Filed: 12/03/2001
• Issued: 11/04/2003
• Est. Priority Date: 12/03/2001
• Status: Expired due to Term

• Current Assignee: Synaptics Incorporated
• Original Assignee: Visteon Global Technologies Incorporated (Visteon Corporation)
• Inventors: Goenka, Lakhi N., Sinkunas, Peter Joseph
• Primary Examiner(s): PELHAM, JOSEPH MOORE
• Application Number:
  US10/007,485
• Publication Number:
  US 20030102297A1
• Time in Patent Office: 701 Days
• Field of Search: 219/400, 219/388, 228/46, 228/180.21, 165/61, 165/64, 165/104.17
• US Class Current: 219/400
• CPC Class Codes: B23K 1/012 Soldering with the use of hot gas
• CPC Class Codes: B23K 3/087 Soldering or brazing jigs, fixtures or clamping means
• CPC Class Codes: H05K 2201/0305 Solder used for other purposes than connections between PCB or components, e.g. for filling vias or for programmable patterns
• CPC Class Codes: H05K 2203/0165 Holder for holding a Printed Circuit Board [PCB] during processing, e.g. during screen printing
• CPC Class Codes: H05K 2203/081 Blowing of gas, e.g. for cooling or for providing heat during solder reflowing
• CPC Class Codes: H05K 2203/111 Preheating, e.g. before soldering
• CPC Class Codes: H05K 2203/1121 Cooling, e.g. specific areas of a PCB being cooled during reflow soldering
• CPC Class Codes: H05K 2203/1581 Treating the backside of the PCB, e.g. for heating during soldering or providing a liquid coating on the backside
• CPC Class Codes: H05K 3/3494 Heating methods for reflowing of solder using integral heating means H05K1/0212

Abstract

A system and method for reflowing solder to interconnect a plurality of electronic components to a substrate is disclosed. The system includes an oven for preheating the substrate and the plurality of electronic components disposed thereon, a supplemental heat source disposed in the oven for providing additional heat energy to reflow the solder, and a pallet for supporting the substrate, wherein the supplemental heat source creates a stream of hot gas that flows transversely across the substrate.

Claims

1. A system for reflowing solder to interconnect a plurality of electronic components to a substrate, the system comprising:

an oven for preheating the substrate and the plurality of electronic components disposed thereon;

a supplemental heat source positioned within the oven for providing additional heat energy to reflow the solder, wherein the supplemental heat source creates a stream of hot gas that flows transversely across the substrate; and

a pallet for supporting and absorbing heat from the substrate.

2. The system of claim 1 wherein the supplemental heat source is a nozzle positioned within the oven, wherein the nozzle has a plurality of vanes for directing hot gas transversely across the substrate.

3. The system of claim 2 wherein the stream of hot gas has a central cone that remains intact when the stream contacts the substrate.

4. The system of claim 3 wherein the central cone has a length of approximately 14 times a diameter of an exit of the nozzle.

5. The system of claim 1 further comprising a cover for covering portions of the substrate not to be exposed to the supplemental heat source.

6. The system of claim 1 wherein the pallet has at least one internal cavity.

7. The system of claim 6 further comprising a phase-transition material disposed within the cavity for absorbing heat from the pallet.

8. The system of claim 7 wherein the phase-transition material is an alloy containing tin and lead.

9. The system of claim 7 wherein the phase-transition material is an alloy containing gallium.

10. The system of claim 1 further comprising a conveyor for transporting the pallet through the oven and under the supplemental heat source.

11. The system of claim 1 wherein the pallet further comprises an open cavity to accommodate electronic components mounted to both sides of the substrate.

12. The system of claim 11 wherein the open cavity further comprises a foam to provide support for the substrate.

13. The system of claim 1 wherein the nozzle has a length substantially equal to the width of the substrate.

14. The system of claim 1 wherein the nozzle has a gas distribution tube that is tapered.

15. The system of claim 2 wherein the vanes are positioned at a 30°

angle with respect to a top surface of the substrate.

16. The system of claim 2 wherein the vanes are positioned at a 60°

to 65°

angle with respect to a top surface of the substrate.

17. The system of claim 2 wherein the vanes are positioned at a 75°

angle with respect to a top surface of the substrate.

18. The system of claim 2 wherein the vanes are positioned at a 30°

to 75°

angle with respect to a top surface of the substrate.

19. The system of claim 1 wherein the nozzle is positioned a distance l above the substrate and the nozzle has an exit opening dimension d, wherein a ratio l/d is less than fourteen.

20. The system of claim 1 wherein a gas having a temperature range between 200 to 500 degrees Celsius is expelled from the nozzle.

21. The system of claim 1 wherein a gas having a temperature of 280 degrees Celsius is expelled from the nozzle.

22. The system of claim 1 wherein the nozzle is pivotable along a nozzle longitudinal axis.

23. The system of claim 1 wherein the oven temperature is between 130 to 250 degrees Celsius.

24. The system of claim 1 wherein the conveyor is moving at a speed of between 10 to 50 inches per minute.

25. A method for reflowing solder to interconnect a plurality of electronic components to a substrate, the method comprising:

inserting the substrate into an oven;

preheating the substrate and the plurality of electronic components disposed thereon;

providing additional heat energy to reflow the solder using a supplemental heat source positioned within the oven;

creating a stream of hot gas using the supplemental heat source, wherein the gas flows transversely across the substrate; and

supporting the substrate with a pallet, wherein the pallet absorbs heat from the substrate.

26. The method of claim 25 wherein inserting the substrate into an oven further comprises transporting the substrate through the oven using a conveyor.

27. The method of claim 25 wherein transporting the substrate further comprises moving the substrate through the even at a speed of between 10 to 50 inches per minute.

28. The method of claim 25 further comprising limiting heat absorption by the substrate to prevent damaging the substrate by adjusting a speed of the conveyor, a distance the supplemental heat source is from the substrate, and a temperature of the gas.

29. The method of claim 25 further comprising providing a pallet has at least one internal cavity.

30. The method of claim 29 further comprising providing a phase-transition material disposed within the cavity for absorbing heat from the pallet.

31. The method of claim 25 further comprising positioning the supplemental heat source a distance l above the substrate and providing a supplemental heat source exit having an opening dimension d, wherein a ratio l/d is less than fourteen.

32. The method of claim 25 further comprising providing a gas having a temperature range between 200 to 500 degrees Celsius.

33. The method of claim 25 wherein preheating the substrate further comprises heating the Psubstrate to between 130 to 250 degrees Celsius.