Method for bonding discrete devices using anisotropic conductive film

Patent metadata

Field	Value
Publication number	US-10420222-B2
Application number	US-201715492230-A
Country	US
Kind code	B2
Filing date	Apr 20, 2017
Priority date	Apr 20, 2017
Publication date	Sep 17, 2019
Grant date	Sep 17, 2019

Abstract

Methods and system which eliminate steps in the mounting a discrete device to an electronic circuit using a conductive film, shortening the time required to attach each discrete device. The methods place a discrete device onto the conductive tape and partially cure portions of the adhesive. The discrete device is then removed from the conductive tape along with the adhesive and conductive particles which have been transferred onto the contact pads of the discrete device. The discrete device is then placed on the substrate and aligned. Pressure and heat are applied to complete the bond.

First claim

What is claimed is:

1. A method of bonding a discrete device to a substrate, the discrete device having contact pads extending from a body portion, and the bonding using a conductive tape, the method comprising:
providing the conductive tape having a layer of adhesive including conductive particles within the layer of adhesive, the layer of adhesive carried on a liner, wherein the layer of adhesive of the conductive tape faces upward;
placing the contact pads of the discrete device on the upward facing layer of adhesive of the conductive tape;
applying pressure and heat to the discrete device located on the layer of adhesive of the conductive tape, the pressure being sufficient to move the contact pads into the layer of adhesive, and the heat raising the contact pads to a temperature above a tacking temperature of the conductive tape sufficient to alter portions of the layer of adhesive corresponding to areas of the contact pads, wherein the portions of the layer of adhesive corresponding to the areas of the contact pads partially tack the portions of the layer of adhesive to the contact pads;
removing the discrete device from the upward facing layer of adhesive of the conductive tape, wherein the portions of the layer of adhesive that have partially cured to the contact pads of the discrete device are carried with the contact pads, and are removed from the liner of the conductive tape;
positioning the discrete device with the contact pads carrying the portions of the partially cured adhesive layer onto a surface of a substrate, wherein the partially cured adhesive layer substantially covers an entire surface of each of the contact pads sufficient to provide an electrical connection between surfaces of the contact pads and the substrate, wherein the substrate includes conductive traces; and
applying heat and pressure to the discrete device to complete bonding of the contact pads of the discrete device to the surface of the substrate.

2. The method according to claim 1 wherein the conductive tape is an anisotropic conductive film.

3. The method according to claim 1 wherein the heat is 60 degrees C. to 90 degrees C. and the pressure applied to the device is approximately 1 MPa to partially cure the adhesive.

4. The method according to claim 1 wherein the heat is between 150 degrees C. to 180 degrees C. and the pressure applied to the device is between 2 to 5 MPa to complete the bonding and curing operation.

5. A method of bonding a discrete device to a substrate, the discrete device having contact pads extending from a body portion, and the bonding using a conductive tape, the method comprising:
providing the conductive tape having a layer of adhesive including conductive particles within the layer of adhesive, the layer of adhesive carried on a liner, wherein the layer of adhesive of the conductive tape faces upward, further including pre-scoring the adhesive layer into pre-positioned locations to match the contact pads of the device, wherein the pre-scoring avoids scoring of the liner;
placing the contact pads of the discrete device on the upward facing layer of adhesive of the conductive tape;
applying pressure and heat to the discrete device located on the layer of adhesive of the conductive tape, the pressure being sufficient to move the contact pads into the layer of adhesive, and the heat raising the contact pads to a temperature above a tacking temperature of the conductive tape sufficient to alter portions of the layer of adhesive corresponding to areas of the contact pads, wherein the portions of the layer of adhesive corresponding to the areas of the contact pads partially tack the portions of the layer of adhesive to the contact pads;
removing the discrete device from the upward facing layer of adhesive of the conductive tape, wherein the portions of the layer of adhesive that have partially cured to the contact pads of the discrete device are carried with the contact pads, and are removed from the liner of the conductive tape;
positioning the discrete device with the contact pads carrying the portions of the partially cured adhesive layer onto a surface of a substrate.

6. The method according to claim 1 wherein the contact pads height above the device is approximately 2 microns.

7. A method of bonding a discrete device to a substrate, the discrete device having contact pads extending from a body portion, and the bonding a using conductive tape, the method comprising:
providing the conductive tape having a layer of adhesive including conductive particles within the layer of adhesive, the layer of adhesive carried on a liner, wherein the layer of adhesive of the conductive tape faces upward;
heating the discrete device at a heating area, the heating raising the contact pads to a temperature above a tacking temperature of the conductive tape;
removing the heated discrete device from the heating area;
placing the contact pads of the heated discrete device on the upward facing layer of adhesive of the conductive tape;
applying a pressure to the heated discrete device for a determined time such that the contact pads and the layer of adhesive are in contact, wherein the temperature of the contact pads is sufficient to modify portions of the layer of the adhesive of the conductive tape associated with the contact pads, wherein the portions of the layer of adhesive partially cure to the contact pads of the discrete device;
removing the discrete device from the upward facing layer of adhesive of the conductive tape, wherein the portions of the layer of adhesive that have partially cured to the contact pads of the discrete device are carried with the contact pads, and are removed from the liner of the conductive tape;
positioning the discrete device with the contact pads carrying the portions of the partially cured adhesive layer onto a surface of a substrate; and
applying heat and pressure to the discrete device to complete bonding of the contact pads of the discrete device to the surface of the substrate.

8. The method according to claim 7 wherein the conductive tape is an anisotropic conductive film.

9. The method according to claim 7 wherein the partially cured adhesive layer substantially covers an entire surface of each of the contact pads sufficient to provide an electrical connection between surfaces of the contact pads and the substrate, wherein the substrate includes conductive traces.

10. The method according to claim 7 wherein the temperature is between 60 degrees C. to 90 degrees C., and the pressure applied to the device is between 1 MPa to 3 MPa in order to partially cure the adhesive.

11. The method according to claim 7 wherein the temperature is between 150 degrees C. to 180 degrees C., and the pressure applied to the device is between 50 MPa to 150 MPa to complete the bonding operation.

12. The method according to claim 7 further including pre-scoring the adhesive layer into pre-positioned locations to match the contact pads of the device, wherein the pre-scoring avoids scoring of the liner.

13. The method according to claim 7 wherein a height of the contact pads above the device body is approximately 2 microns.

14. The method according to claim 5 wherein the conductive tape is an anisotropic conductive film.

15. The method according to claim 5 wherein the heat is 60 degrees C. to 90 degrees C. and the pressure applied to the device is approximately 1 MPa to partially cure the adhesive.

16. The method according to claim 5 wherein the heat is between 150 degrees C. to 180 degrees C. and the pressure applied to the device is between 2 to 5 MPa to complete the

Assignees

• Palo Alto Res Ct Inc

Inventors

• Krusor Brent S
• Mei Ping

Classifications

• H10P72/74

  using temporarily an auxiliary support · CPC title

• H05K3/323 Primary

  by applying an anisotropic conductive adhesive layer over an array of pads · CPC title

• H05K3/0008

  for aligning or positioning of tools relative to the circuit board (H05K3/4638, H05K3/4679 take precedence; for manufacturing assemblages of components H05K13/0015) · CPC title

• H05K2203/082

  Suction, e.g. for holding solder balls or components · CPC title

• B29C2793/0054

  partially cutting through the material · CPC title