STRETCHABLE CIRCUIT CONFIGURATION

• US 20100238636A1
• Filed: 03/22/2010
• Published: 09/23/2010
• Est. Priority Date: 03/20/2009
• Status: Active Grant

• Current Assignee: University of Utah Research Foundation (State of Utah)
• Original Assignee: University of Utah Research Foundation (State of Utah)
• Inventors: Park, Jung Woo, Mascaro, Debra, Mascaro, Stephen, Abu-Khalaf, Jumana
• Granted Patent: US 8,329,493 B2
• Time in Patent Office: Days
• US Class Current: 361/750
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/0295 using plethysmography, i.e. measuring the variations in the volume of a body part as modified by the circulation of blood therethrough, e.g. impedance plethysmography
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: B29C 45/14639 for obtaining an insulating effect, e.g. for electrical components
• CPC Class Codes: H05K 1/0283 Stretchable printed circuits
• CPC Class Codes: H05K 1/183 Components mounted in and supported by recessed areas of the printed circuit board
• CPC Class Codes: H05K 2201/0133 Elastomeric or compliant polymer elastomeric conductor H05K2201/0314
• CPC Class Codes: H05K 2201/10106 Light emitting diode [LED]
• CPC Class Codes: H05K 2201/10121 Optical component, e.g. opto-electronic component
• CPC Class Codes: H05K 2201/10151 Sensor
• CPC Class Codes: H05K 2201/1034 Edge terminals, i.e. separate pieces of metal attached to the edge of the PCB tab H05K2201/0397
• CPC Class Codes: H05K 2201/2072 Anchoring, i.e. one structure gripping into another providing micro- or nanometer scale roughness on a metal surface H05K2203/0307
• CPC Class Codes: H05K 2203/0271 Mechanical force other than pressure, e.g. shearing or pulling
• CPC Class Codes: H05K 2203/128 Molten metals, e.g. casting thereof, or melting by heating and excluding molten solder spraying droplets of molten metal H05K2203/1344
• CPC Class Codes: H05K 2203/1327 Moulding over PCB locally or completely applying non-metallic protective coatings for encapsulating mounted components H05K3/284
• CPC Class Codes: H05K 3/143 Masks therefor H05K3/048 takes precedence
• CPC Class Codes: H05K 3/284 for encapsulating mounted components H05K1/185 takes precedence
• CPC Class Codes: H05K 3/3463 Solder compositions in relation to features of the printed circuit board or the mounting process

Abstract

A stretchable electronic circuit that includes a stretchable base substrate having a plurality of stretchable conductors formed onto a surface thereof, with both the stretchable base substrate and conductors being bendable together about two orthogonal axes. The stretchable circuit also includes a stretchable sensor layer attached to the base substrate with a cavity formed therein which has a contact point exposing one of the plurality of stretchable conductors. The stretchable electronic circuit further includes a surface mount device (SMD) package with a conductor contact protrusion installed into the cavity, and wherein a substantially constant electrical connection is established between the conductor contact protrusion and the stretchable conductor at the contact point by tensile forces interacting between the stretchable base substrate and the stretchable sensor layer.

Claims

1. A method of embedding a surface mount device (SMD) package into a stretchable electronic circuit, comprising:

forming an SMD mold by mounting an outer face of a first SMD package to a rigid plate, the first SMD package having conductor contact protrusions;

positioning the SMD mold onto a stretchable base substrate having stretchable conductors formed onto a surface thereof, and with the conductor contact protrusions of the first SMD package contacting the stretchable conductors;

filling a volume between the base substrate and the rigid plate with uncured stretchable fill material;

curing the fill material to form a stretchable sensor layer;

removing the SMD mold to expose an SMD cavity formed into the stretchable fill layer; and

installing a second SMD package into the SMD cavity, with conductor contact protrusions of the second SMD package being in electrical communication with the stretchable conductors on the base substrate to form a stretchable electronic circuit.

2. The method of claim 1, further comprising pressing the SMD mold against the stretchable base substrate and stretchable conductors during the curing of the fill material.

3. The method of claim 1, wherein the base substrate and conductors are bendable about at least two orthogonal axes.

4. The method of claim 1, wherein obtaining a stretchable electronic circuit further comprises radially stretching the base substrate in at least two substantially transverse directions prior to depositing a conductor material forming the stretchable conductors.

5. The method of claim 4, further comprising stretching the base substrate to at least about forty percent of maximum strain prior to depositing a conductor material.

6. The method of claim 4, further comprising stretching the base substrate with a circular jig having a support ring and a plurality of radially-displaceable miniature clamps coupled thereto.

7. The method of claim 1, wherein each SMD package further comprise a body having conductor contact protrusions extending from the sides thereof to form a T-shaped SMD.

8. The method of claim 1, wherein the stretchable base substrate and stretchable fill material further comprise a stretchable PDMS material.

9. The method of claim 1, wherein the second SMD package is selected from the group consisting of a light-emitting diode (LED) and a photodiode detector.

10. The method of claim 1, further comprising forming a liquid flexible electrical contact by:

forming an external interface mold by mounting at least one protruding structure to a second rigid plate;

positioning the external interface mold onto the stretchable base substrate with the at least one protruding structure contacting the stretchable conductors on the base substrate;

filling a volume between the base substrate and the second rigid plate with uncured stretchable fill material;

curing the fill material to form a stretchable connector layer;

removing the external interface mold to expose at least one connector well formed into the stretchable connector layer;

filling the connector well with a liquid metal material;

installing one end of an external interface lead wire into the connector well to form an external interface to the stretchable electronic circuit;

covering the connector well with a stretchable cap to secure the lead wire to the stretchable electronic circuit and seal the liquid metal within the connector well.

11. The method of claim 10, further comprising forming an anchor at the one end sufficient to inhibit removal of the lead wire from the connector well.

12. The method of claim 11, wherein forming an anchor further comprises forming a curvature along the one end of the lead wire and curing the curvature within the stretchable cap or connector well.

13. A stretchable electronic circuit, comprising:

a stretchable base substrate having a plurality of stretchable conductors formed onto a surface thereof;

both the base substrate and conductors being bendable together about at least two orthogonal axes;

a stretchable sensor layer attached to the base substrate and having an SMD cavity formed therein, the SMD cavity including at least one contact point exposing at least one of the plurality of stretchable conductors; and

an SMD package having a conductor contact protrusion installed into the SMD cavity, wherein a substantially constant electrical connection is established between the conductor contact protrusion and the stretchable conductor at the contact point by tensile forces interacting between the stretchable base substrate and the stretchable sensor layer.

14. The electronic circuit of claim 13, wherein the stretchable base substrate and stretchable sensor layer further comprise a stretchable PDMS material.

15. The electronic circuit of claim 13, wherein the SMD package is selected from a group consisting of a light-emitting diode (LED) and a photodiode detector.

16. The electronic circuit of claim 13, further comprising:

a stretchable connector layer attached to the base substrate and having a connector well formed therein and adjacent to at least one of the plurality of stretchable conductors;

an external interface lead wire having one end installed with the connector well;

liquid metal filling the connector well and establishing a substantially constant electrical connection between the lead wire and the stretchable conductor; and

a stretchable cap layer over the connector well securing the lead wire to the stretchable electronic circuit and sealing the liquid metal within the connector well.

17. The electronic circuit of claim 16, wherein the lead wire includes an anchor to inhibit removal from the connector well.

18. The electronic circuit of claim 16, wherein the liquid metal is at least one of EGaIn, GaInSn and Indalloy 60.

19. The electronic circuit of claim 16, wherein the SMD package further comprises a plurality of light-emitting diodes and photodiode detectors arrayed together, each diode and detector being connected through a connector well to an external interface lead wire and form a sensor system attachable to a curved surface of a human body.

20. The electronic circuit of claim 19, wherein the sensor system is configured to monitor a function of the human body selected from the group consisting of fingernail blood flow and perfusion, pulse-oximetry, photodynamic therapy and combinations thereof.