SYSTEMS, ARTICLES, AND METHODS FOR STRETCHABLE PRINTED CIRCUIT BOARDS

• US 20150065840A1
• Filed: 08/28/2014
• Published: 03/05/2015
• Est. Priority Date: 08/30/2013
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Thalmic Labs Inc.
• Inventors: Bailey, Matthew
• Granted Patent: US 9,788,789 B2
• Time in Patent Office: Days
• US Class Current: 600/384
• CPC Class Codes: A61B 5/296 for electromyography [EMG]
• CPC Class Codes: A61B 5/6802 Sensor mounted on worn items
• CPC Class Codes: A61B 5/681 Wristwatch-type devices
• CPC Class Codes: A61B 5/6822 Neck
• CPC Class Codes: A61B 5/6823 Trunk, e.g., chest, back, abdomen, hip
• CPC Class Codes: A61B 5/6824 Arm or wrist
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/6828 Leg
• CPC Class Codes: A61B 5/6829 Foot or ankle
• CPC Class Codes: H05K 1/0283 Stretchable printed circuits
• CPC Class Codes: H05K 1/148 Arrangements of two or more hingeably connected rigid printed circuit boards, i.e. connected by flexible means
• CPC Class Codes: H05K 2201/0154 Polyimide
• CPC Class Codes: H05K 2201/09063 Holes or slots in insulating substrate not used for electrical connections
• CPC Class Codes: H05K 2201/09263 Meander

Abstract

Improved stretchable printed circuit boards, and fabrication methods thereof, are described. The improved stretchable printed circuit boards include a serpentine conductive trace enclosed by stretchable dielectric material. The stretchable dielectric material has a serpentine shape itself, realized by crenulated edges. The crenulated edges reduce torsional strain on the conductive trace and are formed, for example, by cutting away sections of the stretchable dielectric material proximate segments of the serpentine conductive trace where the serpentine conductive trace changes direction.

Claims

1. A stretchable printed circuit board comprising:

a first dielectric layer formed of a stretchable dielectric material;

a second dielectric layer formed of a stretchable dielectric material, the second dielectric layer carried by the first dielectric layer;

at least one conductive trace carried by the first dielectric layer and positioned in between the first and the second dielectric layers, wherein the at least one conductive trace forms a serpentine signal path that extends along at least a portion of a length of the stretchable printed circuit board and includes a plurality of changes in direction across a width of the stretchable printed circuit board; and

a plurality of cut-away sections in the first and the second dielectric layers, wherein each cut-away section includes a respective section of the first and the second dielectric layers that is removed and each cut-away section positioned at an edge of the stretchable printed circuit board proximate and in between a respective pair of segments of the serpentine signal path where the serpentine signal path changes direction.

2. The stretchable printed circuit board of claim 1 wherein the length of the stretchable printed circuit board is greater than the width of the stretchable printed circuit board.

3. The stretchable printed circuit board of claim 1, further comprising:

a layer of polymer material carried by the first dielectric layer, wherein the layer of polymer material is positioned in between the first dielectric layer and the at least one conductive trace and the at least one conductive trace is carried on the layer of polymer material.

4. The stretchable printed circuit board of claim 3 wherein the polymer material is selected from the group consisting of:

a polyamide material, a polyimide material, and a polyamide-imide material.

5. A stretchable printed circuit board comprising:

at least one conductive trace that forms a serpentine signal path, wherein the serpentine signal path extends along at least a portion of a length of the stretchable printed circuit board and includes a plurality of changes in direction across a width of the stretchable printed circuit board; and

a substantially planar segment of stretchable dielectric material that encloses the at least one conductive trace, wherein the substantially planar segment of stretchable dielectric material has a crenulated shape the includes a plurality of crenulations across the at least a portion of the length of the stretchable printed circuit board, and wherein each crenulation of the substantially planar segment of stretchable dielectric material is positioned proximate and corresponds to a respective portion of the at least one conductive trace where the serpentine signal path changes direction.

6. The stretchable printed circuit board of claim 5 wherein the substantially planar segment of stretchable dielectric material comprises a first layer of stretchable dielectric material and a second layer of stretchable dielectric material, the second layer of stretchable dielectric material carried by the first layer of stretchable dielectric material, and the at least one conductive trace carried by the first layer of stretchable dielectric material and positioned in between the first and the second layers of stretchable dielectric material.

7. The stretchable printed circuit board of claim 5, further comprising:

a layer of polymer material, wherein the at least one conductive trace is carried on the layer of polymer material and the layer of polymer material is enclosed by the substantially planar segment of stretchable dielectric material.

8. The stretchable printed circuit board of claim 7 wherein the polymer material is selected from the group consisting of:

a polyamide material, a polyimide material, and a polyamide-imide material.

9. A method of fabricating a stretchable printed circuit board, the method comprising:

depositing a first layer of stretchable dielectric material;

depositing at least one conductive trace on the first layer of stretchable dielectric material, wherein the at least one conductive trace forms a serpentine signal path that extends along at least a portion of a length of the stretchable printed circuit board and includes a plurality of changes in direction across a width of the stretchable printed circuit board;

depositing a second layer of stretchable dielectric material on the at least one conductive trace; and

cutting away sections in the first and the second layers of stretchable dielectric material, each cut-away section positioned at an edge of the stretchable printed circuit board proximate at least one respective change in direction in the serpentine signal path.

10. The method of claim 9 wherein depositing at least one conductive trace on the first layer of stretchable dielectric material comprises:

forming a flexible printed circuit board, wherein forming a flexible printed circuit board comprises;

depositing a layer of polymer material;

depositing a layer of conductive metal on the layer of polymer material;

patterning the layer of conductive metal to provide at least one conductive trace having a serpentine signal path; and

patterning the layer of polymer material;

and

depositing the flexible printed circuit board on the first layer of stretchable dielectric material.

11. The method of claim 10 wherein the polymer material is selected from the group consisting of:

a polyamide material, a polyimide material, and a polyamide-imide material.

12. A method of fabricating a stretchable printed circuit board, the method comprising:

fabricating a flexible printed circuit board, wherein fabricating a flexible printed circuit board comprises;

depositing a layer of flexible dielectric material;

depositing a layer of conductive metal on top of the flexible dielectric material; and

etching a circuit pattern into the layer of conductive metal, wherein the circuit pattern includes at least one serpentine conductive trace that includes a plurality of changes in direction,

removing at least some portions of the flexible dielectric material that are not covered by the at least one serpentine conductive trace; and

enclosing at least a portion of the flexible printed circuit board in a stretchable dielectric material, wherein the stretchable dielectric material forms a crenulated shape that includes a plurality of crenulations across a length thereof, wherein each crenulation is positioned proximate and corresponds to a respective change in direction in the at least one serpentine conductive trace.

13. The method of claim 12 wherein enclosing the flexible printed circuit board in a stretchable dielectric material comprises:

placing the flexible printed circuit board into a mold that provides a crenulated shape for the stretchable dielectric material;

injecting the stretchable dielectric material, in liquid form, into the mold;

solidifying the stretchable dielectric material; and

removing the mold.

14. The method of claim 12 wherein enclosing the flexible printed circuit board in a stretchable dielectric material comprises:

depositing a first layer of stretchable dielectric material;

depositing the flexible printed circuit board on the first layer of stretchable dielectric material;

depositing a second layer of stretchable dielectric material on the first layer of stretchable dielectric material, wherein the flexible printed circuit board is positioned in between the first and the second layers of stretchable dielectric material; and

cutting away sections in the first and the second layers of stretchable dielectric material, each cut-away section positioned at an edge of the stretchable printed circuit board proximate at least one respective change in direction in the at least one serpentine conductive trace of the flexible printed circuit board.

15. A wearable electronic device comprising:

a first pod structure, wherein the first pod structure includes a first sensor to in use detect an input from a user and a first electric circuit;

a second pod structure, wherein the second pod structure includes a second electric circuit, and wherein the first and the second pod structures are physically spaced apart from one another; and

at least one stretchable printed circuit board that electrically couples the first electric circuit of the first pod structure with the second electric circuit of the second pod structure, wherein the at least one stretchable printed circuit board comprises;

at least one conductive trace that forms a serpentine signal path, wherein the serpentine signal path extends along at least a portion of a length of the stretchable printed circuit board and includes a plurality of changes in direction across a width of the stretchable printed circuit board; and

a substantially planar segment of stretchable dielectric material that encloses the at least one conductive trace, wherein the substantially planar segment of stretchable dielectric material has a crenulated shape that includes a plurality of crenulations across the length of the stretchable printed circuit board, and wherein each crenulation of the substantially planar segment of stretchable dielectric material is positioned proximate and corresponds to a respective portion of the at least one conductive trace where the serpentine signal path changes direction.