Electrical assembly having impedance controlled signal traces

1. A portable electronic device, comprising:

an electrical assembly, comprising: a chassis made from a conductive material and forming a first ground plane; a first dielectric substrate layer overlaying the chassis; and a first signal trace embedded within the first dielectric substrate layer;

a main circuit board mounted to the chassis and including multiple connectors for connecting electronic components, the main circuit board being connected to the first signal trace;

a processor connected to the main circuit board;

at least one input device connected to the main circuit board and to the processor through the main circuit board; and

at least one output device connected to the main circuit board and to the processor through the main circuit board.

2. The device of claim 1 , wherein the first signal trace and the first dielectric substrate layer are integrally formed as part of a flexible printed circuit board.

3. The device of claim 2 , wherein the flexible printed circuit board comprises one or more stripline circuit layers overlaying the first dielectric substrate layer, each stripline circuit layer comprising a pair of ground planes, a second dielectric substrate layer between the ground planes, a second signal trace embedded within the second dielectric substrate layer, and multiple conductive vias extending through the flexible printed circuit for connecting the ground planes of each circuit layer of the flexible printed circuit board to the chassis; wherein all signal traces of the flexible printed circuit are connected to the main circuit board.

4. The device of claim 3 , wherein the flexible printed circuit board further comprises at least one microstrip circuit layer overlaying the one or more stripline circuit layers, the microstrip circuit layer comprising a second ground plane, a third dielectric layer overlaying the second ground plane, a third signal trace overlaying the third dielectric layer, and a fourth dielectric layer overlaying the third signal trace.

5. The device of claim 4 , wherein the chassis is made from a conductive magnesium or stainless steel alloy and the fourth dielectric layer is air.

6. The device of claim 1 , wherein the chassis defines a recess, the first signal trace and the first dielectric substrate layer being received in the recess.

7. The device of claim 6 , wherein the first dielectric substrate layer is attached to the chassis within the recess using a conductive adhesive.

8. The device of claim 6 , wherein the recess includes a first enlarged portion in a top portion of the chassis, a second enlarged portion in a bottom portion of the chassis, and a generally elongate portion which defines a path extending between the first enlarged portion and the second enlarged portion.

9. The device of claim 8 , further comprising at least one first rigid printed circuit board in the enlarged portion and at least one second rigid printed circuit board in the second enlarged portion, wherein the first signal trace and the first dielectric substrate layer connect the at least one first rigid printed circuit board and the at least one second rigid printed circuit board.

10. The device of claim 9 , wherein the first signal trace and the first dielectric substrate layer are integrally formed as part of a flexible printed circuit board.

11. The device of claim 6 , wherein the first signal trace and the first dielectric substrate layer are integrally formed as part of a flexible printed circuit board, and the flexible printed circuit board is received in the recess.

12. The device of claim 1 , further comprising an electronic component connected to the first signal trace, wherein the electrical assembly has a stack-up configured to control the impedance of the first signal trace to within a predetermined tolerance of a predetermined impedance threshold.

13. The device of claim 12 , wherein the first signal trace and the first dielectric substrate layer are integrally formed as part of a flexible printed circuit board, and the flexible printed circuit board has the stack-up configured to control the impedance of the first signal trace.

14. The device of claim 1 , wherein electrical assembly further comprises: a ground layer within the first dielectric substrate layer forming a second ground plane; and multiple conductive vias connecting the first ground plane formed by the chassis to the second ground plane.

15. The device of claim 1 , wherein the chassis is made from a conducive magnesium or stainless steel alloy.