US-20260129750-A1 - FLEXIBLE PRINTED CIRCUIT BOARD FOR SMALL BENDING-RADIUS APPLICATIONS

Abstract

According to various embodiments, a flexible printed circuit board includes: a first flexible dielectric layer that includes reinforcing fibers; a second flexible dielectric layer that includes no reinforcing fibers; and a first conductive layer that is disposed between the first dielectric layer and the second dielectric layer and contacts the first dielectric layer and the second dielectric layer.

Inventors

• BIAO HU
• Yunseok Kim
• Shuang Xu
• Jungho Na
• Xiang Sun

Assignees

• NVIDIA CORPORATION

Dates

Publication Date

20260507

Application Date

20241105

Claims (20)

1. 1 . A flexible printed circuit board (PCB), comprising: a first flexible dielectric layer that includes reinforcing fibers; a second flexible dielectric layer that includes no reinforcing fibers; and a first conductive layer that is disposed between the first dielectric layer and the second dielectric layer and contacts the first dielectric layer and the second dielectric layer.
2. 2 . The flexible PCB of claim 1 , wherein the first flexible dielectric layer includes a first synthetic polymer material and the second flexible dielectric layer includes a second synthetic polymer material.
3. 3 . The flexible PCB of claim 2 , wherein each of the first synthetic polymer material and the second synthetic polymer material includes polytetrafluoroethylene (PTFE).
4. 4 . The flexible PCB of claim 1 , further comprising a first end that includes a first connection area for communicatively coupling to a first rigid PCB and a second end that includes a second connection area for communicatively coupling to a second rigid PCB.
5. 5 . The flexible PCB of claim 1 , wherein the first connection area includes a first stiffener layer, and the second connection area includes a second stiffener layer.
6. 6 . The flexible PCB of claim 5 , wherein the first stiffener layer is disposed on a first side of the flexible PCB, and the second stiffener layer is disposed on a second side of the flexible PCB that is opposite the first side.
7. 7 . The flexible PCB of claim 1 , further comprising: a third flexible dielectric layer that includes reinforcing fibers; and a second conductive layer that is disposed between the third dielectric layer and the second dielectric layer and contacts the third dielectric layer and the second dielectric layer.
8. 8 . The flexible PCB of claim 1 , wherein the first conductive layer comprises one of a signal layer, a ground plane, or a power plane.
9. 9 . The flexible PCB of claim 1 , further comprising a plurality of plated vias that are formed through the first flexible dielectric layer, the second flexible dielectric layer, and the first conductive layer.
10. 10 . The flexible PCB of claim 1 , wherein the second flexible dielectric layer comprises an inner layer of the flexible PCB.
11. 11 . The flexible PCB of claim 1 , wherein the second flexible dielectric layer comprises a metal-clad laminate layer of the flexible PCB.
12. 12 . The flexible PCB of claim 1 , wherein the first conductive layer is included in the metal-clad laminate layer of the flexible PCB.
13. 13 . The flexible PCB of claim 1 , wherein the first flexible dielectric layer comprises an outer layer of the flexible PCB.
14. 14 . A card-based processing subsystem, comprising: a housing; a processor mounted on a first rigid printed circuit board (PCB) that is disposed within the housing; a second rigid PCB that is communicatively coupled to the first rigid PCB via a flexible PCB; and the flexible PCB, wherein the flexible PCB includes: a first flexible dielectric layer that includes reinforcing fibers; a second flexible dielectric layer that includes no reinforcing fibers; and a first conductive layer that is disposed between the first dielectric layer and the second dielectric layer and contacts the first dielectric layer and the second dielectric layer.
15. 15 . The card-based processing subsystem of claim 14 , wherein the second rigid PCB is disposed on an edge of the housing.
16. 16 . The card-based processing subsystem of claim 14 , wherein the second rigid PCB has one or more digital display interface connectors mounted thereon.
17. 17 . The card-based processing subsystem of claim 14 , wherein the first rigid PCB is perpendicular to the second rigid PCB.
18. 18 . The card-based processing subsystem of claim 14 , wherein the second flexible dielectric layer comprises an inner layer of the flexible PCB.
19. 19 . The card-based processing subsystem of claim 14 , wherein the second flexible dielectric layer comprises a metal-clad laminate layer of the flexible PCB.
20. 20 . The card-based processing subsystem of claim 14 , wherein the first flexible dielectric layer comprises an outer layer of the flexible PCB.

Description

BACKGROUND Field of the Various Embodiments The various embodiments relate generally to computer systems and computer hardware architecture and, more specifically, to a flexible printed circuit board for small bending-radius applications. Description of the Related Art Many types of computers are designed to incorporate one or more expansion cards that provide the computer with additional capabilities, such as enhanced video or gaming performance, accelerated video capture, the ability to connect to a network, and/or the ability to connect to a musical instrument, to name a few. An expansion card, which also is referred to as an adapter card, an add-on card, or an expansion board, is a card-based processing subsystem that typically includes a printed circuit board (PCB) that is adapted to connect to an expansion slot on the motherboard of a given computer. Some card-based processing subsystems include a secondary PCB that serves as an input/output (I/O) interface. These secondary PCBs normally have one or more I/O connectors mounted thereon. For example, graphics cards typically include various video interface connectors that are mounted on a secondary PCB, while network interface cards typically include a plurality of network connection ports that are mounted on a secondary PCB. In modern card-based processing subsystems, routing the signals between the secondary PCB and the main PCB can be quite challenging due to the large number of electrical connections (e.g., I/O signals, power connections, and ground connections) that oftentimes are required between the main PCB and the secondary PCB. In addition, the many electrical connections between the main PCB and the secondary PCB have to be routed within a highly confined space, which further complicates the routing problem. Traditionally, multi-conductor cables and wire harnesses have been employed to route large numbers of signals and/or power connections between two PCBs in computing devices, such as desktop computers. In many applications, these cables and wire harnesses can operate with sufficiently low insertion losses and parasitic impedances to transmit the high-frequency signals typically employed in modern computing devices. However, multi-conductor cables are oftentimes too bulky for use in many compact computing devices, including laptop computers, smart phones, and card-based processing subsystems. Instead, large numbers of conductors have to be routed through the confined spaces within these more compact computing devices using flexible PCBs. Flexible PCBs can include multiple layers of miniaturized and insulated conductors and, therefore, are usually more compact than multi-conductor cables or wire harnesses. While flexible PCBs are more flexible than conventional rigid PCBs, the minimum bend radius available to a flexible PCB remains somewhat limited. As a result, the small radius bending that sometimes occur when routing electrical connections within the housing of a compact computing device can exceed the minimum bend radius of the flexible PCB. Such over-bending of a flexible PCB can compromise the continuity of conductors within a bend and cause dielectric cracking on the outer radius of the bend and dielectric wrinkling or separation on the inner radius of the bend. As the foregoing illustrates, what is needed in the art are more effective techniques for routing electrical connections within compact computing devices. SUMMARY According to various embodiments, a flexible printed circuit board includes: a first flexible dielectric layer that includes reinforcing fibers; a second flexible dielectric layer that includes no reinforcing fibers; and a first conductive layer that is disposed between the first dielectric layer and the second dielectric layer and contacts the first dielectric layer and the second dielectric layer. At least one technical advantage of the disclosed design relative to the prior art is that the disclosed design enables electrical connections to be routed through one or more small-radius turns within a compact computing device without any dielectric cracking or dielectric wrinkling or separation and more effectively than what can be achieved with prior art designs. A further technical advantage is that the disclosed design enables electrical connections to be routed within the compact computing device with low insertion losses and low parasitic impedances, which allows the electrical connections of the disclosed design to transmit high-frequency signals. These technical advantages provide one or more technological advancements over prior art approaches and designs. BRIEF DESCRIPTION OF THE DRAWINGS So that the manner in which the above recited features of the various embodiments can be understood in detail, a more particular description of the inventive concepts, briefly summarized above, may be had by reference to various embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, t