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EP-4161221-B1 - RIGID-FLEX PRINTED CIRCUIT BOARD INCLUDING BUILT-IN DIAGNOSTIC

EP4161221B1EP 4161221 B1EP4161221 B1EP 4161221B1EP-4161221-B1

Inventors

  • NARAYANAN, GOMATHI GANESH

Dates

Publication Date
20260513
Application Date
20220915

Claims (15)

  1. A rigid-flex printed circuit board, PCB, (100, 200, 220, 230, 300, 400) comprising: at least one rigid PCB (102a, 102b) including at least one electrical component (103a, 103b); a flex circuit (104) including at least one end connected to the at least one rigid PCB, the flex circuit including at least one signal trace (108) configured to deliver an electrical signal to the at least one electrical component; characterized in that the rigid-flex printed circuit board comprises a built-in diagnostic circuit configured to detect a fault in the rigid-flex PCB, the built-in diagnostic circuit comprising: a diagnostic device (112) installed on the at least one rigid PCB; and a diagnostic trace (110) formed on the flex circuit, wherein the diagnostic device is configured to detect the circuit fault in response to an open circuit occurring in the diagnostic trace, and wherein the diagnostic trace (110) extends from a first edge trace (116a) portion formed on the first rigid PCB (102a), and extends through the first joint region (106a), to a second edge trace (116b) portion formed on the second rigid PCB (102b) and extends through the second joint region (106b).
  2. The rigid-flex PCB of claim 1, wherein the built-in diagnostic circuit comprises: wherein the diagnostic device (112) generates an alert in response to detecting the fault, the fault including one or more of a light alert, a sound alert, a haptic alert, and an interrupt to system software to initiate a safe shutdown or a fail-safe procedure.
  3. The rigid-flex PCB of claim 2, wherein the at least one rigid PCB comprises: a first rigid PCB (102a) including a first electrical component (103a) (the electrical component including, for example, a transistor, capacitor, resistor, logic gate, or processor), the first rigid PCB including a first edge coupled to a first end of the flex circuit to establish a first joint region (106a), a second rigid PCB (102b) including a second electrical component (103b), the second rigid PCB including a second edge coupled to a second end of the flex circuit opposite the first end to establish a second joint region (106b), wherein the first and second rigid PCBs are formed from a rigid material such as, for example, a flat laminated composite board of non-conducting substrate material (e.g., fiberglass), the board including one or more layers of metal.
  4. The rigid-flex PCB of claim 3, wherein the diagnostic trace (110) has a serpentine profile including a first edge trace portion (116a) extending onto an edge of the first rigid PCB and a second edge trace portion (116b) extending on an edge of the second rigid PCB.
  5. The rigid-flex PCB of claim 4, wherein the diagnostic device (112) is installed on the first rigid PCB (102a), a signal source (114) is installed on the second rigid PCB, and the diagnostic trace (110) establishes signal communication between the diagnostic device and the signal source.
  6. The rigid-flex PCB of claim 5, wherein the first edge trace (116a) includes a first proximate end that is connected to the diagnostic trace (110) formed on the flex circuit (104) and a first distal end that is connected to the diagnostic device (112), and wherein the second edge trace (116b) includes a second proximate end that is connected to the signal source (114) and a second distal end that is connected to the diagnostic trace (110) formed on the flex circuit.
  7. The rigid-flex PCB of claim 6, wherein the diagnostic device (112) is a light emitting diode, LED, (113) configured to emit light in response to a closed circuit between the signal source and the diagnostic device, and configured to stop emitting light in response to an open circuit between the signal source and the diagnostic device, or wherein the diagnostic device (112) is a processor (117) configured to execute at least one of a trace conductivity test and a Power on Built in Test (PBIT) in response to powering on the processor, the processor configured to generate the alert in response to an open circuit between the signal source and the diagnostic device.
  8. The rigid-flex PCB of any of claims 2 to 7, wherein the at least one signal trace has a first size (e.g., width) and the diagnostic trace has a second size (e.g., width) that is less than the first width, and/or wherein the at least one signal trace is located between a first portion of the diagnostic trace formed on the flex circuit and a second portion of the diagnostic trace formed on the flex circuit.
  9. The rigid-flex PCB (300) of claim 2, wherein the built-in diagnostic circuit comprises: a first edge trace (116a) that includes a first proximate end that is connected to the diagnostic trace formed on the flex circuit and a first distal end that is connected to a first test pad (302a); and a second edge trace (116b) that includes a second proximate end that is connected to a second test pad (302b) and a second distal end that is connected to the diagnostic trace formed on the flex circuit.
  10. The rigid-flex PCB of claim 9, wherein the first test pad (302a) is configured to be connected to a first input of a diagnostic device and the second test pad (302b) is configured to be connected to a second input of the diagnostic device, optionally wherein the diagnostic device (112) measures (e.g., an ohm meter or volt meter) one or more of resistance between the first test pad and the second test pad, current between the first test pad and the second test pad, and voltage between the first test pad and the second test pad.
  11. The rigid-flex PCB (400) of claim 2, wherein the flex circuit includes a first end coupled to a first edge of the at least one rigid PCB (102a) to establish a first joint region (106a) and a second end coupled to a second edge of a PCB connector (402) to establish a second joint region (106b).
  12. The rigid-flex PCB of claim 11, wherein the PCB connected is configured to establish signal connection with the flex circuit and a second rigid PCB.
  13. The rigid-flex PCB of claim 12, wherein the diagnostic trace (110) has a serpentine profile that meanders from a first edge trace portion formed on the at least one rigid PCB and extending through the first joint region to a second edge trace portion formed on the PCB connector and extending through the second joint region.
  14. The rigid-flex PCB of claim 13, wherein the diagnostic device (120) is installed on the at least one rigid PCB, a signal source is installed on the second rigid PCB, and the diagnostic trace establishes signal communication between the diagnostic device and the signal source.
  15. The rigid-flex PCB of claim 14, wherein the first edge trace (116a) includes a first proximate end that is connected to the diagnostic trace (110) formed on the flex circuit and a first distal end that is connected to the diagnostic device (112), wherein the second edge trace (116b) includes a second proximate end that is connected to a connection terminal (404) installed on the PCB connector (402) and a second distal end that is connected to the diagnostic trace formed on the flex circuit, and wherein the second rigid PCB (102b) includes a signal trace including a third proximate end connected to the signal source and a third distal end connected to a second connection terminal that is configured to establish signal communication with the first connection terminal, optionally wherein the diagnostic device is a light emitting diode, LED, (113) configured to emit light in response to a closed circuit between the signal source and the diagnostic device and configured to stop emitting light in response to an open circuit between the signal source (114) and the diagnostic device.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of Indian Application No. 202111044400 filed September 30, 2021. BACKGROUND Exemplary embodiments generally pertain to electronic circuits, and in particular, rigid-flex printed circuit boards. Printed circuit boards (PCBs) connect electrical components together using discrete wiring, resulting in a complete and functional unit. The three main types of PCBs typically used in electronic application are rigid PCBs, flexible PCBs (sometimes referred to as flex circuits), and rigid-flex PCBs. Rigid PCBs are formed entirely from a rigid material and are therefore inflexible. Rigid circuit boards are popular largely due to their low cost. In conventional electronics, and particularly in consumer electronics, with greater space availability, manufacturers can save significantly by using rigid circuit boards. Flex PCBs, however, are formed entirely from a flexible material, and therefore can be bent or otherwise shaped. Flex PCBs provide several advantages over rigid PCBs such as, for example, physical flexibility allowing for reduced area and space consumption, connectivity, reduced weight, durability, and resilience to environmental conditions. Rigid-flex PCBs are a hybrid of both rigid and flex PCBs. A rigid-flex PCB incorporates flexible materials in conjunction with rigid materials by layering flexible circuit substrates inside of the rigid circuit board materials, ultimately combining the versatility of flexible circuits with the stability, strength and circuit routing densities of rigid PCBs. US2018089984A1 relates to the field of electronic devices and, more particularly, to detecting properties of flexible circuitry. US2018089984A1 relates to bendable printed circuit boards with low failure rates during use including methods and apparatus designed for their manufacturing and applications. US10157527B1 relates to methods, apparatus, and products for an embossed printed circuit board for intrusion detection. BRIEF DESCRIPTION According to a non-limiting embodiment, a rigid-flex printed circuit board (PCB) is provided. The rigid-flex PCB includes at least one rigid PCB including at least one electrical component, a flex circuit, and a built-in diagnostic circuit. The flex circuit includes at least one end connected to the at least one rigid PCD. The flex circuit includes at least one signal trace configured to deliver an electrical signal to the at least one electrical component. The built-in diagnostic circuit is configured to detect a fault in the rigid-flex PCB. The built-in diagnostic circuit comprises a diagnostic device installed on the at least one rigid PCB, and a diagnostic trace formed on the flex circuit, wherein the diagnostic device detects the circuit fault in response to an open circuit occurring in the diagnostic trace. The diagnostic trace extends from a first edge trace portion formed on the first rigid PCB, and extends through the first joint region, to a second edge trace portion formed on the second rigid PCB and extends through the second joint region. In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, the diagnostic device generates an alert in response to detecting the fault, the fault including one or more of a light alert, a sound alert, a haptic alert, and an interrupt to system software to initiate a safe shutdown or a fail-safe procedure. In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, the at least one rigid PCB includes a first rigid PCB including a first electrical component, and the first rigid PCB includes a first edge coupled to a first end of the flex circuit to establish a first joint region. In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, a second rigid PCB includes a second electrical component. The second rigid PCB includes a second edge coupled to a second end of the flex circuit opposite the first end to establish a second joint region. In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, the first and second rigid PCBs are formed from a rigid material such as, for example, a flat laminated composite board of non-conducting substrate material (e.g., fiberglass), the board including one or more layers of metal. In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, the diagnostic trace has a serpentine profile including a first edge trace portions extending onto an edge of the first rigid PCB and a second edge trace portion extending on an edge of the second rigid PCB. In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, the diagnostic device is installed on the first rigid PCB, a signal source is insta