Flexible and Rigid-Flex Printed Circuitry: Defect Analysis and Acceptability Criteria, Exams of Electrical Engineering

A detailed overview of defect analysis and acceptability criteria for flexible and rigid-flex printed circuitry. It covers various aspects such as solder wicking, attachment, marking, cleanliness, solder mask coating, conformal coating, potting material, swaged hardware, insulation, conductor strands, and wire overwrap. Acceptable and defect conditions for different classes of products, offering valuable insights for quality control and manufacturing processes in electronics.

Typology: Exams

2025/2026

Available from 11/15/2025

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Flexible and Rigid-Flex Printed Circuitry - Solder Wicking -> Defect Class 1, 2, 3 -
ANSWER Spacing as a result of solder wicking or plating migration violate
minimum electrical clearance
Attachment -> Acceptable Class 1 - ANSWER Side overhang of flex 10-27
Attachment -> Acceptable Class 2,3 - ANSWER Side overhang10-27
Attachme - ANSWER Wetted solder is visible in 10-27
Marking - ANSWER Provides both product identification and traceability
Marking - Etched - Acceptable Class 1,2,3 - ANSWER Lines of a number or letter
may be broken provided the breaks do not make the marking illegible
Marking Etched (including hand printing) - Defect Class 1.2.3 - ANSWER Lines
forming a character are missing or broken to the extent that the character is not
legible or is likely to be confused with another character
Marking - Screened | Process Indicator - Class 1,2,3 - ANSWER Lines of a number
or letter may be broken (or the ink thin over a portion of
Marking - Screened | Defect - Class 1,2,3 - ANSWER Open areas of characters are
filled and are not legible, or are likely to be confused with another number or
letter
Marking - Stamped | Acceptable - Class 1, Process Indicator - Class 2,3 -
ANSWER - Marking that has been smeared or blurred but is still legible
- Multiple stamped markings are acceptable provided the general intent can be
determined
Marking - Laser | Acceptable - Class 1, Process Indicator - Class 2,3 - ANSWER -
Multiple image is still legible
- Missing marking is not more than 10% of the character
kjlkj - ANSWER
Marking - Lables - Readability | Acceptable - Class 1,2,3 - ANSWER Spots or voids
on printed surfaces or machine is readable code as permiss
Defect- Class 1,2,3 - ANSWER Machine readable code
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Flexible and Rigid-Flex Printed Circuitry - Solder Wicking - > Defect Class 1, 2, 3 - ANSWER Spacing as a result of solder wicking or plating migration violate minimum electrical clearance Attachment - > Acceptable Class 1 - ANSWER Side overhang of flex 10- 27 Attachment - > Acceptable Class 2,3 - ANSWER Side overhang10- 27 Attachme - ANSWER Wetted solder is visible in 10- 27 Marking - ANSWER Provides both product identification and traceability Marking - Etched - Acceptable Class 1,2,3 - ANSWER Lines of a number or letter may be broken provided the breaks do not make the marking illegible Marking Etched (including hand printing) - Defect Class 1.2.3 - ANSWER Lines forming a character are missing or broken to the extent that the character is not legible or is likely to be confused with another character Marking - Screened | Process Indicator - Class 1,2,3 - ANSWER Lines of a number or letter may be broken (or the ink thin over a portion of Marking - Screened | Defect - Class 1,2,3 - ANSWER Open areas of characters are filled and are not legible, or are likely to be confused with another number or letter Marking - Stamped | Acceptable - Class 1, Process Indicator - Class 2,3 - ANSWER - Marking that has been smeared or blurred but is still legible

  • Multiple stamped markings are acceptable provided the general intent can be determined Marking - Laser | Acceptable - Class 1, Process Indicator - Class 2,3 - ANSWER - Multiple image is still legible
  • Missing marking is not more than 10% of the character kjlkj - ANSWER Marking - Lables - Readability | Acceptable - Class 1,2,3 - ANSWER Spots or voids on printed surfaces or machine is readable code as permiss Defect- Class 1,2,3 - ANSWER Machine readable code
  • ANSWER Or barcode
  • ANSWER More than 10% of the label area is peeling Marking - Radio Frequency Identification (RFID) Tags | Target - Class 1,2,3 - ANSWER - The RFID tag is located within the specified distance from the tag reader such that the reader can access teh RF signal
  • The RFID tag is attached to the object in a manner that will not preclude transmission of the RF signal
  • ANSWER - The free-air path between the RFID tag contains The RF signal is distorted to the extent that the data cannot be clearly discerned using the reader
  • ANSWER cleaning information Cleanliness - Foreign Object Debris (FOD) - ANSWER Acceptable` Cleanliness - Chlorides, Carbonates and White Residues | Defects - Class 1,2,3 - ANSWER Metallic areas exhibit crystalline white deposit
  • ANSWER - Flux residue does not inhibit visual inspection
  • Flux residue does not inhibit access to test points of the assembly
  • ANSWER Wet, tacky or excessive residues that
  • ANSWER No-clean flux residue on any electrical
  • ANSWER Colored residues or rusty appearance on metallic surfaces or hardware
  • ANSWER Additional information
  • ANSWER Blisters, scratches, voids that do not expose conductors and do not pridge adjacent conductors, conductor surfaces or create a hazordous condition which wouldallow loos
  • ANSWER Blisters/flaking expose base conductor material
  • ANSWER - Coating blisters/scratches/voids bridge adjacent non
  • Coating blisters/scratches/voids have permitted solder bridges Solder Mask Coating - Discoloration | - ANSWER Burned or charred solder mask material
  • ANSWER A post is broken, but sufficient mounting area remains to attach the specified wires/leads
  • ANSWER Burnishing and eformation No more than 3 radialcracks Any 3 radial splits or cracks are separated by 90°
  • ANSWER Any circumferential splits or cracks Any splits or cracks More than 3 radial splits or cracks Radial splits or cracks are separated
  • ANSWER Flared flange solder criteria is provided in 6.1. Swaged Hardware ** - ANSWER Flange Damaged Segments excessivly deformed Segment missing Table 6- 1 - ANSWER
  • ANSWER Solder fillet is at least 75% of the flare flange height
  • ANSWER Minimum 270 fillet
  • ANSWER Minimum 330 Insulation | Acceptable - Class 1,2,3 - ANSWER Slight discoloration of insulation resulting in thermal processing provided it is not charred, cracked or split Defects - ANSWER
  • ANSWER - Insulation clearance is 2 wire diameters or less
  • Insulation clearance does not Insulation - Clearance | Acceptable - Class 1, Process Indicator - Class 2 - ANSWER The insulation clearance C isgreater Insulation - Flexible Sleeve - ANSWER - Cleaning if required, shall be
  • Heating process used to shrink the
  • ANSWER Insulation sleeving is more than 50%
  • ANSWER Sleeving/tubing is tight on terminal, but not tight on wire/cable
  • ANSWER Sleeving/tubing is not tight on terminal
  • ANSWER df
  • ANSWER LInsulaiton sleeve is loose
  • ANSWER Wire strands have separation exceeding 1 strand Conductor - Strand - ANSWER Wire starnds are birdcaged beyond wire insulation noutside diameter
  • ANSWER dkf
  • ANSWER Stranded wire is uniformly coated with a thin coat
  • ANSWER - The solder wets the tinned portion of the wire and penetrates to the inner strands
  • ANSWER sdf
  • ANSWER Pinholes, voids or dewetting/non-wettign
  • ANSWER Solder does not wet the tinned portion of the wire
  • ANSWER Solder build up or icicles
  • ANSWER When required
  • ANSWER The wire approachaes The direation o fthe stress-releif ebdn places no starin on the mechanical wrap or the solder connection
  • ANSWER - There is insufficient stress relief, see Figure 6- 56
  • The wire is under stress at the wrap, see Figure 6- 56 Wire Overwrap - ANSWER When a wire/lead that is wrapped more than 360° and remains in contact Wire Overlap - ANSWER When a wire/lead that is wrapped
  • ANSWER Wires
  • ANSWER Calibration parts may be ounted ot the tops
  • ANSWER Terminal altered to accept oversized
  • ANSWER Acceptable - Class 1,2.3.