Seven Cable Design Mistakes

IMG_8356As a company that specializes in being a one-stop shop of PCBAs, cable & harnesses and final assembly, Spectrum Assembly’s team works hard to ensure that projects are optimized for efficient assembly. Cables and harnesses are one area where SAI’s expertise comes in handy, since this part of the design is often not scrutinized as closely as PCBAs or the final assembly by customer design teams. Here are seven common mistakes the team at SAI sees:

  • Wrong terminal or contact for specified wire gauge. If the contact is too large, the crimp will be loose and fall off. Conversely, if it is too small the crimp will be too tight and may damage the wire strand immediately or destroy it over time. In some cases, the terminal specification is correct, but an incorrect wire gauge or tolerance is specified.
  • Male connector housing with female terminal. While this mistake is easily fixable, it can generate significant non value-added activity if not caught in documentation.
  • Incompatible materials on header and cable. For example, specifying a gold-plated header on the PCB connector, but using tin on the cable terminal, can create resistance issues immediately and corrosion longer term.
  • Cable documentation shows pinout but doesn’t identify connector. If the pinout only shows a single view and the connector isn’t identified, in the best case it slows down the new product introduction process and in the worst case it can result in an incorrect connector being used. If the pinout is incorrect it results in unnecessary rework.
  • Incomplete or missing wire list. This is a frequent mistake with two-wire connections. It can cause quality issues.
  • Proper crimp tool not specified. The tools used to crimp wire are specifically sized for the cable. Failure to specify the correct tool size or specification of an incorrect tool can create quality issues. IPC-A-620 includes a requirement for specification of crimp height and tool test.
  • Insufficient electromagnetic interference (EMI) shielding or placement too close to sources of EMI. Insufficient EMI shielding or placement of sensitive cables near a power supply can create intermittent product failures.

SAI’s team is expert enough to be able to identify these issues as they occur. However, the best option is to avoid the issue in the first place by working with the intended contract manufacturer as early in the design process as possible. The focus that SAI’s team puts on ensuring cables and harnesses meet the requirements of IPC-A-620 is equal to the level of detail it focuses on in ensuring PCBAs are compliant with IPC-A-610 requirements.

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