The Benefits of a Vertically Integrated Approach to EMS

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Many electronics manufacturing services providers are expert at board-level and box build assembly. However, most do only limited cable and harness assembly in-house.

The benefits of providing cable and harness assembly services in-house to customers are three-fold. First, the business focus on cable assembly ensures that volumes are present for both cost competitive material prices and a level of automation that keeps labor costs competitive. For example, on a medical device with both printed circuit board assemblies (PCBAs) and cables, an EMS firm that has the capability to provide cable and harness assembly will be able to reduce the cost on the product’s cables by leveraging their cable buying power.

Second, doing the work in-house does more than eliminate a layer of supply chain markup; it also decreases lead-time while improving the ability to respond to customer schedule changes.

Finally, expertise in cable assembly adds value when product designs have cable manufacturability issues. The ability to provide expertise in cable assembly can add significant value because cables are often thought of as a less challenging part of product design. Typically, companies put a great deal of focus on design of the PCBAs and the overall unit itself, but the design team may not be expert at cable design.

Some common cable design related issues include:

• Wrong terminal or contact for specified wire gauge: If the contact is too large, the crimp will be too loose and will fall off. Conversely, if it is too small the crimp will be too tight and may damage the wire strand immediately or completely 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 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.
• 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 issue: Insufficient EMI shielding or placement of sensitive cables near a power supply can create intermittent product failures.

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Editor's Note: This article originally appeared in the March 2016 issue of SMT Magazine.

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