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Board-to-board connectors often have 2 fitting nails (name depends on vendor), e.g. Molex 505066-0622: enter image description here

The product specification includes many properties of those fitting nails, e.g. contact resistance: enter image description here

Does this mean that fitting nails can be used as regular pins? So a 6 pin connector such as Molex 505066-0622 has in fact 8 pins? Also as the contact resistance of the fitting nails is lower, they are even better suited for transmitting power?

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Molex Glossary Terms state:

Fitting Nails: Connector component that increases the mechanical retention of the component to the PCB by increasing solder area. Fitting nails relieve stress on solder joints.

From Molex 505066 Product Specification:

enter image description here

The primary purpose of fitting nails is to keep connector on SMD PCB, but are speced for 50V AC or DC at 3A. Therefore they can be used for power.

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Do not rely on fitting nails for signal or power, they are intended for shielding. Tie them to your chassis ground or equivalent. By the way, yes, they can work as you said but it's not good practice (also often they are tied together when the connector is mated)

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  • \$\begingroup\$ that's also what I thought. There is no chassis ground in our application, so we needed to connect them to signal ground. However, the only argument against using fitting nails seems to be that it's not good practice? do you know the reason why it's not good practice? with "tied together" you mean that some connectors connect fitting nails electrically? \$\endgroup\$
    – mpa
    Feb 15, 2021 at 14:20
  • \$\begingroup\$ Some style of connector has the two sides connected. The main reason for the bad practice it that the fitting mating has no guaranteed properties like mating cycles, resistance and so on (well, your has, so I suppose you could use them!) \$\endgroup\$
    – Lorenzo Marcantonio
    Feb 15, 2021 at 15:38
  • \$\begingroup\$ thanks for the clarification \$\endgroup\$
    – mpa
    Feb 15, 2021 at 15:59

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