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I'm investigating the issues related to long term reliability of pluggable terminals of "Phoenix" style. This terminals are available in a range of pitch and configurations (right angle, straight...). Look at the picture as example.

Pluggable terminal connector

In my application I need to supply a control card with power in excess of 10A. Currently the wire coming from the power supply is simply stripped and put into the terminal plug and then fastened with the terminal screw. Is this method considered safe and reliable over many years of use? The environment is clean and stable, no relevant vibrations. Would it be better to pre-tin the stripped wire before screwing it into the terminal? Or should I use single wire terminals like the ones in the picture? Or would it be better to use a pluggable connector which is itself crimpable? I am aware that for reliability reasons, crimping should be preffered to soldering. Am I right?

Wire terminals

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    \$\begingroup\$ Screw terminals, if tightened properly, are reliable (unless maybe if used in high vibration environment). Are you aware that most wiring installed in homes are made with screw terminals? \$\endgroup\$
    – dim
    Dec 21 '16 at 10:00
  • \$\begingroup\$ Yes dim, I'm aware of this. The only thing that makes me worry is that the screw might loosen up with time and/or the contact with the copper of the stripped wire might become ineffective. Why do many designs use crimped wire teminals (like the ones in the picture) before inserting the wire into the terminal block? \$\endgroup\$
    – Francesco
    Dec 21 '16 at 10:05
  • \$\begingroup\$ I believe it is mainly because, with stranded wire, it makes it easier to insert the wire in the hole when it is crimped with the above "sleeve". I think it is more for practicality than reliability reasons. \$\endgroup\$
    – dim
    Dec 21 '16 at 10:21
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    \$\begingroup\$ For US safety testing this type of connector is intended for bare wire. The testing is quite aggressive. \$\endgroup\$
    – Spoon
    Dec 21 '16 at 12:16
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Never used tinned multistranded wire in a compression type connector such as these. The Solder will creep over time and the compression force will weaken. Making products with this particular type of connection will fail safety standards. All connections should have some kind of physical/ mechanical strain relief and not rely just on the interconnect. The crimps offer a strain relief so are a good method - one seen in better quality installations.

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