DEMO — fictional range. Local brief only, NOT SENT. No personal data is collected or transmitted.
MATERIAL
Six materials, and what each one is chosen for.
Board connectors are chosen for contact behaviour first and for mechanical strength second, because the contact is the only part doing work.
Illustrative material record
- Copper alloy
- Contact bodies · carries current and supplies the spring force
- Gold over nickel
- Repeatedly mated contacts · stable resistance, thin and expensive
- Tin over nickel
- Permanently mated contacts · cheap, and the oxide film is resistive
- Glass-filled polyamide
- Insulators · holds the pitch through soldering without creeping
- Die-cast zinc
- Backshells · heavy and cheap, and it casts to the shape of the shell
- Nickel over copper
- Shell finish · the copper is the conductor, the nickel is the wear surface
Illustrative examples for a fictional range. Material selection depends on the cycles, the environment and the current, and is confirmed against a specification rather than a web page.
Why the alloy carries the spring.
Because a contact is a spring as well as a conductor. The force it applies is what keeps the resistance low, and a material chosen only for conductivity may relax and lose that force.
Why glass-filled rather than plain polymer.
Because the insulator goes through soldering. A plain moulding creeps at temperature and the pitch moves, which puts every pin slightly out of position.