The rationale for using press-fit connectors, rather than solder, is four-fold:
The original (1960s) press-fit connector was a ‘force-fit’ type, a ‘crunch connection’ made by inserting a square pin in a round hole. There were inevitable problems with component tolerancing and board finish, with reliability on temperature cycling and after exposure to (corrosive) atmosphere, and with removal and reinsertion because of distortion of the through-hole.
Many attempts have been made to find a practical design which will provide a gas-tight connection, applying continued pressure between pin and board metallisation, and which will survive both the board stress-relieving itself over time and the variable stresses of temperature cycling.
Carry out a web search on press-fit connectors and look for the different design approaches used to try and provide a reliable joint with acceptable insertion force and minimal board damage.
Examine the principle of operation for each, and the way in which the pins
are distorted on insertion so as to maintain contact pressure throughout
life, whilst making it possible to slide the pin in and out of the hole.
Requirements for success in mounting press-fit connectors are: