Post

Here's what a socket looks like for chip scale packages. Each one is custom made for a given chip package. A couple samples of the 0.4mm pitch Baochip CSP devices are laid out on the lower rim of the socket for size reference.

The socket mounts to the board with spring loaded contacts; the carrier board is also custom to the socket. You can see some of the chip test & measurement power supplies on the board near the socket. The socket itself is quite expensive, a couple thousand dollars and some weeks to manufacture.