I got a new laptop with 256G ssd. My question how do you secure format the ssd?
using the ATA secure erase function on the SSD, hdparm does this.
All modern SSDs have a secure erase function. This does differ slightly for manufacturer to manufacturer however the intended outcome it it effectively resets all cells bringing it to a factory state. Nothing is recoverable is the idea.
Following these instructions on your favorite live cd will do the trick
https://ata.wiki.kernel.org/index.php/ATA_Secure_Erase
FYI, the main difference in how its done it how manufacturers implement secure erase and secure enhanced erase.