$re = '/([^\s=;]+=\[[^][]*])|;/m';
$str = 'L=1nH;Tol=0.3nH;Idc=1000mA;Isat=NA;Iacpp=NA;Fr=10GHz;ESR=0.10ohm;Q=[100MegHz 7; 500MegHz 23;1.8GHz 47;2.4GHz 57];dL@Isat=NA;dT@Idc=NA';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php