A pluggable electrical module comprises: a printed circuit board ; a housing for enclosing the printed circuit board therein, the housing includes at least one housing through-hole with a plurality of through-hole segments arranged along its longitudinal direction; a captive screw comprising a screw head and a screw rod including a thread segment, the captive screw passes through the housing through-hole in a forward direction, the captive screw is used to fasten the pluggable electrical module to a chassis; and a metal tab fixed to the printed circuit board , characterized in that the metal tab includes a tab through-hole through which the captive screw passes, and in the assembled configuration of the pluggable electrical module, the tab through-hole and the housing through-hole are coaxial with each other; the screw rod includes at least a first thread segment and a second thread segment , wherein the second thread segment has a diameter greater than that of the first thread segment and is closer to the screw head than the first thread segment ; at least one of the through-hole segments is a truncated tapered through-hole segment whose inner diameter tapers in the forward direction, wherein the inner diameter of the front end of the truncated tapered through-hole segment is larger than the diameter of the first thread segment but smaller than the diameter of the second thread segment , and the inner diameter of the rear end of the truncated tapered through-hole segment is larger than the diameter of the second thread segment , the screw being made captive by passing the second threaded segment completely through the truncated tapered through-hole segment ; and when the pluggable electrical module is fastened to the chassis, the first thread segment passes through the tab through-hole , and the second thread segment presses the metal tab tightly against the chassis. a printed circuit board ; a housing for enclosing the printed circuit board therein, the housing includes at least one housing through-hole with a plurality of through-hole segments arranged along its longitudinal direction; a captive screw comprising a screw head and a screw rod including a thread segment, the captive screw passes through the housing through-hole in a forward direction, the captive screw is used to fasten the pluggable electrical module to a chassis; and a metal tab fixed to the printed circuit board , characterized in that the metal tab includes a tab through-hole through which the captive screw passes, and in the assembled configuration of the pluggable electrical module, the tab through-hole and the housing through-hole are coaxial with each other; the screw rod includes at least a first thread segment and a second thread segment , wherein the second thread segment has a diameter greater than that of the first thread segment and is closer to the screw head than the first thread segment ; at least one of the through-hole segments is a truncated tapered through-hole segment whose inner diameter tapers in the forward direction, wherein the inner diameter of the front end of the truncated tapered through-hole segment is larger than the diameter of the first thread segment but smaller than the diameter of the second thread segment , and the inner diameter of the rear end of the truncated tapered through-hole segment is larger than the diameter of the second thread segment , the screw being made captive by passing the second threaded segment completely through the truncated tapered through-hole segment ; and when the pluggable electrical module is fastened to the chassis, the first thread segment passes through the tab through-hole , and the second thread segment presses the metal tab tightly against the chassis. <EOS>