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 (123a, 123b, 123c, 123d) 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 (123a, 123b, 123c, 123d) 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 (123a, 123b, 123c, 123d) 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 (123a, 123b, 123c, 123d) 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.