plate 41 a respectively and are detachable from each other the reproduction of the semiconductor device unit 110 is performed by means of a cylindrical jig 120 indicated by a double dot chain line in fig7 b the jig 120 is inserted into the hole portion 41 a e 1 to close the engaging spring 111 b so that the engaging pin 110 is pulled out the same operation is performed on the hole portion 41 a d 1 then the faulty lsi package 20 and lga socket 30 a are pulled apart from each other to be replaced with new ones thereafter the semiconductor device unit 110 is again assembled and completed the operation for this reproduction is performed with the capacity of the server being restored to its normal state therefore the operation does not affect an operational condition of the server and it does not especially matter if the operation takes time here a description will be given of the additional installation of an lsi package on the printed board 11 the printed board 11 has numerous lands and four through holes formed on a part on which the lsi package is to be additionally installed the additional installation of the lsi package is performed in the following procedure in step 1 the printed board unit 100 is removed outside from the server in step 2 at the site the stiffener 40 is fitted to the printed board 11 from the lower side thereof and a semiconductor device unit is fitted to the bolts 40 a from the upper side of the printed board 11 before the coiled springs 43 are fitted to the bolts.