automatically and very accurately solder each connection wire 18 between a pad of the chip and a respective pad 16 of the package the marks 24 are placed in a very accurate manner with respect to the pads 16 of the package they are moreover formed in the same plane and with the aid of the same mask and of the same etching or more generally silk screen printing operation thus there is almost certainly a very small margin of positioning error between these marks and the pads but these marks are not very accurately positioned with respect to the edges of the package they are for example at a distance i from a long edge in the direction of the width of the package and a distance l from a short edge along the length of the package as is represented in fig1 the uncertainty in the values of i and l is significant since only the position of the mark with respect to the pads is considered to be significant and because the operations of high temperature firing of the ceramic engender a significant but not very accurate dimensional shrinkage about 15 the invention proposes that the construction of the indexing mark be modified so that the mark possesses an edge aligned with an edge of the package the uncertainty in the positioning of this mark with respect to this edge becomes zero if there is at least one mark on two perpendicular sides there is then at least one mark whose uncertainty of positioning with respect to an edge is zero and another mark whose uncertainty with respect to a perpendicular edge is zero if the marks are silk screen printed or etched by the.