manufacture multi layer ceramic mlc packages or modules 4 consisting of a substrate bottom 6 and a cap top 8 the fixture 9 for assembling these modules consists of a baseplate 10 preferably constructed of one quarter inch thick aluminum preferably having a perimeter slot 12 milled in it a tray 14 fits onto baseplate 10 its precise location being directed by aligning bottom ridge 15 into slot 12 tray 14 is preferably a 34 jedec tray 34 meaning that it conforms to the tray standard of the jedec tray 14 has a plurality of cavities 16 in this case ten such cavities each adapted to fit substrate 6 alignment plate 18 fits on top of tray 14 alignment plate 18 also has a plurality of openings 20 in this case ten such openings each opening having an associated plurality of fingers 21 each opening is adapted to receive cap 8 and each associated plurality of fingers is adapted to accept substrate 6 thus precisely aligning each cap over its respective substrate to tight tolerances if necessary in a preferred embodiment the alignment plate also has a bottom lip 22 along its perimeter that fits together with top ridge 23 of tray 14 thus locating the alignment plate in relation to tray 14 compression plate 24 pivotably attaches to baseplate 10 preferably with a hinge 25 compression plate 24 has a plurality of receptacles 26 each adapted to fit a leaf spring 28 a pressure plate 30 stacks on top of each module assembly 4 on top of cap 8 although the illustrated embodiment uses leaf springs and leaf springs are preferred other springs such as.