Silicon or glass interposers that have not yet been populated with dies are generally treated as parts of integrated circuits rather than finished devices. Once populated and tested as a functional unit, the assembly may reclassify as a finished IC or microassembly. Given the novelty of advanced packaging formats, importers are encouraged to seek a CBP binding ruling to establish a defensible classification before large-volume shipments begin.

The key criterion is specificity of design: an article that is exclusively or principally used in the manufacture or assembly of integrated circuits — such as a ceramic IC package or a gold bonding wire of the gauge and purity used in wire bonding — qualifies as a part. A generic resistor or capacitor used in broader electronic applications would not, even if it appears in an IC assembly process.