The four-way split
The table must be read with its parent descriptions. Heading 3818 concerns doped chemical elements and compounds for use in electronics. The monocrystalline silicon slice branch begins at 7.5 cm in diameter. That lower bound is inherited by the two lines whose individual descriptions say “15.24 cm or less.”
| New code | Diameter | Thickness | Previous classification |
|---|---|---|---|
| 38180012 | 7.5 cm to 15.24 cm, inclusive | Above 220 micrometres | ex 38180011 |
| 38180013 | 7.5 cm to 15.24 cm, inclusive | At or below 220 micrometres | ex 38180011 |
| 38180014 | Above 15.24 cm | Above 220 micrometres | ex 38180019 |
| 38180015 | Above 15.24 cm | At or below 220 micrometres | ex 38180019 |
Printed pages 38-39 of Annex 4 establish the parent scope and the new subdivisions. Both predecessor codes are deleted. The change adds a thickness distinction within the previous diameter branches.
Why focus on 38180015?
This line isolates thinner slices within the larger-diameter branch of the tariff classification. It lets researchers distinguish that combination from thicker slices in 38180014. Before the split, those thickness groups were combined under the predecessor’s scope.
The threshold is greater than 15.24 cm, not a dedicated 200 mm or 300 mm wafer category. Calling 38180015 “China 300 mm wafer exports” would therefore narrow the product definition without evidence. The new line also does not identify a fabrication node, customer process or final chip application.
For the same reason, these four lines should not be presented as a complete inventory of every silicon wafer, photovoltaic wafer or semiconductor product traded by China. They describe a particular branch under heading 3818. A broader study needs a separately justified product basket.
What the new dimensions let analysts compare
The published HS 38180015 export series reports $107,787,434 in January 2026 and $145,178,347 in July, a 34.7% increase between those months. March was higher than either endpoint at $247,181,399. These figures were checked on September 15, 2026 and describe the available release, not a year-on-year comparison.
The March peak is a useful starting point for examining destinations and shipment composition. The aggregate alone does not reveal whether it resulted from more pieces, a different mix of dimensions, or changes in customs unit values. It is especially insufficient evidence for a claim about a particular chip technology.
The most direct comparison is within each diameter branch: thinner versus thicker slices. For the larger branch, a value share based on 38180015 divided by the sum of 38180014 and 38180015 describes the thinner group’s share of that trade basket. A corresponding calculation can be made for 38180013 within the smaller branch.
Keep export and import calculations separate. The two directions can have different product mixes and trading partners. A net value can conceal both sizeable imports and sizeable exports, while a combined total can obscure the question the reader is trying to answer.
Destination or origin comparisons can then show where trade in each specification group is concentrated. They do not identify the fabrication plants, purchasers or end uses behind those flows. Claims about supply-chain dependence should therefore distinguish observed trade concentration from assumptions about production capability.
Why quantity units matter especially here
A quantity recorded in kilograms is not a count of wafers. Thickness and diameter affect how weight relates to individual slices, so a weight-based comparison cannot directly establish that one group contains more wafers than another.
Do not convert weight into piece counts using a representative wafer size: the customs lines contain ranges of dimensions. Even a consistent dollars-per-kilogram measure combines price and product composition. It should remain labelled as a trade unit value, not a wafer price or a measure of technological sophistication.
Comparing the new lines with older data
For a broader diameter-branch history, the official mapping suggests combining 38180012 with 38180013 for the former 38180011 scope, and 38180014 with 38180015 for the former 38180019 scope. Check consistent coverage and statistical definitions before calculating a growth rate across that boundary.
The reconstruction preserves the broader grouping; it does not reveal the missing historical thickness split. A pre-2026 series specifically for thin, larger-diameter slices cannot be inferred from the predecessor total.
For another electronics category newly separated in 2026, see wireless routers under HS 85176295. The new-code tracker lists the wider adjustment.