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HQ 085027

January 31, 1990

CLA-2 CO:R:C:G 085027 TLS


TARIFF NO.: 8504.40.00

Phillip Yale Simons, Esq.
Freeman, Wasserman & Schneider
90 John Street
New York, New York 10038

RE: Classification of thyristor modules

Dear Mr. Simons:

Your letter of May 30, 1989 to our New York office requesting a ruling on the classification of thyristor modules under the Harmonized Tariff Schedule of the United States Annotated (HTSUSA) has been referred to this office for a reply.


The thyristor module consists of six thyristor elements connected in a series, heatsinks, a voltage divided circuit, and electric "firing" circuitry. The components are mounted on a frame of epoxy resin and aluminum. The six thyristors are separated by the heatsinks and are joined end to end to form a column in the center of the module. The module itself is 1200mm long by 900mm wide. You have furnished pictures of the module which illustrate how the thyristors are positioned within it.

The modules are designed to allow flow of electrical current in one direction and therefore have rectifying capabilities. In its capacity to rectify, the module also allows for conversion of alternating current (AC) to direct current (DC).


Under which of the following HTSUSA headings is the thyristor module properly classifiable:

8541, HTSUSA, covering diodes, transistors and similar semiconductor devices; photosensitive semiconductor devices, including photovoltaic cells whether or not assembled in modules or made up into panels; light-emitting diodes; mounted piezoelectric crystals; parts thereof;

8504, HTSUSA, covering electrical transformers, static converters (for example, rectifiers) and inductors; parts thereof.


The General Rules of Interpretation (GRIs) govern classification of articles under the HTSUSA. GRI 1 requires that classification be determined according to the terms of the headings and any relative section or chapter notes. There is no question that the thyristor module is covered in chapter 85 as electrical machinery and/or equipment. You contend that the module cannot function as rectifying apparatus because it must be connected with other machinery to perform this function. Instead, you maintain that the module functions as a semiconductor gate to switch between reverse and forward voltage polarity. It is also maintained that the six thyristors are actually operating individually and therefore do not comprise an apparatus. Thyristors are specifically provided for under heading 8541 but thyristor modules are not.

It is our position that the thyristor module is more than just a series of thyristors with semiconductor capacity. The thyristors represent only a part of the entire module, albeit a substantial part. They are integrated with other components to make up the entire module and therefore cannot be said to stand alone in their collective function. As such, they comprise an "apparatus" as that term has been defined by the Court of International Trade and the Customs Court. An apparatus is a combination of articles and materials which are intended for a specific use. The Deseret Co. v. United States, C.I.T. , slip op. 86-93 (Sept. 17, 1986); Lenkurt Electric Co. v. United States, 63 Cust. Ct. 463, 467-68, CD 3937 (1969). The intended use in this case is the conversion of the electrical current as it passes through the rectifier. There is no doubt that the module is a vital component in this process. Thus, the thyristor module is more like an integrated circuit or a microassembly than a semiconductor device and as such cannot be classified under heading 8541.

The Explanatory Notes (EN), although not dispositive, should be looked to for the proper interpretation of the HTSUSA. See 54 Fed. Reg. 35127, 35128 (August 23, 1989). The EN for heading 8504 provide a more specific description of the module than does any reference under heading 8541. Explanatory Note 8504 (II)(D)(1)(a) explains that among the electrical static converters covered under this heading are semiconductor converters based on the one-way conductivity between certain crystals, including monocrystalline semiconductor rectifiers using, as a converting element, a device containing silicon or germanium crystals, such as a thyristor. The thyristor module meets this description and is therefore properly classifiable under heading 8504.

You have raised the question of whether or not disposition of the present case is controlled by our recent decisions in HQ 084660 and HQ 084659. In HQ 084660, we ruled that Darlington transistors are properly classifiable under heading 8541, HTSUSA, as transistors. In HQ 085659, various transistor modules were also classified under 8541 as transistors. We do not find those rulings relevant to our discussion here, however. We distinguish the thyristor module from the articles at issue in those cases because the transistors operate in conjunction with three or four terminals while the thyristor module operates in integration with other rectifying circuitry. Therefore, we do not find rulings HQ 084660 and HQ 084659 to be controlling in this case.


The thyristor module is classified under subheading 8504.40.00, HTSUSA, as a static converter.


John Durant, Director
Commercial Rulings Division

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