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NY 894219

January 31, 1994

CLA-2-84:S:N:N1:110 894219


TARIFF NO.: 8473.30.1000

Mr. Harold Mistler
Harold Mistler Customhouse Brokers
167-12 146th Road
Jamaica, New York 11434

RE: The tariff classification of Thermal Conducting Modules from the United Kingdom.

Dear Mr. Mistler:

In your letter dated January 19, 1994, on behalf of El Camino Resources, you requested a tariff classification ruling.

The merchandise under consideration involves thermal conducting modules which are designed and used with IBM main frame computers such as the ES/3090 and 9370 series.

The thermal conduction module houses the multi-layer substrate and cools up to 132 chips mounted on the ceramic substrate. High speed ECL logic and support chips are connected to the multi-layer substrate using the IBM C4 interconnection technology. The 38- layer ceramic substrate is unique in large-scale computers, since it has the ability to support up to 132 logic and array chips, and can accommodate 320 centimeters of wiring per square centimeter of surface area. The substrate is clamped between a baseplate and a "hat" equipped with spring-loaded metal pistons. The dual role of the thermal conducting module (TCM) is to package the chips closely together to best achieve high-speed operation, while providing a compact, reliable means to effectively dissipate heat generated by the chips during the operation. Nine TCM's can be mounted onto a 2 layer glass epoxy circuit board which measures 24 x 28 inches and provides connections between the 16,000 pins of the modules and 1,800 additional terminals for cables leading to other subassemblies.

The board-mounted TCM normally occupies the bottom portion of the Model 90 processor unit, and is thus a functional part of the processor unit.

The applicable subheading for the Thermal Conducting Module will be 8473.30.1000, Harmonized Tariff Schedule of the United States (HTS), which provides for parts and accessories of the machines of heading 8471, not incorporating a cathode ray tube, printed circuit assemblies, other than for power supplies for ADP machines. The rate of duty will be free.

This ruling is being issued under the provisions of Section 177 of the Customs Regulations (19 C.F.R. 177).

A copy of this ruling letter should be attached to the entry documents filed at the time this merchandise is imported. If the documents have been filed without a copy, this ruling should be brought to the attention of the Customs officer handling the transaction.


Jean F. Maguire
Area Director

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