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HQ 951321

July 28, 1992

CLA-2 CO:R:C:M 951321 EJD


TARIFF NO: 3921.90.40

District Director of Customs
U.S. Customs Service
511 N.W. Broadway Federal Building
Portland, Oregon 97209

RE: Request for Internal Advice No. 55/91; Epoxy Prepreg; Subheading 7019.20.20; HQ 087721; GRI 2(b); GRI 3(b); Headings 3921, 7019, 8546, 8547, and 8548

Dear Sir:

This is in reference to your memorandum of March 6, 1992, forwarding a request for Internal Advice No. 55/91 filed by the law firm of Gibney, Anthony & Flaherty, on behalf of Tektronix Asia Ltd., concerning the classification of material referred to as epoxy prepreg.


Epoxy prepreg is a composite material that is manufactured by Matsushita Electric Works in Japan. It is made of woven glass cloth material that is thoroughly and completely impregnated with an epoxy resin through a dipping and drying process, and then placed on rolls or sliced into sheets for shipment. After importation, the prepreg is cut to shape and subsequently assembled with other components into printed circuit or wire boards (PCBs). In the PCBs, the prepreg will act as an insulating base, will perform the essential role of the bonding agent or adhesive which joins or, literally, "glues" the several layers of the PCB together, and will act as structural support.

The importer's submission states:

* * * PCB fabricators first slice prepregs from the rolls and trim the sheets to the size of the PCB being manufactured. If the prepregs are imported in sheet form, only the trimming step is necessary.

During assembly of the PCB, the fabricator places the prepregs in an automated hole puncher which punches up to 4 small holes for later positioning only. The prepreg then moves to the PCB press, where it is properly positioned in relation to the other PCB components by spindles which match the location of the holes. The press then applies heat and pressure to the prepreg and other components, which causes the resin to flow. The resin acts as an adhesive which bonds or, literally "glues" together two or more layers of copper foil laminates (formed by joining copper foil and prepreg together under heat and pressure). Upon cooling, the resin again hardens or cures, forming a rigid multi- layer board, consisting of alternating layers of copper- clad laminates and prepreg.

The National Import Specialist responsible for this type of commodity has classified the merchandise under the provision for glass fiber woven fabric, in subheading 7019.20.20, Harmonized Tariff Schedule of the United States (HTSUS).

The importer believes that the prepreg is classifiable under the provision for electrical insulators of any material, in heading 8546, HTSUS, or, in the alternative, under one of the following headings: 8547, HTSUS, which provides for insulating fittings for electrical machines, appliances, or equipment; 8548, HTSUS, which provides for electrical parts of machinery or apparatus; 3921, HTSUS, which provides for other plates, sheets, film, foil and strip, of plastic; or 7019, HTSUS, which provides for other woven glass fibers and articles thereof.

The importer's submission states:

Epoxy prepregs are complex, "hi-tech" electronic components which are specifically designed and constructed for one purpose: as electrical insulators. More specifically, prepregs are electrically insulating substrates of PCBs. * * *


What is the proper classification of epoxy prepreg under the HTSUS?


Merchandise is classifiable under the HTSUS in accordance with the General Rules of Interpretation (GRIs). GRI 1 states in part that for legal purposes, classification shall be determined according to the terms of the headings and any relative section or chapter notes, and provided the headings or notes do not require otherwise, according to GRIs 2 through 6.

GRI 2(b) provides that a reference to a material in a heading shall be taken to include mixtures or combinations of that material with other materials and that any reference to goods of a given material shall be taken to include goods partly of that material; if goods consist of more than one material, then classification will be according to GRI 3.

GRI 3(a) requires that where two or more headings describe the merchandise, the more specific will prevail; or if two or more headings each refer to part only of the materials in the goods, then classification will be by GRI 3(b). GRI 3(b) states that the material or component which imparts the essential character to the goods will determine their classification.

After reviewing the file on this matter, by memorandum dated April 10, 1992, the Customs Office of Laboratories and Scientific Services has furnished us with the following information.

* * * The prepreg is in a semicured state allowing the prepreg sheet to be handled easily during laminating operations as it is reasonably stiff and not tacky or oily (as in the case of uncured epoxy resins). It is during the laminating operations, completed domestically, that the prepreg is totally cured.

The prepreg product under consideration is used to manufacture a product which is known as an electrical laminate, a product in which epoxy resins are commonly found. Epoxy resins have gained wide acceptance in electrical applications due to their exceptional combination of properties such as toughness, adhesion, chemical resistance and superior electrical properties. Epoxy resins which are used to produce electrical laminate sheets, such as the prepreg, are present due to its excellent electrical properties as well as its adhesive properties.

Information in the file shows that the prepreg layers are used to separate layers of copper foil and/or printed circuits in the construction of multi- layer printed circuit boards. Therefore, it appears that the prepreg is being used not only for its excellent insulative (electrical) properties but also for its adhesive properties and its ability to cure to a rigid infusible machineable (engineering plastic) state. These characteristics are given to the prepreg by the epoxy resin and not the fiberglass component. Therefore, although the prepreg would probably not be excluded from Heading 7019 and directed to Chapter 39 by Exclusionary Note (a) to that Heading, the prepreg sheet in its cured state most definitely would.

We note that fiberglass is an excellent insulative material in its own right. However, in the case at hand, it appears that the fiberglass material is used as a carrier for the epoxy resin in its precured state and acts as a reinforcement material in the finished product. An analogous situation is the molded fiberglass components of auto bodies. The components are fiberglass fabrics which have been impregnated with a thermoset plastics material and then is molded and cured. In the cured state, the presence of the fiberglass is not noticeable until the body part is dented or smashed. It appears that in the case of the prepreg, fiberglass fabric is used as the carrier and reinforcement agent because it is a highly non- conductive material and it is more resistive to heat than ordinary fabrics of organic composition. Based on our experience with plastics sheeting materials, we are of the opinion that the primary purpose of the fiberglass is to act as a carrier for the prepreg and a reinforcement material for the finished product. The fiberglass material's insulative and thermal properties simply make it more suitable for usage in the product than any other reinforcement fabric.

In its condition as entered, the prepreg has the identity of a glass cloth and epoxy resin composite material, and does not meet the criteria in GRI 1 analysis of a merchandise of any of the following headings: 8546, HTSUS, electrical insulators; 8547, HTSUS, insulating fitting; or 8548, HTSUS, electrical parts. Even after the imported product has been cut to shape and processed into its finished state, electrical insulation is just one of several important functions it performs.

In addition to the information furnished by the Office of Laboratories and Scientific Services, the various functions of the product are described in Manas Chanda and Salil K. Roy, Plastics Technology Handbook (1987), which at pages 462-463, states:

* * * The main attributes of properly cured epoxy systems are outstanding adhesion to a wide variety of substrates, including metals and concrete; ability to cure over a wide temperature range; very low shrinkage on cure; excellent resistance to chemicals and corrosion; excellent electrical insulation properties; and high tensile, compressive, and flexural strengths. In general, the toughness, adhesion, chemical resistance, and corrosion resistance of epoxies suit them for protective coating applications. * * *

For electrical and electronic applications epoxy formulations are available with low or high viscosity, unfilled or filled, slow or fast curing at low or high temperatures. Potting, encapsulation, and casting of transistors, integrated circuits, switches, coils, and insulators are a few electrical applications of epoxies. With their adhesion to glass, electrical properties, and flexural strength, epoxies provide high-quality printed circuit boards.

In a relative new development, epoxy photopolymers have been used as solder masks and photoresists in printed circuit board fabrications.

Adhesion properties of epoxies, complete reactivity with no volatiles during cure, and minimal shrinkage make the materials outstanding for adhesives, particularly in structural applications. * * * A novel, latent curing system, which gives more than one year pot life at room temperature, has increased the use of epoxies for specialty adhesives and sealants, and for vinyl plastisols. * * *

Epoxies are used in fiber-reinforced composites, providing high strength-to-weight ratios and good thermal and electrical properties. * * *

Pursuant to GRI 2(b), the merchandise is described by and prima facie classifiable under heading 3921, HTSUS, as other sheets and film of plastics, and heading 7019, HTSUS, as articles of glass fibers. Therefore, it must be determined whether the glass cloth or epoxy resin gives the merchandise its essential character.

In Headquarters Ruling letter (HQ) 087721, dated March 5, 1992, Customs classified polyimide prepreg. Customs determined
that polyimide plastics is a very specialized type of plastics with unique insulating and heat resistent properties. As such, while it appears that the glass fiber fabric in the instant merchandise has similar properties, those properties merely make the glass fiber fabric more suitable as a carrier for the polyimide plastics material. On the basis of all the information that we have available, it appears that it is the polyimide plastics which provides the primary insulative attributes to the prepreg. Accordingly, it is the polyimide plastics which imparts the essential character to the imported merchandise[.]

In view of the above, and other product information, we are of the opinion that the essential character of the subject composite good is derived from the epoxy resin material.

GRI 3(b) requires that the epoxy prepreg is classified under subheading 3921.90.40, HTSUS, which provides for "[o]ther plates, sheets, film, foil and strip, of plastics...[o]ther... [o]ther...flexible," with a rate of duty of 4.2 percent ad valorem.


The subject composite merchandise is classifiable under the provision for other flexible plates, sheets, film, foil, and strip of plastics, in subheading 3921.90.40, HTSUS.


John Durant, Director

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