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NEW PROCESS FOR BUILDING MASKS TO BE USED FOR SELECTIVE METALLIZATION AND PAINTING PURPOSES

IP.com Disclosure Number: IPCOM000006955D
Original Publication Date: 1993-Jun-01
Included in the Prior Art Database: 2002-Feb-12
Document File: 1 page(s) / 89K

Publishing Venue

Motorola

Related People

Ileana Isern-Flecha: AUTHOR [+2]

Abstract

Often, plastic parts must be selectively metallized or painted in order to properly comply with its intended use. A good example is to metallize the inside surface of an enclosure for an electronic device, such as a com- puter or a two-way radio, to impart electrical conductiv- ity to the otherwise non-conducting plastic enclosure. Conductivity allows shielding of the device from elec- tromagnetic interference (EMI) generated by other elec- tronic devices andprevents the device from emitting its own EM1 in excess of FCC regulations. An easy way to accomplish this is to metallize all exposed surfaces of the plastic part. However, one of the great advantages of plastics is that they can be fabricated into parts of spe- citic color without the need for a subsequent painting operation. Metallization of the entire part for the pur- poses of shielding reintroduces the need for cosmetic painting, which adds to the manufacturing cycle time, cost, and might introduce another potential problem, i.e., delamination of the paint. Therefore, a preferred proc- ess is to selectively metalliie only the inside surfaces of the enclosure, thereby imparting the required conduc- tivity, with the exterior of the part maintaining its origi- nal, desired appearance (i.e., color and texture).

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MOTOROLA INC. Technical Developments Volume 19 June 1993

NEW PROCESS FOR BUILDING MASKS TO BE USED FOR SELECTIVE METALLIZATION AND PAINTING PURPOSES

by lleana Isern-Flecha and Stephen D. Hunt

  Often, plastic parts must be selectively metallized or painted in order to properly comply with its intended use. A good example is to metallize the inside surface of an enclosure for an electronic device, such as a com- puter or a two-way radio, to impart electrical conductiv- ity to the otherwise non-conducting plastic enclosure. Conductivity allows shielding of the device from elec- tromagnetic interference (EMI) generated by other elec- tronic devices andprevents the device from emitting its own EM1 in excess of FCC regulations. An easy way to accomplish this is to metallize all exposed surfaces of the plastic part. However, one of the great advantages of plastics is that they can be fabricated into parts of spe- citic color without the need for a subsequent painting operation. Metallization of the entire part for the pur- poses of shielding reintroduces the need for cosmetic painting, which adds to the manufacturing cycle time, cost, and might introduce another potential problem,
i.e., delamination of the paint. Therefore, a preferred proc- ess is to selectively metalliie only the inside surfaces of the enclosure, thereby imparting the required conduc- tivity, with the exterior of the part maintaining its origi- nal, desired appearance (i.e., color and texture).

  Plastics are metallized by any of a variety of processes, including plating (both electroless- and electro- plating), vacuum metallization, conductive paints, and flame-arc spray, Common to all is the fact that unless a specially designed, ancillary piece part called a mask is employed, all exposed surfaces of the part will receive metal, which was described above as undesirable. The purpose of the mask, then, as its nameimplies, is to 'hide' a portion of the part from the process being deployed, thereby prohibiting the material being applied from residing in the hidden areas. As such, a mask must be custom-designed for a given part, and its tit to the part must be exact. In this example, the mask must con- form to the...