Shot molding

Co-injection molding involves injecting two or more different materials into a mold, generally in sequence. To accomplish this, molding machines are fitted with multiple injection units (Figure 14-53). Two-shot molding, the most common version, often utilizes an indexing mold. In this process, the mold is rotated 180° after the first shot fills a portion of the cavity, then the second shot finishes the part... 

This chapter presents an overview of performance plastic polymers in commercial planar and 3-dimensional circuit board products, and describes in detail one approach (two-shot molding) developed as an integrated 3-D circuit manufacturing technology. The distinctions between conventional planar (2-dimensional) circuitry, based on thermoset laminates and "subtractive etching processes, and the enhanced design flexibility afforded by expanded interconnection capacity in three axes are discussed. Specific examples of 3-dimensional interconnect protoypes and products are described and pictured. 

MOLDING/METALLIZATION. Molded thermoplastic circuit board substrates may be rendered selectively conductive by several additive process techniques including conductive polymeric thick film inks (PTF), and semi and fully additive electroless/electrolytic platings. Of the various chemical process methods developed to produce circuitry on a molded plastic substrate, one method practiced by Pathtek, A Kodak Company, combines both "catalytic" and "non-catalytic" resins in a highly automated commercialized two-shot molding/selective metallization process. 

Figure 5. Two-Shot Process First shot molded insert.

Short shot Mold not filled completely Inject pressure too low lack of material... 

Two-shot molding Unit cost hig labor cost high investment moderate to high Limited Somewhat restricted Not critical Good durability Two molding operations Gocxl where maximum abrasion resistance necessary... 

One-shot molding n. A process for molding polyurethane foam in which the reactants, usually an isocyanate, a polyol, and a catalyst, are fed in separate streams to a mixing head from which the mixed reactants are discharged into a mold. The polyol and catalyst are sometimes combined along with other additives prior to mixing, but the isocyanate is always fed separately to the mixing head. 

See also one-shot molding, isocyanate, polyol, polyether foam, reticulated polyurethane foam, and integral-skin molding. 

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