Two-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. 

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... 

The expressions also used for this process are bicomponent injection, coinjection, or two-shot molding. When a plastic part, previously molded in a specific mold, is introdnced in another mold, in the same way as a metal insert, and a different plastic is molded over it, the expression overinjection is sometimes nsed. 

Figure 7-30. Du Font s Ary Ion polyary late and Rynite TP-polyester resins eliminate parts and simplify assembly of Xetec Corp. s three-dimensional circuitboard for lighting ballasts. A special two-shot molding process removes the need for metal fabrication and yields a low-cost, reliable component for use in rapid-start fluorescent lighting ballasts.

Rgure 1.67 Two-shot molding with rotating mold. ... 

Two-shot molding for instrument panels started in mid-1990s. Will likely grow. 

Two-shot molding (also starting to be used in exterior trim, e.g., rocker panels in European models) ... 

MID antennas have become mainstream in recent years, and nowhere more so than in the mobile-communications sector. Units of this kind are manufactured in very high numbers in Asia. Molex announced the production of its twenty millionth LPKF-LDS antenna [76] back in 2009, and a large proportion of MID antennas are two-shot moldings. The sector is further expanding to include tablet PCs, with demand leaning more toward larger antenna structures. RFID antennas for very widely varying applications constitute yet another sector. 

The following sections set out the purely materials-related and tool-related prerequisites for the two processes now most commonly used in MID production two-shot molding and laser direct structuring (LDS). Chapter 3 of this book deals in depth with the workflows, possibilities, and boundary conditions associated with these manufacturing processes. It also contains information about the production methods such as hot embossing and film insert molding, neither of which is considered in more detail here from the materials point of view. 

In the past, two-shot molding or two-shot injection molding generally referred to a process in which a first shot of material is subsequently enclosed within a second shot. In MID technology, however, the process is one in which the second-shot plastic compound is applied on top of the first shot. In the course of time two main versions of this basic process have established themselves for MID technology [48] ... 

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