Electronic Military & Defense Annual Resource

2nd Edition

Electronic Military & Defense magazine was developed for engineers, program managers, project managers, and those involved in the design and development of electronic and electro-optic systems for military, defense, and aerospace applications.

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Technology standard non-plateable resin to define the desired area to be plated. This area is metalized initially with copper, followed by nickel and, optionally, gold plating. The following are a few of the advantages of MID two-shot technology: • Design flexibility for complex 3-D geometries • Ability to integrate multiple functions into one component • Tightest tolerance for pattern registration to carrier • Fewest manufacturing steps and processes • Higher yields • Improved scalability LDS is a three-step process. The antenna substrate, which is often the enclosure of the finished radio, is molded in a standard thermoplastic molding process. A laser then etches the part surface where the antenna is to be patterned. The etching process exposes a special- ized plating additive in the polymer resin. Finally, the antenna is placed in an electroless nickel plating bath where the plating adheres only to the plastic that has been activated by the laser. LDS allows narrow traces as fine as 0.15 mm and the flexibility to change patterns during production. One advantage of the LDS process is that the pattern of the metal can be changed by simply changing the laser pattern, rather than redesigning the mold. Figure 2 shows the steps. surface soldering, inclusion of metal inserts for contact pins, and circuit traces (see Figure 3). MIDs for cell phones are routinely supplied as subassemblies with the RF connector and cable, ready for connection to the main circuit board. The resins used in the enclosure meet a wide range of temperature, fluid, and chemical resistances; impact strengths; corrosion resistances; and other application needs. Choices range from cost-effective polycarbonate and acrylonitrile butadiene styrene (ABS) to high-per- formance materials like polyether ether ketone (PEEK). Not only does PEEK offer excellent strength and chemi- cal resistance, it has a temperature range from -100˚C to +200˚C. Figure 3: MIDs can accommodate circuit traces, connector pins, and other features (photo courtesy of TE Connectivity). New composites offer strength and durability com- parable to or exceeding that of metal housings; equally significant, they offer resistance to corrosion, chemicals, and sustained high temperatures. For electromagnetic interference (EMI) protection, conductive polymers act by absorbing emissions rather than reflecting them. Add in weight savings of around 40% compared to aluminum and 80% compared to stainless steel. Figure 2: Laser direct structuring (photo courtesy of TE Connectivity) The plating is composed of three metal layers: electro- less nickel, copper, and gold. The final plating thickness ranges from 5 to 20 microns. The nickel offers excel- lent plating adhesion to the molded substrate. Unlike a printed circuit board where the copper is epoxied to the substrate, the MID plating adheres to the exposed plat- ing additive in the molded part. The result is superior plating adhesion in high-vibration and thermal cycling applications. The copper thickness can be varied to carry currents up to 10 A in embedded traces. The gold surface finish allows for through-hole and surface sol- dering directly onto polymer parts, with careful choice of solder profile. Advantages Of MIDs One advantage of MIDs is that capabilities go beyond embedding an antenna. Secondary operations include 16 Electronic Military & Defense ■ www.vertmarkets.com/electronics The ability to create precise antenna patterns embed- ded in a plastic enclosure yields many operating benefits: • Multiple antennas embedded onto a single enclosure: Today's smartphones use GPS, GSM, and Wi-Fi antennas simultaneously. The latest advances include MIMO (multiple-input and mul- tiple-output) and beam-steering capabilities with multiple antennas on cellphone cases. • Size, cost, mechanical robustness, and ergo- nomics improvement compared to external alternatives. • Increased power and range: Beginning in the early part of this decade, antennas needed to become anisotropic in order to radiate increased power without radiating a considerable portion toward the user's head. Tactical radios with radio- mounted external antennas radiate a considerable fraction of the total power toward the soldier's back. Embedded antennas — based on experience

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