Circuit board-attached connectors

In addition to wire harness connectors, printed circuit board-attached connectors, for automotive or electronic applications, also benefit from many of SPS s performance characteristics, including low viscosity, which helps to fill thin walls and heat resistance to maintain dimensional stability through lead-free reflow soldering operations (see Table 15.2). The trend toward miniaturization in automotive electronic control modules has increased the need for compact surface mount connector technology, as opposed to bulkier through-hole and wave-soldered alternatives. 

Fig. lab. Some types of electronic connectors, (a) Receptacle for dual-in-line package (DIP) semiconductor integrated circuit, (b) Connectors for printed circuit boards having edge contacts two-piece connectors have male and female connector halves, one of which is attached to the printed circuit board. 

Manufacture of Printed Wiring Boards. Printed wiring boards, or printed circuit boards, are usually thin flat panels than contain one or multiple layers of thin copper patterns that interconnect the various electronic components (e.g. integrated circuit chips, connectors, resistors) that are attached to the boards. These panels are present in almost every consumer electronic product and automobile sold today. The various photopolymer products used to manufacture the printed wiring boards include film resists, electroless plating resists (23), liquid resists, electrodeposited resists (24), solder masks (25), laser exposed photoresists (26), flexible photoimageable permanent coatings (27) and polyimide interlayer insulator films (28). Another new use of photopolymer chemistry is the selective formation of conductive patterns in polymers (29). 

The prime function of adhesives is to mechanically attach or bond devices, components, heat sinks, wire, connectors, and other parts onto a circuit board or an interconnect substrate. Adhesives are also used as pastes or films to attach lids in sealing cavity packages and as dielectric films in fabricating multilayer interconnect substrates. The most important consideration in obtaining a reliable adhesive bond is the ability of the adhesive to flow and wet the surfaces. For a reliable bond, strong adhesion to both surfaces and strong cohesion within the adhesive are necessary. 

Polymer adhesives have found their place in numerous electronics applications. Major uses include eommercial/consumer products computers and military, space, automotive, medical, and wireless communications. Some adhesives may be used aeross several applications while others have been formulated to meet applieation-specific requirements. For example, reworkability is not a consideration for high-production, low-cost consumer products such as cell phones or calculators, but is important for high-value, high-density printed-wiring boards (PWBs) used in military and spaee electronics. Further, thermal stability at high temperatures is required for near-engine electronics in automobiles, aircraft, and for deep-well sensors, but not for office computers. The major applications for polymer adhesives are to attach and electrically insulate or to electrically connect components, devices, connectors, cables, and heat sinks to printed-circuit boards or to thin- or thick-film hybrid microcircuits. In addition, over the last several decades, new uses for adhesives have emerged for optoelectronic (OE) assemblies, microelectromechanical systems (MEMS), and flat-panel displays. 

The USB-to-IDC connectors, as shown in Fig. 27.6, were redesigned for this garment [10]. The circuit board for the connector was designed so that it could be sewn to the ribbon with the communicalion bus. This design choice was intended to help improve durability of the connection. This connection also provided strain relief [10]. Fig. 27.7 shows how these connectors attached to the bus, which was sewn onto the grosgrain ribbon. The strain rehef, which was provided by the two slots on either side of the IDC, provided mechanical stability to the wires on either side of the IDC, enabling the rigid connections to be placed upon a flexible fabric substrate. 

Electronic connectors are attached to printed circuit boards in four ways (see Fig. 49.1) ... 

Originally, FFC connectors were developed for laminated cable with flat conductors to connect to another circuit board. A similar construction of flexible circuits was developed to attach the connector. At this time, the standard pitch of the connectors was 2.54 mm. Due to increased trace densities of flexible circuits, small-pitch FFC connectors are now required. The newest connector can make 0.3 mm pitch connections for 30 traces. Zero in force (ZIF) mechanisms were introduced for easier handling. Due to hmited height requirements for thin board assembly, a 1.0 mm high connector from the board surface is now available. 

---