Printed circuit boards solderability

Surface mount refers to a method of securing connectors to the conductors of a printed circuit board by soldering appropriately shaped contacts to the board surface. Higher contact densities can be achieved and the need to drill holes in the board is avoided. Contact spacings may vary from about 0.5 cm for large current-carrying appHcations to 0.18 cm or less when miniaturization and high density is a requirement. 

In the thermal profile measurement experiment, a fine-wire thermocouple is soldered onto the center of an 8 inch by 11 inch copper clad FR- printed circuit board (The solder was an alloy of 63% tin and 37% lead which melts at 183 C). The thermocouple used was an American Wire Gage 30 chromel-alumel wire which had a maximum use temperature of... 

Fixing adhesive Adhesive used for the fixing of components prior to further processing, for example, components on printed circuit boards before soldering, wire ends for coils after winding. The adhesive layer is usually not exposed to mechanical stress. 

There are other products available—dispersions, paints, coatings, blends—for industrial commercial applications or R D use outside of polymer electronics printed circuit board final solderable finish antistatic coatings screen printable electrodes antistatic and anticorrosion coatings. 

Bono, D., The Assessment of the Corrosivity of Soldering Flux Residues Using Printed Copper Circuit Board Tracks, Solder Surface Mount Technology, No. 2, June 1989, pp. 22-29. 

Fine patterns of polymeric material are widely used in the electronics industry. They are required in the manufacturing of integrated circuits, printed circuit boards and solder masks for the latter. However, photopolymerization finds only limited application in this area. Photocrosslinking and photochemical enhancement of the rate of dissolution are primarily used. Larger structures can also be made by screen printing. In this technique, the photopolymerizable material is deposited pattern-wise and then irradiated in an overall exposure. 

Material such as plastic and ceramic component bodies, lead and pad metallurgies, solder, printed circuit board laminate, solder paste flux, and adhesives all absorb infrared radiation at different rates. Therefore, the direct radiative approach is known to cause overheating of some components and underheating of others. For this reason, direct IR heating is no longer the preferred method for reflow. 

The widely recognized use of Pb-Sn solders in electronics assembly is in the Level 2 interconnections. Level 2 interconnections are solder joints that attach device packages to the printed circuit board. The solderability and, ultimately, the reliability of Level 2 interconnections are determined by the materials used for the package input/output (I/O) and those used for the circuit board. 

Because of the ease with which they can be soldered, electroplated tin—lead coatings of near eutectic composition (62 wt % tin) are extensively used in the electronics industry for coating printed circuit boards and electrical coimectors, lead wires, capacitor and condenser cases, and chassis. 

Printed circuit board component such as laminates, conformal coatings, solder masks, masking tapes, component attachment adhesives, vibration dampers and photoresists. 

The generally very good electrical insulation properties coupled with heat resistance and non-burning behaviour indicate usage in coil bobbins, printed circuit boards (which resist heat of soldering), lamp bulb bases and TV... 

These qualities have also lead to its use on printed circuit boards and on electrical connectors, although the persistent oxide film obstructs easy solderability and produces too high a contact resistance for satisfactory switching at low voltages. 

Lead alloy solder is critical to the transistors, relays, and other components in the printed circuit boards used in all computers and advanced electronic equipment. 

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). 

Until recently, halogen-free products were only available in Europe, but Sony has now adopted global design specifications to ensure that all their projects meet the same standards. Sony aims to have all product lines free of brominated flame retardants by the end of 2005 if substitutes are found to be safer. They also aim to phase out all uses of polyvinyl chloride (PVC) by 2005 as well as lead solder, and specified heavy metals. For example, a Walkman model has PVC-free cables and no brominated flame retardants or lead solder in the printed circuit board. 

Electronic cleaning Defluxing of printed circuit boards Soldering rosin... 

Finally, steps can also be taken to prevent the contaminant from ever entering the process. For example, the development of low-solids no clean rosin fluxes for soldering printed circuit boards completely eliminates the need for a cleaning process (Sapre, 1990). 

Trichlorotrifluoroethane (CFC 113) was widely used in the electronics industry for the removal of soldering flux residues from printed circuit boards, for degreasing components in the precision engineering industry, and for the dry cleaning of garments. 

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