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Because some flaws can be generated by the automated machines during the manufacturing process, all printed circuit boards undergo strict visual and electrical inspections. Sometimes components are misplaced on the printed circuit board or shifted before final soldering. Other times there has been too much solder paste applied to the board, which causes the excess solder to flow and bridge across two adjacent printed circuit paths. Also, when the solder is heated too quickly in the final reflow process, it creates a “tombstone” effect where one end of a component lifts up off the board and doesn’t make contact. To ensure their output is within the desired limits, complete printed circuit boards are also tested for functional performance. Some boards are even subjected to environmental tests to determine their performance under extreme temperatures, humidity, vibration and impact. The solder used to make electrical connections on a printed circuit board contains lead, which is considered a toxic material. The fumes from the solder are considered a health hazard, and the soldering operations must be carried out in a closed environment. The fumes must be given appropriate extraction and cleaning before being discharged to the atmosphere. Many electronic products containing PCBs are becoming obsolete within 12-18 months. The potential for these obsolete products entering the wastestream and ending up in landfills has many environmentalists concerned. Recycling efforts for electronic products include refurbishing older products and reselling them to customers that don't need, or have access to, newer, state-of-the-art electronics. Other electronics are disassembled and the computer parts are salvaged for resale and reuse in other products. In many countries in Europe, legislation requires manufacturers to buy back their used products and render them safe for the environment before disposal. For manufacturers of electronics, this means they must remove and reclaim the toxic solder from their PCBs. This is an expensive process and has spurred research into the development of non-toxic means of making electrical connections. One promising approach involves the use of water-soluble, electrically conductive molded plastics to replace the wires and solder. The miniaturization of electronic products continues to drive printed circuit board manufacturing towards smaller and more densely packed boards with increased electronic capabilities. Advancements beyond the boards described here include three-dimensional molded plastic boards and the increased use of integrated circuit chips. These and other advancements will keep the manufacture of printed circuit boards a dynamic field for many years. MadeHow.com. “Printed Circuit Board.” How Products Are Made Vol. 2. 1 Feb. 2010 [http://www.madehow.com/Volume-2/Printed-Circuit-Board.html].
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