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44 SMT Magazine • December 2014 room temperature. Component suppliers usual- ly provide specifications for room temperature co-planarity, using either the seating plane or regression plane measurement method. As long as the value is under 8 mils, the co-planarity is deemed within specification. Empirical data suggests that the JEDEC specification is no longer adequate. For high pin count packages with small pads and lower solder vol- umes, production data sug- gests that component warp- age exceeding 3.5 mils can cause problems during re- flow, with a high potential for HOP defects. Manufactur- ers of consumer devices may discard or recycle defective boards, but this is not an op- tion for an advanced comput- ing or communications PCBA costing over $10,000. Time- consuming and expensive 3D X-Ray testing is necessary with assemblies susceptible to HOP defects. In 2015, EMS providers will continue to drive changes including advocating for im- proved plastic material compounds, along with working with JEDEC to tighten the standard warpage specification to closer to 3.5 mils for high pin count devices. challenge No. 4: building PcbAs robust enough for mission-critical Industrial environments Industries such as oil and gas use electronic assemblies in very demanding environments. Drilling and exploration tools used two to three miles below the earth's surface can cost upwards of $2 million, and operate in environments up to 350°F. This equipment must continue to per- form with precision, despite high temperatures and pressure, vibration, mechanical shock and corrosive environments (oil, mud, moisture, and chemicals). PCBAs deployed in these environments re- quire high-temperature solders that are not generally suited for current surface mount or automated pin through-hole manufacturing. Most of these PCBAs are still soldered manu- ally. While high-Pb solders are excluded from the current RoHS legislation, there is an inter- est for alternative high temperature soldering materials, especially for environ- ments up to 350°F. This research will continue in 2015, as OEMs and EMS companies work to develop better materials and processes. Looking Ahead SMT will continue to push the competing technical boundaries of signal integrity, miniaturization and increas- ing I/O counts. While de- vices with pad pitches in the range of 0.3 mils are already being assembled with auto- mated surface mount equip- ment, this pad pitch cannot be commonly used for high pin count devices due to limi- tations in PCB technology (via escape) and package warp. Vacuum soldering, which eliminates voids, will likely become more mainstream. Vacuum-assisted re- flow soldering (vapor phase or modular reflow, which involves adding a vacuum zone) equip- ment currently costs 1.2 to 1.3 times more than more conventional equipment. As equipment prices drop, vacuum solder- ing is likely to become more common. Other challenges in 2015 are not unlike those the electronics industry has faced over the past 10 years, but solutions will continue to require more advanced process technology and equip- ment. The result will be new processes, PCB and PCBA technology that would have been viewed as unachievable just a few years ago. SmT FEATurE SUrFAce mOUNT TecHNOLOGY AdvANcemeNTS IN 2015 continues Mulugeta Abtew is vp of process technology development at Sanmina. For high pin count packages with small pads and lower solder volumes, production data suggests that component warpage exceeding 3.5 mils can cause problems during reflow, with a high potential for HOP defects. " "