CircuiTree - February 2009 - (Page 29)

lated with ﬁne pitch devices, it dispenses small amounts of solder paste. The other side of the same board may contain an analog section, for example, with lightly populated components and the laser printer can be changed and controlled to handle this contrast in population density. In this instance, with the analog portion and its larger devices, considerably higher paste dispensing is required, and the laser printer can be changed to operate accordingly. Solder paste and its chemistry play a large role in ﬁne pitch assembly. If solder paste is more granular, meaning it has a more thick substance within the granules of the paste mixture, it tends to overshoot when printing is performed. This means nongranular or slightly less granular paste should be used for ﬁne pitch SMD pads. This way, pads are properly covered to produce a perfect or near perfect solder joint. An effectively developed thermal proﬁle is another factor in the proper mix for accurate ﬁne pitch assembly. The correct proﬁle coupled with placing the thermal proﬁles at the right sections of the board is essential. There One important aspect of successful ﬁne pitch assembly is for the ﬁnish to provide an extremely ﬂat surface. is no room for error here. If ﬁne pitch devices are not properly placed due to a poorly created thermal proﬁle, or they are skewed for whatever reason, then costly rework will ultimately result. Conclusion Correctly and accurately performing ﬁne pitch device placement requires leading-edge technology. EMS providers using older placement technologies confront an array of issues. Therefore, it is critical to have the capability to effectively deal with extremely small devices; for example, highly accurate 16 mils (0.4 mm) placement for micro-BGAs. When certain ﬁne pitch SM devices, like micro-BGAs, are used, chances are other ﬁne pitch components like 402s and 201s are used on a board as well. Hence, an EMS provider is technologically stretched to the limit as well as challenged by this shrinking PCB real estate size. Consequently, to maintain the highest caliber of accuracy for ﬁne pitch assembly, EMS providers must continue to be ahead of the technology curve. ■ Zulki Khan is founder and president, NexLogic Technologies, Inc., San Jose, Calif. Email: zk@nexlogic.com EXCEPTION PCB A proud Taiyo Partner. www.exceptionpcb.com (LEFT TO RIGHT) STEVE CAMPISI, Taiyo America JOHN FIX, Taiyo America GORDON HOLDEN, Managing Director LIAM LYNCH, Lamar PHIL CRABB, Quality Engineer ROB HUNTER, Quality Manager DISTRIBUTED BY: circuitree.com • February 2009 CT02094Taiy.indd 1 29 1/5/09 9:04:00 AM http://www.exceptionpcb.com http://www.taiyo-america.com http://www.taiyo-america.com http://www.circuitree.com

Table of Contents Feed for the Digital Edition of CircuiTree - February 2009

CircuiTree - February 2009 Contents Lead Wire The Wire Tech Talk Flexible Thinking Are Better PCB Design Tools and Manufacturing Enough to Stay Competitive? The Strategist Fein-Lines The Big Deal Over Fine Pitch Assembly Asian Section View From the Middle Market Outlook Technical Product Spotlights Classified Ads Upcoming Events Ad Index

CircuiTree - February 2009

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