The report reveals how aperture dimensions must increase to ensure adequate wetting forces and prevent tombstoning as paste-to-pad and component-to-pad offsets occur. Such offsets are unavoidable, implying that manufacturers must re-optimize stencils for Pb-free printing to ensure yield rates comparable to Pb-rich processes. According to the report, this issue is more prevalent with smaller components (0402s and below).
 
By testing 67 new aperture characteristics, including varying dimensions, aspect ratio, shape and stencil thickness, DEK identified the necessary changes in aperture characteristics. According to the team leader and author of the report, Clive Ashmore, the main concern is to ensure a higher volume of paste to compensate for the lower wetting forces exerted by Pb-free pastes. When placing small chip devices such as passive components, these wetting forces help retain the component during reflow. Slight misalignment between the component, solder deposit and paste leads to imbalance in wetting forces, which increases the risk of tombstoning.
 
Ashmore, Global Applied Process Engineering Group Manager at DEK Printing Machines, said, “A perfectly centred screen printing process will perform well whether Pb-rich or Pb-free paste is used. But such processes can only be sustained under laboratory conditions, which obviously cannot be provided in a production context. Assemblers must, therefore, take steps to ensure their stencils are optimised for Pb-free printing. Our findings show that continuing to use legacy stencils that meet the Pb-rich design rules will result in significantly higher numbers of defects.”
 
Understanding Stencil Requirements for a Lead-Free Mass Imaging Process is available at dek.com.
 

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SAN JOSE -- North American-based manufacturers of semiconductor equipment posted $1.1 billion in orders in October on a three-month average basis. The book-to-bill ratio was 0.95, according to SEMI.

A book-to-bill of 0.95 means that $95 worth of orders were received for every $100 of product billed for the month.

The three-month worldwide bookings average was up 12% over revised September levels and 20% below October 2004.

The three-month average of worldwide billings in October 2005 was $1.16 billion, up 6% from revised September figures but down 19% from last year.

The numbers also include revised August bookings.

"Bookings and billings for North American based semiconductor equipment providers have been stable for the past six months," said Stanley T. Myers, president and CEO of SEMI. "It is encouraging to see the recent improvement in bookings as the industry continues to ramp 300 mm production and is beginning to invest in 65 nanometer technology."

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WEST CHICAGO -- Price erosion of surface mount connectors during the past five years has been significant and painful, says Bishop and Associates.

The research firm cites as the main reason the migration of manufacturing to China. "There is no doubt that connector prices have been significantly influenced by the lower costs [of China]. The lower prices are a function of the lower manufacturing costs."

Once the manufacturing migration to China has “run its course” and China prices are fully implemented, connector prices will stabilize, Bishop said. "In effect, the China influence on lower prices is a one-time occurrence. That is, once China pricing is in the marketplace, connector prices stabilize and stop declining. Once the lower costs are passed along, it’s over. There is no more to give the OEMs."

Prices have begun to level, Bishop wrote. "We have already started to achieve connector price stability.  Feedback from the industry suggests that the 7-10% price erosion of the past few years has slowed to the historical norm of 3-4% price erosion."

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Bermuda-based Tyco International plans to close 16 of its electronics manufacturing factories in North American and Europe and may even spin off some businesses. The conglomerate will take a restructuring charge of up to $175 million, $60 million in fiscal 2006.

 

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