Shield Eases Installation, Boosts Protection

Metallized plastic provides performance, manufacturing tolerance, and accessibility

By Design News Staff -- Design News, February 17, 2003

Once in a while, a product offers improved performance, lower cost, and greater ease of use all at the same time. Such is the case with W. L. Gore & Associates' snapSHOT^™ EMI shield for multicavity devices. The metallized thermoformed plastic shield is insulated because of its inner plastic surface, so it can snug right up against components and leads on a PCB, leading to overall thinner products. "Existing metal shields can't come in contact with the components being shielded and need a standoff space," notes Global Product Manager Lois Mabon.

The snapSHOT shield can be formed into intricate, multicavity shapes and is easy to install and remove in the event of production rework or repair. Metal shields must be soldered to the boards, which can be problematic in providing a complete shielding enclosure if a board or the shield has a warp or bend. The plastic shield snaps on to the PCB with a patented attachment method. This mechanism consists of BGA-type solder spheres applied to the board using a standard stencil printer with a special head. After the board is populated with components and reflow soldered, a special mating tool snaps the shield into place over the solder balls. The shield/ball contacts positively engage once the shield is pushed more than halfway over the balls. Such deflect-and-latch action allows the use of boards and shields that may not be perfectly flat or coplanar, Mabon notes. The metal balls also provide electrical connection to the ground plane.

"The system puts down the balls on a board using processes OEMs already know," adds Mabon, while providing more compact and easier-to-handle shielding. "And with the shield readily removable, any rework or servicing doesn't require a desolder machine. The shield's lightweight, low cost, potential for more compact products, and shape freedom are attributes OEMs are looking for—especially for wireless devices where component sections need EMI protection from one another," she concludes. W.L. Gore & Associateswww.gore.com/electronics Enter 689

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