Here we look at how one manufacturer is overcoming the inability to solder aluminium to produce a lightweight shield.

It has become a maxim that while the personal communications marketplace continues to expand, manufacturers need to find ways to shrink their products and reduce product weight.
When making purchasing decisions consumers also expect more functionality and increased ease of use. As manufacturers continue to discover, this trend leads to a convergence of technologies. Wireless phones serve as paging devices, help users organise their day and connect them to the internet.
For instance in the USA alone, by 2003 more than 50 per cent of internet users will access the web via wireless products, according to Meta Group a United States consulting firm based in Stamford, Connecticut.
Of course all of these challenges have a direct impact on product designers and engineers. Electromagnetic interference (EMI) created by internal or external sources can have a negative impact on product performance. More circuitry is packed into a smaller space, which in turn increases the need for a higher concentration of EMI shields. These shields are necessary to prevent unwanted EMI and to meet various governmental regulatory limits on radiated emissions. As concern over weight increases, the density of EMI/RF shields made from traditional materials are becoming more of an issue.
A lightweight shield, introduced by BMI offers a solution. Shield-Lite is more than 50 per cent lighter compared with conventional shields due to its aluminum base. Prior to this product, aluminum was not an option because of its inability to be soldered. The manufacturer focused on this issue and was successful in overcoming the solderability challenge.
The product also offers increased thermal conductivity over tin plated steel and experiences less corrosion, which helps improve the reliability of the end product. Furthermore, because Shield-Lite can be surface mounted and is easy to install with typical pick-and-place equipment, manufacturers can cut costs.
Jerry English, a materials scientist at BMI, says: "We set out to design a product that performs as well, if not better than, current options. At the same time, we want to give engineers and designers more flexibility from initial prototype development through production when developing lighter-weight products. So far, our customer feedback indicates we're meeting our goals."

This lightweight surface mountable shield is readily available off the shelf or can be customised to meet specific engineering needs. Shield-Lite is packaged in standard EIA481 tape and reel formats, for automated surface mount installation. It's available in many JEDEC sizes, including 52pin quid flat pack (TQFP), 256 position ball grid array (BGA) and 84pin plastic leadless chip carrier (PLCC) packages.
Less is more in today's electronic marketplace, and manufacturers can find an important competitive advantage by reducing the weight of their products. Lighter weight components are sure to have a significant impact on the handheld device industry.

Table. 1. Shield-Life specifications.
Raw material Aluminium
Thickness 0.127 to 0.300 mm
Heat treatment N/A
Finish Matte
Plating Tin
Comments The density of steel is 7.9 gram/cc while the density of Shield-Lite is 3.3 grams/cc

ENQUIRY No 32

BMI Inc is based in Palatine, ILL, USA. www.bmiinc.com