Shields up

An EMI shielding product known as Form/Met can be quickly customised to snap-fit tightly into a product such as a mobile phone.

A well-known electronics manufacturer had been producing EMI shielding solutions for mobile telephones through a combination of procedures including injection moulding the housing, metallising the parts and applying conductive gaskets to the plastic housing.

But limitations included multiple vendor management, a huge amount of lead-time and freight cost. Worse, the shielding devices were either made from heavy metal or were extremely hard to disassemble and strip for recycling.

Realising the need for a more streamlined assembly process, the company turned to a solution called Form/Met from CA-based Shielding For Electronics Inc.

With Form/Met, the shielding assembly procedure was cut in half. The manufacturer simply provided the injection moulded housing and Form/Met was customised to snap-fit tightly into the product, producing a shield in a lot less time and cost. The shield is also produced from a lighter, more environmentally-friendly substance that can be recycled.

Shielding For Electronics’ Form/Met solution gave them an EMI shield that saved them over 30% in material costs and eliminated the assembly lag time associated with sending components outside for EMI shielding.

Sidebar: four ways to do it.

There are several traditional ways to shield a system, Conductive paints, metal enclosures and conductive gaskets to name but three. Form/Met is a forth alternative; a patented EMI/RFI shielding product, it comprises a thermoformed plastic film covered by a conductive aluminium layer applied through a vacuum metallisation process.

It can be used in three ways.

The first approach is to create a metallised, thermoformed enclosure around a printed circuit board that conforms to or fits within the inner geometries of a housing to create a ‘Faraday Cage.’ The shield is custom designed based on the EMC, mechanical and thermal requirements of the user.

The second approach involves a board level shield. In this case, a larger can-like integrated shield structure is designed to accommodate the height and size of an isolated part of a PCB, attaching it to the grounding traces that surround the EMI emitting component. This structure uses a conductive adhesive on its 2mm flange to attach to the PCB trace.

The third approach, a component level shield, uses Form/Met to touch down on the printed circuit board along the grounding traces between circuits and thus replaces multiple metal cans or form-in-place conductive gasketing or shield frames within the coated housing. A single compartmentalised, integrated insertible shield structure is designed to accommodate the height and size of all the circuits on a PCB. The shield can be designed with a non-conductive gasket on the ‘back’ of the shield to account for stack tolerance, but in most cases the use of any gasket can be eliminated with the form design.