GORE-SHIELD® SMT EMI Gaskets FAQ

What is a GORE-SHIELD SMT EMI gasket?

The GORE-SHIELD SMT gasket is an EMI gasket that mounts on the PCB. It has three layers: 1) Top layer - soft, compressible EMI gasket; 2) Bottom layer - solderable metal shim; and 3) Center layer - adhesive bond between the gasket material and the metal shim.

Is this product compatible with my current SMT equipment?

The SMT gasket and tape-and-reel packaging conform to EIA standards, which makes them compatible with all standard SMT equipment. Parts are currently available on 4 mm pitch carrier tape in widths of 12, 16, and 24 mm.

How much do SMT gaskets cost?

The total price depends on part size and mix, total volume, and most significant, how many SMT blocks are actually required to provide the necessary shielding. Individual standard SMT parts are available with a unit price as low as one cent each.

How fast can I pick and place these parts?

Pick-and-place speeds vary significantly, depending on machine type, feeder mechanism, and vacuum-nozzle configuration. Chipshooters have picked and placed GORE-SHIELD SMT parts with cycle times of nine parts-per-second at greater than 99 percent yield.

What thicknesses/widths/lengths are available?

There are two standard SMT thicknesses: 0.45 mm and 0.65 mm (including shim). Available SMT part widths are 1.10 mm and 1.25 mm (0.75 mm under development), with lengths of 5.65 mm and 8.05 mm. Longer lengths are under development.

Can you make SMT gaskets with curves or non-rectangular shapes?

While this is technically possible, it defeats the purpose of making standard parts that can be used as building blocks to form a complete design. Curved features can be sufficiently approximated by straight segments, especially if considered early in the PCB layout.

Do I need to butt the SMT parts together, without gaps, to get sufficient shielding?

While continuous gaskets provide optimal performance, gaps do not necessarily degrade performance significantly. The level of performance degradation caused by gaps depends on system architecture and frequency.

Shielding is purely a z-axis phenomenon, which is why discretely placed, BeCu contact spring fingers work in some handset designs. Strategically placed gaps will have little to no effect on measurable shielding performance.

We recommend starting with butt joints, then incrementally removing SMT parts, measuring the effect on overall system performance and radiated-emissions compliance.

Will the EMI gasket material and adhesive survive solder reflow?

GORE-SHIELD SMT gaskets survive multiple solder reflow cycles at standard reflow temperatures. The adhesive that secures the gasket material to the metal shim actually improves adhesion at higher temperatures. Even after three reflow cycles, the compressive modulus of the gasket material changes less than two percent.

Will the SMT parts move during solder reflow?

Extensive trials have shown that, during reflow, even misplaced parts will self-align to the boundaries of the PCB ground trace. Therefore, it is actually beneficial to make the ground-trace width equal to the width of the SMT part. This allows more efficient use of space on the PCB.

Who is using this product?

The product is being used in electronic products from cellular telephones and base stations to vacuum cleaners. All major CEMs have used the product.

Is this a patented product?

The GORE-SHIELD SMT gasket concept is patented.

What is the metal shim material made of?

The metal shim layer is a half-hard copper alloy, tin-plated for enhanced solderability and resistance to oxidation.

What happens if I need to repair a soldered SMT part?

We recommend peeling off the damaged SMT gasket layer from the soldered shim layer. Install a fresh, pre-cut piece of Gore GS5200 gasket material in its place using a pressure-sensitive adhesive.

What is the shelf life of the SMT parts?

We recommend that you use SMT parts within one year of the purchase date, but we believe shelf life to be longer. The oxidation rate of the shim's tin plating is the critical factor.

What are the electrical/ mechanical/ environmental properties of the SMT part?

The properties of the SMT part are identical to those of Gore's proven GS5200 gasket material, which has outstanding mechanical and electrical parameters, established through extended environmental testing.

What happens if I want to change the gasket design?

You can make rapid design changes (and prototypes) by reprogramming your SMT placement equipment and, in some cases, ordering a new, inexpensive solder-paste stencil and/or solder mask.

How can I reduce the installed cost of this SMT solution even further?

A simple way to reduce cost is to strategically reduce the total number of SMT parts in the design, piece by piece. This reduces both total piece-part cost and number of pick-and-place cycles.

Is there a tooling charge or NRE for SMT parts?There is no tooling charge or NRE for standard GORE-SHIELD SMT parts. Custom or non-standard parts will incur an NRE charge.

What is the typical lead time for reels of standard SMT parts?

Typical lead times for standard SMT part reels are four-to-five weeks.

How many parts per reel is standard?

A standard 13-inch reel contains 15,000 parts.

Can the SMT part survive cleaning solutions?

The parts are not affected by water and most cleaning solutions. Check with W. L. Gore & Associates for information on your specific application.