01-1392-6791

CHO-TR43 September 1997 TEST REPORT Comparison of SOFT-SHIELD® 1000, 2000 and CHO-SEAL® S6305 EMI Gaskets and Competitive EMI Gaskets Prepared by: Chomerics, div. of Parker Hannifin Corp. R&D Department 77 Dragon Court Woburn, MA 01801 Chomerics, div. of Parker Hannifin Corp. / 77 Dragon Court / Woburn, MA 01888 Tel: (1) 781-935-4850 / Fax: 781-933-4318 Parker Hannifin PLC - Chomerics Europe / Parkway, Globe Park Estate / Marlow, Bucks., SL7 1YB, United Kingdom Tel: (44) 1628 404000 / Fax: (44) 1628 404090 www.chomerics.com EMI Gasket Comparison Test Report Chomerics SOFT-SHIELD® 1000, 2000, 4000 and CHO-SEAL® S6305 VS. Gaskets from Other Manufacturers This report presents performance data on EMI gaskets rated for commercial equipment in indoor (office) environments. Tests included are: shielding effectiveness, surface resistance, through resistance, multi-deflections and compression set. Purpose The purpose of this test program is to establish relative performance levels of Chomerics commercial EMI gaskets vs. gaskets produced by other manufacturers. Summary of Results The data generated in this series of tests demonstrates that Chomerics EMI gasket materials compare favorably with gaskets produced by other manufacturers, and that Chomerics materials offer a broad range of performance options. Readers of this report should be cautioned that not all performance characteristics were evaluated during this test sequence. Characteristics such as use temperature range, tear strength, abrasion, etc., may be of concern in a specific application It should also be noted that the EMI gaskets evaluated included a mix of gasket types. While most of the samples incorporated foam-filled cores, CHO-SEAL S6305 material is a conductive elastomer and competitor samples 131, B2, and B3 are conductive elastomer materials extruded over a nonconductive core. Also note that there are differences in cross sectional sizes and shapes among the gaskets tested. In such cases, comparisons may not be perfectly valid. Scope The scope of the testing included the following electrical and mechanical properties: -shielding effectiveness -surface resistance -through resistance -multi-deflections -compression set The EMI gaskets chosen for the test program include foam based gaskets produced by various manufacturers vs. Chomerics SOFT-SHIELD 1000, 2000, and 4000 series gaskets. Also tested was CHO-SEAL S6305 nickelplated-graphite filled silicone extrusion vs. a conductive elastomer extrusion produced by another manufacturer. Details on all gaskets tested are provided on the following pages. Test Procedures Shielding Effectiveness - Testing conducted by Chomerics Test Services. -Standard CHO-TM TP08 "Shielding Effectiveness Test Method for Commercial Style EMI Gaskets". -The gasket configuration is a square "picture frame" assembled from 4 mitered strips (each a nominal 24 inches long). Gaskets are mounted to a 0.25 in. thick 6061-T6 aluminum test plate. The test plate is placed over the open 24 inch square brass test fixture. Nonconductive fasteners and various non-conductive compression stop spacers provide 50% deflection of gaskets. -Shielding Effectiveness measurements were performed at 15 different frequencies (20 MHz to 10 GHz). Data Recorded: -Reference level and gasketed panel level. Data Calculated/Reported: -Shielding Effectiveness = reference level gasketed panel level. Surface Resistance -Surface Resistance measurements were made using the surface probe method, MIL-G-83528, para. 4.6.1 1. Only the measured surface resistance is reported (not the calculated volume resistivity.) Data Recorded: -Surface resistance. Data Calculated/Reported: -Surface resistance Through Resistance -Through resistance measurements are made with two 3 - inch diameter x 0.25 in. thick disks. The disk set for these samples consisted of one aluminum and one brass disk. Each gasket sample was 2.5 inches long, compressed to 50% of initial height during the test. Data Recorded: -Resistance level for each sample/disk combination. Data Calculated/Reported: -Average of resistance levels Multi-deflection • Deflect samples 10,000 cycles. Load on each 3 - inch sample is 0.6 pounds per linear inch (50 psi pressure setting for two 3 inch samples.) No compression stops used. • Modified ASTM C165 test procedure. -Crosshead speed of 0.1 inch/minute. Data Recorded: -Graph resistance vs. crosshead travel and load vs. crosshead travel for each sample. Data Calculated/Reported: -Visually evaluate the change in load and the change in resistance. Rank the change from 0 to 5 (0 = no change, 5 = significant change). Add the ranking in load change to the ranking in resistance change (0 = no change in either load or resistance and 10 = significant change in both load and resistance.). Compression Set (at low and high humidity) • Standard ASTM D395, Method B, Unmodified. • Compression Set - compressed 25% for 22 hours at 85°C and 70°C. • Low relative humidity (RH) - 3 samples placed in an air circulating oven. • High relative humidity (RH) - 3 samples placed in a Tenney environmentally controlled chamber at 85% relative humidity. Data Recorded: -Initial height, height at 25% deflection, and final height. Data Reported/Calculated: -Compression Set (%) = f ( t; -tf)/( t; - t25% )1 x 100; t; = initial height, tf = final height, t25% = height at 25% deflection. Gaskets Tested Chomerics -Material: SOFT-SHIELD 1000 gasket -Size/Shape: 0.25 inch x 0.25 inch square profile strip -Part No: 01-0901-6595 -Knitted Ferrex™ mesh over urethane foam core (Ferrex is Chomerics' tradename for tin-plated-copper clad steel wire) Chomerics -Material: SOFT-SHIELD 2000 gasket -Size/Shape: 0.25 inch x 0.25 inch square cross section strip -Part No: 01-1392-6791 -Silver plated yarn over thermoplastic foam core Chomerics -Material: SOFT-SHIELD 4000 (CWA) gasket -Size/Shape: 0.15 inch x 0.30 inch rectangular cross section strip -Part No: Custom size for test -Fiberglass reinforced aluminum foil over urethane foam core Chomerics -Material: SOFT-SHIELD 4000 (CWF) gasket -Size/Shape: 0.15 inch x 0.30 inch rectangular cross section strip -Part No: Custom size for test -Nickel-plated fabric over urethane foam core Chomerics -Material: CHO-SEAL S6305 gasket -Size/Shape: 0.15 inch x 0.25 inch "D" shape profile extruded strip -Part No: 19-05-1 1441-S6305: -Nickel-plated graphite filled silicone Competitor A -Material: A1 -Size/Shape: 0.5 inch x 0.5 inch "V" cross section strip -Nickel-plated fabric over foam core Competitor A -Material: A2 -Size/Shape: 0.13 inch x 1.19 inch rectangular cross section strip -Nickel-plated fabric over foam core Competitor A -Material: A3 -Size/Shape: 0.14 inch x 0.25 inch "D" cross section strip -Nickel-plated fabric over foam core Competitor B -Material: 131 -Size/Shape: 0.15 inch diameter hollow "0" cross section strip -Appearance: beige-colored exterior over orange-colored elastomer core. -Silver-plated-aluminum filled elastomer extruded over silicone core Competitor B -Material: B2 -Size/Shape: 0.19 inch x 0.18 inch hollow "D" cross section strip -Silver-plated-aluminum filled elastomer over silicone core Competitor B -Material: B3 -Size/Shape: 0.13 inch diameter hollow "0" cross section strip -Silver-plated-aluminum filled elastomer over silicone core Competitor C -Material: C1 -Size/Shape: 0.20 inch x 0.20 inch square cross section strip -Silver-plated fabric over foam core Competitor C -Material: C2 -Size/Shape: 0.5 inch x 0.5 inch "V" cross section strip -Silver-plated fabric over foam core Competitor C -Material: C3 -Size/Shape: 0.24 inch x 0.23 inch rectangular cross section strip -Silver-plated fabric over foam core Competitor C -Material: C4 -Size/Shape: 0.16 inch x 0.25 inch "D" cross section strip -Silver-plated fabric over foam core Results -Average Shielding Effectiveness (20 MHz - 10 GHz) The test results in Table 1 show the superiority of the Chomerics' CHO-SEAL S6305 nickel-plated-graphite filled silicone elastomer. Note that the SOFT-SHIELD 4000 series gaskets of reinforced aluminum foil or conductive fabric over foam demonstrate superior shielding effectiveness. All Chomerics gaskets tested provide at least 75 dB average shielding effectiveness. -Surface Resistance The results shown in Table 2 show the extremely low surface resistance of the SOFT-SHIELD 4000 family of gaskets. Note, however, that despite the relatively high surface resistance of CHO-SEAL S6305 conductive elastomer material, its shielding effectiveness (as shown in Table 1) is higher than all other gaskets tested. This result clearly indicates the danger of considering only surface resistance to predict shielding effectiveness. -Through Resistance Table 3 shows the low through resistance of SOFT-SHIELD 4000 and CHO-SEAL S6305 gaskets. Through resistance is a better indicator of shielding effectiveness than surface resistance, but is still not a recommended method of predicting shielding performance, as can be seen by the CHOSEAL S6305 material data. - Multi-Deflection Table 4 shows that none of the EMI gaskets tested degrade appreciably in a 10,000 cycle deflection test. -Compression Set Table 5 shows the results of compression set testing per ASTM D 395, Method B, which is a standard rubber test. This particular test method requires the compression set to be expressed as a percentage of the deflection, not of the initial height. To determine percent recovery, subtract 1 /4 of the ASTM D 395 Method B stated compression set from 100%. Table 6 shows this recalculation as per cent recovery. ASTM D 3574 might be considered a more appropriate test method for foam based products. ASTM D 3574 requires a 22 hr. test at 50%, 75% or 90% deflection at 70°C. The results are expressed both as a percentage of deflection like ASTM D 395 Method B and as a percent of initial height. In order to clarify the results of this test program, Table 6 shows the ASTM D 395 method B results at 70 °C expressed as a percent of initial height. - Summary Table 7 summarize the results from all tests. Conclusion Chomerics' EMI gaskets show good to excellent performance vs. gaskets produced by other manufacturers. SOFT-SHIELD 4000 (CWA and CWF) and CHO-SEAL S6305 gaskets showed consistently superior performance. As already mentioned, direct comparison of different types of EMI gaskets and/or different cross sections is not always possible. The reader is cautioned when making direct comparisons. Ranking of Competitive Testing SHIELD3.XLS Ranking of Competitive Testing SHIELD2.XLS Ranking of Competitive Testing SHIELD1XLS Ranking of Competitive Testing DEFLECT.XLS Ranking of Competitive Testing COMPRESS.XLS Ranking of Competitive Testing COMPRES2.XLS NSUMMARY.XLS