EMI Shielding Test Charts

These charts show the results of shielding effectiveness tests on 16 perforation and material combinations at 13 frequency levels, from 30 MHz to 18 GHz. The tests were commissioned by the Industrial Perforators Association and carried out by Intertek Testing Services in Boxborough, MA. Read the summary on the EMI shielding page.

How to Read the Charts

Hole Dia. – the diameter of the round perforations, in inches.
60° Center Spacing – the distance between hole centers on a 60 degree staggered pattern, in inches.
% Open Area – the share of the sheet that is open. Higher open area means more light and air, and usually less shielding at high frequencies.
Thick / Mat'l – sheet thickness in inches and material: aluminum (Alum.), cold rolled steel (C.R.St'l) or other listed metals.
Frequency columns – results at each test frequency. The first chart is in decibels (dB) of shielding attenuation; the second shows the same results as a percentage of attenuation.

A shielding effectiveness of 40 dB corresponds to 99.000% attenuation and is the targeted minimum in most applications. The highest value found in the tests, 92 dB, corresponds to 99.997% attenuation. The 51% open area rows correspond to the open area used in the InvisiPerf™ pattern on STORM SHIELD Hurricane Barriers.

Shielding Effectiveness in dB

Shielding effectiveness in dB by perforation pattern and frequency
Hole Dia.	60° Center Spacing	% Open area	Thick	Mat'l	Sample Size	30 MHz	100 MHz	300 MHz	1 GHz	2 GHz	4 GHz	6 GHz	8 GHz	10 GHz	12 GHz	14 GHz	16 GHz	18 GHz
.040	.055	48.00	.022	Alum.	24"x24"	70	70	80	56	55	48	57	35	48	44	42	41	42
.062	.093	40.00	.027	C.R.St'l	24"x24"	61	67	66	56	45	48	46	44	33	34	38	36	35
.062	.125	23.00	.025	Alum.	24"x24"	92	84	90	68	65	60	67	35	45	41	38	35	33
.072	.100	47.00	.038	C.R.St'l	24"x24"	64	70	90	62	55	52	40	33	37	34	33	29	27
.075	.125	32.70	.049	C.R.St'l	24"x24"	72	70	90	72	68	63	68	43	48	39	38	38	37
.078	.109	46.10	.027	C.R.St'l	24"x24"	66	75	72	63	55	54	45	41	39	28	24	21	28
.079	.115	42.80	.036	C.R.St'l	24"x24"	60	64	88	66	60	56	62	33	40	31	30	30	28
.100	.187	25.90	.040	Alum.	24"x24"	66	70	77	69	62	62	67	41	48	31	26	30	27
.125	.187	40.30	.030	Stainless	24"x24"	58	62	57	49	40	37	34	31	26	29	31	33	31
.125	.187	40.30	.030	Alum.	24"x24"	62	63	61	51	44	38	34	31	28	19	16	19	16
.125	.187	40.30	.060	Alum.	24"x24"	71	72	69	58	49	48	39	35	34	31	30	31	22
.125	.187	40.30	.125	Alum.	24"x24"	85	84	84	73	68	84	73	63	51	43	41	42	39
.156	.187	63.00	.057	C.R.St'l	24"x24"	57	58	59	48	40	35	31	29	26	19	16	13	11
.156	.250	35.40	.057	C.R.St'l	24"x24"	59	64	61	53	43	43	41	36	31	25	25	25	22
.187	.250	51.00	.027	C.R.St'l	24"x24"	52	52	49	37	31	24	21	19	18	18	21	18	16
.187	.250	51.00	.057	C.R.St'l	24"x24"	55	56	55	46	36	33	30	27	24	22	24	25	16

Shielding Effectiveness as % Attenuation

Shielding effectiveness as % attenuation by perforation pattern and frequency
Hole Dia.	60° Center Spacing	% Open area	Thick	Mat'l	Sample Size	30 MHz	100 MHz	300 MHz	1 GHz	2 GHz	4 GHz	6 GHz	8 GHz	10 GHz	12 GHz	14 GHz	16 GHz	18 GHz
.040	.055	48.00	.022	Allum.	24"x24"	99.97	99.97	99.99	99.84	99.82	99.60	99.86	99.22	99.60	99.4	99.2	99.1	99.2
.062	.093	40.00	.027	C.R.St'l	24"x24"	99.91	99.96	99.95	99.84	99.44	99.60	99.50	99.37	97.76	98	98.7	98.4	98.2
.062	.125	23.00	.025	Alum.	24"x24"	100.00	99.99	99.97	99.96	99.94	99.90	99.96	98.22	99.44	99.1	98.7	98.2	97.8
.072	.100	47.00	.038	C.R.St'l	24"x24"	99.94	99.97	99.97	99.92	99.82	99.75	99.00	97.76	98.59	98	97.8	96.5	95.5
.075	.125	32.70	.049	C.R.St'l	24"x24"	99.98	99.97	99.97	99.98	99.96	99.93	99.96	99.29	99.60	98.6	98.7	98.7	98.6
.078	.109	46.10	.027	C.R.St'l	24"x24"	99.95	99.98	99.98	99.93	99.82	99.80	99.44	99.11	98.88	96	93.7	91.1	96
.079	.115	42.80	.036	C.R.St'l	24"x24"	99.90	99.94	100.00	99.95	99.90	99.84	99.92	97.76	99.00	97.2	96.8	96.8	96
.100	.187	25.90	.040	Alum.	24"x24"	99.95	99.97	99.99	99.92	99.92	99.92	99.96	99.11	99.60	97.2	95	96.8	95.5
.125	.187	40.30	.030	Stainless	24"x24"	99.87	99.92	99.86	99.65	99.00	98.59	98.01	97.18	94.99	96.5	97.2	97.8	97.2
.125	.187	40.30	.030	Alum.	24"x24"	99.92	99.93	99.91	99.72	99.37	98.74	98.01	97.18	96.02	88.8	84.2	88.8	84.2
.125	.187	40.30	.060	Alum.	24"x24"	99.97	99.98	99.86	99.87	99.65	99.60	98.88	98.22	98.01	97.2	96.8	97.2	92.1
.125	.187	40.30	.125	Alum.	24"x24"	99.99	99.99	99.99	99.98	99.96	99.99	99.98	99.93	99.72	99.3	99.1	99.2	98.9
.156	.187	63.00	.057	C.R.St'l	24"x24"	99.86	99.87	99.89	99.60	99.00	98.22	97.16	96.45	94.99	88.8	84.2	77.6	71.8
.156	.250	35.40	.057	C.R.St'l	24"x24"	99.89	99.94	99.91	99.78	99.29	99.29	99.11	98.42	97.18	94.4	94.4	94.4	92.1
.187	.250	51.00	.027	C.R.St'l	24"x24"	99.75	99.75	99.65	98.59	97.18	93.69	91.09	88.78	88.78	87.4	91.1	87.4	84.2
.187	.250	51.00	.057	C.R.St'l	24"x24"	99.82	99.84	99.82	99.50	99.42	97.76	96.84	95.53	93.69	92.1	93.7	94.4	84.2

Results depend on a tightly sealed electrical contact around the edges of the panel. The largest single source of leakage is along contact surfaces between two parts; if a tight connection is not made, leakage through the interface can be greater than through the perforated sheet.