Today, suspect counterfeit ESD control and non-compliant packaging is a growing issue throughout the global supply chain. Not only are EEE parts (ESD sensitive devices) damaged, but components can also be destroyed. Suspect counterfeit static control or non-compliant electrostatic discharge (ESD) shielding bags can be purchased from the internet, catalogs, brokers, authorized distributors or directly from the manufacturer.

The author is the First to Present on Suspect Counterfeit ESD Materials in the Supply Chain at the NASA Quality Leadership Forum 2010, Cape Canaveral, Fla. No longer can a supplier’s Technical Data Sheet serve as proof of compliance for a static control shielding bag. A site undergoing certification for ANSI/ESD S20.20-2014 (ANSI/ESD S20.20) compliance must now demonstrate that products used in the ESD Protected Area (EPA) have traceable in-house or third party test data.

Today, the Grid Bag (Fig. 2) is sold to protect ESD sensitive circuit cards; however, one must go beyond a visual inspection process and take physical measurements for ANSI/ESD S20.20-2014 compliance.

In this article, all specimens originate from the Asia Pacific Region and qualification testing will demonstrate whether ANSI/ESD S20.20-2014 compliance has been met.

The standard for ESD Packaging & Materials (ANSI/ESD S20.20) is ANSI/ESD S541-2008. ANSI/ESD S11.4-2102 constitutes the commercial bag qualification requirements for Static Control Bags. The document requires marking the bag with designated ANSI/ESD S8.1-2012 symbols. ESD S11.4 section 6.0 Markings calls out: All bags should be marked with information that allows traceability to the packaging manufacturer and to the manufacturer’s date / lot code information.

In addition, ANSI/ESD S541-2008 states in section 8.2.3 Traceability – Packaging should be marked with information that allows traceability to the packaging manufacturer and to the manufacturer’s date/lot code information. The date/lot code should allow traceability to quality control information pertaining to the manufacture of the specific lot of packaging. The Military Mil-PRF-81705E-2010 under section 3.6 requires date and lot code information, manufacturer and class of bag type. The military marking is illustrated in Fig. 3.

An example of markings for ANSI/ESD S20.20-2014 compliance is illustrated in Fig. 4 for a Type 1 moisture barrier bag. One observation is that the grid bag used for testing in this article is marked only with an ESD military symbol and Caution, Electrostatic Sensitive Device; there was no manufacturer, date and lot code information.

Several testing methods employed for a formalized ESD qualification testing at 12%+/-3%RH, 73^°+/-5^°F for 48 hours minimum are as follows:

1. Surface Resistance; inside and outside of bags per ANSI/ESD STM11.11-2015 at <1.0 x 10¹¹ Ω
2. Volume Resistance; inside of the bag to plate per ANSI/ESD STM11.12-2015 at <1.0 x 10¹¹ Ω
3. Electrostatic Decay per Mil-STD-3010C, Method 4046-2013 (5kV to 0 volts) at a 2.0 second limit
4. Charge Retention (Faraday Cup) per ESD Adv.11.2-1995 at <1.0 nC
5. Static Shielding; 12%RH and 50%RH per ANSI/ESD STM11.31-2012 at <20 nJ

Individual agencies or corporations may require more of less testing to meet specific requirements. Electrostatic decay is not a test method of ANSI/ESD S541-2008; however, it does represent an end-user requirement and is included in this article.

Terms and definitions¹

ANSI/ESD S541: Resistance of Dissipative Materials: A static dissipative material shall have a surface resistance of greater than or equal to 1.0 x 10⁴ ohms but less than 1.0 x 10¹¹ ohms, or a volume resistance of greater than or equal to 1.0 x 10⁴ ohms but less than 1.0 x 10¹¹ ohms.

ANSI/ESD S541: Resistance of Conductive Materials: A surface conductive material shall have a surface resistance of less than 1.0 x 10⁴ ohms. Volume conductive materials shall have a volume resistance of less than 1.0 x 10⁴ ohms.

ANSI/ESD S541: Resistance of Electric Field Shielding Materials: Within the conductive materials classification per ANSI/ESD S541-2008, electric field shielding materials shall have a surface resistance of less than 1.0 x 10³ ohms or a volume resistance of less than 1.0 x 10³ ohms. Other methods may also define the electric field shielding classification.

ANSI/ESD S541: Resistance of Insulative Materials: An insulative material per ANSI/ESD S541-2008 shall have a surface resistance of greater than or equal to 1.0 x 10¹¹ ohms, or a volume resistance of greater than or equal to 1.0 x 10¹¹ ohms.

ASTM D257: 3.1.11 resistivity, surface, (rs), n—the surface resistance multiplied by that ratio of specimen surface dimensions (width of electrodes defining the current path divided by the distance between electrodes) which transforms the measured resistance to that obtained if the electrodes had formed the opposite sides of a square.

ASTM D257: 3.1.12 resistivity, volume, (rv), n—the volume resistance multiplied by that ratio of specimen volume dimensions (cross-sectional area of the specimen between the electrodes divided by the distance between electrodes) which transforms the measured resistance to that resistance obtained if the electrodes had formed the opposite sides of a unit cube.

ANSI/ESD S541: ANSI/ESD STM11.31 (Shielding Bag Test) sets 12% and 50% RH as the benchmark. According to John Kolyer, Ph.D. (Boeing Retired) a human is capable of producing a greater spark at higher RH than lower relative humidity. 

ANSI/ESD S11.4-2102	Mil-PRF-81705E-2010
Level 1: Moisture Barrier Bag for Device Packaging   Level 2: Moisture Barrier Bag for General Packaging   Level 3: Static Shielding Bag	Type I – Watervaporproof, electrostatic protective, electrostatic and electromagnetic shielding.   Type III – Transparent, waterproof, electrostatic protective, electrostatic shielding.

In this article, the military designation will be used as Type 1 for the moisture barrier bag and Type III for the vacuum deposited aluminum static shielding bag.

Surface resistance versus relative humidity (RH)

At the insulative range, materials become nonconductive and hold static charges for several seconds or more.  In practice, however, a lower cut-off is often desired for packaging materials because dry air may be encountered in shipping and handling. In cold and dry climactic conditions, relative humidity can reach <4% or below. Surface resistance testing constitutes an accurate method for the evaluation of materials. At 1.0 x 10¹¹ ohms, materials become nonconductive and hold static charges for several seconds or more. Resistance rises and falls when relative humidity (RH) changes with humidity dependent materials. At 1.0 x 10¹¹ ohms, materials exhibit insulative properties. A low cutoff is desired for static control materials since dry air may be encountered in shipping, storage and handling. In use, tribocharging can contribute to damage by Field Induction. Table 1 illustrates resistance readings of air at various relative humidities.

Both surface resistivity and surface resistance are illustrated in Table 1. Said table represents the resistance classification found in ANSI/ESD S541-2008 (ESD Standard for Packaging & Materials).

 

 

 

 

The author utilized a concentric ring fixture to measure the outside and inside of bags illustrated in Fig. 4. Although the electrometer and concentric ring are in calibration, a favorable reference measurement of 1.0011 x 10¹² Ω was taken for compliance to ANSI/ESD STM11.11-2015.

 

 

 

 

 

 

 

 

 

 

For reference, the Type 1, gray and silver static control aluminum moisture barrier bags (MBB) were numbered A-1 to A-10 (silver) and B-1 to B-10 (gray); the Type III vacuum deposited metallized static shielding bag was numbered A-1 to A-7. The ESD bags in Table 2A were in compliance at <1.0 x 10¹¹ Ω; the grid bag was not compliant.

Table 2A: ANSI/ESD STM11.11 at 11.9%RH, 73.4^°F for 72 hours

A-1 to A-6 Surface Resistance			A-1 to A-6 Surface Resistance
Inside	STM11.11	C.V.	Outside	STM11.11	C.V.
1	1.11E+10	100v	1	3.90E+10	100v
2	7.82E+09	100v	2	2.69E+10	100v
3	7.93E+09	100v	3	1.75E+10	100v
4	7.84E+09	100v	4	1.83E+10	100v
5	7.82E+09	100v	5	1.82E+10	100v
6	8.13E+09	100v	6	2.27E+10	100v
Average	8.44E+09	MBB	Average	2.38E+10	MBB
Median	7.88E+09		Median	2.05E+10
Minimum	7.82E+09		Minimum	1.75E+10
Maximum	1.11E+10		Maximum	3.90E+10
St. Dev.	1.30E+09		St. Dev.	8.27E+09
A-1 to A-6 Surface Resistance			A-1 to A-6 Surface Resistance
Inside	STM11.11	C.V.	Outside	STM11.11	C.V.
1	1.44E+10	100v	1	1.30E+10	100v
2	1.12E+10	100v	2	1.02E+10	100v
3	1.16E+10	100v	3	1.14E+10	100v
4	1.06E+10	100v	4	1.11E+10	100v
5	1.06E+10	100v	5	1.14E+10	100v
6	1.10E+10	100v	6	1.12E+10	100v
Average	1.16E+10	Static Shielding	Average	1.14E+10	Static Shielding
Median	1.11E+10		Median	1.13E+10
Minimum	1.06E+10		Minimum	1.02E+10
Maximum	1.44E+10		Maximum	1.30E+10
St. Dev.	1.44E+09		St. Dev.	9.13E+08
B-1 to B-6 Surface Resistance			B-1 to B-6 Surface Resistance
Inside	STM11.12	C.V.	Outside	STM11.12	C.V.
1	7.88E+09	100v	1	1.39E+10	100v
2	6.21E+09	100v	2	1.03E+10	100v
3	6.20E+09	100v	3	1.29E+10	100v
4	6.62E+09	100v	4	1.10E+10	100v
5	6.72E+09	100v	5	1.21E+10	100v
6	6.53E+09	100v	6	1.31E+10	100v
Average	6.69E+09	MBB	Average	1.22E+10	MBB
Median	6.57E+09		Median	1.25E+10
Minimum	6.20E+09		Minimum	1.03E+10
Maximum	7.88E+09		Maximum	1.39E+10
St. Dev.	6.19E+08		St. Dev.	1.36E+09

Grid Bag Surface Resistance			Grid Bag Surface Resistance
Inside	STM11.11	C.V.	Outside	STM11.11	C.V.
1	2.381E+11	100v	1	1.238E+04	100v
2	4.639E+11	100v	2	1.494E+05	100v
3	5.819E+11	100v	3	1.591E+04	100v
4	7.982E+11	100v	4	1.224E+04	100v
5	4.193E+11	100v	5	1.391E+04	100v
6	4.583E+11	100v	6	1.392E+04	100v
Average	4.933E+11	Grid	Average	3.629E+04	Grid
Median	4.611E+11		Median	1.392E+04
Minimum	2.381E+11		Minimum	1.224E+04
Maximum	7.982E+11		Maximum	1.494E+05
St. Dev.	1.863E+11		St. Dev.	5.542E+04

 

 

For the grid bags, the inside was insulative and the outside measured in the low static dissipative range. Therefore, the grid bags are not ESD safe for storage, transport or staging.  Said bag type may be considered suspect since the surface resistance values do not appear to reflect the actual product claims.  

In short, the Asia Pacific static shielding (Type III) and gray/silver moisture barrier bags (Type I) did exhibit favorable surface and volume resistance readings while the grid bag did not.

Volume resistance per ANSI/ESD STM11.12-2015:

ANSI/ESD STM11.12 defines the standard test procedure, equipment, sample preparation, and conditioning needed to achieve reproducible volume resistance test results on static dissipative planar materials. This test will determine if charge bleed-off could occur when a static control bag is opened in the ESD Protected Area (EPA).

 

 

 Table 3A: ANSI/ESD STM11.12 at 11.9%RH, 73.4°F for 72 hours

 

In short, the ESD static shielding bags and moisture barrier bags provide volume resistance while the grid bags do not.

Electrostatic Decay per Mil-STD-3010C, Method 4046 (1 Aug 2013):

The latest revision for Mil-STD-3010C, Method 4046 (1 Aug. 2013) section 5.4.3.4.2 (after 160^°F oven conditioning for 14 days) states: Test environment. Immediately after preconditioning, unless otherwise specified in the test plan, all specimens shall be placed in the electrostatic test chamber (maintained at 73±5^°F and 12±3% relative humidity) for a minimum of 24 hours before testing. Testing shall be performed under these same conditions.

 

Said 3” x 5” samples were cut after completion of the other electrical tests.

 

 

 

After preconditioning, the six samples were evaluated for electrostatic decay from +/-5kV to 0 volts. In Mil-PRF-81705E, Table 1, a limit of not greater than 2.0 seconds for electrostatic decay is required. Said Unit was validated at 0.28 and 0.27 seconds respectively and is within level of acceptance (Fig. 11).  

 

 

 

Table 4A: 12%RH, 74.2^°F after 48 hours

Static Shielding Bag			Static Shielding Bag
Inside	Mil 3010C (sec)	C.V.	Inside	Mil 3010C (sec)	C.V.
1	0.02	5000v	1	0.02	-5000v
2	0.01	5000v	2	0.01	-5000v
3	0.01	5000v	3	0.02	-5000v
4	0.02	5000v	4	0.02	-5000v
5	0.02	5000v	5	0.03	-5000v
6	0.01	5000v	6	0.01	-5000v
Average	0.02		Average	0.02
Median	0.02		Median	0.02
Minimum	0.01		Minimum	0.01
Maximum	0.02		Maximum	0.03
St. Dev.	0.01		St. Dev.	0.01

Table 4B: 12%RH, 74.2^°F after 48 hours

Gray Moisture Barrier Bag			Gray Moisture Barrier Bag
Inside	Mil 3010C (sec)	C.V.	Inside	Mil 3010C (sec)	C.V.
1	0.01	5000v	1	0.01	-5000v
2	0.01	5000v	2	0.01	-5000v
3	0.01	5000v	3	0.01	-5000v
4	0.01	5000v	4	0.01	-5000v
5	0.01	5000v	5	0.01	-5000v
6	0.01	5000v	6	0.01	-5000v
Average	0.01		Average	0.01
Median	0.01		Median	0.01
Minimum	0.01		Minimum	0.01
Maximum	0.01		Maximum	0.01
St. Dev.	0.00		St. Dev.	0.00

Table 4C: 12%RH, 74.2^°F after 48 hours

Silver Moisture Barrier Bag			Silver Moisture Barrier Bag
Inside	Mil 3010C (sec)	C.V.	Inside	Mil 3010C (sec)	C.V.
1	0.01	5000v	1	0.01	-5000v
2	0.01	5000v	2	0.01	-5000v
3	0.01	5000v	3	0.01	-5000v
4	0.01	5000v	4	0.01	-5000v
5	0.01	5000v	5	0.01	-5000v
6	0.01	5000v	6	0.01	-5000v
Average	0.01		Average	0.01
Median	0.01		Median	0.01
Minimum	0.01		Minimum	0.01
Maximum	0.01		Maximum	0.01
St. Dev.	0.00		St. Dev.	0.00

Table 4D: 12%RH, 74.2^°F after 48 hours

Grid Bag			Grid Bag
Inside	Mil 3010C (sec)	C.V.	Inside	Mil 3010C (sec)	C.V.
1	0.30	5000v	1	0.50	-5000v
2	0.40	5000v	2	0.40	-5000v
3	0.20	5000v	3	0.60	-5000v
4	0.05	5000v	4	0.05	-5000v
5	0.30	5000v	5	0.40	-5000v
6	0.40	5000v	6	0.50	-5000v
Average	0.28		Average	0.41
Median	0.30		Median	0.45
Minimum	0.05		Minimum	0.05
Maximum	0.40		Maximum	0.60
St. Dev.	0.13		St. Dev.	0.19

 

Often, electrostatic decay testing is required by the end user organizations and the results in Table 4E indicate passing. However, Military Handbook 263B states in Appendix I: “… Decay time measurements, for an induced voltage on a given sample, may not correlate with surface or volume resistivity measurements for materials of complex construction. Additionally, decay time measurements can become complex from the viewpoint of understanding exactly how materials of complex construction, that is, laminates/ multilayer materials, are performing…” Thus, this test is better suited for static dissipative materials which are homogeneous in nature.

Charge Retention using a Faraday Cup per ANSI/ESD Adv.11.2 (Modified):

ESD Adv.11.2-1995, Appendix D and EIA 541-1988 calls out a Faraday Cup charge retention test that has not been elevated to a standard test method and is required by some end-users in the ESD Materials Qualification Process. Said test requires skill to reproduce findings without human influence. This test was conducted at 12%RH +/-3%RH after 48 hours of preconditioning. In Figure 13, the static shielding bag is represented; in Figure 14, the gray moisture barrier bag is illustrated and the silver moisture barrier bag is seen in Figure 15 with the grid bag in Figure 17. Said bags were charged to 1000 volts and then removed from the charge plate by the evaluator wearing static dissipative gloves with resistance to a groundable point of 1.0 x 10⁶ Ω.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Six bags per sample type were allowed to free fall into the Faraday Cup. The results are illustrated in Tables 5A and 5B; the grid bag failed the test with a peak charge of 7.61nC.

 

Table 5A:  12%RH after 48 Hours of preconditioning

Static Shielding			Gray Moisture Barrier Bag			Silver Moisture Barrier Bag			Grid Bag
Side 1	nC	Start V	Side 1	nC	Start V	Side 1	nC	Start V	Side 1	nC	Start V
1	-0.480	1000v	1	-0.008	1000v	1	0.007	1000v	1	2.700	1000v
2	-0.397	1000v	2	-0.031	1000v	2	0.008	1000v	2	2.000	1000v
3	-0.216	1000v	3	-0.050	1000v	3	-0.035	1000v	3	0.816	1000v
4	-0.397	1000v	4	-0.031	1000v	4	-0.012	1000v	4	7.610	1000v
5	-0.316	1000v	5	-0.036	1000v	5	0.004	1000v	5	3.210	1000v
6	-0.453	1000v	6	-0.020	1000v	6	-0.014	1000v	6	0.480	1000v
Average	-0.377		Average	-0.029		Average	-0.007		Average	2.803
Median	-0.397		Median	-0.031		Median	-0.004		Median	2.350
Minimum	-0.480		Minimum	-0.050		Minimum	-0.035		Minimum	0.480
Maximum	-0.216		Maximum	-0.008		Maximum	0.008		Maximum	7.610
St. Dev.	0.097		St. Dev.	0.014		St. Dev.	0.017		St. Dev.	2.580

 

 

 

 

Electrostatic Shielding per ANSI/ESD STM11.31-2012:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mil-PRF-81705E calls out ANSI/ESD STM11.31 with a limit of 10nJ max. ANSI/ESD S11.4-2012 calls out a limit of <20nJ. Six discharges per bag were conducted.  ANSI/ESD STM11.31 provides a test method for determining the shielding capabilities of electrostatic shielding bags.  Said method employs a capacitive sensor inside the package. A 1KV discharge to the outer package was conducted; the fixture then measures the current across a resistor connected to the fixture’s upper and lower sensing plates. The current and resistance are utilized to calculate energy seen inside the package during the discharge event. This test has the objective of measuring energy per specified RH levels (at 12% or 50%).

 

 

 

 

 

 

 

 

 

 

Static Shielding Bag Results at 12% and 50%RH

 

 

Static Shielding Bag Results at 12% and 50%RH

 

 

Static Shielding Bag Results at 12% and 50%RH

 

Static Shielding Bag Results at 12% and 50%RH

                       

 

 

In Figure 18, the reader can view the grid bag being subjected to a 1kV discharge. A calibration discharge (conducted without a bag) produced 50,108.7nJ. A static shielding bag should not see more than <20nJ.  The grid bag, however, allowed 2,000.87nJ to penetrate the structure. In contrast, the static shielding bag (Type III) produced <5.0nJ.  Moreover, the silver Type I moisture barrier has a peak of 0.3nJ. The gray Type I moisture barrier bag protects to <0.18nJ.

In summary, the test methods utilized for formalized ESD qualification testing are as follows:

Table 7

Testing Protocols	Results
​Surface Resistance; inside and outside of bags per ANSI/ESD STM11.11-2015 at <1.0 x 1011 Ω	Static Shielding, Gray and Silver Moisture Barrier Bags Passed while the Grid Bag Failed
​Volume Resistance; inside of the bag to plate per ANSI/ESD STM11.12-2015 (Modified)	Static Shielding, Gray and Silver Moisture Barrier Bags Passed while the Grid Bag Failed
​Electrostatic Decay per Mil-STD-3010C, Method 4046-2013 (5kV to 0 volts) at <2.0 seconds	Static Shielding, Gray and Silver Moisture Barrier Bags and Grid Bag  Passed
​Charge Retention (Faraday Cup) per ESD Adv. 11.2-1995 at <1.0 nC	Static Shielding, Gray and Silver Moisture Barrier Bags Passed while the Grid Bag Failed
Static Shielding at 12%RH and 50%RH per ANSI/ESD STM11.31-2012 at <20 nJ at <1.0 x 1011 Ω	Static Shielding, Gray and Silver Moisture Barrier Bags Passed while the Grid Bag Failed

 

In short, the testing methods for evaluation which are traceable to ANSI/ESD S541-2008 are sound; however, the electrostatic decay testing method for Type I & Type III ESD bags is questionable.  If one used this testing method solely for qualification, electrostatic decay would not represent an indicator for an ANSI/ESD S20.20 compliant material. Electrostatic decay may be better suited for static dissipative planar foams or polymer ESD safe materials.

This article clearly demonstrates that quality ESD control packaging products can be  secured from the Asia Pacific Region. As with any static control product from the U.S., Europe. and Asia-Pacific, a formalized qualification process needs to be enforced before using ESD bags in an ANSI/ESD S20.20-2014 ESD Protected Area. Moreover, this practice should be combined with a periodic verification of incoming materials and packaging.

The author wishes to thank Tham Wai Mun of Dou Yee Enterprises for providing Type I (Moisture Barrier Bags) & Type III (Static Shielding Bags) specimens and selected illustrations.

References

1.    ESD Adv. 1.0-2009
2.    ANSI/ESD S541-2008
3.    ANSI/ESD S20.20-2014
4.    ANSI/ESD STM11.11-2015
6.    ANSI/ESD STM11.12-2015

1.    ANSI/ESD S11.4 (Static Shielding Bag Standard)
2.    Following ESD Materials Validation Process, Controlled Environments, Bob Vermillion, August 26, 2010
3.    A US Army DAC Study, March 2012, Vermillion and White
4. ESD from A to Z, Second Edition, Kolyer & Watson, Chapman & Hall, 1996
5. Humidity & Temperature Effects on Surface Resistivity, John Kolyer and Ronald Rushworth, Evaluation Engineering, October 1990, pp. 106-110
6. Pin Holes & Staples Lead to Diminished Performance in Metallized Static Shielding Bags, In Compliance, September 2013, pp 42-48, Bob Vermillion

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Bob Vermillion, CPP/Fellow, is a Certified ESD and Product Safety Engineer-iNARTE with practical and “hands-on” expertise in the mitigation of material Triboelectrification on a Mars surface and in troubleshooting robotics or systems in aerospace, disk drive, medical device , pharmaceutical, automotive and semiconductor sectors. Bob is Co-Chair of the SAE G19 Sub-Committee for Suspect Counterfeit Packaging. A co-author of several ANSI level ESDA documents. Bob conducts ESD Seminars on site at RMV, a NASA Industry Partner, located onsite at NASA Ames Research Center, and abroad, including guest speaker engagements for California State Polytechnic University, San Jose State University, University of California at Berkeley, Lawrence Berkeley National Laboratory and Clemson University. In 2015, Bob was invited to conduct the first Suspect Counterfeit Packaging & Materials Seminar at Oxford University. Bob is Founder and Chief Technology Officer of RMV Technology Group, LLC, a 3rd Party ESD Materials Testing, Training and Consulting Company. In 2015, RMV received the Top Corporate Award for Innovations in Packaging Engineering in protecting the Warfighter on behalf of the National Institute of Packaging & Handling Logistics Engineers (whose members include the DOD, DLA, DCMA and the prime contracting community). [email protected]