How to create a Compliance Verification Plan
Each component in an ESD protected area (EPA) plays a vital part in the fight against electrostatic discharge (ESD). If just one component is not performing correctly, you could harm your ESD sensitive devices potentially costing your company a lot of money. The problem with many ESD protection products is that you can’t always see the damage – think wrist straps! By just looking at a coiled cord, you can’t confirm it’s working correctly; even without any visible damage to the insulation, the conductor on the inside could be broken. This is where periodic verification comes into play.
ESD protected area (EPA) products should be tested:
- Prior to installation to qualify product for listing in user’s ESD control plan.
- During the initial installation.
- For periodic checks of installed products as part of IEC 61340-5-1 Edition 2 2016 clause 5.2.3 Compliance verification plan.
|Checking an ESD Lab Coat using a Surface Resistance Tester|
“A compliance verification plan shall be established to ensure the organization’s fulfilment of the requirements of the plan. Process monitoring (measurements) shall be conducted in accordance with a compliance verification plan that identifies the technical requirements to be verified, the measurement limits and the frequency at which those verifications shall occur. The compliance verification plan shall document the test methods used for process monitoring and measurements. If the organization uses different test methods to replace those of this standard, the organization shall be able to show that the results achieved correlate with the referenced standards. Where test methods are devised for testing items not covered in this standard, these shall be adequately documented including corresponding test limits. Compliance verification records shall be established and maintained to provide evidence of conformity to the technical requirements.
The test equipment selected shall be capable of making the measurements defined in the compliance verification plan.” [IEC 61340-5-1:2016 clause 5.2.4 Compliance verification plan]
Components of a Verification Plan
As outlined in the User Guide 61340-5-2:2008, each company’s verification plan needs to include:
1. A list of items that are used in the EPA and need to be checked on a regular basis
This would include ESD working surfaces, personnel grounding devices like wrist straps or foot grounders, ionisers etc. It is recommended to create a checklist comprising all ESD control products: this will ensure EPAs are checked consistently at every audit.
2. A schedule specifying what intervals and how each item is checked
The test frequency will depend on a number of things, e.g. how long the item will last, how often it is used or how important it is to the overall ESD control programme.
As an example: wrist straps are chosen by most companies to ground their operators; they are the first line of defence against ESD damage. They are in constant use and are subjected to relentless bending and stretching. Therefore, they are generally checked at the beginning of each shift to ensure they are still working correctly and ESD sensitive items are protected. Ionisers on the other hand are recommended to be checked every 6 months: whilst they are in constant use, they are designed to be; the only actual ‘interaction’ with the user is turning the unit on/off. If however, the ioniser is used in a critical clean room, the test frequency may need to be increased.
|It is recommended that Wrist Straps are checked before each shift|
The user guide offers a solution: “Some organizations may want to increase the time between verifications of an ESD control item after it has been in use for a period of time. This is typically done by monitoring the failures of the ESD control item. Once the organization has evidence that there is an acceptable period of time where no failures were found, the time between verifications can be increased. The new verification interval is then monitored. If an unacceptable level of failures is identified, then the verification frequency should revert back to the previous level.” [User Guide 61340-5-2:2008 clause 4.3.3 Verification frequency]
The industry typically uses 2 types of verification to achieve maximum success: visual and measurement verification. As the name suggests, visual verification is used to ensure ESD working surfaces and operators are grounded, ESD flooring is in good shape or wrist straps are checked before handling ESD sensitive items.
Actual measurements are taken by trained personnel using specially designed equipment to verify proper performance of an ESD control item.
3. The suitable limits for every item used to control ESD damage
IEC 61340-5-1:2016 contains recommendations of acceptable limits for every ESD control item. Following these references reduces the likelihood of 100V (HBM) sensitive devices being damaged by an ESD event.
Please bear in mind that there may be situations where the limits need to be adjusted to meet the company’s requirements.
4. The test methods used to ensure each ESD product meets the set limits
Tables 1 to 3 of IEC 61340-5-1:2016 list the different test methods a company has to follow. If a company uses other test methods or have developed their own test methods, the ESD control programme plan needs to include a statement explaining why referenced standards are not used. The company also needs to show their chosen test methods are suitable and reliable.
It is recommended that written procedures are created for the different test methods. It is the company’s responsibility to ensure anybody performing the tests understands the procedures and follows them accordingly.
5. The equipment used to take measurements specified in the test methods
Every company needs to acquire proper test equipment that complies with the individual test methods specified in Tables 1 to 3 of IEC 61340-5-1:2016. Personnel performing measurements need to be trained on how equipment is used.
|Checking ESD Working Surface using a Surface Resistance Tester|
6. A list of employees who will be performing the audits
Part of the verification plan is the choice of internal auditors. A few suggestions for the selection process:
- Each induvial is required to know the ESD Standard IEC 61340-5-1 AND the company’s individual ESD programme.
- It is essential that the selected team member recognises the role of the ESD control programme in the company’s overall quality management system.
- It is recommended that each nominated worker has been trained on performing audits.
- The designated employee should be familiar with the manufacturing process they are inspecting.
7. How to deal with non-compliance situations
Once an audit has been completed, it is important to keep everyone in the loop and report the findings to the management team. This is particularly vital if “out-of-compliance” issues were uncovered during the audit. It is the responsibility of the ESD coordinator to categorise how severe each non-conformance is; key problems should be dealt with first and management should be notified immediately of significant non-compliance matters.
Results of audits (especially non-compliance findings) are generally presented using charts. Each chart should classify:
- The total findings of the audit
- The type of each finding
- The area that was audited
It is important to note that each company should set targets for a given area and include a trend report. This data can assist in determining if employees follow the outlined ESD control programme and if improvements can be seen over time.
Here is an example of a Verification Plan using ESD flooring for demonstration purposes. A few notes:
- Our sample company has 2 different areas where ESD floor matting is used: the packaging area and the main EPA.
- Flooring is not used for grounding personnel handling ESD sensitive items
- Our sample company has established that the limits outlined in the standard are suitable for their internal requirements.
Bear in mind that ALL your ESD control items need to be included in your verification plan. So if your company uses wrist straps, smocks, chairs, gloves etc. then ALL of them have to be listed as part your ESD control programme.