ESD (Electrostatic Discharge) damage may be available in each single component, no matter big or small, due to transportation, friction or direct contact and the damage brought by ESD should be minimized in every procedure of electronic product manufacturing. It will affect the quality and the performance of finished boards.

In this passage, we are going to provide the measures of controlling ESD damage. Please check and read the content we prepare for you to learn more professional knowledge.

If you want to order PCB product, please check and custom your order online.  

How does ESD damage occur?

ESD can occur in a variety of forms. One of the most common is through human contact with sensitive devices. Human touch is only sensitive on ESD levels that exceed 4,000V.

A recent investigation found the human body and its clothing capable of storing between 500V and 2,500V electrostatic during the normal workday. This is far above the level that damages circuits yet below the human perception threshold. Other sources of ESD damage to equipment include:

·  Troubleshooting electronic equipment or handling of printed circuit boards without             using an electrostatic wrist strap;

·  Placement of synthetic materials (i.e. plastic, Styrofoam, etc.) on or near electronic                 equipment; and

·  Rapid movement of air near electronic equipment (including using compressed air to           blow dirt off printed circuit boards, circulating fans blowing on electronic equipment, or       using an electronic device close to an air handling system).

In all of these scenarios, the accumulation of static charges may occur, but you may never know. Furthermore, a charged object does not necessarily have to contact the item for an ESD event to occur.

How to prevent ESD damage?

The constant improvement of antistatic measures implementation depends on normalized regulations in SMT assembly workshop. As soon as any issue is exposed concerning ESD, suitable measures should be made in time to prevent ESD damage.

In accordance with the application or frequency of different infrastructure, equipment and system, inspection should be made once a week, a month or a quarter. ESD manager should be available in each manufacturing area and inspection items should cover environment, equipment, instrument, tools, fixture, staff, antistatic equipment, materials etc. The inspection results should be provided as a file surrounding previous problems concerning ESD.

It's unlikely you can eliminate ESD completely from any site. However, experience has shown that the following guidelines are helpful:

·  Keep all synthetic materials at least 4 in. away from electronic equipment.

·  When cleaning printed circuit boards, use a spray labeled as non-static forming.

·  When troubleshooting electronic equipment, always wear a static wrist strap that's grounded to the frame of the device. Also, wear the wrist strap when handling printed circuit boards.

·  Treat carpets and floors with compounds that reduce the buildup of static charges.

·  Use static floor mats where necessary.

·  Make sure the grounding system for equipment has a low impedance for ESD currents to dissipate to an earthing reference.

How to process ESD damage inspection?

To effectively stop static electricity from being generated and ensure the security of ESD, inspection tools and equipment should be inspected to meet its reliability standard including antistatic wrist band, antistatic shoes, ion fan etc.

The tools and equipment for ESD inspection that are usually used in SMT assembly workshop mainly include:

• Surface resistance checker

• Megger

• Static field meter

• Ion fan

• Ion balance tester

• Non contact voltage tester

• Wristband tester

• Human body comprehensive static tester

Equipment and system for ESD protection should be inspected under the practical guidance of QA (Quality Assurance) and QE (Quality Engineering). Generally speaking, appropriate tools and methods should be applied t be compatible with different material and tool requirement. For example, when a simple surface resistance checker is being used on some soft material such as overall with rough surface, cystosepiment or bubble bag, pressure should be put valuing 4 to 6 kilograms so that the contact will be excellent between test electrode and material surface and test should be valid as well. Additionally, as a megger is used to measure the surface resistance of tested material, a megger should be picked up with 100V DC.

Wanna know PCB knowledge? Check and read for more.