SMART BEGINNERS GUIDE

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SMART BEGINNERS GUIDE TO ESD: PART 1 SMART-e-W ebinar 13 th October 2015 Dr Jeremy Smallwood E lectrostatic Solutions Ltd www.electrostatics.

1 SMART BEGINNERS GUIDE TO ESD: PART 1 SMART-e-W ebinar 13 th October 2015 Dr Jeremy Smallwood E lectrostatic Solutions Ltd Your Delegate Webinar Control Panel Open and close your panel Full screen view Submit text questions during or at the end NPL Management Ltd - Commercial 2 1

2 SMART BEGINNERS GUIDE TO ESD: PART 1 SMART-e-W ebinar 13 th October 2015 Dr Jeremy Smallwood E lectrostatic Solutions Ltd 2

3 In this presentation Why worry about ESD? How static electricity works How to prevent ESD damage ESD Packaging In summary WHY WORRY ABOUT ESD? 3

4 What is ESD? ESD is an ElectroStaticDischarge Like the shock you sometimes feel when you touch a metal object, person or your car We need about 4000V on the body to feel an ESD shock We can damage some components at less than 100V Static electricity is a local build up of charge Produces a high voltage Like snow resting on a mountain top ESD is like an avalanche Charges suddenly move from place to place Fast moving charge (high electrical current) can do a lot of damage very quickly! Why don t we want ESD? ESD damages ESD Sensitive components, PCBs and modules (ESDS) ESD causes product failures or worse unreliability Damaged components can pass tests and fail later Failures cost money, repair time and delays Failures and unreliability damage the product and it's reputation Customers get annoyed or worse Bad company or product reputation can lead to lost sales or even jobs What would failure or unreliability of your product mean to your customer and cos t your company? 4

ESD damage to an IC SEM microscope photos ESD damage often needs expensive

Photos courtesy of Rohm Electronics (UK) Ltd Components on circuit boards can

ESD damage to a component, or it may reduce it.

5 ESD damage to an IC SEM microscope photos ESD damage often needs expensive analysis to identify it ESD has punched through an oxide layer, damaging a track Photos courtesy of Rohm Electronics (UK) Ltd Components on circuit boards can also be damaged by ESD Assembling a component to a PCB can increase the risk of ESD damage to a component, or it may reduce it. There's no easy way of telling for a particular board Assume that the board is as sensitive as the most sensitive component. 5

6 The main sources of ESD damage Charged people ESD occurs when they touch a device Charged metal machine parts, objects or tools ESD occurs when it touches a device Charged components or PCBs ESD occurs when they touch a conductive (e.g. metal) object or surface Electrostatic fields cause voltage differences between items that lead to ESD HOW STATIC ELECTRICITY WORKS 6

7 Where does electrostatic charge come from? Every material is made up of electrostatic charge Negative electrons Positive atomic nuclei When charges are present in equal numbers, and their electrostatic effects cancel When we find more of one type, we notice static electricity effects How does charge become unbalanced? When two materials touch, charge moves between them When materials separate they take their new charge with them One material is charged positive, the other has equal negative charge The charges will try to move to return to balance, if they are not stopped from doing so

Why don t we always get static charge build up?

is generation faster than it is can move away then the level quickly builds up

Insulators stop charge moving away Insulators stop charge moving away and

8 Why don t we always get static charge build up? if charge can move away faster than it is generated, then no build up if charge is generation faster than it is can move away then the level quickly builds up No problem Problem! Insulators stop charge moving away Insulators stop charge moving away and encourage static charge build up Charge build up gives high voltages High voltages give high electrostatic fields and risk of ESD Plastic bags, boxes Dry paper & cardboard Rubber 8

We don't want charged insulators near ESDS Insulators bring a risk of ESD Our first choice would be: Don't have insulators anywhere near ESDS Some insulators are an essential part of the product or

9 We don't want charged insulators near ESDS Insulators bring a risk of ESD Our first choice would be: Don't have insulators anywhere near ESDS Some insulators are an essential part of the product or build process If we can't remove these "essential" insulators, we have to reduce the ESD risk somehow Conductors allow charge to move around Conductors allow charge to move around quickly enough to avoid charge build up A conductor is anything which is not an insulator! Includes conductive and dissipative ESD materials Conductors must be grounded (earthed) to avoid charge build up Ungrounded conductors are a strong source of ESD E.g. people! Metal Water Damp card and paper People 9

10 What is grounding? Grounding provides an electrically conducting path for charge to move to ground wire material A ground path must be continuous to earth Like a drain, it is no good if there is a block Conductive or dissipative materials in the EPA must be grounded to prevent them becoming charged and a source of ESD HOW TO PREVENT ESD DAMAGE 10

11 Everyone has a part to play If you handle an ESD sensitive component or board. its life is in your hands! Learn to be aware of ESD threats to recognise the ESDS in your facility the correct ESD procedures who to go to for help on ESD control Your role in ESD prevention How can we protect product against ESD damage? ESD Sensitive components and product must only be handled within an ESD Protected Area (EPA) Outside the EPA, they must be protected by ESD protective packaging Never take an ESDS out of its protective packaging unless you are in an EPA! 11

12 What is an ESD Protected Area (EPA)? An EPA is an area in which static electricity is controlled to a low level It must have a clear boundary Otherwise, how would you know if you were inside it or outside? The ESD control equipment and processes we use within the EPA are designed to prevent ESD damage We must never take ordinary items into an EPA! How do we control static electricity in the EPA? the principles Always ground personnel who handle ESDS Use wrist straps or footwear and flooring Don t have any unnecessary insulators in workstations where ESDS are handled Use only ESD packaging Don t have papers and other static generators don't take in materials and equipment not specified for EPA use Ground all conductors Use ESD control equipment and make sure it is grounded Prevent discharge between ESDS and metal objects We'll see later what this means in practice 12

ground disconnected Check wrist straps and footwear Check your wrist straps and ESD footwear before starting work and always use

13 Wear a wrist strap or ESD footwear Body voltage is controlled by grounding By wearing a wrist strap By wearing ESD footwear with ESD flooring A continuous ground path is required Just touching a grounded object doesn't work well enough voltage reappears when ground disconnected Check wrist straps and footwear Check your wrist straps and ESD footwear before starting work and always use them! Wrist straps must be in good constant contact with the skin of the wrist Always wear a wrist strap when seated and handling ESDS 13

14 EPA floor A conducting EPA floor is often used for grounding personnel, trolleys, racks, chairs and other equipment standing on it This will only work if Personnel are wearing ESD footwear Trolleys and racks are EPA compliant and grounded through their feet or wheels Chairs are designed for EPA use with conductive feet or wheels EPA bench surfaces EPA bench surfaces are conductive or static dissipative and grounded. They normally have high electrical resistance so that a charged ESDS placed upon them does not suffer a damaging ESD They act to gently take charge way from any conducting item placed upon them Tote boxes Packaging ESDS tools 14

ESD chairs An ESD chair doesn t charge up or give electrostatic fields that could damage ESDS They are grounded through the EPA floor Ordinary (non ESD compliant) chairs can

prevent electrostatic fields from charged clothing reaching ESDS They must fit cover the upper body clothes, and be fastened correctly They work best if in good contact with

15 ESD chairs An ESD chair doesn t charge up or give electrostatic fields that could damage ESDS They are grounded through the EPA floor Ordinary (non ESD compliant) chairs can give high electrostatic fields in this case nearly 12,000V ESD coats and smocks Wear an ESD coats or smock if required by your ESD control program These are often used to prevent electrostatic fields from charged clothing reaching ESDS They must fit cover the upper body clothes, and be fastened correctly They work best if in good contact with the skin, usually at the cuff Ordinary clothing should not be taken off in the EPA Ordinary clothing can give high electrostatic fields when removed in this case nearly 7,000V 15

16 Visitors ALL visitors to the EPA must comply with ESD prevention measures If not themselves trained in ESD prevention, they must be accompanied by an ESD trained person ESD PACKAGING 16

17 Different types of ESD packaging can have different functions Some protect against electrostatic fields Electrostatic field shielding Some protect against direct electrostatic discharge ESD shielding Some just don t charge up very much Low charging Some have many or all of these properties ESD bags Pink poly bags do not give ESD protection to ESDS They are low charging and help reduce charge build up Black polythene bags are electrostatic field shielding but not ESD shielding Metallised shielding bags are ESD shielding and give protection against direct ESD 17

18 What is the right ESD packaging? If an ESDS is to go outside the EPA it must be in either packaging defined by your ESD control program packaging agreed with your supplier or customer ESD shielding packaging system (e.g. box) or bag Packaging used in the EPA Any type of ESD control packaging can be used within an EPA if allowed by your ESD Progra m Pink polythene bags are best used for documents and non ESD sensitive items only Don't take ordinary packaging materials into an EPA Only use ESD protective packaging Don't put ordinary packaging into a kit for EPA use! 18

When receiving ESDS Unwrap a package only as far as the ESD protective packaging ESD package marking can be variable know the ones you expect to see ESD protective packaging must be opened only

19 When receiving ESDS Unwrap a package only as far as the ESD protective packaging ESD package marking can be variable know the ones you expect to see ESD protective packaging must be opened only within an ESD Protected Area ESDS parts that are not packaged in correct ESD protective packaging might be damaged X X stands for S shielding D dissipative C conductive L low charging IN SUMMARY... 19

20 Make sure you Recognise the ESDS in your facility, and the packages that contain ESDS Know the EPA workstation areas in your facility Check your wrist straps and ESD footwear and be sure to use them Use the ESD procedures, tools, materials and equipment specified in your ESD control program Know what to do if you find a non compliance Know the right ESD packaging for ESDS Don't take non compliant packaging, tools and equipment into the EPA IN PART 2, MORE ABOUT HOW IT S DONEINPRACTICE 20

ESD control-esd control during manufacture. ESD damage during manufacture can be prevented by adopting the following strategy:

Principles of ESD prevention ESD control-esd control during manufacture ESD damage during manufacture can be prevented by adopting the following strategy: sensitive components are only handled in an ESD