Anda boleh mendapat kejutan elektriksewaktu keluar dari kenderaan atauberjalan di atas karpet.

Berkemungkinan ada sedikitpercikan api apabila anda membuka bajuatau menyikat rambut dengan sikatplastik.

ESD = Electro Static Discharge

ESDS = Electro Static DischargeSensetive

EPA = ESD Protected Area

ESD Protected Area.(EPA)

Kawasan perlindungan ESDmerujuk kepada keluaran produkatau bahan yang sensitifyterhadap ESD yang bolehdikendalikan pada kadarrisiko kerosakan yang minimumdisebabkan oleh oleh elektrik statik.

Anda tidak dibenarkan memasukkan

bahan yang berpotensi menyebebkan

cas melebehi 100 volt ke dalam EPA

(kaw. perlindungan ESD)

There are EPA:s of different sizes

Sebagai contoh:

* Keseluruhan bangunan, dewan kilang atau kaw.pengeluaran.

* A ground-connected service-table, where minor

errors can be attended.

* Jurujual(supplier) yang datang untuk tujuanmembuat demontrasi hanya dibenarkanmembawa contohnya ESD-mat yang kecil.

**PERHATIAN:

ANDA TELAH

KELUAR DARI

KAWASAN ESD

600 tahun sebelum masehi, kaum GreekPurba mendapati sekiranya kismis digosokpada bulu, ianya boleh mengangkat daunkering atau partikel yang lain.

Perkara ini dianggap sihir dan ahli silapmata telah menggunakan fenomenaelektrik statik ini untuk meneruskankehidupan.

Kita akan cuba untukmengangkat cebisan-dengan sebatang plastik.

An other big phenomenon is thunder,the biggest discharge we know oftoday. After a hot sommar´s daywarm water vapour evaporateupwards and hits the ice crystals inthe clouds, a friction happens andthe clouds get a positive charging,which have an impact on thenegative electrons on the groundswhich are pulled upwards. Minusattracts plus. When the air no longercan carry the resistance, a dischargewill occur towards ground.

+ + + + + ++ + + + + + +

- - - - - - - - - - -- - - - - - - -

negative

positive

Extremes meet and similaritiespart.

Exactly like the electrons onground, which are attracted tothe positive clouds.

melalui:

We have a neutralcircuit board.

The electrons can flowfreely, because a circuitboard consists mainlyof metal whereelectrons move easilyand distributethemselves evenly toestablish a balance ofplus and minus.

I am made ofplastic and

very negative !

If a highlycharged objectcomes nearthe circuitboard, theelectrons areredistributedbecause ofstronginfluence,externalinfluence.

- - - -

- - - --

The positive charging of the board isattracted to the stronger negativeplastic bottle since extremes attractone another.

If we nowtouch theboard, theexcessiveelectronswill emit viayour-selftowardsground.

I am made ofplastic and

very negative !

- - - -

- - - --

- - - -

- - - --

The circuitboard has gotits first ESDbang and weare left witha positivelychargedboard, whichstays neutralas long asthe plasticbottleremains.

I am made ofplastic and

very negative !

ESD bang number two

The risk of ESD damages decreasesif you expand the distance.

The longer the distance betweentwo objects, the bigger charge isrequired to cause a discharge inbetween. A small charge can cross asmall distance. Imagine a stream,someone with long legs can cross abroad stream ( high charging ) whilesomeone with short legs may not beable to cross the same stream ( lowcharging ). But someone with shortlegs can also cross if only the wateris small enough (distance).

Through testing, aranking order isestablished of differentmaterials depending ontheir ability to emit orattract electrons.

The ranking order iscalled the Tribo-electric series . Tribomeans friction, so it isalso namned thefriction series.

More distance in theseries, the biggercharges you getbetween the differentmaterials.

Air

Human hand

Glass

Human hair

Wool, fur

Led, aluminium

Cotton, paper

Steel

Wood, rubber

Nickel, copper, silver

Gold, platinum

Polyester, orlon

PVC

Silicon

Teflon

Chargespreferablypositive

Fairly hardto charge

Chargespreferablynegative

In Malaysia for example there is a humidity of air of 60%Rh and they do not have anyESD problems. We can get problems when buying components or other ESD sensitivematerials from there, because they do not consider packing it in ESD envelopes to proventdamages when it arrives here with lower humidity of the air. Instead Malaysia has moreproblems with moist in their machines and test equipments.

Most ESD damages happen during wintertime since the humidity of the air is so low

In high humidity you do not accumulatecharges, which later can result in adischarge and an ESD damage, but youemit constantly small discharges via thehumidity of the air. But it never builds up toa big ESD, causing harm.

A person crossing a textile carpet will, summertime charge 1500Vwith a humidity of the air of 70%Rh.

And in the winter charge 35000V with a humidity of the air of 10%.

A person walking on plastic floor willsummertime charge 250V with a humidity ofthe air of 70%Rh.

And in the winter charge 12000V with ahumidity of the air of 10%Rh.

From: ”Electronics in the North” no 7 year 2000.

”An investigation was first carried out duringwinter, w2-10, 1998, and reached a quota of errorsof 17,4%. Half a year later the investigation wasrepeated, w23-31, after having informed theirquality department of the great influence of airhumidity. Then the quata of errors had decreased to11,7%, without having taken any kind of measures.”

When hearing that the amount of volt is so high in adischarge of static electricity, you may wonder why you arenot hurt or feel sick. If you enter your fingers into a wallsocket of 220V, you will not feel very well. We pointed outthat an ESD could reach 10 000V.

This has to do with the speed of ESD and the fact that thecurrent involved is not very strong.

An ESD stops immediately, while in the socket there is aconstant pulsation of current and the resistance in your bodymakes the current increase.

Rub a piece of cloth against a plastic pole, approach thecharged pole to a fluorescent tube in your other hand.

Possibly rub the plastic pole along the tube.

What happens?

Inflate a balloon and rub it against your hair.

What happens?

Rub the balloon against your hair and then approach itto a fine spray of water without touching the water withthe balloon.

What happens?

The fluorescent tube flickers, you can make the lightmove along the tube. We achieved a floating ofelectrons inside the tube.

Your hair and the balloon are charged against eachother, the balloon gets negative and the hair getspositive to the tribo-electrical series. Your hairfollows the balloon , plus attracs minus.

The water spray bends either against or away from theballoon depending on the amount of plus or minuscharging in the water at that moment.

Rub a piece of cloth against a plastic pole, approach thecharged pole to a fluorescent tube in your other hand.

Possibly rub the plastic pole along the tube.

What happens?

Inflate a balloon and rub it against your hair.

What happens?

Rub the balloon against your hair and then approach itto a fine spray of water without touching the water withthe balloon.

What happens?

This is an electronic tube.

They were common in thesixties, one function onetube.

To build a calculator oftoday´s capacity, a wholeroom filled with electronictubes would be required.

3-4cm

In the seventies and eighties the components had becomemore sophisticated and many more functions were includedthan had been the case in the electronic tube.

Hole mounted circuits were common, the components isinserted with its legs in a hole of the board and soldered fromthe back.

Circuit board

IC

In the ninetiessurface mountedcircuits becamecommon, thecomponents werenow smaller andmore efficient withmore functions. Asurface mountedcomponent has nolegs to be inserted ina hole, but they aresoldered on thesurface of the board.In this way it ispossible to mountcomponents on bothsides of the board tosave space andminimise size.

Noticing the short distance between the conductors inour circuits you can easily understand why it is nothard for the electrons to cross over and cause harm.

It is not noticeable in a component if there is anESD damage without using a microscope andx-ray equipment .

It is difficult to single out which electroniccomponents who are ESD sensitive. Considertherefore all electronic products without a cap orsimilar protection as ESD sensitive materials.

Wrist-band is 100% protection against ESD.

It contains a resistance of 1 M OHM ( one mega, one million ohm )

which makes a controlled diversion to prevent it from happening too fast. Thenyou avoid ESD damages when handling the ESD sensetive articles.

There are also other aids: in order not to get charged up when walking (rubbingyour shoes against the floor) you can wear special shoes with soles containingcoal diverting the ESD onto a special floor, also containing coal. This is an aide,not 100% protection since the shoes do not have constant, direct ground-contanct.

There are also other aids, like a protective coat, containing coal fibres.

Coal is a very useful material, which does not get charged easily, it also diverts ESD ina controlled way towards ground and it prevents, by shielding, electrons frompenetrating.

Consequently we cannot charge objects by rubbing it against the coat. It also sheildsthe clothes we wearing under, preventing them from influencing anything via induction.

There are also other aids.

A rolling wheel is both rubbing andseperating at the same time, which makestransport vehicles easily charged, which caninfluence objects near to. All trucks andcarriages must have diverting wheels inorder to divert while rolling. Finally they areconnected to ground to divert all charges..

There are also other aids,like special bags andplastic folders.

The pink bags areantistatic in order not toget charged but they arenot approved if you needto carry ESD sensetivematerials outside EPA:s.They cannot stop flashesof lightning, which willpass right through, andwould harm the ESDsensetive inside. Insteadyou need a metallizedbag, which works like aFaraday-cage..

The pink colour came about when a man heard that there was arequest for bags with antistatic finish. He succeeded in makingthem antistatic but could not understand why they never gotpopular. He consulted his wife and she thought the bag lookedlike any other bag and therefore no one would pay anything extrafor it. He gave it a good thought and decided to change the colourto pink since that was the favourite colour of his wife. Since thenvery many ESD products are pink, buy new colours areintroduced more and more.

This phenomenon was once foundout by Faraday, when placing himselfinside a metallic ball connected aresistance. An electron alwayschooses the quickest possible wayback to ground, which means no

voltage inside the ball.

Something metallized allaround. It stops electrons frompenetrating to what is inside.The electrons are lazy anddislike going through anythingslow and full of resistance, sothey run on the outside.

Cars and microwave ovens can also be considered as Faraday cages.

Conducting materials e.g metals, which are pure high-waysfor electrons, the speed is very high, too high if it goes towardground.less than 1 M

Isolating materials e.g plastics, mean completely stop for theelectrons, they can go nowhere. All electrons are piled up, thecharges get high since there is no way to discharge towardsground.1 T and upwards ( one terra ohm ) .

Dissipative materials, semi-conducting. Are good, since weget a controlled diversion towards ground. The electrons are”knocking at the door asking” if they may take this waytowards ground.1 M up to 1 T

In a company, the management group isresponsible to make an ESD enviromentpossible if needed.

They must fund purchase of ESD protectivearticles, which are more expensive than othersimilar products, but rewarding in the long run.

Floors, shoes,wristbands, tables,chairs etc are to betested frequently.