ESD @Bahasa Malaysia 120806

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Anda boleh mendapat kejutan elektrik sewaktu keluar dari kenderaan atau berjalan di atas karpet. Berkemungkinan ada sedikit percikan api apabila anda membuka baju atau menyikat rambut dengan sikat plastik.

ESD

= Electro Static Discharge

ESDS = Electro Static Discharge Sensetive EPA = ESD Protected Area

ESD Protected Area.(EPA) Kawasan perlindungan ESD merujuk kepada keluaran produk atau bahan yang sensitify terhadap ESD yang boleh dikendalikan pada kadar risiko kerosakan yang minimum disebabkan 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 tujuan membuat demontrasi hanya dibenarkan membawa contohnya ESD-mat yang kecil.

**PERHATIAN: ANDA TELAH KELUAR DARI KAWASAN ESD

Kita akan cuba untuk mengangkat cebisandengan sebatang plastik.

600 tahun sebelum masehi, kaum Greek Purba mendapati sekiranya kismis digosok pada bulu, ianya boleh mengangkat daun kering atau partikel yang lain. Perkara ini dianggap sihir dan ahli silap mata telah menggunakan fenomena elektrik statik ini untuk meneruskan kehidupan.

An other big phenomenon is thunder, the biggest discharge we know of today. After a hot sommars day warm water vapour evaporate upwards and hits the ice crystals in the clouds, a friction happens and the clouds get a positive charging, which have an impact on the negative electrons on the grounds which are pulled upwards. Minus attracts plus. When the air no longer can carry the resistance, a discharge will occur towards ground.

+ + + + + + + + + + + ++positive

- - - - - - - - - - - - - - - - - negative

Extremes meet and similarities part. Exactly like the electrons on ground, which are attracted to the positive clouds.

melalui:

We have a neutral circuit board. The electrons can flow freely, because a circuit board consists mainly of metal where electrons move easily and distribute themselves evenly to establish a balance of plus and minus.

If a highly charged object comes near the circuit board, the electrons are redistributed because of strong influence, external influence.

The positive charging of the board is attracted to the stronger negative plastic bottle since extremes attract one another.

I am made of plastic and very negative ! -------

If we now touch the board, the excessive electrons will emit via your-self towards ground.

I am made of plastic and very negative ! -------

The circuit board has got its first ESD bang and we are left with a positively charged board, which stays neutral as long as the plastic bottle remains.

I am made of plastic and very negative ! -------

ESD bang number two

The risk of ESD damages decreases if you expand the distance. The longer the distance between two objects, the bigger charge is required to cause a discharge in between. A small charge can cross a small distance. Imagine a stream, someone with long legs can cross a broad stream ( high charging ) while someone with short legs may not be able to cross the same stream ( low charging ). But someone with short legs can also cross if only the water is small enough (distance).

Through testing, a ranking order is established of different materials depending on their ability to emit or attract electrons. The ranking order is called the Triboelectric series . Tribo means friction, so it is also namned the friction series. More distance in the series, the bigger charges you get between the different materials.

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 Charges preferably negative Fairly hard to charge Charges preferably positive

Most ESD damages happen during winter time since the humidity of the air is so low In high humidity you do not accumulate charges, which later can result in a discharge and an ESD damage, but you emit constantly small discharges via the humidity of the air. But it never builds up to a big ESD, causing harm.In Malaysia for example there is a humidity of air of 60%Rh and they do not have any ESD problems. We can get problems when buying components or other ESD sensitive materials from there, because they do not consider packing it in ESD envelopes to provent damages when it arrives here with lower humidity of the air. Instead Malaysia has more problems with moist in their machines and test equipments.

A person crossing a textile carpet will, summertime charge 1500V with 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 will summertime charge 250V with a humidity of the air of 70%Rh. And in the winter charge 12000V with a humidity of the air of 10%Rh.

From: Electronics in the North no 7 year 2000. An investigation was first carried out during winter, w2-10, 1998, and reached a quota of errors of 17,4%. Half a year later the investigation was repeated, w23-31, after having informed their quality department of the great influence of air humidity. Then the quata of errors had decreased to 11,7%, without having taken any kind of measures.

When hearing that the amount of volt is so high in a discharge of static electricity, you may wonder why you are not hurt or feel sick. If you enter your fingers into a wall socket of 220V, you will not feel very well. We pointed out that an ESD could reach 10 000V. This has to do with the speed of ESD and the fact that the current involved is not very strong. An ESD stops immediately, while in the socket there is a constant pulsation of current and the resistance in your body makes the current increase.

Rub a piece of cloth against a plastic pole, approach the charged 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 it to a fine spray of water without touching the water with the balloon. What happens?

Rub a piece of cloth against a plastic pole, approach the charged pole to a fluorescent tube in your other hand. Possibly rub the plastic pole along the tube. What happens?The fluorescent tube flickers, you can make the light move along the tube. We achieved a floating of electrons inside the tube. Your hair and the balloon are charged against each other, the balloon gets negative and the hair gets positive to the tribo-electrical series. Your hair follows the balloon , plus attracs minus.

Inflate a balloon and rub it against your hair. What happens?

Rub the balloon against your hair and then approach it to a fine spray of water without touching the water with the balloon. The water spray bends either against or away from the What happens?balloon depending on the amount of plus or minus charging in the water at that moment.

This is an electronic tube. 3-4 cm They were common in the sixties, one function one tube. To build a calculator of todays capacity, a whole room filled with electronic tubes would be required.

IC

Circuit board

In the seventies and eighties the components had become more sophisticated and many more functions were included than had been the case in the electronic tube. Hole mounted circuits were common, the components is inserted with its legs in a hole of the board and soldered from the back.

In the nineties surface mounted circuits became common, the components were now smaller and more efficient with more functions. A surface mounted component has no legs to be inserted in a hole, but they are soldered on the surface of the board. In this way it is possible to mount components on both sides of the board to save space and minimise size.

Noticing the short distance between the conductors in our circuits you can easily understand why it is not hard for the electrons to cross over and cause harm. It is not noticeable in a component if there is an ESD damage without using a microscope and x-ray equipment . It is difficult to single out which electronic components who are ESD sensitive. Consider therefore all electronic products without a cap or similar 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. Then you avoid ESD damages when handling the ESD sensetive articles.

There are also other aids: in order not to get charged up when walking (rubbing your shoes against the floor) you can wear special shoes with soles containing coal 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 groundcontanct.

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 in a controlled way towards ground and it prevents, by shielding, electrons from penetrating. Consequently we cannot charge objects by rubbing it against the coat. It also sheilds the clothes we wearing under, preventing them from influencing anything via induction.

There are also other aids.A rolling wheel is both rubbing and seperating at the same time, which makes transport vehicles easily charged, which can influence objects near to. All trucks and carriages must have diverting wheels in order to di